Nistune Forums

Hi Guys,

I have an R33 GTS-T Series 2 (RB25DET) which I am going to tune on 100 octane fuel from United (10% ethanol, 90% 98 octane petrol). I'm just curious as to whether anyone has some advice/experience regarding target AFRs (entire range, based on petrol lambda would be great). Car is being used for track use - hence I mainly want to run this fuel for the slight knock protection benefits. E85/flex will be my next upgrade.

Also if anyone knows how consistent this fuel is so I can judge how much of a safety margin I put into the timing if needed.

Thanks in advance!

for real track use,specially in hot amb.conditions, I wouldnt mess with AFR with this fuel,which is quite common anyway. I would target to 11-11.5:1 at full boost/high load. Use ign.timing trimming to get som more power from 100 oct.fuel.

I'd be tuning around 11.5:1. Give yourself a good safety margin in the IGN maps (keep well clear of knock threshold) as it's a track car.

It's also important to make sure your cooling system is up to the task for track cars. They'll go fine if coolant temps are kept at safe levels but some guys let them get too hot on the track due to poor cooling systems and then you'll still get detonation even if your AFR's and IGN timing were good on the dyno.

Consistency of ANY pump fuel can be an issue. It always worries me when I read "May contain up to xx% ethanol" at the bowser. That could mean that it has no ethanol at all! It varies from season to season. So be careful. I'd be going flex fuel ASAP. Or at least get an ethanol content display. E10/E85 is wonderful stuff but you need to know how much ethanol is actually in there.

PL