I know I know, there are dozens if not hundreds of “how much boost” questions on this board, but thinking about it, I don’t think that the question has ever been asked/answered in exactly this context and it’s something that should be useful to people here.

How much boost have you gotten away with running on a stock/stockish TPI engine (L98 or LB9, they both had similar compression, cam timing and head/chamber designs so the maximum that I should tolerate should be about the same)? I don’t know that I really care if it was turbo or supercharger, and I don’t think bolt ons, or even minor cam changes should make that big a difference with the final answer (maybe if you did a cam swap list it so people can make their own mind up)…

I’m curious, there are pretty well known limits for other GM performance engines, for example, typically the LT1’s will tolerate 6-8psi for a while with their high base compression, but eventually with the first minor bit of trouble they tend to lose pistons/rings towards the rear of the engine (usually 7, sometimes 5 or 8…), but I’ve never seen that kind of data for TPI cars.

 

seen in car craft a stock bottom end with 22pounds of boost on a tpi engine with aftermarket fuel management going low 9s. It's all in the fuel available and the tune. He logged over 50 passes and hundreds of street miles.

 

yeah i have heard of that car that is in the 9's at over 140mph on stock L98 shortblock, or other stock 350 shortblock.

i dont think that should be considered the norm. i know my buddies full bolt on L98 car with mild cam swap didnt live too long with 12psi on a procharger.

i guess its in the tune and depends on the motor. some are beefier or better condition than others

my general idea is with aluminum heads, keeping the stock 9.3 to 1 compression, you can get away with 10psi on a great tune. gotta keep the revs down tho. thats another key. dont rev it

 

the reason they blow is typically the tune, or one moment of detonation. I plan on 15 pounds with a stock bottom end with iron heads so we'll see what happens

 

That’s not even close… If I remember right that was some truck block with a TPI on it, and with different heads installed so it was at a lower compression.

Orr89RocZ, slap some aluminum heads on it and you’re playing a different game.

We all know the answer to that one, slap some larger cc aluminum heads onto a stock short block and with careful tuning and a lot of boost you can go quite fast before you drive over your crank. That’s not the question.

The question is what about a stock(ish) long block? Lets assume at least iron heads and something around the stock 9.3:1 compression.

That L98 car with a cam swap sounds more like it, what was the failure at 12psi?

 

If you are talking about cast pistons I would think the question would be how much boost can you have (tune) with absolutely no detonation and to what lengths you will go to accomplish that (water inj, alk inj, tune octane)

 

Most thirdgen boost people have heard about Marty's 9sec car. He also fed it race gas. The only thing the engine had to do with a thirdgen was the fact that it was installed in a thirdgen. It also had a TPI intake on it. Everything else was different. Anyone notice how many hours of dyno time he had? Yeah, that would cost normal people thousands of dollars for all that time. People never seen to mention that.

Compression isn't the killer of boost engines. Too much pressure for a given fuel is. You can run all the compression you want but with less than optimal octane you have to pull timing to reduce the cyl pressure. Those that leave the cyl pressure high with inadequate octane tend to break pistons. That is, high compression with a fair amount of spark advance. The timing determines how much cyl pressure is created. With a high CR, go low boost w/ decent timing on the street. At the track, good gas and more timing.

Bone stock 1986 305ci TPI (9.5:1 CR). Stock heads, cam, TB, intake, ignition, everything. Engine had about 130K miles on it. I put 3K miles on it with the new boost setup. Peak boost is 12PSI, 93 octane, IC, water/alky. So far so good....no broken stuff yet.

 

it was a rod bearing and/or broken rod. I'm not sure, i think that is what broke. Motor was just a L98 with full TPI bolt ons, rough tune, with procharger on 12psi. not sure of the mileage, i think it was up near 80-100K miles.

 

Here is a pic of a piston that I shattered the rings on with just a split second of detination from not enough octane at 15psi (roots)..........it is a 7.0:1 forged blower piston (ie: larger top ring land) now imagine what a cast piston would of looked like

Also as junkcltr mention you can add a intercooler to that list of detination control items

 

Also for people that may be reading this that are not familiar with different type of blowers......the reason I add (roots) to my answers is while certain principals of boost apply to all blowers there are inherent differences between centrifugal and roots blowers the biggest is that the charge out of a roots is much hotter than a centrifugal which in-turn changes how you need handle such things as detonation levels. But in the end any detonation is deadly so you need to anticipate that before it happens or you will be replacing parts.

