Boost levels

[aspect]

Hey guys,

I've noticed that people throw a lot of boost numbers around on here, but I've never seen some real data to back them up. Stuff like, "over 10psi is bad without IC" in a recent thread.

Does anybody have any real data or experience to validate any of these forum-rumor limits? Something like, "the AFR starts to lean because the injectors are maxed out at X psi", or "I was running Y psi without IC, I added a saab IC and my EGT's dropped by Z degrees".

I was up at Rocket Rally racing a few weeks ago (North american rally champ 2005 Pat Richard's shop) and his crew chief was telling me he was running 15psi on his legacy turbo wagon daily driver with no intercooler. This is a guy who builds racing subarus all day.

All the P4 class rally legacies I've seen were running that kind of boost as well, with no IC. I've never heard of an engine failure related to it.

So can someone explain to me where the "boost limits" that show up on this forum come from? And why it's ok to run higher boost with a crappy saab intercooler? Seems to me that you would actually run higher effective compression *with* an intercooler, and besides, even with a WRX scoop the air cooling compared to an actual WRX setup is pathetic. If it's such a big difference in terms of engine damage, wouldn't people be risking their motors by driving their boosted evo or STi when it's really hot out, or when the car is totally heatsoaked?

[aspect]

Found this thread: http://bbs.legacycentral.org/viewtopic.php?t=20704

Suggests that people are starting to lean out around 16 psi intercooled.

Also notes that at 12psi intercooled on a vf11, the MAF is topped out.

It would be interesting to see how much boost is required w/o intercooler to hit 5v on the MAF signal...that would give us a pretty good idea of the difference in actual air volume I'm guessing.

[free5ty1e]

12psig with a VF11 was determined to not max out the MAF, that was an issue of confusion. The 16G maxed out that particular MAF at 12psig.

Also, we have two MAF sensors available to us, the plastic and the aluminum cased ones. I forget which but one has a higher range.

I have no direct experience with running more than 10psig unintercooled (at sea level), because I didn't turn my boost any past that until I had at least a top-mount IC.

[Legacy777]

The black plastic JECS sensor has a higher range.

[Imprezive]

like the one off of an earlier wrx? If we are both talking about the same MAF, then you need to rewire the connector correct? I happen to have the plastic black MAF.

[dzx]

Like the one off of early N/A legacy's. One wire needs to be grounded, but the harness fits.

[NICO]

i still cant max out my maf and i run 19psi 18g, i did how ever max it out at 7psi thats when the plate was left on.