Squeezing Power Out Of Stock R33 Turbo And Fuel System

[tezflow]

Hey guys. I was wondering how much boost the standard rb25 turbo can hold b4 dieing. I have read here some ppl saying 14psi, while others say anything over 12psi 'makes no difference because the turbo is working past its efficiency'

I know this has beens asked b4.Yes I did do a search but there seems to be conflicting answers. does anyone know for sure, is 14 psi too much? i wanna know because i will be replacing the bleed valve with an Electronic BC and getting the car tuned so wanted to raise the boost a bit more. And also if the turbo can handle 14psi will that increased amount of fuel entering the motor be fine as far as the standard fuel pump etc is concerned or will that need to be upgraded. Thanks

[RANDY]

nah, at 14psi I think the exhaust wheel can just shatter... spinning too fast.

12 is the commonly quoted "maximum" you would ever want to run, but to expect much shorter lifespan out of the turbo.

10 is the safety level that people run their stockers at.

Having said that though, i've seen guys say they run their stock turbo at 14psi every day for 2 years with no problems.

Depends if you want to take the risk for the extra power or not. I'm still running 7psi using a manual controller, and might go up to 10 once I have my exhaust sorted.

[RB SANDY]

some people run 17psi but I dont and will not, I run 12 and have had on problems for 2 years.

[Col-GTSX]

Matt Spry tuned my car when i bought my pfc...

He set my SBC ID-III to 13.4 psi and said not a peeny more and not a penny less...

He did clearify that the tune needs to be almost perfect to keep it reliable... If you do a dodgy tune you will break it...

It achieved a round 200rwkw with really impressive responce...

Then from there i was not happy so i spent 7 grand on a bottom end and new turbo...

I ran my stocker at 14-15-16-17psi for a few days trying to break it and i could not break it...

[Munna1]

Its the heat that kills the turbo mate and boost for extented periods generates heat so for short burts you could probably get away with 14psi. On a tack day mind you people have seen these turbos let go at 10psi.

After 10-12psi the turbo is running out of effecincy you may gain an extra 5-10 rwkw but is that little extra power worth risking the turbo for? I think not personally, I run 10.5psi max and dont plan to run any more boost than this.

cheers

[Munna1]

Just thought id note I have wond the boost up to 13-14psi for short boosts on a couple of occasions just for interest and if anything the car was seemed slower.

cheers

[paulr33]

i find the stock turbo a great all rounder. i have no issues with keeping up with cars on the street, although single spinner diff is annoying. can take down xr8's, xr6turbo's, and the usual stack of vlts and what not. 0 to 100 in 4.88 but pretty crappy 1/4 due to single spinner and cold track

[Col-GTSX]

I understand that long periods of time running high pis like 14-16 or what ever will break the turbo.

I just could not do it...

I ran 3-4 track days at 13.4psi and never had an issue...

Im not saying that the turbo is great and you get heaps of power, thats why i upgraded to a gt30 but the stock turbo is good for 200rwkw all day...

[LTHLRB]

running my turbo on 11.5 - 12psi. Havnt had a problem and making around 210rwkw

[Sydneykid]

There is conflicting information because there isn’t one solid answer that fits ever car, every driver and every situation. The right answer is, it depends on how well the car is tuned, what it is used for and what it is driven like. Ceramic in the cat disease is caused by three things working together, heat, torque and turbo shaft rpm. There are various combinations of the 3 causes, but lots of all 3 is certain death.

So I boil it down to 3 answers;

1. The guys that actually USE the power that 12 psi (or so) generates. They have killed a turbo or 2, and found that for what they use the car for, 10 psi is about as high as they can go before its ceramic in the cat time. They know from experience that the 10 psi keeps the shaft rpm down. So their continual hard driving may build up heat, but the shaft speed is low enough so the turbine survives. The lower boost means less torque loading on the turbine blades (turning the compressor). The car makes good power because it is tuned with reasonably lean (power making) A/F ratios.

2. The guys that cruise around and hardly ever use the 12 psi (or so). They give it a burst occasionally for a second or two. The car makes good power because it is tuned with reasonably lean (power making) A/F ratios. But they don’t really USE the power for any length of time. So the heat doesn’t build up. Hence they get away with the higher boost.

3. The cars that run 12 psi (or so) but run rather rich, so they don’t really develop the power to justify running 12 psi (or so). They can run the boost for reasonable periods because rich A/F ratios = a cooler turbine. Similarly they get away with the higher boost.

So the answer is which category do you belong to?

Personally I’m a #1, a few laps of the circuit at a supersprint or a track day or a long blast up Mooney Mooney Hill and I would kill a turbine, if I used more than 10psi. Take a look at the other responses and judge for yourself what category they fall into.

cheers

[RANDY]

I don't think anyone can put it better. =-]