Mark it's been awhile, if I remember correctly you are pretty well versed in turbo boost arn't you?

 

Yea, I’ve been around, just not as active as I was in the past, and yea, I’m pretty comfortable with this stuff. I guess that I might have multiple ulterior motives with asking the question, but I also thought that in this form it would be something interesting to the rest of the group.

WRT to my own ulterior motives… there’s a few things going on, one, I may try running some boost through a _stock_ 100and some thousand mile LB9 and am debating how stock I’m willing to leave it before I mess with it (at this point more stock makes more sense, but also less fun). Secondly, as always I’ve been playing with the numbers behind this and junkcltr you mention pressure for a given fuel… after looking at how BMEP is calculated on the dyno and what assumptions are usually made based on that and different fuels (pump gas specifically) I believe that I’m seeing some inconsistencies that I’m hoping to decide if “it just looks that way” or if there is some factor messing with the results by seeing what people have gotten away with. To a large extent, looking at boosted engines removes some of the variables because they tend to have lesser extremes (especially peak cylinder pressures) than making the same torque (let’s take rpm out of the equation) using other means.

I’m hoping that I didn’t just kill my own thread…

 

Your thread is fine. You didn't kill it. The stock LB9 I am running was out of an auto trans. rig so it has the smaller cam. I had to pull about 7* of timing from the AXXF (730 ECM) bin at around 60-80 KPA at 3200-3600 RPM to keep it from knocking in a 5,000lb vehicle. The cyl pressure was too high with the cam and tuned TPI for the vehicle weight. The removed timing was also reflected into boost KPA. I could add timing back in after 3600 RPM.

I have run the engine at 16PSI of boost, but it was more of an accident. I haven't been happy with the fuel mileage. I was hoping for much better. Around town I am getting 11 MPG and it is tuned to run lean in the 20-50 KPA area using a WBO2 as the closed loop O2 sensor.

In the 350ci car I was seeing about .58 BSFC, but I haven't done the numbers for the LB9.

If I was to do it over again. I would have put in a 200* to 208* I/E, 114 LSA cam in it. Elgin has a few non-rollers that are cheap but I don't want to rip it apart at this point. It has over 100K miles so at some point I will need to take it apart for new bearings and will put a cam in it then.

EDIT: I don't know what kind of HP you are looking for. The LB9 at 9-10PSI went 15.0 sec in a 5,000lb vehicle. That comes out to about 295 RWHP. It has a 10-bolt rear, NP208 transfer case, 700R4 trans. The HP should put a thirdgen in the 13.xx sec range.

 

Now you are getting into electronic fuel management with boost and you are gonna leave this carbureted caveman behind

 

i'm still holding on...

 

295 for 10 psi? for some reason that seems low to me but i guess aint bad for a stock 305 with that boost. it will put a thirdgen in the 12's easily if properly equipped. i touched 12's with 254whp

 

or the fact that it has a cast crank, rods that probably aren't even designed to handle 400hp, etc.......

thats like the people that are like "my t5 handles 10000000hp and it lasts forever"

congratulations, 1 person got lucky.......all that is, is an interesting anecdote.....other than that its just bad information to supply someone that might not know better

 

Edit......Had a response to this but never mind, just one of the reasons I don't post on here any more.......Mark good luck with the thread (I am still going to learn from it), Steve good luck with your new set up hope to see it sometime soon.

 

Oh common, no reason to drop out because of that, carbureted and even mechanical advance is just another way of doing the same thing as FI and ecm's. The fact is that when you get into these ragged edge discussions it's just a factor of what you can dial in better

now I'm curious...
----------
nobody gets lucky… there’s a reason behind everything, you just have to know how to look at the information critically and figure out what it’s really telling you.

Rotating assembly living… heh, it’s all about RPM, if you take that out of the equation how hard do you think that you’d have to push on a rod to crush it?

 

730? This is way off topic but how are you programming a 730 for boost? Why did you choose to do that rather then just converting to $58 or whatever in that same ecm?

You know, I’ve run 13.4’s with a stock LB9 305 long block with no head or cam work, so to be honest, I’d be really disappointed with that kind of result. My L98 runs 13.5’s with stock everything besides cold air intake and cat back exhaust, no headers, converter, gears or even sticky tires.

