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Guys, I'm working with a stock '95 Camero LT-1, a new Comp 276HR-12 cam, and DNA stainless headers.
I have a stock '87 Garret GN turbo (w/ intercooler), and a stock Garrett GTP-38, from an early 7.3 Powerstroke. The plan is to mount these in the rear, and control them with appropriate shunt valving.
I have maps, etc, for the GN unit, but can't seem to unearth much pertaining to the GTP. I am making the assumption that they are sized about right for my intended purpose, but feel free to chime in if you have any further knowledge or experience with these two blowers.
I did see another post here where someone used a GN & a TP (not a GTP) on a 4.8 LS, with no sequential valving at all, and had good results. So that was encouraging...
Last edited by Rich...; Jun 3, 2020 at 01:46 AM.
Reason: misspelled word
Gtp38 should be near a 65 mm compressor and flow 58-60 lb min. Turbine is larger than p trim 65/74 turbines so thats good.
i honestly dont think you should mess with sequential. Just use the single gtp38. It will spool quick as along as you use something like 2.5” pipe over half way and then maybe neck it down to 2.25” before the turbo some. Wrap the exhaust or have it coated
my 305 tpi motor spooled a p trim 70 mm quickly. You should be fine with the larger lt1. Esp if it has any bolt ons and or a cam
Gtp38 should be near a 65 mm compressor and flow 58-60 lb min. Turbine is larger than p trim 65/74 turbines so thats good.
i honestly dont think you should mess with sequential. Just use the single gtp38. It will spool quick as along as you use something like 2.5” pipe over half way and then maybe neck it down to 2.25” before the turbo some. Wrap the exhaust or have it coated
my 305 tpi motor spooled a p trim 70 mm quickly. You should be fine with the larger lt1. Esp if it has any bolt ons and or a cam
Orr, thank you for your reply.
That thought had occurred to me, and would certainly be a lot easier, but it just seemed to me that the turbine ports were too restrictive for the amount of exhaust volume that I'd expect to have at higher rpm under load. Of course I'm no expert on this subject, and I could be wrong about that.
I had planned to shunt everything to the GN turbo initially, then when boost reaches 5-6#, begin opening a balance valve to one side of the GTP, then after 12-15#, begin opening the other side also.
I'm shooting in the dark to a large extent, and mainly working off of intuition. But unless the two turbos *are* actually too big when combined, I had surmised that this scheme should provide me with a very fast inititial spool, a smooth transition, and plenty of breathing room at the top.
I appreciate your opinion, and will definitely take it into account.
BTW, if it matters, I also have another GN turbo, two Garrett TP-38s, a 280ZX turbo, and a Mercedes 300SD unit.
I honestly dont think both are too big together. If you can split load between them. I am not experienced in going sequential but i get the concept to an extent. I just not familiar with how to control it
being a remote mount your exhaust energy is reduced. With this you could get away with a smaller turbine and housing
a single gtp38 on the front would be rather small but likely ok for 500 hp or so On low boost and instant spool. Its kinda like the old popular T60-T70 master powers that had the p trim turbines. They were great for stock motors looking for low boost moderate power under 600 hp. Not good for big engines or built engines unless you go twins
with it at the rear the turbine sees less energy so it acts like its on a smaller engine imo. But its only a 65 mm Comp wheel That flows enough for near 600 flywhee hp. If thats ok For target then it should work good imo and spool fast.
I honestly dont think both are too big together. If you can split load between them. I am not experienced in going sequential but i get the concept to an extent. I just not familiar with how to control it
being a remote mount your exhaust energy is reduced. With this you could get away with a smaller turbine and housing
a single gtp38 on the front would be rather small but likely ok for 500 hp or so On low boost and instant spool. Its kinda like the old popular T60-T70 master powers that had the p trim turbines. They were great for stock motors looking for low boost moderate power under 600 hp. Not good for big engines or built engines unless you go twins
with it at the rear the turbine sees less energy so it acts like its on a smaller engine imo. But its only a 65 mm Comp wheel That flows enough for near 600 flywhee hp. If thats ok For target then it should work good imo and spool fast.
Anyone else have this problem here?: I write up a reply, hit the "post reply" button, and poof... it just disappears! I'll have to remember to copy everything before posting, just in case.
Anyway, thank you Orr, for your thoughts. I am an engineer by trade, and usually my intuition is pretty well on target. But I pick up a lot and learn quickly when conversing with people like yourself, who already have hands on experience.
I am not *dead set* on this sequential arrangement, but at this point in my thinking process, it still makes sense to me. I know I can do the valving and control without a tremendous amount of extra effort, and at least in *my* mind, the extra CFM and reduced backpressure at the top, would be healthier for the engine, and translate into free HP, basically.
I don't think I mentioned it, but for reference, this is a street car, and my goal was around 800hp at the flywheel.
Bear in mind that these turbos will not actually be *that* far from the engine. I am building a compartment for them where the back seat would normally be. I think I may be able to efficiently fit the intercooler in there also...
BTW, I plan to run my mufflers ahead of the turbos, unless you see a problem with that arrangement. Everything I've read, says it's vitally important to keep backpressure behind the turbos to an absolute minimum...
Lol i know what you mean about back seat lol. I just feel its abit more complicated than just running a proper sized single. But i like being different and the challenge
Lol i know what you mean about back seat lol. I just feel its abit more complicated than just running a proper sized single. But i like being different and the challenge
is this a thing now? i had planned to put turbos in that spot years ago and then orr popped up with them. i was shocked really, because i hadnt really seen anyone else do that. and now rich is doing it too. lol
i would save up some coin and get an appropriate sized single since you are shooting for 800. Also, doesnt the gn turbo have that funky flange on it? seems like it would all get overly complicated for the amount of savings not to mention the compromises of using a combination of not ideal parts.
is this a thing now? i had planned to put turbos in that spot years ago and then orr popped up with them. i was shocked really, because i hadnt really seen anyone else do that. and now rich is doing it too. lol
i would save up some coin and get an appropriate sized single since you are shooting for 800. Also, doesnt the gn turbo have that funky flange on it? seems like it would all get overly complicated for the amount of savings not to mention the compromises of using a combination of not ideal parts.
I don't know, Dirk... It made sense to me, so I thought I'd try it. I guess Orr just happened to have the same idea.
But now you've gone to talking bad about my flanges, etc... Don't you guys ever make parts from scratch?
Hell even try twin gtp38’s lol and setup them sequentially to get one lit before running both
Hey, as I say, I'm no expert on turbos, and I'm doing this for kicks as much as anything. But two 38s seem like they would be a little too much for a 350, according to *my* dillitatious logic...
The GN guys claim to get over 400hp out of the 231ci engine with the stock turbo, a cam, and bolt-ons. The GTP is twice the size of the GN unit, with a higher A/R. Surely the two of them will get me close to where I want to be..?
The GN guys claim to get over 400hp out of the 231ci engine with the stock turbo, a cam, and bolt-ons.
Those guys claim that power not realizing they are running a 49 turbo and not a stocker, because it is difficult to distinguish between the two. Grand Nationals will sometimes swap hands with those turbo's already installed on them, so the new owner is of course surprised when they are somehow pushing high tens in the quarter mile with the "stock" turbo...
