I have ran a procharger D1-SC blown motor, a couple of nitrous motors (one of which is current). After adding up the cost of bottle refills alone over almost 4 seasons, i could shoot myself for not doing another blower of better yet, turbo build!. Here's the deal, i've spent a lot of time combing turbo forums.com(not a member, just use the search feature) and think i have the kowledge to put together a turbo motor SAFELY lol! I was just gonna tear my 355 nitrous motor and just change the pistons to get the desired CR(8:5:1) with 65cc chamber AFR 195cc eliminator heads....the crank and rods are 4340 forged units and run a T4 flanged S475 with 1.10 a/r turbine and call it good....but i'm getting the 383 S480 T6 flanged with the 1.20 or the 1.32 a/r turbine bug, one thing turning me off from this one is the MAMMOTH size of the S480 T6 turbo!! will it fit in a thirdgen or is it easier to go twin T60-1s with .68 a/r turbines with 3" dp instead of the S480's 5" dp.....where the hell would i route that on a thirgen? granted i have no ac stuff, flat panel on the firewall, battery relocated, no charcoal cannister etc.

 

Where there is a will, there is a way

You could probably get a big single in the area between the engine and battery tray on the passenger side. With no AC box you can get a huge downpipe in place. If you go twins I'm thinking 2.5" downpipes would be fine and certainly easier to route for the driver side. Anyway, keep us updated on your project. It will be a blast!

 

ZZ3Astro, how does your car feel with boost? i've never driven a "good" turbo car before....my girl has a WRX but that doesn't count everybody at my track with boost says i'll never look back!! At the last test n tune a few days ago before the track closed for winter, i was talking to a guy with a buick GN...he was running 11.40s @ 122 on 18psi with a V6granted our track altitude is a stinking 5280ft above sea level(denver). That just put in perspective what i could do with a built 383ci with the right turbo(s)

 

I can tell you this.. last week I was planning to hurry up and get the 6AL and fuel pump upgrade installed so I could turn up the boost. But then I decided I like it where it is right now for the time being. Part of that is I want to have the money available to resolve any problems that might come along with higher boost and part of it is that it's so much fun already. I can't stop myself from taking the car out for a drive all the time. I can't imagine something breaking and being without it, so I decided to take it easy and work on some cosmetics before going crazy. I'm seeing full boost pretty fast, especially considering I don't have a stall yet. If I'm cruising along at say 2500 rpm and stomp the pedal, and say "one thousand one" I will have full boost by "one thousand o.." Of course full boost being 7 psi but it ramps up very quickly once it starts and I think it would hit 15 just about as fast. The feeling of a turbo car to me is kind of like being a passenger in a fast car. The turbo decides when you will get full power, and you are along for the ride. I don't mean it has to be laggy - there is just something about putting the pedal down and getting a certain amount of power, and then even more follows. Thinking about it makes me want to go drive it right now!

 

I see why you are getting full boost so fast.....you're running an mp t70 with p-trim wheel on a 350 right? whats the a/r on it, .81, .96? a t70 will generally have a quick spool on 350ci motor based on what i've read but be careful of backpressure up top though as the turbine wheels offered on a t70 is a little on the small side for a 350ci motor, a t76 will treat you right on a 350/355ci motor, i've heard from many reputable sources. How much hp/tq are you making on 7psi and what are the engine specs if you don't mind.

 

It's a .96 A/R and you're right, it's relatively small with a maximum of 450-500 hp. My engine is a completely stock 5.7 except for injectors and the megasquirt. I'm planning to keep the engine specs close to stock when I rebuild it, except for forged internals and a slightly better cam. Debating on heads as well, but I'm not trying to set any records with this one. I figure when I get 20 psi out of it, the performance will be quite satisfactory! Most likely I'll end up with a 67mm turbo and around .82 A/R when all is said and done.

 

leeperryracing,
What are your goals? Personally, I wouldn't go any smaller than the 96mm TW, 1.32 A/R turbine for a race 355+ CI engine. The BW S400 series can fit up to a 88mm inducer wheel with the JD/race compressor housing. Dave said it is a $550 upgrade and flows about 1500 FWHP. The 80mm is good for about 1200 FWHP.
You could always go the MP T70 twin route. The BW is a stronger unit and I think is more reliable for high boost ratios.

As for downpipes.........The size depends on the HP you want. It isn't a matter of twins or single. A single 5" pipe has an area of 19.6 in^2, two 3" pipes is only 14 in^2. So the 5" has more HP potential, but do you really need it? It all depends on you HP goal. A 4" single DP would probably work fine for you if you are under 900 FWHP.