I’m assuming that you’re talking about a cam swap to decrease midrange/low end cylinder pressure so you could run more timeing, and at that point I wonder since those numbers are pretty close to the stock TPI cam which my LB9 car should have already. I also have a comp roller 224/224/114 sitting here that was intended for something else, and I wish I had a set of decent 64cc heads sitting around doing nothing (actually I do, a set of iron, late model LT1 heads, but If I took and rerouted the water passages on those I’d have a more bastardized setup than 99% of people out there).

You’re asking how much horsepower… I’d be tempted to try to pull ~400 from a totally stock long block, more like 500-600 out of something that I wasted the time to swap heads/cam in. OTOH, I can see getting gready and turning up the wick till I carry it home in a bucket. Of course, I’m not asking “how do I make X hp,” I can answer that question myself

 

I think that's what he did, maybe he meant '730 memcal.... :dunno:

 

there is a good reason behind everything......there are 2........dumb luck, and lies.

a stock l98 shortblock runs in the 9's and lasts forever......if you seriously believe that, you have problems......thats what we like to call a pipe dream.

either it hasn't broken yet, or its not really a stock short block.....if that was the case why bother making parts to handle that kind of power? If you spend enough time in the racing world, most of this stuff becomes fairly obvious to you.

second of all rods almost NEVER crush unless something else catastrophic happens first, con rods almost always fail in tension.....the highest load on the rod/rod bolts/cap is at WOT at redline when the throttle is suddenly closed, and the rod accelerates from dwell at TDC downward in the bore. Thats the highest rate of acceleration the rod sees, and also the weakest direction the rod can see a force in (other than laterally).......take the weight of the piston and pin and calculate the inertia it takes to accelerate in that direction.....now add in the resistance caused by the partial vacuum caused by the piston travelling downward at say 7000rpm, when the throttle is snapped shut and the available air for cylinder filling is almost cut off.

the rod bolt is the weak link, whether you're using a stock rod bolt, an arp 3.5, arp 2000 or some insane carillo custom age 625+ exotic bolt.....its still weaker than the rod

 

So correct me if I misunderstand what you are saying.....that anyone that says they have 500hp on a stock bottom end has either "dumb luck" or is liar.

 

thats a ridiculous statement without qualification isnt it? if you're talking about an LSX, hardly........

an l98 tpi engine??? not then either......but thinking you're going to make 500hp on it and beat the **** out of it, reliably forever and ever....thats foolish......

do you think they make stronger parts just for fun?

and thats not what im talking about im talking about 700, 800, 900hp and run low in the 9's on a stock l98 short block......its not going to last long.....because its not about the tune, its about strength of materials....

having a really sharp tune and good oil pressure, isn't going to stop the crank which is undulating like a snake at those power levels, from blowing the center out of the main caps.......it's not going to cut down on the stress in the rod bolts, and its not going to make the pistons stronger.

you can make 1,000hp in a briggs and stratton if you want, if you only want to do it for 1 second........every once in awhile someone gets lucky, but time is the great equalizer, over a long enough time scale the survival of all engines drops to zero.....if you have really strong well engineered racing parts, that timeline is ALOT longer.

 

Yes, and the more rpm you run the more stress is on the parts.

the key too more power and longevity is keeping the rpms down.

inertial loads in the motor are proportional to the square of the rpm increase. 2 times increase in rpms is 4 times greater load. 3 times rpms is 9 times greater loads, etc. Then you got power loads from the compressive air/gas mixture that burns/explodes. these act in opposite directions. but the power load is greater than the inertial loads, the most dangerous damaging load is like you say the tensile loads while the motor is expelling burnt gas or sucking in new air, and the piston is thrown to TDC or BDC

this is all basic info from Maximum Boost by corky bell. with a boosted motor, when you double power at a given rpm, the power load on the piston/rod/crank is NOT doubled. The power output can double without doubling the combustion chamber pressure. Power is a function of average pressure in the cylinder/chamber over the entire stroke of the piston. You can change that average alot without changing the peak pressures that much, since its an average

Another thing the book points out is peak pressure in the chamber is reached when only 18-20% of the mixture is burned. so if you double the mixture volume, only 18-20% of that mixture will burn to generate peak pressures...its only gonna be a marginal increase in peak pressure. so its impossible to double the total pressure by shoving in double the mixture. But the power gains are huge

boosted motors can keep cylinder pressures up higher throughout the crank cycle over n/a motors, obviously, but when you look at the total pressures in the chamber, the pressures around 90 degrees of the crank cycle are alot less than peak and continue to drop from there but not as rapidly as a n/a motor. Alot of the times pressures at around 90 degrees are less than peak pressures the n/a motor has which is making less power!

