hi friends i have a question regarding timing using 91oct
iam using ecuflash for loging and the xede for tuning in which a friend has helped me a lot
--- timing-------- afrs
is ok to have at 4000rpms 6.3*---------12.
at 5000rpms 8.9*---------------------------11.7
at 5500rpms 9.3*----------------------------11.6
at 6000rpms 9.4*---------------------------11.3
at 6500 rpms 13.8*--------------------------11.2
at 7000 rpms 16*----------------------------11.0
at 7500 rpm 18*-----------------------------10.8

this was a 3erd gear pull on 20psi of boost and zero knock sums
what ive noticed is that if i add one more psi of boost i start to get knock i sy with 91oct dont push it more then 20psi.

what do you guys think is it a conservative timing with a conservative afr?
thanks

 

That looks too lean up to 6k, too much timing for 91, and not enough boost to get maximum power. My .02

 

so what afr do you think 11.0 all the way to redline?
an increase boost 1psi more?

 

On a VIII, I would say....

AFR - 10.8 tapering to 10.6 up top

Timing - like 4-6 @ peak boost, 16-22 timing up top

But you always go with what the car likes.

If you can do multiple logs with no/minor knock, then its ok.

 

its OK to be at 11.5:1 at peak torque(around 3000-3500rpm for the stock 8 turbo), then tapering down to 10.9-11.0:1 at peak power until revlimiter. As for timing, its hard to say what the car is going to want. Start at about 3* at 3000rpm and 13* at 7500rpm. That should be a good starting point. If you have no knock, bring timing up 1 deg at a time from 3000-7500rpm until you see knock. Remember to watch your AFRs as you advance timing. Advancing timing will cause you to lean out slightly!! When you run into knock, retard timing 2 degs in that area, then advance timing across the board from 3000-7500rpm 1 deg and keep going until you see knock. Repeat this process until you are at peak ignition advance across the rev range, then retard ignition timing 1-2 degs from 3000-7500 rpm and double check AFR's. If AFR's are good, call it a day.

Good luck!

CJ

 

I fully agree with you that ~20 psi is what is safe to run on 91 octane gas.
IMO, as long as you do not have knock and the lack of knock is CONSISTENT run after run, then keep things as they are. So keep logging and testing. Tuning on 91 octane is very tricky and requires constant logging to get the best tune out of it.

 

thanks to all
nj our fuel sucks they dont have quality controls here in my country
maybe whats helping me is my higher altitude iam at 3300' above sea level and that my stock cam timing is set at -5,-5 on my gears.
but thanks to all

 

I would have thought that you were too lean in the 4k range but if the car is not knocking then don't changte a thing....Also, I really don't understand why so many people are tuning their cars so rich (especially up top)...I would think that 11.5 is more than rich enough and 10's are overly rich and could cause problems....

 

91oct ...it's crappy gas...u have to tune richer and less aggressive when working with 91oct.

 

91oct ...it's crappy gas...u have to tune richer and less aggressive when working with 91oct.