EDIT: In terms of sizing the turbo, pic a peak HP goal and compressor. Then a desired spool rpm and turbine. You need to be realistic in that you don't choose a giant compressor with a tiny turbine. The turbine would choke it. A forged assembly with AFR heads and mild to race cam would work great with a 75mm or 80mm inducer S400 with a 1.32 A/R turbine, 96mm TW.

EDIT AGAIN:
I forgot to mention something. You said you are just searching TTF.com. You are missing out on not being able to see the turbo classified ADs there. It only shows up when you are logged in so you need to be a member so see it. Some good deals there. I picked up a used MP T70 (70mm CW and .96 A/R turbine) for $120 shipped. I see some large Garrett and BW S400 series for sale there for decent prices. Anyway, I think becoming a member just for that is worth it.

 

Those cars flat out kick @ss. I'm still contemplating the purchase of a TTA, as now is the time because you can pick one up for very cheap. My buddy John ran a 10.98 with a bone stock Grand National (full weight), running an itty bitty TA49 turbo....

http://www.youtube.com/watch?v=hPKzLU3r-1E

 

junkcltr, to be really honest with you i'm looking to break or set any track records....just want a nice running, reliable car that can go head to head with the best of "em. I KNOW i can can get into the mid-low 10s with the 355ci with the right turbo, even at this altitude especially when i see countless fox-body guys over at TTF.com running sick times with tiny 302,306,331ci motors. I'm more than likely gonna get a 3.75" crank and go with the 383 if i'm gonna tear into the motor that far to change pistons I've always noticed that you are one of very few on TGO that know their stuff about turbos.....my goals with the 383 is/will be around 750-800RWHP ONLY because i'll want the 700-r4(bowtie od level 2 w/edge 9.5 converter) behind it to stay alive long enough until i pony up for a bullet proof TH-400 with a gear vendors overdrive unit. The question is, if going single with a desired full spool time of around 34-4000rpm, no later, which single would you recommend? and if i decide to go twins with around the same spool time, which twins? I plan on shifting around 6200rpms with 6500 being the absolute MAX....I think its stupid to wind blown/turbo motors to 6800+ rpms.

P.S- I think i will go a head and become a member on TTF.com so i can catch some deals! thank you.

 

I would go with a 75mm or 80mm inducer CW, and a 87mm or 93/96mm TW. Since you favor decent spool time over exh. back pressure I would go with the 80mm CW and 87mm TW. The Garrett GT4508 and a flavor of the BW S400 would work great. As for twins, a 60mm CW unit from MasterPower would work well. Overall, the best band for the buck is the S400 with a 87mm TW and 80mm CW when going with a single. The MP twins would run about the same price.

Why go with a TH400 with the 4th gear unit when the 4L80E will do everything you need and do electronic shifting? I have been messing with the 427_ECM that controls a 4L60E/4L80E. I hope to have it running a 4L60E with 2-bar boost by next spring.

 

the 4L80E??.....I don't know about those really, i've heard they're just glorified 700r-4s and will crap out behind REAL power also, not to mention they want a small fortune for them. I've changed my mind permanently this time....i'm going the twin turbo 383 route with two master power t61 units with a .68 a/r, I know a single or tt 355 would be more than enough but there's a greedy side of me that i can't contain

 

I will go with 4L80e this winter. ( and maybe twins next winter)

anyhow I have a friend who has beeting the crap out of a 4L80E for 3-4?years until it broke, he has around 1000hp in a 4'th gen. running mid 9.

Also read about Jobys build here on thirdgen, he also have a 4L80 behind his turbo 350cui. with plenty of power.

/N.

 

i'll be looking out for your 4l80e swap, make sure you make a thread about it!

 

I will, and I will follow your turbo build since I'm thinking of getting turbo(s) for my 415" if not my F1 will be enough ...................

 

It's turbo time!!!

 

spoke to my engine builder today and he talked me out of a stock block and into a Dart SHP block(4.125 bore with 350 mains) and they're already clearanced for a 3.75" crank so im gonna end up with 400.98ci, 401ci pretty much...i'll have to step up to 2 master power t64s intead of 2 t60s that i had planned for the stock block 355/383

 

I would just go right to the MP T70 if putting twins on a 400ci Dart block. If you want to run on the lower side of HP and desire fast spool go with the .68 A/R turbine housings. You can always buy the .96 A/R turbines later on if you want more peak HP. Keep an eye on the exhaust back pressure if you decide to try and go high HP with the small turbines.
The turbines are relatively cheap and you see people wanting to swap sometimes at the turboforums.