So basically you can burn a LOT more fuel/air while only marginally increasing pressures/loads on the motor.

there is a point where too much is too much, but for the most part, as long as you keep rpms down, manage the heat, and tune it well to avoid detonation and such, i can see stock "400" hp rated rods/crank/pistons holding alot more than that and doing it reliably.

 

you don't need corky bell to tell you that though its just basic statics and dynamics.......the point being, "as long as you keep rpm's down" but unfortunately horsepower is a function of RPM.....you're not going to make 900hp in a 350ci engine at 4500 rpm.........

thats why parts have the ratings they have.........a crank thats "rated" at 2500hp like mine is, thats sort of an arbitrary number.....sure if you do something foolish to it, it'll break at a far lower figure than that....because the real danger is the forces and moments acting directly on it, not the HP........however, theres certain assumptions one can make.....that in 99.99% of all cases, if you're going to make xxxx horsepower, you're going to be turning over xxxx rpm.....so you can summise.....its just a guideline.

but, if you get way outside the lines the difference becomes so large that theres no compensating for it........the reciprocating apparent weight on an engine making 900hp, is going to be way to much for a 2 bolt, cast iron main cap........in pretty short order especially in a racing situation......never mind over the long term.

saying that the secret to more power and longevity is keeping the rpm's down, is sort of a quasi-oxymoron......because in order to make that big power you're going to need big torque......and in order to produce that torque you're going to need big cylinder pressure at lower RPM, which is going to create a problem for you.

honestly this is a dumb, dumb argument.........people are trying to argue that a stock OEM 100,000 mile short block is a great reliable platform for an 800+ hp race car.

seriously......grow up and live in the real world

 

If this OEM shortblock lasts 1 season, then pops....I can purchase another one for $300 all day long if not less. I could build how many low buck motors before I get to ONE highly built motor? I'm not shooting for 900hp so aftermarket blocks aren't anything I need to get into. Let's say I keep adding boost and pop my 5k shortblock....I'll be pretty upset because I don't know how to tune it, but if I have $500 tops into my present shortblock and it pops, I'm out 6 hours of my life to put another one in. Maybe after popping 2 or 3 I'll get fed up but for now, it's been 8 years and 7 motors, all being sprayed, etc and a total investment is STILL less than 1 built block and I've learned tons along the way. Until I'm fairly confident in my next setup, I wouldn't want to risk high dollar parts at it.

 

I re-wrote the AUJP code in 2006 when I did my first boost project in the Camaro. Before that I had the $58 code in it and disliked from the start. I disliked it after hours of tuning and many gallons of wasted gas. I stopped fabbing stuff for months and just worked on re-writing the AUJP code to handle 2-bar boost. I use a stock 730 ECM with a 730 MEMCAL with the custom AUJP boost code. For the LB9 I use the AUJP boost code with a lot of the AXXF CAL parameters. It was a long project and lots of bench testing for the boost AUJP but worth every minute of it compared to the $58 code. The AUJP code has lots of room for extra code. The difficult part was the algorthym and finding enough free RAM space. The $58 code was good in boost, but aweful for N/A driving. I get PMs about the boost AUJP but will not release it. Mostly due to how others have treated me when inquiring about their boost code.

I was disappointed in the ET at the track. It "felt" like it would have a better ET on the street. Keep in mind that the setup was built for torque and not HP. It spools at 1700 RPM and pulls good. At the track it would fry the tires (posi with 235/75/15 (29") Wrangler RTS stock air pressure) in first and into second. Maybe there was more in it in terms of ET, but the MPH and weight come out to 295 RWHP. I also had a total advance of 18* during those runs. Maybe there is more in it with more timing? I removed the stock mufflers and installed some better ones and hope that helps when I take it to the track when it opens again. The other thing is that I run the track with the engine hot, no hood open thing or cool down. Run like it would on the street.

