Help me make heads and tails of turbo selection/compressor maps

[blueapplesoda]

no gt2876 (t25 flange is a nono for flow)

we used a gt3076 for 6-7 years on a stock s50b30 with arp studs and stacked headgaskets (stock+copper), and it took 50,000 race miles to blow a headgasket (bridge 3 and 4), ran around 12 psi.

We are now using a gt3582 (gt35r) on a t4 housing and built motor, and its a bit big but fuck does it make punch. serious oomph. 16psi aswell.

[Dj Buttchug]

Im going to chime in here. Although im not doing a s5x turbo setup I know alot of ppl that have.

the best advice I can give you if you want to reach 400 some hp is to build the motor. While replacing the head gasket with a cometic oversized will work to lower the compression its not going to last very long at all. the best way to do this is to sack up, spend the money and get lower compression forged pistons then run a stock head gasket.

As far as a turbo goes. I would consider running a gt35r or something close to that. With this compressor your going to have reasonable (but manageable lag) while being more than capable of a bar of boost.

[BigD]

Wow really?

[SwiftE30]

You gotta go top mount. The s5x engine bay with a bad ass turbo and headers is the sweetest looking setup possible. I am currently In the middle of sn s52 OBD2 turbo build myself. Look at Good & Tight top mount manifolds on here. They look awesome, and way cheaper than FAB 666's.

[BigD]

Exhaust manifold I meant. But yeah the m50 is good till around 15-20 I think. I remember matt saying somthing that they flex around 25psi I think.

Oh exhaust, d'oh. Um, I was thinking about a top mount, because I have no AC and there's a huge lonely void there, just begging to be stuffed. But I didn't know that you need the maf to be upstream of the turbo, Matt just told me today. So it looks like I'll get his or FAB666's bottom mount, with Matt's motor mount to have clearance. Or maybe I'll hack out a high beam to make room for the filter + maf and go top mount.

[e30s52]

Exhaust manifold I meant. But yeah the m50 is good till around 15-20 I think. I remember matt saying somthing that they flex around 25psi I think.

[BigD]

/\ I havent driven my car in about 6 or 8 months :(. But for the s62 I would go with standalone along with some new cams and a light wieght flywheel. Still toying with the idea though. I can get them for cheapish so thats why I was thinking about it.

What manifold are you thinking about using?

The flywheel will only make a difference in the short gears, where it'll all be tire smoke anyway. I never really understood the appeal of standalone - the idea that you can do better than BMW M, with their limitless tuning budgets, tools and expertise, with some home made computer, the internet and some weekends seems far fetched.

I want to do as little hacking as possible, so I'd like to stick with my M50 manifold. Should be ok right? I'm not looking to run any ball busting pressure.

[nando]

generally, a cam that is meant for a NA car does not do well on a FI engine. For a turbo motor, more overlap = bad. You are better off to stick with your stock cams and spend your money elsewhere on the turbo system. This is not my opinion from personal experience, but just my understanding after reading the book "Maximum Boost."

wrong, wrong, wrong and wrong. ;)

you'll have a much easier time reaching 400whp with a good set of cams than you will without them.

[e30s52]

/\ I havent driven my car in about 6 or 8 months :(. But for the s62 I would go with standalone along with some new cams and a light wieght flywheel. Still toying with the idea though. I can get them for cheapish so thats why I was thinking about it.

What manifold are you thinking about using?

[BigD]

/\ Yeah the z06's are going way down in price but alittle to crampt for me. I have been thinking about an s62 swap though instead of going FI.

An S62 only has 400hp and an even lamer 365 ft lbs (or something like that). For a 5L solid lifter, ITB V8 that's downright weak. Plus if it blows up you're out another 5 grand or whatever they go for nowadays, if you can find one. If you blow an S52 you go on ebay for 2500.

I just took my car out for a spin to make sure it didn't magically die in the winter. Man I forgot all about how hard this car pulls. Having no cats is awesome too. I punched it in 2nd, it took off making it's usual fat woman startling roar (made 3 jump) then off throttle it burbles and pops like mad. Thinking about trying the same thing under boost gives me a chubby.

[e30s52]

/\ Yeah the z06's are going way down in price but alittle to crampt for me. I have been thinking about an s62 swap though instead of going FI.

[BigD]

Cool. I'm not aiming quite that high. I really love this car, it's an amazing track whore but I also can't ignore how cheap C5 Z06s are becoming. If I can get this thing to around 400 ponies, I won't even look at a C5 again. So my target is around 350-400 wheel.

Looks like the GT35r is gonna be my snail.

[e30s52]

Around the same power as you. About 400-450 wheel. I am not going to change the internals at first but after I run the motor for awhile I will tear it apart again. I plan on using the gt35r turbo along with the .140 headgasket. Once I tear the motor apart I am going to get some eagle rods and wiseco pistons or maybe JE and some new arp headstuds.

Right now I am still thinking about what I am going to do and how I am going to put it down. So its all subject to change.

[BigD]

Nailed it dead on. I plan on going FI too. The sunbelts though are great cams though if your motor is set up for them and you plan on staying na.

Thanks man. Can you share some of your plans? Do you plan to change the internals? If not, what kind of power are you aiming for, what's your turbo choice, what thickness gasket you plan to run etc?

[e30s52]

generally, a cam that is meant for a NA car does not do well on a FI engine. For a turbo motor, more overlap = bad. You are better off to stick with your stock cams and spend your money elsewhere on the turbo system. This is not my opinion from personal experience, but just my understanding after reading the book "Maximum Boost."

Nailed it dead on. I plan on going FI too. The sunbelts though are great cams though if your motor is set up for them and you plan on staying na.