 

junk, wouldn't 2 mp t70s with .68 a/r be good enough for 400ci up to say 750rwhp? i think they're also offered with .70 a/r also.....don't know if there will a noticeable difference going from .68-.70 though, i doubt it. Orr89Rocz and i are gonna have pretty much identical setups as far as cubes and turbo layout but he's always said the mp t60s on his comes on INSTANT and i wouldn't want that, which is why i was thinking t64s but with the same .68 a/r as the t60s....in theory i should spool a little later than his does. Max hp is not my ultimate goal so i'm wanting to be fully spooled or near there by 4000rpm max so i don't have to rev to moon....my bottom end and valvetrain will be happier i think.

 

well there's no looking back now, the dart block will be here in a week!!

 

Turbine wheel size and A/R have more of an affect on spool time.
If you want 750 RWHP and quick spool I would go with the MP T70's with the .68 A/R turbines. The .70 A/R you mentioned would be a zero difference change from the .68 A/R.
Later on if you want to up the HP to 1000-1200 RWHP then swap in the .96 A/R turbines.

With the .68 A/R turbines I am estimating your exhaust back pressure (EBP) ratio to be 1.8 - 2.3. Fine for a street setup with good peak HP. Depending on heads and cam you should be in the 16 PSI-ish range on the intake side. Good luck getting it to hook up on the street.

EDIT: Put good flowing mufflers on the thing to get the EBP as low as possible. Look at the Dynomax website. They give the CFM flow rating and equiv. HP for their mufflers. You want mufflers that flow about 500 HP each. That means something like two of the 3" IN/OUT ultraflows. Personally, I think they are too loud without turbos, but with turbos adding to the muffling affect then it makes them fine.

 

I think i can have a LOT of fun with twin mp t70s with the .68 a/r at the track and the street. Considering my 355 this past season was running consistent 11.50s @ 119 on a 125 shot up here at 5280ft elevation....you sea level guys have it made! With the new setup i should be in the 10s easily....i'll be limiting it to high 10s probably so that this 700r-4 will live until i fork over for a manual valve body, transbraked 4l80e(i gotta have the overdrive lol!) then i'll switch to the .96 a/r exhaust, crank up the boost and let her sing.

 

I wonder what mine is... I am thinking of going to the 64mm or 70mm turbos or just swapping to the .96 a/r housings on my 60mm's. The twin 60's are doing great so far...definately capable of mid 9's if i had a trans brake or could hold more rpm on the footbrake. The mph is good for mid 9's.
Just wondering if 64-70mm turbos with .68 a/r would give me more power at the same boost levels due to less back pressure, as I think i'm pushing these 60mm units pretty hard. I think these turbos are good to 1000-1100 fwhp but i've heard some mustang guys running 60-1's to 1200+hp and those turbos are comparable to my 60's. Then again i dont know how much a .96 housing will help on my 60's. I was afraid twin 70's with .96 would be way to large for my mild cam 401. Those are good to over 1000whp which I dont think i want to try to reach on this setup. The .68 housings would maybe help with spool but dont think it would help backpressure much. The master power P trim is the same turbine wheel for 60mm and 70mm compressors, so I may need the .96 housing.

Either way I agree, good luck hooking up on the street. If i'm not doing 55-60mph in third gear when I go full throttle on 13.5 psi, i'm not hooking up at all... its not much fun.


I got the dynomax ultraflo on my car, single 4" exhaust with 3" downpipes. Its very quiet on my car. Same exhaust as last year with my 11 to 1 compression 383 and its completely different. Car sounds like a stock full exhaust L98 at idle in noise volume. Compare my 383 racing vids with my turbo racing vids with same camera, same distance apart. Its HUGE difference in sound. Turbo cars with low compression really do tame the sound

 

this is the only way to fit a s475 in a third gen...with a 4inch downpipe no mufflers....

and jus to help you out if you do go s475 dont do 1.32 with the 96wheel...its to big do the 1.10 with the 83...

 

Setups like that scare me alittle because the radiant heat would bake that radiator and my car runs super hot as it is, no way i could cool down a setup like that on my car. My buddy's turbo Ls1 has turbo mounted on the radiator like that but he runs ok, not too hot but definately not cool like n/a motors

 

custom 3 core griffin rad and the biggest flexlite fans electric water pump restrictor plate and water wetter on a half filled block with strenghtening plugs and runs 180 even hotlappin at the track.

