I figured out by doing some test on my evo9 (stock enginge&turbo/catback), that there is no reason to set the boost pressure over 18 Psi @ 7500rpm. Why I am writting this? It's because I often see people having a boost pressure of 23 Psi @ redline and they seem to have all low numbers of ignition advance (may be 'cause of hot air waiting in front of the inlet valve).

Is there anybody supporting me in my statement or do I am the only one with only 18 Psi at redline.

Marcel

 

Actually at my altitude I go down to 17ish... I do agree with you about blowing hot air into the engine.... But it depends on the car.. some cars love it...others want the timing to make it happy!

 

With good fuel, cool air temperatures, intake improvements and no catalytic converter, I found that 20 PSI at red line was good.

23 PSI with a good intercooler and race fuel may well be useful.

It is useful to plot load and MAP vs RPM and see how they diverge at various boost levels at high RPM, this shows the dropping volumetric efficiency. On the IX UK/JDM model I also had the benefit of being able to log inlet manifold air temperature.

 

I tried running 24psi to redline and I had to take out quite a bit of timing. My car makes more power with boost tapering down and timing raised.

stock turbo
all the bolt-ons you can think of
93-octane pump gas

 

This is very true!!!

 

i taper down to 18psi most of the time, and the rest of the time it drops to 17psi because i found out the same thing that holding the boost to about 6000-6300 and then letting it taper the car feels much better

 

I taper down to around 20.5 and can still run a bit of advance. The car likes it there. It all really depends on the fuel and cooling.

 

IX's seem to prefer timing to boost up top that is for sure. VIII's are a little more ambiguous on this matter Either way, big FMIC will help keep air going into the engine as cool as possible, and consistent.

 

same here. I try to keep WGDC under 95%. I figure anything below that the turbo isn't killing itself to make boost.

 

Same here, I'm tapering to around 20-21 and my car is very happy.

 

If you are at the track trying to run a number, the car will likely go faster by upping the boost to the absolute maximum when using high quality fuel. But for everyday use, I tend to keep boost fairly conservative. I use to run my 2G on a GT2871R at 25 PSI on 91 octane daily. The car and turbo held up fine for 2 yeas at that and the car was pretty quick. I slapped a T67 and FP2 cams on it though and at 20 PSI there was no comparision. The T67 on 20 PSI and 91 octane was faster then the GT2871R on 30+ PSI and race gas.

If you want to go fast on low quality gas, buy a big turbo and some aggressive cams. That little 16G will never be THAT fast on low octane gas.

 

timing up top really does nothing for me, boost is where its at. When I first got my meth kit I pretty much left the boost alone and up the timing a whole lot and it did pretty much nothing.
but this is my car so..

 

Im running a ported evo 9 turbo and 50/50 meth stock motor and head at 30psi. Im using a jdm map and gm bcs for boost control and my waste gate duty is only 80% at 7-7.5k and I get around 23-24 psi at redline.

Also running around 4-5 degrees at peak and 19-20 and redline.

 

W/ my IX, Ive found that my car likes 21 - 20.5psi @ 7000 w/ 10 - 11* and 20psi @ 7500 w/ 12 - 13*

 

hmm good discussion i am thinking about 20 psi on my car @ redline.

however the next question is how high to spike boost and what they should be at the respective rpm.

e.g. aryder said, he let boost fall off @ 6000rpm. what should it be before that?