95 Camaro w/LT1 ehh? I knew a guy who pulled the LT1 in favor for a single turbo LC2 in a '93 Formula, and makes the same power you're now looking for. Consider staying single...
Those guys claim that power not realizing they are running a 49 turbo and not a stocker, because it is difficult to distinguish between the two. Grand Nationals will sometimes swap hands with those turbo's already installed on them, so the new owner is of course surprised when they are somehow pushing high tens in the quarter mile with the "stock" turbo...
95 Camaro w/LT1 ehh? I knew a guy who pulled the LT1 in favor for a single turbo LC2 in a '93 Formula, and makes the same power you're now looking for. Consider staying single...
Rob, pardon my ignorance; but what is an "LC2"?
Maybe you're right about them being confused about their turbo size, but it's mighty hard for me to believe, considering who we are talking about... Those Buick guys are a different breed. Meticulous about every detail.
I have an 86 GN engine, if I wanted to go that route. But I don't... I hate the sound of a six cylinder, and bigger is always better, in my book. If I had more money to blow on this project, I'd put a 383 kit in that LT-1, and use the two TP-38s on it.
BTW, I think you may have misunderstood... I hope it doesn't disqualify me here, but the only thing "Camero" about this project, is the engine. It's going into an '85 MC.
Not at all. The LC2 is the engine code for the Grand National/T-Type. I was definitely not encouraging you to go with a V6 over a V8, but the concept was that if a single turbo V6 can produce the numbers that you're looking for, then a single turbo V8 can do it that much easier. I bought myself a Turbo Buick a few months back as well, and stock it shall remain lol...
Not at all. The LC2 is the engine code for the Grand National/T-Type. I was definitely not encouraging you to go with a V6 over a V8, but the concept was that if a single turbo V6 can produce the numbers that you're looking for, then a single turbo V8 can do it that much easier. I bought myself a Turbo Buick a few months back as well, and stock it shall remain lol...
- Rob
Okay. LC2=GN. I learned something today.
Regarding the single turbo route: I'm well aware of the fact that it only takes one big turbo to make big hp, but the issue there, is always how to get that big fan spinning at lower rpms, and the corresponding lag time, even at higher rpm.
Eliminating this issue, is the purpose of the sequential arrangement. It's an attemp at achieving the best of both worlds: driveability + performance.
The concept behind sequential turbo's were ideally for engines that made no torque down low. In this case, the 300ZX, VR4 3000GT and Stealth, are great examples. A pushrod V8 does not have that problem, it is simply wasted energy for a SBC. In the single turbo pushrod Grand National's case, this is why they came with so much camshaft overlap, and Powermaster for the braking system (now we have hydroboost). Turning a T76 turbo with a SBC compared to a V6 engine is an entirely different scenario. Turbo's love camshaft overlap because unlike superchargers, it is not wasted energy. You don't need twins, let alone sequential turbo's to reach your power goals, and you will be building boost in the two thousand RPM range even with a larger turbo. Therein lies the difference. But if you have your heart set on sequential turbo's, then definitely go for it...
- Rob
Last edited by Street Lethal; Jun 4, 2020 at 03:32 PM.
The concept behind sequential turbo's were ideally for engines that made no torque down low. In this case, the 300ZX, VR4 3000GT and Stealth, are great examples. A pushrod V8 does not have that problem, it is simply wasted energy for a SBC. In the single turbo pushrod Grand National's case, this is why they came with so much camshaft overlap, and hydroboost for the braking system. Turning a T76 turbo with a SBC compared to a V6 engine is an entirely different scenario. Turbo's love camshaft overlap because unlike superchargers, it is not wasted energy. You don't need twins, let alone sequential turbo's to reach your power goals, and you will be building boost in the two thousand RPM range even with a larger turbo. Therein lies the difference. But if you have your heart set on sequential turbo's, then definitely go for it...
- Rob
I've had several GNs, and they were all slow to spool. I figure that same turbo should spin up about right on a 350. Of course it'll run out of breath very quickly, but that's where the GTP would come into play.
I don't have my heart set on anything, except making that LT-1 feel like a 427 down low, and not having to wait around all day on my turbo to do it's thing. This was the only way I could figure out how to do it. And it doesn't hurt that I already have the turbos on hand, of course.
Maybe there's a better way? Again, I'm not claiming to be any kind of expert. Just trying to use my common sense to achieve a goal.
I'm very surprised that your stock turbo GN's were slow to spool. The stock stall was in the low to mid 2000 RPM area, and these engines normally spooled instantaneously from the factory with the stock turbo. Even with a 44 turbo, the stock stall was more than sufficient for the street. The TTA had a slightly higher stall speed, but wasn't that much of a difference. Guy I used to hang with was in the nines, quarter mile wise, running a 2800-RPM converter, and a fairly larger turbo than stock. You don't run those numbers with that low of a stall running a laggy turbo due to small cubes. But I digress. Bottom line is do what makes you happy...
I'm very surprised that your stock turbo GN's were slow to spool. The stock stall was in the low to mid 2000 RPM area, and these engines normally spooled instantaneously from the factory with the stock turbo. Even with a 44 turbo, the stock stall was more than sufficient for the street. The TTA had a slightly higher stall speed, but wasn't that much of a difference. Guy I used to hang with was in the nines, quarter mile wise, running a 2800-RPM converter, and a fairly larger turbo than stock. You don't run those numbers with that low of a stall running a laggy turbo due to small cubes. But I digress. Bottom line is do what makes you happy...
- Rob
Rob, your idea of "spooling", and mine, may be different. I expect real boost "now". Not after a couple of seconds of standing on both the brake and accelerator at the starting line.
I think most would agree that dragstrip performance does not necessarily equate to street performance, and certainly not to driveability.
If one big turbo could comfortably do it all on a big street V8, it stands to reason that companys like BMW, Mercedes, and Rolls Royce, would not all be working feverishly on sequential/compound turbo setups for their flagship V8 powered vehicles... Am I right?
no need to reinvent the wheel. just copy one of the ten thousand sbe ls turbo setups out there and apply that to your LT1. the chances of everything working well together would be much better that way. i would get a vr racing or borg turbo over doing the sequential turbo deal. spend the rest of your time/money/energy on the trans/converter/gear/fueling kinda stuff. if you havent done a bunch of turbo setups, i would try and keep it simple to avoid having a bunch of time and money in a setup that doesnt work very well.
Rob, your idea of "spooling", and mine, may be different. I expect real boost "now". Not after a couple of seconds of standing on both the brake and accelerator at the starting line...
Rich, a couple of seconds sounds a little bit extreme, don't ya think? If you want immediate boost pressure then consider a roots blower. But then again, maybe you're right, maybe we have different ideas of what "spooling" really is. For example, when I see a full weight street oriented car with two less cylinders, less cubic inch displacement, single turbo, trapping 175-mph with an extremely low sixty foot, then yes... I think any V8 needing twin turbo's to match that is a bit on the extreme side in comparison, but that is just me. I look at it this way, my car will never ever run those numbers, so why would I need twin turbo's on my V8 when it has already been done running a single turbo with a V6? But like I said earlier, I am digressing, so just do whatever makes you happy...
no need to reinvent the wheel. just copy one of the ten thousand sbe ls turbo setups out there and apply that to your LT1. the chances of everything working well together would be much better that way. i would get a vr racing or borg turbo over doing the sequential turbo deal. spend the rest of your time/money/energy on the trans/converter/gear/fueling kinda stuff. if you havent done a bunch of turbo setups, i would try and keep it simple to avoid having a bunch of time and money in a setup that doesnt work very well.
