If I said you could only boost 18psi safe would you only boost 18psi? Hell who really knows other than what the internet says. I think it should hold 25psi with a better head gasket and head studs and a good tune with some C16. I haven't gotten that far yet so I can't say for sure.

 

Well it depends on the size of the turbo, as a bigger one makes more power on less boost. Lets just say you can make 350whp conservatively on a good tune. So, with a t3/t4 50 trim, you should be at about 18 psi (again conservative). If you had a small t3 (.48 ar) you could run more like 23 psi.

 

you dont want higher boost pressures, what you want is increased airflow.
with more pressure comes higher cylinder pressures which leads to knock and detonation.
you want a turbo that is efficent at a low psi so you dont have to run alot of boost to get the power you want.
right now my car makes ~400whp on 17psi, which isnt terrible but i would like it to make 400 on 14 (not gonna happen because a turbo like that would be laaaaagy).

 

Yeah good point. With proper tuning, of course you can keep knock and detonation to a minimun, but yes it is definitely more probable at higher boost. I plan on doing an sc61 turbo to make about 350-400 hp, but the sc61 is a 630hp turbo. Just as Carl stated, he can make the same horse at lower boost on a bigger turbo, so it just depends on the size of the turbo. I would say max of 25 psi assuming a smaller turbo, but of course a smaller turbo may not be efficient at that high psi.

 

ok thank you for your imput now one more question how much boost can i run on the stock set up( including the stock turbo, with a FMIC and a B/O valve... and i mean this isnt a daily driven car but i do want to sqweeze out some numbers...

 

while this has been covered before, the max reccomended boost is no more than 14psi., else watch for flying turbine wheels.

 

Ok this is what you need to do then..Go to a dyno run 16psi and see what happens 2 minutes later. Yeah it will make a really cool noise too!:thumbsup yeah im j/k

seriously if you want hp out of the RB20 you really cant use the stock turbo..

 

I had a boost controller that fucked up and I spiked 23 psi on the stock turbo. Just hit it for a second before I lit the fuck out of the tires at 60mph, blew off an ic pipe and shot a nice fireball out the exhaust. Didn't hurt a thing though, because the car shut down right away with no ic pipe. So I told my friend he was a jackass for giving me a boost controller that didn't work and I went and bought a hallman in cockpit bc. I run 14-15 psi everyday. No problems yet.

 

You may of not had a problem yet but you will...the epoxies they use can't take the constant abuse of high boost pressures.

 

i have replaced the stock turbo on my rb25 once...thanks to my boost controller wanting to hit 17psi...pretty much roasted the stock little t28. this one now is showing signs of wanting to call it quits...pretty sure the bearings are taking a shit. my new manifold,turbo, and wastegate awaits . i really wouldn't run 14psi daily...more like 10-12psi..just my $.02

 

hi guys

9psi in daliy drive
and
17psi in weekend

at least I am in this setup at lest 3 month and no problem till now

stock turbo
FMIC
custom 3" Exhust

 

I'm sure it greatly depends on the condition of the turbo.. but this thread was in reference to the motor. You want to stay withing the efficiency range of the turbo while not putting too much on the motor. The possibilities listed above by Carl and I give you some reasonable expectations.

 

If I remember correctly mohnissan, you've had lots of problems.

 

my stock setup i hooked up a boost gauge and a third gear pull hits 16 psi then drops to 15 and hold it all the way to 7500.... i was like wtf. no need for my greddy profec b spec 1 i guess. this motor looks bone stock had 12k miles on it and everything looked new ... maybee aftermarket wategate ? i really dont know. no adjustments on it or anything. maybee i need to lube it up .. some rust development around where wastegate goes into turbo. well or a different boost gauge. any suggestions ?

 

What does it hit in other gears? I'd say you either have an old broke wastegate, or an upgraded one depending on what you hit in different load in other gears. Possibly the spring was faulty from the manufacturer? Is this on the stock turbo? You're going to blow that in quick order if so.

 

2nd 3rd 4th and 5th gear when i full throttle it springs right up to 15 psi and holds! maybee i should get a aftermarket or another stock one! let me know what you think

 

hi guys

9psi in daliy drive
and
17psi in weekend

at least I am in this setup at lest 3 month and no problem till now

stock turbo
FMIC
custom 3" Exhust

You're almost doubling your boost for weekends? On a stock turbo? I hope you're tuned and not just turning the knob for your weekend jollies..

 

you kids are crazy. I ran 14psi on my stock turbo and even swapped in the stock ecu for shits just for a night. I was pingin like crazy when I hit full boost. I upgraded the turbo shortly there after, but I was curious. Even if you can achieve a great amount of boost pressure with the stock turbo your probably not making much power after 14psi with these turbo's. I mean think of how fast that wheel is turning?!? I've heard for a long time a t25 at 14 psi will be hitting 250,000 rpm. I mean fuck... that is just frothing the air right there causing more heat than anything. You have serious efficiency problems at that point.