legacycentral bbs

Ok. I have been dieing to know this for some time now.

How much boost can the stock motor take before it lets go? And when i mean stock i mean you did nothing to the bottem end, nothing to the valve train, you didnt swap the cams and heads. I mean nothing! All you did was a intercooler, injector, turbo swap, ecu. How much could you run with a setup like that before melt down?

Thanks!

PS. I have hurd 20psi but not sure about that. Anyone to back me up??

Cummins, 28psi

The cummins turbo may take a while to spool up, but when it does WOW!

More to the point, your question is how much boost? I think a more appropriate question would be "how long"..

with a properly tuned setup its not the boost pressure that will kill the motor, it's hp.

if stock honda motors make upwards of 400hp on stock bottom ends i wouldnt be surprised to see stock 5-600hp subie on a good tune..but what do i know!

Hmmm. So its more about having a good tune than anything else. Makes sense to me! So what are some of your guy running for boost?

cummins, 28psi!

Damm 6500rpm redline!

Do some searching about a guy named Xypher, he was running around 28psi on a stock block - albeit he bought a brand new block from Subaru to run. He ran 28psi on his daily for a long time. I think he has since upgraded to a EJ257 block nowadays.

The man also knew his stuff and had it set up right.

Wedge over on RS25 ran a EJ22T shortblock for years at 22lbs before it let go. I'm 90% sure his internals were stock EJ22T. I know the con rods were because thats what went when it finally did pop. Put a rod through the top/side of the engine. From what I understand the EJ22T rods are the weakest part of the internals but they will still take some abuse. I've got '22T rods and crankshaft in my EJ25 hybrid engine and I just started running 11lbs (up from 8lbs).

Ok cool! So i can run a fair bit of boost without killin it.
I just want around 20ish. So nothing like 28! Thats nutty.

Sweet

impreza_GC8 wrote:Wedge over on RS25 ran a EJ22T shortblock for years at 22lbs before it let go. I'm 90% sure his internals were stock EJ22T. I know the con rods were because thats what went when it finally did pop. Put a rod through the top/side of the engine. From what I understand the EJ22T rods are the weakest part of the internals but they will still take some abuse. I've got '22T rods and crankshaft in my EJ25 hybrid engine and I just started running 11lbs (up from 8lbs).

He had Wiseco pistons & stock rods on that car.
ej22t rods are the same as any set of 1.8, 2.0, & 2.2 rods - nothing great there

As far as how much boost its all relative as a given boost level from a VF11 is not the same as that boost level from a GT35R since the bigger turbos flow more CFM of air @ a given pressure level...
I suggest you take it easy & increase boost slowly to make sure the rest of your set-up can handle the increased boost levels.

Boost really doesn't matter, as was said before. How much air you are getting into the engine and how much cylinder pressure you are creating is what does matter, aka hp or torque. The turbo is going to be the biggest factor, with the stock heads being next in line.

If you have a much larger turbo and the capability to control it, the heads are going to become a major bottleneck. It took 21psi out of GT2871R for me to make 300whp with stock heads and delta cams. I think Phil's old car ended up making 378 whp or something like that on a stock longblock and a 50 trim. That was with a 3:1 ratio of pump gas to 100 octane, iirc.


If your turbo can support a high enough pressure ratio and you can control your fuel and timing, then go for it.

So really my max boost question is really about, how well of a setup i create. My parts that i have ready to rock are as followed:

Vf39
04Sti injectors
Cobb/Lsp TBE

Parts that i plan to get:
AWIC. All i do is city drive.
Revtronix ecu management stage 3 or X
Fuel pump of some sort

Thats the major parts to my creation i want. So basically i just want this setup to be as effective a humanly possiable. And i dont think ill need to get the boost over 20psi to make this setup hot!

You probably do not want to push a VF39 over 20psi anyways. I can't find a real compressor map for it as IHI seems to not want to give that data out. I did find this, but it is a joke without any efficiency islands or compressor speed lines. http://www.ihi-turbo.com/turbo_RHE-RHF.htm



I seriously suggest you spend the extra couple hundred bux on a wideband. Not knowing what is going on in your engine is like dancing with the devil.

Wooo wooo. Wideband? What be that? A wideband 02 sensor?