Well Dirk, if you knew me, you would also know that I rarely ever do what everyone else does. If you can't do something different, and hopefully better... what's the point of doing it at all? I also get a lot of enjoyment out of taking what other people throw away, and turning it into something attractive and useful. I'm not pursuing this just so I can go fast. I already have faster cars than this will ever be. I'm just doing it for kicks.
The only thing that worries me at all about this setup, is the computer control for the fuel injection and ignition. I can see myself getting bogged down with either many hours of patching something together with stock components, or else spending a small fortune on a Holley or FAST system.
Rob, you just keep missing the point. Like I said previously: There's a big difference between dragstrip performance, and street performance.
Rich, I think you are missing the point. You stated you just want your LT1 to "feel" like a 427, well it doesn't take boost to make that happen, let alone sequential boost. You stated, rather implied that a single turbo gives you lag, but running sub 1.4x sixty foots at the track with a single turbo proves that theory wrong. You also stated that a stock GN turbo lagged, which was ludicrous. You boasted about "Flagship" vehicles, but these vehicles undergo relentless compliance testing, so twin turbo is both the most efficient way of making power without jeopardizing streetability from a sales perspective, not to mention helps with sales. But again, by all means, go sequential. I don't think anyone has done that on this forum, so it would be interesting to see where it takes you...
We have drag cars, including my own street car that have no problem making boost on the trans brake, and getting up into boost fast after release, but are very slow to spool on the street from a roll lol
then i have had cars making boost part throttle or going into boost near instantly making it hard to control
its all a balancing act on what you want to achieve. Its nice to have a setup that can make boost fast on its own, that way you can use electronic boost control to achieve boost ramp rates that suit your needs. You can always slow boost down with wastegate control but you cant speed it up if it just physically cant do it early enough
spool can be controlled with torque converter stall speed somewhat. Ideally match turbine size and housing to a desired rpm and put the converter around that rpm so when you go wot, it will flash closer to that rpm and allow enough energy to get spinning. Compromise is its gotta be a tight enough converter to not slip too much under power at peak hp and under more and more boost. A converter set for 800 hp isnt gonna be loose in a 300 hp lt1 all motor lol.
now I don’t know what trans you are going with but th400 or 4l80 for automatics are needed for that power and longevity. Ptc converters are the right stuff for th400’s. Possibly circle D for the 80e. My buds around here have had good luck.
only issue i worry about with the sequential setup is control. Hopefully both turbos can reach same boost pressure at same time and feed the engine and not back feed each other.
im not sure what size the gn turbo is but i know i’ve seen them and they are tiny. That thing will be making boost off idle no doubt. My 305 could spool a p trim 70 mm turbo few psi at 2000-2200 i believe it was under 40% throttle lol. And thats a weak motor compared to a cammed lt1.
i like your idea but i feel it may be tough to control without a holley efi with alot of sensors to monitor things maybe? Its very customizable you can create alot of tables to do whatever you want. Do a 24x ring from efi connection and cam sync cover and run ls coil packs. Get a holley ls1 harness. Make it fit, easy software to use. Honestly best bet. 2000$ or so?
just keep in mind boost at low rpm creates alot of cylinder pressure and can be tougher on bottom end parts. Be careful with timing down there and it will live. You can pull alot to keep turbos starting up, and once rpms build you can put it back in to make your power
Rich, I think you are missing the point. You stated you just want your LT1 to "feel" like a 427, well it doesn't take boost to make that happen, let alone sequential boost. You stated, rather implied that a single turbo gives you lag, but running sub 1.4x sixty foots at the track with a single turbo proves that theory wrong. You also stated that a stock GN turbo lagged, which was ludicrous. You boasted about "Flagship" vehicles, but these vehicles undergo relentless compliance testing, so twin turbo is both the most efficient way of making power without jeopardizing streetability from a sales perspective, not to mention helps with sales. But again, by all means, go sequential. I don't think anyone has done that on this forum, so it would be interesting to see where it takes you...
- Rob
Lol... I '"boasted" about flagship vehicles'? I didn't brag about owning one. I haven't "boasted about *anything*... it's just an automotive fact.
You claim that my statement about GN turbo lag is "ludicrous". Have you ever even driven one? I had several of them in the late eighties, and they are definitely laggy from my perspective. This only proves my point; that your definition of "lag", is quite different than mine.
Orr, I like the way you think. Much of this I know, but I'm driving right now, and will reply in more detail later today.
Okay, now that I'm off the road, and can write more efficiently:
I read your post over again, and as I say; most of your advice consists of things that I already knew from experience, or had read and was in agreement with. However don't take that the wrong way... In no way does that diminish my appreciation for your charitable efforts. I recognize it as good advice, and the fact that we are in agreement serves to solidify my previous intentions. (Great minds think alike.)
Now to address your concerns: As for one turbo overriding the other at maximum levels; I see no reason why this cannot be easily solved by virtue of the appropriate check valves, which are already part of the plan.
Regarding control of the *active* valving; I think I can achieve a satisfactory level of precision through the use of conventional pressure/vacuum servos, but if it comes down to it, I am fairly adept at building solid state controllers for this sort of thing. It's a part of the engineering work that I do for a living. Either way, a big part of the fun is trying different strategies, and experiencing the results.
Transmission wise; for starters I'm going to run a GN 200-4-R, (and it's stock converter) that I previously used in my 434 MC SS. It has been built up with the best parts that were available 20 years ago. It's pretty stout, and may, or may not, hold up on the street w/ street tires. But it won't take long to find out...
I just noticed your "555" byline, BTW... Sounds like a real beast..! Like to see more photos, if you have them online somewhere.
Coincidentally, I was originally planning to build a 10" tire, pro-street GN, with a setback 540 Cadillac and twin turbos hidden in the back seat area. This MC is just sort of a more civilized trial run in that regard.
Stock GN turbos are tiny and should spool near-instantly, they're the biggest of the T03's, but you'll never see 400hp out of one, I'm not even sure you'll get much over the low 300's with one. 2 of them would be on the small side for the LT1 (which by the way, is a high compression engine, what are you planning for detonation control???), would spool very quickly (nothing is going to be instant in a rear mount, though you could make it feel like it is with good converter choice and engine management) and they'd be all done and out of breath well before the LT1 is, again, a horrible combination for a high compression engine unless you're doing something special for detonation management. You'll build massive cylinder pressure below your torque peak hammering the engine.
Going from memory about the GTP38, I've never had one in my hand, but back in the day people did try to run them on a few aftermarket setups, be aware, they use specific hot side and oil feed/drain flanges, NOTHING else will swap into this setup you build. Also, be aware that pre-emissions diesel turbos tended to have disproportionately large hot sides which will play into your high compression problem, but will go against your rear mount and instant spool ideas.