If you ran 13.4's with stock tires and pressure that time is very good. With the cam I have it drops off at 5000 RPM so I shift at 4800 RPM. I am curious what RPM you shifted the LB9 at.

Yes, the cam swap would be to decrease mid range cyl pressure and gain a little HP in the 4500 RPM and up range. The stock cam I have is the 178/194 cam (from memory). The cam I would like is the later cam which Elgin or Speed Pro has for cheap. The goal for this engine is towing torque so I don't want to go too far with the cam. I would also like to see high 13sec so it is a trade-off. I am not ready for the cam just yet. The reason being that the truck went from 16.0 sec to 15.0 sec ET just by adding about 8* of timing. I am still on the conservative side and slowly creeping up on it. My LB9 is a non-roller block.

Your 400 goal is close to my goal. Assuming a 1.20 (4WD parts) drivetrain loss it comes out to 295*1.20 ~= 350HP at the crank at 9 PSI (track runs were 9.2 PSI to be exact). Since the IAT is low with the IC & water/alky you can use: (9+14.7)/14.7 * 210HP = 340 HP. That is close to what the track HP was. My end goal for this Summer is 13-14 PSI and 420-430 BHP to get the 13.xx ET. I think it is possible.
If you put the cam and heads the 500-600 is possible. I think you could get there with just the 224/224 cam and ported stock heads. Probably be in the 18 PSI range and need some straight meth. to spray it with or some race gas.

Your project differs from mine in that I wanted low RPM towing torque and not much HP. My LB9 will hit 10+ PSI in the 2000-3000 RPM range. I *think* you are looking for more HP in a better vehicle (thirdgen).

 

I will try to get more out of my engine in my 1984 Corvette.

Stock engine block.
Stock crank.
Stock rods.
Stock pistons.
ARP bolts.
CompCams 12-404-04 cam (LSA 114, duration 222/225 @0.050, lift 0.464/0.464
CompCams 858-16 Pro magnum Hydraulic lifters
CompCams 1412-16 magnum roller rocker arms
AFR 190 heads with 74cc chamber size.
Holley Stealth Ram that I modified to clear the stock hood.
Haltech E6K
120 lbs injectors.
SX fuel pressure regulator.
Twin BOSCH fuel pumps and a surge tank in the rear right fender.
Dana44
4L80E controlled by a TCI T-Com
Vigilante converter
Front mount XS Power intercooler with 24"x12"x4" core.
HKS 'style' 50mm wastegate
Garrett GT4288N turbo from a Volvo semi truck
E85 ethanol fuel.

It is not a stock engine, but the short block is stock except for ARP bolts.

Last summer I went to the dyno and got 627 rwhp @ 4200 rpm.
Tourqe peaked about 800 lbs/ft @ 4000 rpm.
Boost peaked at 18 psi before 4000 rpm.

I maxed out that turbo, both compressor and turbine, at that rpm. By 5000 rpm the engine made 100 hp less and exhaust pressure was up to 43 psi. Boost was down to 13 psi.

I am installing a larger turbo now.

Old and new:

 

most of what i was talking about was aimed at the thing about the guy running deep in the 9's on an l98 shortblock.......

i know what you're saying but that would be like me swapping a new t5 into my car every other week (or pass down the track) instead of buying one good trans putting it in once, and not worrying about it.

if you worried about popping a motor due to a bad tune or a lean condition etc........put cheap head gaskets on it, and they'll pop long before the motor does.

 

This is what a lot of the Grand National guys do, as it's obviously cheaper to simply blow a head gasket, then to rebuild the entire engine over and over. Used to laugh when I'd come across that ad (forget which brand) embellishing, "Piston gives, but the head gasket lives", as most racers would obviously want it the other way around....


-Rob

 

ya mine are copper, so thats what would happen lol.......but a regular head gasket wouldn't make it just with the cylinder pressures i'm going to be dealing with at 30psi

 

i agree with that, i'm just talking about good condition lower mileage setups making less hp than that. certainly the norm is NOT gonna be 800+hp on stock internals and living a long time.

Like above, JoBy's car is running over 600whp at a measly 4200rpms...thats impressive. you can build power at lower rpms.

 

Ok, we’re doing a lot of dancing around without really getting to the meat of anything new.

