Hi Shiv,

Which is in higher priority, ignition timing or leaner AFR?
I've tuned my 91 octaned EVO to around 11.3 AFR, it knocked and I had to retard quite a bit of timing to reduce it. It's actually running somewhere around 5 degrees in mid-range and 10-14 degree from 6000-7000RPM now. It seems to be a bit low compare to stock timing (I am still running 19psi and tappered to 17 psi by redline).

Should I run a bit richer so I can run a little more timing, or I should keep it what it is to have a leaner AFR at 11.3 all the way to redline with a less advanced ignition timing? I know I've seen some tuner tune the EVo at 10.5 AFR to reduce knocks, but I am not sure if you would suggest the same.

Thanks!

 

What EM are you running?

 

I am using an Autronic and I just started tuning. Does it make a difference which EM in terms of AFR and ignition timing?

 

Yes it does. With a stand alone (or any aftermarket computer with fixed fuel and timing maps), one has to be a lot more conservative with ignition advance and fueling. On the street, it's not unusual to retard timing an extra 2 degrees and 2-3% more fuel from what seemed optimal when mapping on the dyno.

Hope that helps...

shiv

 

So does 11.3 AFR with 91 octane seems about right? Or should I tune to 10.5 like one of the tuner suggested in DSports Magazine?

 

I really don't know. Depends on what you car wants to run. That is, how rich can you make it, holding all other things equal, without losing substantial power? Of course, this assumes you have a reasonable timing curve. But honestly, its a two variable equation so you cant just solve for one without solving for the other.
shiv