If this is really a path you want to pursue, the way I'd make it work and make it cool and different is run 2 GTP38's and take advantage of their split exhaust scroll- rig a flapper with a wastegate actuator to block off one of the exhaust scrolls so you run off of basically half the exhaust scroll till the wastegate actuators open the second side. With some creativity, you should be able to get the turbos to light off quickly and be able to tune a boost curve that comes in gradually so that you don't get the parts breakage and cylinder pressure/detonation down low but still have a lot of turbo and flow available everywhere but especially up top and the coolness factor in that you're managing it by doing something that 99% of turbo people even know you can do.
Hey Rich, just so we are on the same page... it doesn't matter to me if you have a third gen or not, you are more than welcome on this website to share your build, and to ask questions. However, many of us have been through builds, and have seen builds, so when someone new comes along with an idea that many of us feel might not be the best route to take, you have to expect criticism. Don't take it personally, its just quite a few of us don't want to see you making the same mistakes. Years back I was very big on builds like Calloway's early twin turbo C4's, the car's produced tremendous torque down low, and were geared to hang with the fastest exotics on the highway. Rate of acceleration topped out early though due to RPM restrictions, so tall gears out back were necessary to compensate. So I am not exactly anti twin or anti multiple turbo's. However I am against an engine that does not need two turbo's to get the job done. But if that is what you want, then go for it. There is no reason to argue about it, just do it and let us see how it turns out. I am not being sarcastic when I say that, I really do want to see your build work out for you... so perhaps you're the one reading my words the wrong way at times.
I read your post over again, and as I say; most of your advice consists of things that I already knew from experience, or had read and was in agreement with. However don't take that the wrong way... In no way does that diminish my appreciation for your charitable efforts. I recognize it as good advice, and the fact that we are in agreement serves to solidify my previous intentions. (Great minds think alike.)
well thats good. Sometimes people ask questions here and just dont know at what level of knowledge they are coming from so sounds like you have a good understanding of whats goin on.
Stock GN turbos are tiny and should spool near-instantly, they're the biggest of the T03's, but you'll never see 400hp out of one...
Exactly. Boost comes in way too soon. I think Marty tried using two of them with his SBC build, I don't remember. I mentioned the 49 earlier because that is what mine came with, though it is not the former owners fault, he did now know. Even with the 49 though, boost is immediate. What many people seem to forget, or simply fail to realize, is that the efficiency of the engine is also pulling the compressor wheel, it is not just all in the exhaust, so the efficiency of the engine is tremendous in terms of spool time. But you also bring up excellent points; with no forged assembly, he is immediately limited to the amount of power he wishes to make, so this really isn't going to go anywhere. It's going to again turn into one of those threads where everyone argues what worked best for them, or stroking each other's egos lol, yada yada yada, rather than seeing an actual build take place. Nothing's going to happen, guaranteed. Will we see a sequential build take place? No way Jose. Is it fun to talk about though I guess, sure why not....
Stock GN turbos are tiny and should spool near-instantly, they're the biggest of the T03's, but you'll never see 400hp out of one, I'm not even sure you'll get much over the low 300's with one.
What am I missing here?
They can push right at 600cfm... According to my figures, that number will support over 400hp...
2 of them would be on the small side for the LT1 (which by the way, is a high compression engine, what are you planning for detonation control???)
E-85, timing retard, boost control...
, would spool very quickly (nothing is going to be instant in a rear mount, though you could make it feel like it is with good converter choice and engine management) and they'd be all done and out of breath well before the LT1 is, again, a horrible combination for a high compression engine unless you're doing something special for detonation management. You'll build massive cylinder pressure below your torque peak hammering the engine.
Going from memory about the GTP38, I've never had one in my hand, but back in the day people did try to run them on a few aftermarket setups, be aware, they use specific hot side and oil feed/drain flanges, NOTHING else will swap into this setup you build. Also, be aware that pre-emissions diesel turbos tended to have disproportionately large hot sides which will play into your high compression problem, but will go against your rear mount and instant spool ideas.
Pardon, but I've yet to understand why the "odd flanges" thing, is such an issue for everyone..? Don't you guys ever build anything from scratch? I do it every day. Sorry... I just don't understand why people see such a simple thing as a deterrent..?
IQUOTE] If this is really a path you want to pursue, the way I'd make it work and make it cool and different is run 2 GTP38's and take advantage of their split exhaust scroll- rig a flapper with a wastegate actuator to block off one of the exhaust scrolls so you run off of basically half the exhaust scroll till the wastegate actuators open the second side. With some creativity, you should be able to get the turbos to light off quickly and be able to tune a boost curve that comes in gradually so that you don't get the parts breakage and cylinder pressure/detonation down low but still have a lot of turbo and flow available everywhere but especially up top and the coolness factor in that you're managing it by doing something that 99% of turbo people even know you can do.[/QUOTE]
Okay, well that's a good trick and I appreciate the tip, but I had already figured that one out. I think I mentioned this in my first couple of posts in this thread.
When I originally took the GTP off the Iengine, I put it up on the bench, and was experimenting with blowing shop air into one side or the other, as apposed to both. I observerd right away that that the turbine reacted much more quickly that way.
The idea here is to have a sort of three stage arrangement:. First the small turbo, then one side of the larger GTP, and finally, all three ports would be opened.
I can't use two GTPs (as you suggested), because, well first of all I think that would be too much turbo? But mainly because I only have *one* to work with.
I do have two TP-38s... and if I'm not mistaken, they also have the same kind of split entry. But there again, I don't feel like I have enough cubic inches to support dual TPs...
If you know the exact measurements of the compressor diameter and turbine wheel diameters, i could get a better idea of what they are capable of
if they are around 65mm compressors, flowing 60 lb min from what i googled, that will do 600 hp. Give or take. Two would def be larger than you need but it would be pretty efficient at 800 hp on lower boost to get there.
but if the turbine side is more like a Q trim (read gtp38 is slightly bigger than P trim) then you wont spool them that fast with a mid mount setup. They wouldnt be bad with a small housing and higher stall speed. Or wouldnt be bad as a front mount unit.
i had twin 60 mm p trim turbines on my first 400” sbc. Spooled fast but converter was too loose so that helped with spool lol.
so yeah you will need to piggyback the GN turbo on top of one gtp38 to get your power as you know. Even if the gn makes 300-350 hp max thats gonna add well to 500-550 inthe gtp efficiency range lol
you have alot of room in back seat area to plumb it. I have twin s480’s back there the size of basketballs
Stock GN turbos are tiny and should spool near-instantly, they're the biggest of the T03's, but you'll never see 400hp out of one, I'm not even sure you'll get much over the low 300's with one. 2 of them would be on the small side for the LT1 (which by the way, is a high compression engine, what are you planning for detonation control???), would spool very quickly (nothing is going to be instant in a rear mount, though you could make it feel like it is with good converter choice and engine management) and they'd be all done and out of breath well before the LT1 is, again, a horrible combination for a high compression engine unless you're doing something special for detonation management. You'll build massive cylinder pressure below your torque peak hammering the engine.
