How much boost?

[JCAP_Tuning]

I know that it is not recommended to run over 12 psi on stock turbos. How much boost is everyone with stock turbos on their RB25's running?

[HybridOne]

i'm running 12psi on my RB20DET. Though, it went there on it's own. 3" downpipe+exhaust, and a cone intake....and a sidemount intercooler.

[hashiriya13]

just 7 but sometimes 12 just for the extra kick. But will be running much more soon.

[JonPowell]

I run 7PSI also, just stock for now

[PROJECTRB240SX]

DUNNO NO BOOST GAUGE YET.

[rbsileighty]

Careful man... here are two close but different opinions from another forum for someone (32man) who was detonating with a 25 @ 12psi on a R32GTS-T fuel pump:

"If you are running RB25DET's in your R32, and using the stock pump i'd say thats def an issue. But running1bar on a 25t engine without doing anymore mods? your keen.. Also having higher compresion means they are more like an N/a turbo hybrid basically compared to the RB20DET (better low down torque and less lag) but this equals not liking huge amounts of forced induction... Def look at an SAFC or something to at least map your fuel so its safe..

32man, on standard internals, small fuel pump and i assume you have a stock intercooler stick with round the 10 mark max till you have fuel sorted... 1bar is pushing it abit"

"1st thing you should do.... walk out to the car and turn down the boost to like 0.6 bar... or like 6~7psi.

Or you might be on your way to a engine rebuild.

then come back to the computer and sit down and find out how to tackel the problem"

Personally, I would not up the boost on the 25 until you have access to a dyno, wideband O2, and some sort of fuel control (be it SAFC, HKS Super AFR, HKS F-Con or whatever you choose). You are flirting with an unfriendly boost CR of 9:1, so fuel tuning is critical (really is with all turbo cars... but 9:1 raises the importance).

Here is some additional info on upping the boost on a 25 that that I found that might be useful:

"Hi Brisbane_Skyline, your is an R33 GTST, right? It has overboost protection at 12 psi, the ECU will cut fuel and ignition if that is exceeded. If you want to go more than 12 psi you will need a so called "boost cut defeater", there are a number of brands around."

Hitting fuel cut on a turbo car is not a good thing fyi (you probably already know)... Just think, you are (in theory) upping your CR by forcing more air into your combustion chamber, so at 12 psi your theoretical CR is 16.35:1. This would mean that you would be igniting an extremely lean mixture at 16.35:1... bad stuff.

Ok... this is my $1.50 on the subject... hope it helps.

[JCAP_Tuning]

I was planning on running 10psi max, I am running a 255lph Walbro fuel pump, custom intake manifold and a Isuzu NPR front mount intercooler. Although I agree, I need to get some fuel management before giving it much boost over stock.

[rbsileighty]

Luckly these motors tend to run rich from the factory... with the stock 370cc injectors you should be good for a while on fuel capability (most likely within your stock turbo's output capacity depending on how clean they are), but I would definitely stay at 10 or below until you put it on a dyno with a wideband and some sort of fuel control. The only time I would consider a fuel cut defender is if you are flirting with 12psi (where it is said fuel cut is) without a boost controller. They just trick you ecu into thinking you are running less boost than you are, which could lead to lean conditions. Got to run...

For the record... this is only my opinion.

[thephatone]

the stock turbo on a rb25 is a what size? my friend runs 18 psi on his eclipse 2nd gen with a fuel pump and slighty bigger injectors...hmm odd

[tyler03]

I have talked to 2 diffrent people that have had rb20's, one runs 14psi all the the time, the other has ran up to 17 but the turbo eventually went. I have a/f gauge,a mbc, and plan on runing about 9-10 for daily driving and about 14 at the track.

[Yellow4g63]

I thought the RB20 came with 270cc injectors? It dosen't sound like alot of fuel for 12psi? Did anyone put a wide band to it to make sure it's not leaning out on the top end?

[tyler03]

im pretty sure they came with 370 injectors. And on another note, I forgot to mention (maybe everyone already knows this) that rb20's have a lower compression= less likely to detonate,and can maybe boost a little higher. but regaurdless the turbo can only boost 12+psi for so long before going.

[Yellow4g63]

http://www.meggala.com/injectorscss.htm

Says RB20 is 270 and RB25 is 370.

[tyler03]

but i think the 270 is for the rb20de and the 370 is for the rb20det?

[leroy0053]

right now i am running 1 bar of boost i am running a stock turbine super afc II stock fuel pump. the norm over here is 1 bar. hell there are some guys drifting on 1.1 , 1.2 but 1 bar is safe make sure u have an air/fuel ratio gauge also. you dont wanna lean that motor out. by the way my motor is an rb20

[leroy0053]

rb20's come stock with 270 injectors

[Yellow4g63]

rb20's come stock with 270 injectors

I knew I was right. Thanks for the info