elhalisf

iTrader: (171)

So i am new to the world of 91 octane. I moved from michigan, where the world of 93 octane, 24psi, 8*+ timing, 11.8afr (dyno afr) was beautiful.
Well, i moved to arizona.
So i am looking for advise for the 91 octane tuning.
I just had time to redo timing. See the below picture for current high Octane ignition map. Too much? Can i go more?
Also, I am gonna street tune for 11.8afr dropping to 11.5 around 6500 rpm on 3rd gear (will be 11.2 on 4th gear) and 22psi with the evo 9 turbo.
I am looking to have a fairly agressive tune on 91 octane, so suggestions for improvement would be great.

cpoevo

iTrader: (1)

I run 91 in Socal. I tune for about 11.2 afr at 6k up. I know I am leaving power on the table, but 91 sucks and I dont want to grenade my engine. My car is also very sensitive on its tuning. I am still trying to get dialed in good.

C6C6CH3vo

iTrader: (9)

91 oct should knock less as elevation increases but Phoenix is what, 2500 ft?

Timing looks on the extreem side (to me) at about 4000 - 5000 rpm for 91oct to me, but if your not knocking... But your probably hitting higher load cells anyway with the 9 turbo so that won't matter

elhalisf

iTrader: (171)

at which load? remember the load axis has been rescaled to 280.

and elevation is more around 1100ft.

SophieSleeps

iTrader: (19)

How about you go about tuning the exact same way you did with 93 octane.
Why is it any different?
If it knocks, back off of it.

JohnBradley

iTrader: (30)

Some of the 91 octane maps that I have helped with we had the timing backed down another 2* or so from where you have it with the AFR's still about 11.5 or so. Boost was 22-3 psi for reference (according to whatever gauge they had, not mine).

Karacing

iTrader: (1)

yeah, exactly

nj1266

iTrader: (6)

First, welcome to the world of **** poor gasoline. CAN gas is the worst gas in the world.

Second, the best advise I can give you is to find a gas station that sells 100 octane and 91 octane and mix to get the desired 93 octane. That is what I do in CA and I love it.

Third, if you insist on running 91, then here is what I would do:

1. Back off the boost to 20-21 psi.
2. Run an AFR that is @ 11:1 and taper it to 10.9-10.8:1 from 5500-7500 rpm.
3. Run very retarded timing. My timing map is attached and even with this one I was getting 6-8 counts of knock. I have since backed off about 0.5*-1* depending on the rpm.

Fourth, If you really want to run an aggressive tune on 91, then you will need water injection.

The Evo is designed to run on 93 octane or more. IMO, if you run it on 91 it is going to knock. Even stock Evos knock on 91. The Evo is a high boost car and 91 octane just cannot be compressed that much w/o it self igniting and becoming volatile. High boost cars require high octane gas. The Evo require high octane gas.

I have been running 93 octane gas on my car since June of 06 and I have not looked back. Two weeks ago I was forced to run 91 and no matter what I did, the car would knock. Those who tell you that their cars do not knock on 91 octane are the ones that usually do not log on a daily basis. If they did, then they would see KS of 5-6 in their logs.

Ultimate CC

iTrader: (122)

alky ftw...

nj1266

iTrader: (6)

Agreed...Either that or the cheaper route of water injection.

Ultimate CC

iTrader: (122)

the best is a 50/50 mix...

nj1266

iTrader: (6)

I wish it was that easy. I have tried that and on some runs the car would knock and on others it would not and so on...It gets frustrating really quickly. The reason is the EVO is a high boost car and 91 octane when compressed that much becomes volatile and self-ignites. Add to that that here in CA they run a different blend for almost every month (exaggeration).

Just when you think that you got your tune right and it is not knocking, then a few days later you do a log and here you have 5-6 counts of knock. It is like plugging holes in a colander