Going from memory about the GTP38, I've never had one in my hand, but back in the day people did try to run them on a few aftermarket setups, be aware, they use specific hot side and oil feed/drain flanges, NOTHING else will swap into this setup you build. Also, be aware that pre-emissions diesel turbos tended to have disproportionately large hot sides which will play into your high compression problem, but will go against your rear mount and instant spool ideas.
If this is really a path you want to pursue, the way I'd make it work and make it cool and different is run 2 GTP38's and take advantage of their split exhaust scroll- rig a flapper with a wastegate actuator to block off one of the exhaust scrolls so you run off of basically half the exhaust scroll till the wastegate actuators open the second side. With some creativity, you should be able to get the turbos to light off quickly and be able to tune a boost curve that comes in gradually so that you don't get the parts breakage and cylinder pressure/detonation down low but still have a lot of turbo and flow available everywhere but especially up top and the coolness factor in that you're managing it by doing something that 99% of turbo people even know you can do.
Originally Posted by Street Lethal
Hey Rich, just so we are on the same page... it doesn't matter to me if you have a third gen or not, you are more than welcome on this website to share your build, and to ask questions. However, many of us have been through builds, and have seen builds, so when someone new comes along with an idea that many of us feel might not be the best route to take, you have to expect criticism. Don't take it personally, its just quite a few of us don't want to see you making the same mistakes. Years back I was very big on builds like Calloway's early twin turbo C4's, the car's produced tremendous torque down low, and were geared to hang with the fastest exotics on the highway. Rate of acceleration topped out early though due to RPM restrictions, so tall gears out back were necessary to compensate. So I am not exactly anti twin or anti multiple turbo's. However I am against an engine that does not need two turbo's to get the job done. But if that is what you want, then go for it. There is no reason to argue about it, just do it and let us see how it turns out. I am not being sarcastic when I say that, I really do want to see your build work out for you... so perhaps you're the one reading my words the wrong way at times.
To borrow words used by Balboa.... go for it.
- Rob
Rob, your opinion/advise/criticism is welcome. I'm a big boy, no problem... and I probably need all the help I can get.
However, you accused me of "boasting", though I clearly was not. Then you said my personal experience regarding the GNs I owned, was "ludicrous".
That was uncalled for. And I did feel as though you stepped over the line a little there, as I know quite well what I experienced.
To be clear; I *did* ride in a GN once that responded quickly. But it was highly modified, w/a different cam, huge downpipe & exhaust, etc... Those cars did not spool fast from a roll, when stock.
Now, regarding low rpm boost specifically; though it's simple to understand, somehow you keep missing the point of what I mean to accomplish... Maybe it will help if I put it another way... I'm trying to build a turbo setup, that acts and feels more like a crankshaft driven centrifugal supercharger.
If you know the exact measurements of the compressor diameter and turbine wheel diameters, i could get a better idea of what they are capable of
if they are around 65mm compressors, flowing 60 lb min from what i googled, that will do 600 hp. Give or take. Two would def be larger than you need but it would be pretty efficient at 800 hp on lower boost to get there.
but if the turbine side is more like a Q trim (read gtp38 is slightly bigger than P trim) then you wont spool them that fast with a mid mount setup. They wouldnt be bad with a small housing and higher stall speed. Or wouldnt be bad as a front mount unit.
i had twin 60 mm p trim turbines on my first 400” sbc. Spooled fast but converter was too loose so that helped with spool lol.
so yeah you will need to piggyback the GN turbo on top of one gtp38 to get your power as you know. Even if the gn makes 300-350 hp max thats gonna add well to 500-550 inthe gtp efficiency range lol
you have alot of room in back seat area to plumb it. I have twin s480’s back there the size of basketballs
Yeah, I think you have it figured about right.
I have all the information on the GN turbo, and I'll gather up everything I can find on the GTP, and get all that to you later today.
Really helps to have someone more experienced looking over my shoulder. I am good at guessing. But occasionally like anyone else, I guess wrong.
What am I missing here?
They can push right at 600cfm... According to my figures, that number will support over 400hp...
Yea, everyone does that, they pick the highest point on the compressor map and find some conversion rule of thumb... great but that's not how it works real world. Take into account pressure ratio, adiabatic efficiency, other losses and then tell me where you end up. When do your exhaust ports give up, what are you using for manifolds, when are the exhaust housings too small, downpipes... (FWIW, I've owned a few LT1 cars, I currently own an LT1 headed 3rd gen that is built for boost/turbos, and I've used a pair of T3's on a small block before, I've done jy diesel turbo small block builds, as well as know and been at Mike Sitar's and his dad's house, the guy that could pretty much be credited with starting the twin JY turbo T3/small block build thing like 20years ago. Believe me when I say you'll never see that flow any small block.)
E-85, timing retard, boost control...
E-85 is the wild card, I haven't had that available to me till about a year ago and I haven't had time to play with it.
STILL, realize that the LT1 will have a compression ratio in the 10's (they've measured higher than GM claimed) and is prone to busting the rear pistons when you put boost on it. Any boost that hits below the torque peak will jack cylinder pressure so fast that I doubt that even E85 will let you get away with it. Short version, you do not want to see significant boost below your torque peak on most engines, and you DEFINITELY don't want to see it on an LT1. If you don't want to be bringing the engine home in a bucket, size your turbos to not be doing much below about 4200rpm and be at full chooch at around 6500rpm or maybe a little more and then put valve springs in the thing that will control the valves (the rest doesn't need to be messed with to make the power you want) and then MAKE sure that the rear cylinders are getting enough fuel, because the LT1 manifold under boost gives them more air than the rest and lean tuning makes them go boom.
Pardon, but I've yet to understand why the "odd flanges" thing, is such an issue for everyone..? Don't you guys ever build anything from scratch? I do it every day. Sorry... I just don't understand why people see such a simple thing as a deterrent..?
I understand being able to and wanting to build everything, I hear the "what's the big deal? I know that others can't fab all this stuff up but I'm going to act like it's nothing to make it because I can," but listen to me.
I got started in f-bodies in '91, before that I played with early '80's ford turbo stuff. At one point I worked for a speed shop doing custom fabrication/installs (if it didn't exist it went home with me as an idea/project and came back as a part), and I've always been one to build, not buy. Most of my life I've spent money on tools to build things rather than the actual things and the few times I gave in and "just bought the right parts," (according to the forums) I've been disappointed by the abysmal quality and performance. I've always had stuff around that when your average car guy sees it they look at it and go "what the..."
My current f-body project is an 305 SBC with worked 90's aluminum LT1 heads on it, a 70's vintage Victor Jr which someone totally reworked the plenum in the '80's, and I made fit the LT1 heads, converted to EFI, that has a fabricated elbow that mounts an LS1 style throttle body. The cam is a completely custom 4/7 swap setup that I came up with while talking to Comp's head engineer who thought "it's a cool project, but a ton of all custom work." The engine is 8.6:1 compression (setup for turbo) idles almost like stock and revs well into the 7000rpm range. I built my own ECM, I'm using PWM to control fan speed and water pump speed to be able to keep the whole assembly in a very tight temperature window no matter what is going on outside. I wanted a progressive, programmable shift light so I build an Arduino powered one. I built a 3D printer to print things like custom bezels for the shift light. The TA, LCA's, Panhard rod are all made by me, the rear axle started as a Moser 9" housing that I made all the brackets for, everything is fully adjustable with multiple pickup points. I've fabbed up my own 2" drop front spindles (not on the car yet) and have everything sitting around for weight jacks when I get to it... It just keeps going, and this is one of my less customized projects.
