Max boost on 91 octane?
 

Hey guys,
I'm running a stock port S5 13BT with a TO4B 60-1, .96 rear, .70 comp housings. It's a P-trim exhaust wheel.
I have the car running about 15.5 psi at the moment, and have taken it up to 18 psi (feels really good :)). I was wondering how much I can jack up the boost on 91 octane fuel. If possible, I'd like to run 20psi. Does anybody know approximately what timing I'd have to run to pull this off? At the moment I'm at about 15* BTDC with ~13* split at 15psi (I believe). AFR is right around 11-11.5:1. Also, I've got a decent IC (NPR front mounted), so intake temps are <120*F (50C) at pretty much all times.

Thanks!,
Manolis

I won't run more than 16 on 93 octane. Get some race gas or avgas and play it safe.

i ran 19 psi with my rx6 b but that was for a short period

blew my motor doing several runs at 1.3 bar with 91 octance. i was trying to fix a non-regulating boost problem and left off the gas as soon as I saw the boost needle creep past 1 bar but i guess my foot reaction wasn't fast enough. keep it at 1 bar. t51rkai/nb apex seal motor. very costly mistake for me.

i am a regular 1.15 bar driver on 93 octane. 20 psi is the max i have ever allowed it to go on pump gas but i have a t78 and a huge front mount intercooler so my charge air isnt really overheated.

ExFasWS6: Yeah, I've got a nice FMIC too. Last night playing around on the freeway my intake temps never got over 97*, and dropped from that to 71* in 15 seconds (!) doing 80mph. I think I'm going to up the boost to 1.15 bar (16.5psi) and leave it there. If I want more than that I guess I'll look into water injection or something. I have the Haltech tuned so it goes crazy rich (richer than 10:1) over 16-17psi, and doing 60-90 runs at 16psi yielded better results than at 18psi :) The runs, btw, averaged ~3.5 seconds, with the best at 3.45. This was done with a passenger. Z06 here we come :)

Thanks,
Manolis

20 psi is waaay to much for pump gas on a rotary. You will blow up. Spend the extra bucks on race gas or spend alot more when you blow up. Some get away with running 18psi and water injection and that helps keep it relatively safe, but 91 octane is piss water and you will detonate sooner or later.

according to XS, on a properly tuned FD, the safest I is 1 bar on 91 octane

I didn't think you could safely run 15* advance with 91 Octane at 15psi

I'm running 12* at that boost level. Guess I can crank it up a bit...:)

17psi max with 91 oct.

I have gone as high as 19psi on 91 octane with some magic elixir (octane booster), but the a/f's were also way rich in the 10.5:1 range.. I wouldn't do it with straight 91, in fact on unknown everyday gas I hold back to 12-14 psi as my safety margin, sometimes what you think is 91 is actually 87, and Premium on the pump is a relative term, premium compared to what, is the question...
Recently I burnt a tank of 94 octane, running 19 psi, no problems..
My timing is around 13 degrees at 15 psi, and starts tapering up slightly as the rpm's climb past 6000 rpm..Max

Toluene and water injection!

j/k I don't know much about all of this stuff.. I am just a little street boy.

so 16-17 psi is about the most you should run on pump gas?

but you see, running high boost and (low 91) octain, leaves u a little margin of ERROR, if temp changed etc..your pretty much fudged..

well that's gay

Why are you guys using 91 and not 93?

cause we lice in california... or well i do

91 is the highest octane you can get at the pump in California and other western states. The rare station will have 93 or 100 but that's very hard to find and very expensive. Just one more reason this state sucks.

up in oregon we only have 92.. so i add toluene(local fuel depot) for some added insurance i do about 10-15% ratio.. thats with 1 bar..

for shits and giggles, here's the link to the homebrew gasoline additive site.

* i have no experience with this and do not accept any responsibility for anyone's misfortunes*............ but let me know if it works :D
http://www.vtr.org/maintain/gasoline-octane.html

nb's?
ouch..arent those as much as ceramics.
any impressions on them? Dont know anyone in north america who is using them.

we have 93 here.