now that i finally have a real 4 port engine to put my s5 turbo on i am starting to wonder what the limits the stock s5 setup can take for how long. my plan is to run an e6k on a street ported s4 motor, 720 secondaries with walbro, and either front mount the stock ic or find me an npr one. my goal is to make as much power as possible for at least this summer before refreshing the turbo or motor. the engine is being rebuilt as of the moment and the turbo seems to have very minimal miles on it showing no abnormal marks or play. i hear there is no reason to run more than 10 psi on the stock turbo because of exhaust mani, and if you run higher your turbo will die extremely fast. what i want to know is what would be the reccommended amount of boost to run on my setup and goals. ALSO i want to know about the whole wastegate thing. i know it's like a must to port it and since i want to run higher boost i know creep will be a common occurance. but since i will have upgraded injectors, pump, and ic, will i want to at least try and control it? or does it even matter? https://www.nopistons.com/forums/pub...IR#>/wacko.png

Because of the small turbine side you mean.

I've heard beyond 9psi the stock turbo starts to choke itself on the small hotside. The backpressure creates intake reversion. This inturn promotes detonation.

I've also heard that high psi overworks the stock bearings and frys them with continued use. But this was not on fresh or new turbos. I guess we will just find out https://www.nopistons.com/forums/pub...IR#>/bigok.gif

yeah what he said

10-12psi is a kind of happy spot because, the turbo stays alive, the engine is pretty safe, and makes a fun amount of power.

You can safely run 14psi on the stock turbine. It will last for years on a stock motor like that. I am not sure of the gains when going from 12 to 14psi but it is pretty standard to boost 1k or 14psi here in Japan.



You said that the turbo was S5......if so then there is no need to port the wastegate. the S5 has two holes, one large one small as where the S4 only has one hole. I have had more problems with boost falling off than creeping on S5 turbines. As for intercoolers I would just use the stock one until you upgrade the turbine I think the pressure drop of a front mount would leave you wanting with the stock turbine.

I ran 8psi without the haltech

Got a haltech and stock injectors and ran 12-13psi for a while

Turned it up to 15 and ran that for a few months still on stock injectors and IC

I seriously advise against going past 15 though. Heat soak happens VERY fast at anything higher and you get really small gains. I think it actually becomes inefficient after 12, but who knows. Ive never seen a compressor map for it.

I do know that my turbo survived a night of an overtightened boos controller where it saw 21psi though.





But anyways, the long of the short is, if you have a haltech and at least 4x 550cc injectors, its gonna be pretty hard to blow the engine using the stock turbo ( provided you tune well enough ). Run what you want, see what you like, and know that its not a whole lot of money to get another stock turbo.





EDIT: I guess I should add that I had a Walbro through all this too. Thats probably kinda important.

hahaha that sounds like my old t25... i ran it at close to 30psi(at the turbo) it was coming out as 22psi and that was pushing though a stock s13 cooler, ouch

so since you had supporting mods to compensate for the creep, did you bother porting your wastegate?

and what about this? like you were saying you dump boost like when you shift? TII777 i think is still having this problem among many others, but is that normal for the stock wastegate setup to dump a ton of power up high? did you/can you, do anything to remedy it?

I'm gonna see what the diff gains are next time i go dyno my car on diff psi levels.