Because of core shift in the factory castings, one of the ported cylinder heads had a thin wall in an intake port that started leaking coolant (I had them pressure tested after porting, it was just one of those things that sometimes happened, I've already had a few problems with this head for the same reason), during a video shoot with a popular Youtube car channel. I tore it down "hoping for it to be just ahead gasket," which is a big enough deal, I use completely custom head gaskets, I have my own Cometic part number, but I found the leaking port. For assorted reasons I didn't have the time to try welding it, the Bridgeport is buried under other projects so I couldn't just work another set of heads (I have 2 sets sitting around). If I didn't build _everything_ I could have just bought another head, slapped it on, and had it running again in a day or 2. Instead, there is no cylinder head that will just bolt on in existence, I haven't had time to make a new one or weld up the one that's there. The car has sat at the end of my driveway, cylinder head off bores probably rusting for over a year now.
Yes, on the scale of things that flange is easy, but at the same time you're locking yourself into just that turbo. No easy bolt on upgrades, possibly no easy replacement if something happens to the one you have. Sure, you could just cut the flange off and make a new one, and while you're at it, the turbo is a different shape so I want to move it like this, and while I'm at it I wonder if I can get XXX and use it to YYY... suddenly what would have been a few hour R&R becomes the car is down for the rest of the season. There are only so many hours in a day or in a lifetime. Choose your battles so you can do as much of what you want to do as you can.
If this is really a path you want to pursue, the way I'd make it work and make it cool and different is run 2 GTP38's and take advantage of their split exhaust scroll- rig a flapper with a wastegate actuator to block off one of the exhaust scrolls so you run off of basically half the exhaust scroll till the wastegate actuators open the second side. With some creativity, you should be able to get the turbos to light off quickly and be able to tune a boost curve that comes in gradually so that you don't get the parts breakage and cylinder pressure/detonation down low but still have a lot of turbo and flow available everywhere but especially up top and the coolness factor in that you're managing it by doing something that 99% of turbo people even know you can do.
Okay, well that's a good trick and I appreciate the tip, but I had already figured that one out. I think I mentioned this in my first couple of posts in this thread.
When I originally took the GTP off the Iengine, I put it up on the bench, and was experimenting with blowing shop air into one side or the other, as apposed to both. I observerd right away that that the turbine reacted much more quickly that way.
Great, good for you.
The idea here is to have a sort of three stage arrangement:. First the small turbo, then one side of the larger GTP, and finally, all three ports would be opened.
Ok, lets make it too small, even more complicated and less necessary. Let me be blunt- if you go down this staged setup path I doubt that we'll ever see it done, and if you do manage it, it will be 5 or more years down the road, you'll end up with less turbo than you expect, it won't work right, nowhere near the 800hp you expect and you'll blow up the LT1.
Here it is, the stock LT1 with no turbo will melt the tires at will, will let you go sideways at will, let you hoon all you want. Instant boost will not make it more fun or faster, it will break parts and turn this thing into a headache. Staged turbos are a thing for little motors that make no torque. You don't have one of those.
I can't use two GTPs (as you suggested), because, well first of all I think that would be too much turbo?
We're all telling you no it won't be.
But mainly because I only have *one* to work with.
I do have two TP-38s... and if I'm not mistaken, they also have the same kind of split entry. But there again, I don't feel like I have enough cubic inches to support dual TPs...
Well then get something else. you can buy the right size turbo for less than you'll spend making a staged turbo, and you'll have something that works. OTOH I wouldn't build stuff around an oddball part that you only have one of and can't seem to get another.
Rob, your opinion/advise/criticism is welcome. I'm a big boy, no problem... and I probably need all the help I can get.
However, you accused me of "boasting", though I clearly was not. Then you said my personal experience regarding the GNs I owned, was "ludicrous".
That was uncalled for. And I did feel as though you stepped over the line a little there, as I know quite well what I experienced.
Seems like most of your responses are coming across that way. And we're all disagreeing with you on how stock GN's respond because many of us are old enough to remember stock ones. They put little tiny turbos, just a hair bigger than what other manufacturers were using on 2L engines on a medium-sized 3.8L engine. They responded damned near instantly. They had more low end then their competition, the TPI V8 in the corvette/f-body. We have no idea what you've ridden in/owned/whatever, but if it was different something was wrong with it/it wasn't stock.
Now, regarding low rpm boost specifically; though it's simple to understand, somehow you keep missing the point of what I mean to accomplish... Maybe it will help if I put it another way... I'm trying to build a turbo setup, that acts and feels more like a crankshaft driven centrifugal supercharger.
I don't think anyone has missed that at all. My daily driver is a Taurus SHO with the Ecoboost. You drive that and it feels like you have a big block under the hood that actually revs. You don't feel any lag or when the boost kicks in. It just feels like one big engine. Before I straight piped it you didn't have any clue it was turbocharged just going for a ride (now you can hear it).
My other driver is a Cummins Ram with big tires and stuff... It cruises at around 6-9psi boost. When your right foot goes down there is no lag. It's 4 tons of 37" tire frying fun.
Now go back and read my responses again, I wrote those knowing this, having owned LT1 cars (for years my Daily and my race car was a '97 WS6 that I bought new), having an LT1 on a stand in the garage that used to have twin turbos on it, having owned turbocharged small blocks, having built a number of Eaton supercharged vehicles including an Eaton, Whipple and KB blown V8's.
Last edited by 83 Crossfire TA; Jun 5, 2020 at 05:22 PM.
I have all the information on the GN turbo, and I'll gather up everything I can find on the GTP, and get all that to you later today.
Really helps to have someone more experienced looking over my shoulder. I am good at guessing. But occasionally like anyone else, I guess wrong.
Here are the TP38 specs: GARRETT TP38 Compressor wheel inducer diameter: 59.87 mm (60 mm) Compressor wheel exducer diameter: 80 mm Compressor housing A/R: 1.10 Turbine wheel inducer diameter: 76.2 mm Turbine wheel exducer diameter: 69.84 mm (70 mm) Turbine housing A/R: 1.15
The GTP is somewhat similar, but is visually larger, has a 1.00 A/R, and a modified turbine that some day is prone to surge at low rpms (on the diesel engine).
Here is a map that someone claimed to be the right one for it, but it's labeled as (and probably is) TP-38: TP-38 map
And here is what I found for the GN turbo: 87 GN turbo
Any boost that hits below the torque peak will jack cylinder pressure so fast that I doubt that even E85 will let you get away with it.
e85 will take anything you throw at it basically. It doesnt seem to detonate but does preignite if the spark plugs are too hot for the combo and are glowing lol i’m over 1500 whp on 19 lbs at 10:1 with my bbc. My friends lsx turbo has gone 7.17 at 193 on 28-30 psi on e85 at almost 11:1 comp. well intercooled ofcourse
boost dont scare me as long as you have alot of timing out at peak torque
i also agree i wouldnt try 800 hp on stock bottom end lt1. Forged internals and good hardware im sure it would take some power for awhile.