To summarize your few paragraphs there, with boost you increase average pressure without significantly increasing peak pressure, and to some extent, if you maintain the same RPM you can significantly increase hp output without significantly increasing load on most of the parts of the engine. You start breaking things when you start increasing peak loads on parts (this spikes when you see detonation), or increasing tension by raising rpm.

383… it’s almost like you’re setting out and trying to ruin our fun

Here’s the thing, forget the arbitrary ratings and the “you would normally have to turn X to make Y hp.” Part of the point here is going outside the normal box some and stretching the “normal” limits of parts. As far as the “normal” deal goes we’re all on the same page, my point was that you normally don’t experience enough compression in parts to break them, and you agree with that. So lets look at this from the perspective of increasing BMEP as high as possible without changing peak pressure more than you absolutely have to, since peak pressure is what’s going to break ring lands, hammer out bearings…

Only if you proportionately increase rpm. But you pick an interesting point anyway, since 900hp appears to be about the point here stock blocks no matter what you do to them or how good the parts you add to them are, are not really rigid enough anymore, where the bottom end starts flexing, bearings/caps walk…

Again, you can get around part of this argument as long as you’re careful about peak vs average pressures…

I don’t think that anyone one here has said anything about reliability. I will say that I know plenty of people that every season or so hit the junk yard, grab a new truck short block, bolt on their induction and then run 9’s for a while till the next one.

 

no its not only if you increase rpm......power is power, if you make enough power you will annihilate parts that aren't big enough........a 2 bolt cast main cap isn't going to last long making a ton of power.....period. would you use dental floss to hold up a bowling ball, and say "well it'll be fine as long as it doesnt get bounced around" thats an exact analogy to the rpm argument,

and, 900hp isnt the point where the block "flexes" and ruins bearings, breaks cranks etc.....its the point where the oem blocks split wide open........thats what happened to my buddy (and the world famous around here) preston smith....then he went to a bow tie

 

I would like to think there are many guys out there that we dont know of that are not on this site that are using OEM blocks at those hp levels and are fine.

I'm not sure how different the LT1's are, but i've seen quite a few pushing big numbers and holding fine. My local shop has a F1-R blown LT1 running 1100hp, and so far so good. I do believe its a stock block with good internals.

I guess its safe to say that general ratings for parts are just that...general ball park estimations. Clearly some ppl have held bigger numbers on stock blocks/internals than most would even think to run. But like my one buddy has done, he has blown a L98 with 12psi on a base procharger kit.
I still think tune and rpm has a huge effect on the outcome of the combination. building boost early and not revving high with a safe tune and no detonation will give you the best chance of high hp/tq and reliability/longevity. it wont be as reliable as a new block/forged interal setup, but it could give you a season or two of racing.

 

data for the original topic:

350, stock replacement crank, rods, hyper' pistons (9.4:1), vortec heads, 204i 216e @.050" cam, tpi intake, stock fpr, twin turbo intercooled. I consider this: one step above stock. thats how I talked my parents into letting me build the motor back in highschool (before the turbos of course).

38pph injectors @ 98% duty cycle at 14psi and 5700rpm with 13 degrees of timing (12:1AFR) on 93 octane.

motor is still great, trannies (4) and rears (2) not so great. I think the trick to getting the motor to last is to bring the boost in late. The boost creep from my undersized wasegates worked just fine. 3500 rpm=8psi, 5500rpm=14psi.

 

wow 98% DC, you should get some 42lbs injectors soon nice combo, what power did you put down?

 

never tested it for power, never made a full track pass. The holley commander 950 software estimates 545 at the flywheel. I'm not new to the longevity theories stated above... so I bought new wastegates and turned the boost to a constant 8 psi. I probably sacrificed nearly 100 hp, but thats the price you pay for a daily driver that lasts.

 

Ttype, thanks for the data point, that’s just the kind of thing I’m looking for… BTW, you’re local (I’m in Laurel, work in columbia) we should get together sometime, I’d love to see the car.

Yea, but we all know that the crossfire stuff was far superior


I didn’t realize that you were running a haltech, how do you like it? My brother’s car runs one, on one level it’s primitive, on another it’s cake to dail in and run fast/well

What 120pph injectors are you using?

Huh I’ve always sort of liked the idea of a surge tank. Are you using the stock pump to fill the surge tank or one of the bosch’s? do you have pics/explanation on your web site somewhere?

