How much boost is safe?

[screaminglemon]

2JZ octane vs. PSI maps will not translate evenly to a 7M, I'm afraid. You need flow vs compression to baseline it.

well yeah, you are right. it looks like its time for me to read corky bell.:icon_wink

however, that doesnt mean this info is completely useless. we know that the compression ratios are nearly the same (mk3 8.4:1 vs. mk4 8.5:1) and we know that the mk4 head flows better than the mk3 head. so at any given psi, the pressure in the cylinder will be higher for the mk4. that makes detonation more likely. this is assuming an equal air intake temp post intercooler. this assumption is probably ok as long as we stay within the efficiency range of the turbos.

so the numbers in the 2jz octane vs. psi chart can be used to get a conservative safe estimate number for max psi. at least it could be used as a starting point.

this is all rather pointless anyway if we are talking about the stock ct-26 as it starts cooking the air at about 15-16 psi anyway. so the number of 14 -15 psi for max safe boost on 91 pump octane still holds for the ct-26.

all that being said, every car is different and only experimentation will yeild actual usable numbers for your particular car.

 

[MK3Brent]

I remember when Malloy and I were talking when his motor blew.

Mike: "Hey man what's up?"
Me: "Nothing much."
Mike: "Hey... are you suppose to see this much of the piston through the side of the block?"

Me: "Hahaha!"

I think it was either #5, or 6 that completely went through the block after his hydro-lock flooding problem.

 

[hammerhead]

hey you guys are awesome. from all this info i basically gather that I will boost prob up to 13 - 15 psi, depending on how the turbo will perform. I am running pump gas, stock injectors, stock intercooler... my mods include HKS 3" downpipe, custom 3" exhaust, HKS Dragger muffler, HKS BOV, fluidyne radiator w/ electric fans, HKS FCon fuel computer, HKS Turbo Timer, and putting in the HKS EVC III as soon as my rebuild is complete with the ARP head bolts and the HKS MHG. After that i plan to get guages, then more boost maybe with a bigger turbo.