Monsterbox

Can you guys please give me some feedback on this situation. I took my car to the dyno for a few runs at different boost levels on the preset maps for my PFS Purple ECU.



@ 10lbs car produced 254RWHP with 11 AFR, taking out fuel at 5.5k up to 11.5AFR Produced 270RWHP!



Is it safe to run 11.5AFR...what IS the actual IDEAL AFR for twin turbo FD...does the ideal AFR lower as you increase boost?



For ex. at 15PSI and a 10.5AFR the car only produced 325RWHP...Im sure tuning to 11.5 in the powerband would yeild at least 335





and lastly,



my charts, especially the 15lb run, show really lean mixture at the beginning of the rpms...like 3500rpms at WOT show 13.5!!!!!! (15lbs of boost here)....but the afr slowly drop to the transition and hold 10.5 to redline...is this correct for all boost levels on the twins?



There is no information out there showing the ideal afr curve for stock twins...

j9fd3s

imo i wouldnt go leaner than 11.5 on the stock twins, and at 15psi it should almost be as rich as you can make it.



you need the extra fuel to keep the motor together, its worth giving up the 10hp

Monsterbox

so should i tune all boost at 11.5? is this like PUSHING THE LIMIT or is it completely safe? if im doing track runs should it be at 11afr instead of 11.5? and are you saying i should lower the afr more to 10.5 at higher boost? is there a method to this..like 12LBS=11 AFR, 13=10.5, 15=10lbs for safety or something?



and what about he beginning of the rpm curve...should it be a straight line afr or a curve from high 13.5 down to steady 11.5?

j9fd3s

it depends. if you're drag racing 11.5 is fine, if you're doing top speed runs, or road racing it might be lean. you're running it richer than best power because you're using the excess fuel to keep the inside of the engine cooler. if it gets too hot in there, it will go into preignition, and pop.



less boost = less heat = less need for excess fuel.

Monsterbox

thank you for the tips I will be tuning my 10psi map for 11 afr..better be safe than sorry and as i increase to 13-15psi ill take it down to 10.5 as turbos generate a higher IAT at this level (correct?) good idea guys?



please look at this graph and tell me if the low end is incredibly lean? I should not be making 245hp at 3400rpms!....and up top the boost controller was freaking out explaining the wave effect

j9fd3s

that chart looks ok, id add a bit more fuel down low, and then work on the boost curve