The gtp sounds nice if indeed abit bigger. Def better match.
twin tp38’s be awesome if that housing was a .68 t4. Lol. It would be slow to spool i think with 1.00-1.15’s in a t4. If thats a 1.0 t3 or similar since it may be custom flange idk, then it may work well
Pardon, but I've yet to understand why the "odd flanges" thing, is such an issue for everyone..? Don't you guys ever build anything from scratch? I do it every day. Sorry... I just don't understand why people see such a simple thing as a deterrent..?
odd flanges are an issue for me because its just going to add to the complexity, time involved, and expense of getting that style flange instead of a vband. -on an already questionable combination of questionable used parts. and then once you find the turbo is sized wrong or wont work for some reason, you are stuck with that oddball flange and wont be able to swap a typical vband unit in there unless you redo your piping. wastegate will be using the small hole on the turbine outlet side on those housings.
im trying to envision putting this setup into the car and its just not forming a picture. my advise is still if you want it to light off super quick put a small turbo on it and forget the 800hp goal. if you want 800hp put a 76-80 or something on it and loosen the converter. this whole setup you are wanting to do is an experiment that imo, someone able to pull it off and get it going probably wouldnt normally be in a forum such as this asking questions. no offense, ive just seen this sort of thing many times in the past and honestly hate seeing guys fall into an abyss. however, if you decide to do it, make a thread in here and i will no doubt follow along. would be very interesting especially if you were able to get it going.
The map you posted is worthless without flow numbers on it. I'm not going to waste my time on the GN, but here is the TP38 (the GTP has a larger, more efficient housing that flows a little less, has a little bump to the left in the surge line about half way up, I have it somewhere but can't find it right now, with a smaller turbine that spools faster). The red dots are half of a stock LT1 (or a stock LT1 with 2 on it) with a pretty efficient intercooler, the blue are a stock LT1, notice you'll be doing nothing but blowing hot air with one turbo. Now go re-read what I already wrote to make it work. If it bothers you that you're not in the middle of the efficiency island then port the cylinder heads a little or do any performance mods to the combination and all the dots move to the right, and you'll be smack dab in the middle with 2 turbos. Of course, I have no idea what I'm talking about.
Seems like most of your responses are coming across that way. And we're all disagreeing with you on how stock GN's respond because many of us are old enough to remember stock ones. They put little tiny turbos, just a hair bigger than what other manufacturers were using on 2L engines on a medium-sized 3.8L engine. They responded damned near instantly. They had more low end then their competition, the TPI V8 in the corvette/f-body. We have no idea what you've ridden in/owned/whatever, but if it was different something was wrong with it/it wasn't stock.
I don't think anyone has missed that at all. My daily driver is a Taurus SHO with the Ecoboost. You drive that and it feels like you have a big block under the hood that actually revs. You don't feel any lag or when the boost kicks in. It just feels like one big engine. Before I straight piped it you didn't have any clue it was turbocharged just going for a ride (now you can hear it).
My other driver is a Cummins Ram with big tires and stuff... It cruises at around 6-9psi boost. When your right foot goes down there is no lag. It's 4 tons of 37" tire frying fun.
Now go back and read my responses again, I wrote those knowing this, having owned LT1 cars (for years my Daily and my race car was a '97 WS6 that I bought new), having an LT1 on a stand in the garage that used to have twin turbos on it, having owned turbocharged small blocks, having built a number of Eaton supercharged vehicles including an Eaton, Whipple and KB blown V8's.
"We"? I don't know what the others are actually thinking, but so far only two of you have claimed GNs had "instant boost". Once again, his (and your) definition of "instant" is obviously quite different than my own... Their response was NOT "instant" by any means. As I've already said repeatedly, I've owned several of them.
As for the rest of your assertion, regarding your Ecoboost Ford, etcetera, it seems to me that you are just disproving your own previous argument. Are you trying to say that an LT-1 is somehow magically alone in the engine universe?
Yea, everyone does that, they pick the highest point on the compressor map and find some conversion rule of thumb... great but that's not how it works real world. Take into account pressure ratio, adiabatic efficiency, other losses and then tell me where you end up. When do your exhaust ports give up, what are you using for manifolds, when are the exhaust housings too small, downpipes... (FWIW, I've owned a few LT1 cars, I currently own an LT1 headed 3rd gen that is built for boost/turbos, and I've used a pair of T3's on a small block before, I've done jy diesel turbo small block builds, as well as know and been at Mike Sitar's and his dad's house, the guy that could pretty much be credited with starting the twin JY turbo T3/small block build thing like 20years ago. Believe me when I say you'll never see that flow any small block.)
E-85 is the wild card, I haven't had that available to me till about a year ago and I haven't had time to play with it.
STILL, realize that the LT1 will have a compression ratio in the 10's (they've measured higher than GM claimed) and is prone to busting the rear pistons when you put boost on it. Any boost that hits below the torque peak will jack cylinder pressure so fast that I doubt that even E85 will let you get away with it. Short version, you do not want to see significant boost below your torque peak on most engines, and you DEFINITELY don't want to see it on an LT1. If you don't want to be bringing the engine home in a bucket, size your turbos to not be doing much below about 4200rpm and be at full chooch at around 6500rpm or maybe a little more and then put valve springs in the thing that will control the valves (the rest doesn't need to be messed with to make the power you want) and then MAKE sure that the rear cylinders are getting enough fuel, because the LT1 manifold under boost gives them more air than the rest and lean tuning makes them go boom.
I understand being able to and wanting to build everything, I hear the "what's the big deal? I know that others can't fab all this stuff up but I'm going to act like it's nothing to make it because I can," but listen to me.
I got started in f-bodies in '91, before that I played with early '80's ford turbo stuff. At one point I worked for a speed shop doing custom fabrication/installs (if it didn't exist it went home with me as an idea/project and came back as a part), and I've always been one to build, not buy. Most of my life I've spent money on tools to build things rather than the actual things and the few times I gave in and "just bought the right parts," (according to the forums) I've been disappointed by the abysmal quality and performance. I've always had stuff around that when your average car guy sees it they look at it and go "what the..."
My current f-body project is an 305 SBC with worked 90's aluminum LT1 heads on it, a 70's vintage Victor Jr which someone totally reworked the plenum in the '80's, and I made fit the LT1 heads, converted to EFI, that has a fabricated elbow that mounts an LS1 style throttle body. The cam is a completely custom 4/7 swap setup that I came up with while talking to Comp's head engineer who thought "it's a cool project, but a ton of all custom work." The engine is 8.6:1 compression (setup for turbo) idles almost like stock and revs well into the 7000rpm range. I built my own ECM, I'm using PWM to control fan speed and water pump speed to be able to keep the whole assembly in a very tight temperature window no matter what is going on outside. I wanted a progressive, programmable shift light so I build an Arduino powered one. I built a 3D printer to print things like custom bezels for the shift light. The TA, LCA's, Panhard rod are all made by me, the rear axle started as a Moser 9" housing that I made all the brackets for, everything is fully adjustable with multiple pickup points. I've fabbed up my own 2" drop front spindles (not on the car yet) and have everything sitting around for weight jacks when I get to it... It just keeps going, and this is one of my less customized projects.
