doesn't knock but anyway, isn't it lean ?

p.s. 98 RON (93 for US rating I guess)



hosting images

 

if the timing is good, no.

Rally cars that we have tuned run as lean as 13.5:1 without major problems.

Other people would say to tune to about 11.5:1, over to you though.

 

theres no advantage to you running this lean ,only the risks.

 

Personally I'd bring it down to at least 12.0 for safety's sake, to make sure EGT's stay in check

So they only have minor problems? Just playing with you!

 

Generally you want to start with fuel rich and timing low, set your boost then set your afr then add timing until you get knock or stop gaining power. I run 12 - 12.2 afrs at the same load (~250) but my load is peaking a over 290 (where I run 12) also looks like I am running a bit more timing but I'm also using methanol injection.

By this procedure your basically setting your fuel to a target and then using timing to tune. Lean mixtures burn quicker than richer mixtures so the leaner you run the less timing advance you can run, the richer you go the more timing advance you can run. Thats because what your actually changing is how fast the flame front in the combustion chamber moves either through fuel or timing you'll probably reach the same power. HOWEVER if you go a little richer that extra fuel absorbs heat (not very well) and excess heat in the cylinder is what can cause pre detonation (read knock). This is why alot of people choose to run 11.5 and just run more timing.



I could stand to richen it up a bit and have considered it but the car runs great as it is. In my opinion if your not knocking your probably ok. Generally peak power occurs at 12.5 afr and anything richer than that is just using fuel for cylinder cooling (read safety). If your not knocking and you don't want the added cushion then go for. I was running 12.5 at spoolup for a while but decided I wanted a little safety margin.

Here is a log if you want something to compare it to.




Hope it helped.

 

depends where the wb o2 sensor is on the pipe etc, but 12.6 sounds lean.. id drop it into the 11's.

 

^
good catch, O2 was in tailpipe

thanks for advices guys