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.

yeah i still havnt figured out why it falls on its face into gears. I didnt know you could safely run over 12psi on stock ic and fuel

Someone read my signature of mods, and tell me how much boost that I can run safely. With no boost controller it's pushing 3 1/2 psi.. -_-

he had a walbro, kinda in same boat you are in, kinda risky...

so what's up is this a conspiracy or something? nobody has any others thoughts or experience on these topics? https://www.nopistons.com/forums/pub...R#>/unsure.png

Nope. Never ported the wastegate either. Creep was never a problem since boost would always start to bleed anywhere above 5.5~6k. All the stock turbos do it. Only way to fix the bleeding problem is to get a different turbo.

Depends on what wheel you have in the T04 cold side. Also depends on what your fuel pressure is.

I'm a little confused by this thread. The stock setup will open the wastegate at anything over 5 or 6 psi on an S4, 7 or 8 on an S5 (I think). That's assuming you don't have a boost controller. If you have no boost controller, then you are simply fighting the stock wastegate while it's trying to do its job.



My stock S4 turbo had no trouble pushing 8 psi through the stock intercooler, and it certainly didn't fall off at high rpms. Now that I'm running the hybrid, I'm running about 10 psi (limited by a manual boost controller). Again, no problem with boost falling off.



If you feel like the stock wastegate is "dumping a ton of power up high", that's exactly what it was designed to do! Get a boost controller!

To address the original question, I won't run over 12 psi on my current setup, which is stock ECU and injectors with an upgraded turbo and fuel pump. It will be interesting to see how much quicker she is in the quarter going from 10 to 12 psi.

I used to run 15 psi on the stock S4. Just driving around, it would be awesome. Its when you stop and sit that hurts the TMIC. A nicely designed cold air intake and box helps cool it quicker and get lower temps in to the IC. I had 2 fuel pumps with the stock injectors and a SAFC. It flew. But the stock turbos are inefficient compared to a higher end turbos. Our turbos werent entended for alot of boost so they werent designed for it. You can do it, you just need to cool the charge a little bit better.

TI777 is having a different problem. His car in the upper gears dumps all boost no matter what the rpm. Its like going into limp mode...

so say i front mounted the stock ic, or got a starion one for example, what about the "pressure drop" that ranzo was talking about?

Looks like you need a T-1000. 50psi should do it.

we just finished the starion core on a stock turbo car, and its fine. if you want with a really huge ic then it might be a problem

what i want to know is if the ported wastegate can control like 13 psi or if it will still creep if it is ported. and if not, will it continue to build boost above like 15 psi?

OK from what I have seen the S5 actuator is just weak. It is supposed to be the same as the s4 just the shape of the rod is different. That being said I have seen boost creep on a S4 with just muffler and air cleaner....I once blew an engine with NO boost controller and A fuel cut defencer. It boosted 1.2kilos and at 6000rpm is **** a seal. https://www.nopistons.com/forums/pub..._DIR#>/sad.png



Unfortunatley there is not much you can do with the stock turbine......I have never seen an aftermarket actuator for a FC turbine, although some might be altered to fit. However on my Hiflo turbines I have a trick......the hi flo turbines have a metal adaptor that the actuator bolts onto, this is to compensate space for the larger compressor side, on this plate I add about 1/2 inch or so of washers to make the spring bind harder and keep the wastegate door closed harder. It has worked flawlessly for me for years and I can boost 14psi all the way to redline. The problem with the stock turbine is that it dosen't have this adaptor........now if you could make one or get ahold of one that would be a different story.



Nissan guys have been using washers for a long time and it is a cheap mans boost controller on a good actuator.



As far as pressure drop ...........I just installed a Trust FMIC in my girls car and there was a very noticable drop in boost response. The car was faster from just before 4000 on but it was not as "peppy" there in the very low RPMs. Playing with the Gain on the VVC and some other adjustments helped tremedously though. A starion intercooler will probably have less pressure drop than say my Trust one but I think the piping on the FC is what adds all the loss. Just read an article in Drift Tengoku magazine and by shortening the piping on a Sylvia they gained torque and it happened at a earlier RPM. Just something to think about.

So what Ranzo is saying is that the stock S5 wastegate actuator is too weak and the wastegate flapper gets pushed open by exhaust flow at anything over 5.5k rpm?



I have a home made boost controller on my S5 engine/turbo that is set to 12 psi. I get 12 psi around 2700 rpm in 4th gear but of course it is falls on its face over 5.5 k rpm. Its around 6 psi by 6.5k rpm. i always thought it was just that the stock compressor side was too small and couldnt flow enough to make the boost up high.

hks has an actuator for the fc

Yeah my boost completely dies at higher rpms. It'll hit about 11 at 4500 and then by the time i get to 6 its down to 7, 7 rpm sees about 5psi.

The wastegate on my T3/T4 has a stock boost setting of 3 1/2 psi, lol, funny ain't it? :P



How much boost could I push safely on my setup without over-heating the engine too much or just flat out blowing the seals?

Thats hard to say since you don't have the stock turbo. Get on the dyno or get a w/b.

this thread is so opinionated and digressed it's worthless! can't get a straight answer ****!



drunk