Because of core shift in the factory castings, one of the ported cylinder heads had a thin wall in an intake port that started leaking coolant (I had them pressure tested after porting, it was just one of those things that sometimes happened, I've already had a few problems with this head for the same reason), during a video shoot with a popular Youtube car channel. I tore it down "hoping for it to be just ahead gasket," which is a big enough deal, I use completely custom head gaskets, I have my own Cometic part number, but I found the leaking port. For assorted reasons I didn't have the time to try welding it, the Bridgeport is buried under other projects so I couldn't just work another set of heads (I have 2 sets sitting around). If I didn't build _everything_ I could have just bought another head, slapped it on, and had it running again in a day or 2. Instead, there is no cylinder head that will just bolt on in existence, I haven't had time to make a new one or weld up the one that's there. The car has sat at the end of my driveway, cylinder head off bores probably rusting for over a year now.
Yes, on the scale of things that flange is easy, but at the same time you're locking yourself into just that turbo. No easy bolt on upgrades, possibly no easy replacement if something happens to the one you have. Sure, you could just cut the flange off and make a new one, and while you're at it, the turbo is a different shape so I want to move it like this, and while I'm at it I wonder if I can get XXX and use it to YYY... suddenly what would have been a few hour R&R becomes the car is down for the rest of the season. There are only so many hours in a day or in a lifetime. Choose your battles so you can do as much of what you want to do as you can.
Great, good for you.
Ok, lets make it too small, even more complicated and less necessary. Let me be blunt- if you go down this staged setup path I doubt that we'll ever see it done, and if you do manage it, it will be 5 or more years down the road, you'll end up with less turbo than you expect, it won't work right, nowhere near the 800hp you expect and you'll blow up the LT1.
Here it is, the stock LT1 with no turbo will melt the tires at will, will let you go sideways at will, let you hoon all you want. Instant boost will not make it more fun or faster, it will break parts and turn this thing into a headache. Staged turbos are a thing for little motors that make no torque. You don't have one of those.
We're all telling you no it won't be.
Well then get something else. you can buy the right size turbo for less than you'll spend making a staged turbo, and you'll have something that works. OTOH I wouldn't build stuff around an oddball part that you only have one of and can't seem to get another.
This post is so long, I really hesitated to use the "quote" option to reply. And I still don't know how to adequately address all the different points you have raised in detail, but I'll try not to leave anything out.
I get your point about making too many one-off parts that cannot be easily duplicated or replaced, and I can see how you've managed to paint your own self into a corner by doing that.
You strike me as the kind of person that enjoys impressing others with his extraordinary/unique abilities. Believe me, I understand.
If you have actually done all that you say, then you are an exceptional individual. If for no other reason, than the fact that you are industrious enough to push yourself that hard. Good for you.
I don't know what you are talking about when you refer to these LT-1s as being able to "melt the tires at will"? I have two Corvettes with LT-1s. One of them is a Lingenfelter car, and built to the gills. They're both fairly quick, I quess... but they do not have what I would call "tire melting torque".
Now back to me and this project:. I have already been down that road myself, and I think I'm smart enough to know the most efficient ways to approach an engineering adventure like this. Additionally, I'm well aware of my own strengths and limitations.
For instance; I could care less if a turbo has some kind of unique mounting flange, because I can draw it and cut it within only a few minutes. If I need another one later on, it's even quicker the next time, because I already have the drawing on file. I can do this a lot faster, cheaper, and usually better, than buying the parts ready made.
You seem to be extremely concerned about compression ratio... Are you aware that lots of people are running 30+ pounds of boost with pump gas, on ordinary LS engines that also have high compression? With race gas, some are running 14:1 compression and 60+ pounds of boost now.
I understand that more compression makes it trickier, but with E-85 I'm satisfied that I can accomplish what little I want to do. And if my engine does come apart because I overlooked something... well, that'd be a great excuse to install a 383 kit. Or alternatively, I have three more LT-1s sitting here in the floor. Either way, I can afford to chance it.
I appreciate the tip about the uneven intake air distribution, and I can definitely see where that could cause catastrophic problems. But I think I'm ahead of you there, as I had already planned to raise the plenum roof, change it's shape, and move the throttle bodies to the rear, where they will be connected to the charge pipes.
Look, don't sell me short... I'm no genius, but I'm smart enough to get by. I've been around a long time, and as they say; this ain't my first rodeo. I could do this without any help, but I can do it faster and better with the right kind of advice.
I'm listening to what you're saying, but everyone has to do things in their own way. Don't get twisted out of shape if I don't do everything the way you think I ought to. It's my project, after all... My sweat, and my money. If I do crash and burn, then you'll have the satisfaction of laughing at me.
odd flanges are an issue for me because its just going to add to the complexity, time involved, and expense of getting that style flange instead of a vband. -on an already questionable combination of questionable used parts. and then once you find the turbo is sized wrong or wont work for some reason, you are stuck with that oddball flange and wont be able to swap a typical vband unit in there unless you redo your piping. wastegate will be using the small hole on the turbine outlet side on those housings.
im trying to envision putting this setup into the car and its just not forming a picture. my advise is still if you want it to light off super quick put a small turbo on it and forget the 800hp goal. if you want 800hp put a 76-80 or something on it and loosen the converter. this whole setup you are wanting to do is an experiment that imo, someone able to pull it off and get it going probably wouldnt normally be in a forum such as this asking questions. no offense, ive just seen this sort of thing many times in the past and honestly hate seeing guys fall into an abyss. however, if you decide to do it, make a thread in here and i will no doubt follow along. would be very interesting especially if you were able to get it going.
Dirk, here again I think you are overcomplicating things in your own mind...
This setup is going into a relatively huge area behind the seats. I don't have to cram it all into an impossibly tight space around the engine, as you are used to doing.
There is nothing complicated about the plumbing involved. It is child's play in comparison to the piping and valving in some of the machines that I build.
The only unknown factor in my mind (as far as the system itself is concerned), is the turbos themselves. Here I can only make educated guesses.
Consider, that even if I used the two TP-38s as some are suggesting, I would still have to go through an even more complicated plumbing process to get them to spool effectively.
The gtp sounds nice if indeed abit bigger. Def better match.
twin tp38’s be awesome if that housing was a .68 t4. Lol. It would be slow to spool i think with 1.00-1.15’s in a t4. If thats a 1.0 t3 or similar since it may be custom flange idk, then it may work well
I wasn't able to follow all that you said regarding the frame sizes, etc., but I will be glad to gather up any information you need in order to sort this out.
Crossfire seems to be convinced that two TP-38s are not too large. But I'm gathering from the map he posted, that they actually are a little too much, and would be very lazy about spooling.
Perhaps that could be remedied by valving one side of each of them shut at low rpms... That should effectively reduce them to half their size on the turbine side, I would think. Something to think about...
One thing I do like about the idea, is that they would offer a little less exhaust restriction at high rpm, and that is basically free HP.
Last edited by Rich...; Jun 6, 2020 at 11:55 AM.
Reason: Misspelled word.