I think I said this before, that I didn’t think that there was a GT 4288 but there is a GT4088, and it’s map would match with you topping out in the 600’s, you should be able to go well past that with a GT42.

What’s the new turbo, is that a garrett TV series, like a 71xx or 75xx?

If I do this I have a really nice HX52 that has a turbine side that should be just about perfect, and a compressor side that should move enough air for me to drive over the crank at will that I’ll probably try, even though I have 2 nice hx40’s sitting around that would be more sensible (should be right between a GT4088 and GT4294). I’m a little worried that the HX40’s will put me in junkcltr’s shoes with too much boost before the torque peak. What fun is a turbo that’s only good for 750-800hp anyway

 

I've been running 16psi on my stock 91 LB9 for quite some time now. I honestly dont know the mileage on the engine, but its spent most of its life (probably over 100k) with a Vortech attached to it. So far its holding up ok... its the trans that doesnt like it.

No alky here as of yet.

 

I like it. The tuning software uses DOS and that is atually a good thing. The old laptop I use had a hd crash but I made a bootable floppy with the tuning software


I don't know. They were on a intake I bought. I measured the flow and got about 120pph. It looks like they are rebuilt or modified.


http://www.joby.se/corvette/mods/200...8_fuel_supply/


http://www.joby.se/turbo/gt4288n/
I searched using the part numbers on the turbo and it is a GT4288N made for Volvo. The compressor side matches the GT4088 on http://www.turbobygarrett.com
The turbine inducer is 82mm and that makes it a GT42. The GT40 has a turbine inducer of 77mm.

I searched on the part numbers and it seems to be a TBP7501.
The turbo originally had a huge internal wastegate housing so the one I am using is from another Garett.

 

sounds good... waiting for my vigilante torque converter and I'll be back on the road asap. I got fed up with blowing up t5's and realized I was probably making too much torque for any manual tranny under $2grand... maybe I'll pop this "pro-street" 700r4 too ($700 for parts and the same for TC)?

 

that 700R4 is doomed. TH400

 

I am going to guess that it has a 75-76mm inducer wheel. How big is that exhaust wheel? I have a TV75 here and I am curious how the exhaust wheels compare.

Not to ruin your thread 83 Crossfire TA, but I think most of the main turbo users that analyze data have responded by now. Your thread is one that is looking for details and actual results that were calculated or looked at critically. Many of the turbo installers just slap it on and call it good.

 

Compressor ind/exd 75mm/102mm.
Turbine ind/exd 98mm/87mm.

 

No real data to offer but some things to consider. Pay attention to your ring gaps, tune to the leanest cylinder. Pay attention to your design of carb hat and try to keep the distribution as even as possible. Keep an eye on your bearings.

The question is tough to answer because failures are caused by a variety of things related to boost that can be individually managed. How an someone manages these factors using the stock parts will affect the ultimate reliability of the whole package.

You really have to ask something like at what point will it detonate and what can be done to stave off detonation. IE: cam choice, a/f ratio, a/f distribution, head material, chamber / piston coatings, valve materials, head gaskets, chamber porting, thermostat temp, oil squirters, oil cooler, intercooling method (charge temp) yadda yadda.

You really need to go through each way that it can fail from this perspective.

 

Wanna let it live even after detonation! Take out the extra bolt and put a pipe plug in it(Turbo Buick bottom end saver). That'll give you the 4 bolts necessary to lift the head during detonation.

JK! But it would prolly work..........

The cylinder pressure will blow the gasket before the load gets transfered to the piston(for a certain amount of time, eventually it'll die though!)


Don't forget to mention an alky kit for detonation resistance.....

 

Im running around a 228% overdrive on my 144 blower and see 10psi boost. Im running a stock refurbished bottomend with cast pistons and DART S/S 1.94/1.50 valved heads. No ARP bolts in the bottomend what so ever. Only ARP bolts in the motor are head,intake bolts and carb studs

I've logged on 3500 miles so far and lots,lots and lots of 1/4 passes everywere I go. My timing is very conservitive at 28 deg,using cold plugs and always good gas. It can be done,just stay away from detonation,lean mixtures and high rpms.

 

83 Crossfire TA,
What did you decide on? Are you going to boost the 305ci in stock form?

 

I was running 16-17Ibs all summer with no problems, mods are in the sig but pretty much stock engine with some bolt-ons.