 

thats why i'm going twins....to me two "small" turbos are easier to fit in any thirdgen compared to an S400 and the cool factor of the twins is just icing on the cake,

 

based on my results i think you'll have a good time with twin 64+ mm setups. I'd suggest the .96 a/r too as it should limit back pressure. .68 may not be too small tho for a 70mm twin setup..i just think i may be driving the 60's too hard with the .68 and should go for a .96 or a 64mm setup

 

Orr, twin t70s with .96 a/r would be a b*tch to spool right? unless you're running mega cubes and the spool time is directly affected by the exhaust housing not the compressor housing? or will the compressor size have some effect on spool time too? Based on your experience Orr, what would you recommend? twin 64s with .68 or .96 a/r or twin 70s with .68 or .96 a/r? A 1200hp rated rossler TH-400 will make it into the car so turning up the boost shouldn't be a problem....these places want a fortune for 4l80e trannies!!

 

Knowing you are going to use larger heads and probably a slightly bigger cam than me, and you are looking for alittle larger power numbers, I think 70's could fit the bill. A decent 400+ inch motor looking to make 1000whp should easily spool those up with .96 a/r, but its hard to say. Same P trim turbine spins that 70mm wheel as does my 60mm wheel and its only a 3" downpipe. So higher power numbers may need that .96 a/r to keep pressure down. I think my .68 is spooling too quick and is hurting my top end alittle bit, but compressor size also has some effect on spool rate. Also manifold design I guess has influence on backpressure. Some variables here.

I cant remember who's setup it was but i read of a twin 70mm setup that made great power and the guy compared spool time with the different a/r housings. The .96 i think came on by 4000 or so rpm which aint bad if you plan to spin to 6000+ rpm. The smaller housings were spooling a good 500+ rpm sooner, but I believe limited top end.

My setup, I'm going to call the guy who sold me the turbo stuff and ask his opinion again. I believe I will end up going to .96 housings and possibly 64mm turbos if i can swing the cash. I think that will be a great combo that is capable of 1000whp, even tho I do not plan on approaching that. 800 is all i need to run high 8's or darn close to it i believe based on what i do now with about 650-660whp (mustang dyno through loose converter). I really need some gear and a much tighter converter i think.

Mid high 9's are easily doable with 60-61mm turbos but i'd get the .96 a/r housings just to be safe. Any faster and I'd consider the larger 64-70mm units and possibly same .96 a/r. It may be too big and the old .81 would be perfect but they dont make it anymore, atleast MP doesnt. The .68 just seems so small for such large amounts of power even for a twin setup but I'd rather hear from people who have that combination to see.

I know my setup has some oil leak issues that seem to be partially from crankcase pressure and that may be directly caused by too much exhaust backpressure from the small turbo housing. I'm kinda new to this and trying to figure out whats going on. Sad thing is I will not have time to figure it before the end of the year and not sure when I will have a chance to play with the car again

 

I heard you can buy .81 housings from garret, precision, turbonetics etc to fit master power turbos and you're right, if mp made those housings, they'd be perfect for what we want from our motors. I'll check into this though and if doesn't/can't work, then i think i'll go with the twin 64s with .96 a/r.

 

It would be worth it to install a bung and plain old tire pressure sensor on the turbine outlet and inlet to check the pressure. I would also put an IAT right before the throttle body. This will tell you if it is the post turbo or pre turbo pressure causing a problem. The IAT will tell if you are running out of compressor as you increase boost. My guess is the turbine A/R being the biggest problem. You mentioned not much more HP as you increased boost which could also be the compressors being maxed out and the IAT will reveal that.

 

If i do end up going with twin t64s with .96 a/r, i think i could get used to seeing a chute on the back of my car

 

So i think i finally made up my mind...i'm going with twin t70s with .68 a/r and to fight back pressure, i'll be running the two 3" dp into dual 3.5" piping and then out through 2 3.5" dynomax ultra-flow straight thru mufflers. If a 401 with that setup can't get it done, i give up!

 

The dual 3.5" will get you there. The 3.0" setup mathematically flows pretty close to what you desire. I think the 70mm CW, and the .68 turbines should work great. The post exhaust flows plenty and will not need to be changed if you go with the .96 A/R and increase the boost.

 

What are you running for an intercooler? I would argue that and how you have it mounted would make a bigger impact on cooling than anything else. the turbo sitting back behind the radiator like that should have almost no affect on it.

Man, when you guys start the 4L80 swaps I hope I don't miss the threads. I have a 4L80e out of a 94 GMC that I've done most of the transgo upgrades to (haven't finished the pump upgrade, got sidetracked when I wondered if I would be able to get it back together if I took it appart), but haven't even looked to see if it will fit/what I will do for a crossmemeber/TA. Now I'm sort of wondering if I should seriously consider a built up TH350 or even a TH700r4 since they've gotten so much better since I started this, just to save some weight and $$$