Here’s one for andre’s area of expertise

so I will be tuning a 4g63 sprint car with race fuel I intend to use renegade hr102 as the msa don’t allow octane over 102 long story short Andre given your history with the engine I’m unlikely to be knock limited so how advanced timing do you think I could get away with before I’m at risk of head lift from excess cylinder pressures engine spec is

2.3 liter stroker +1 oversized valve his 280 cams

wire rang head stock mls head gasket arp l19 head studs torqued to 95ftlb currently 535hp 530ftlb on 98oct pump fuel I intend to throw in a extra 10 degrees of timing

thanks in advance for any advice

Hi Dan, first up it's a little hard to give you recommendations on ignition advance without knowing what sort of boost you intend to run or what your CR is. Ultimately on our drag engines I had the head sealing to a point where we would run to MBT in the higher rev range, however I would purposely keep the timing conservative around peak torque where we would be seeing maximum cylinder pressure. Where as I'd use 14-16 degrees through peak torque and maybe 26-28 at 8-9000 rpm with 40 psi boost, what you can use may well be different sadly. It really comes down to how well your head sealing is working in the first pace.

Thanks Andre I only intend on running 30psi the small Gt3076 seems unable to maintain more on this 2.3 and being a weekly used sprint car I need to find an extra 100hp as safely as it can be done I am already running 30 psi but with very conservative timing it’s been doing 510hp and 530 Ftlb at the flywheel for over a year without fault and driver wants alittle more now

With a turbo that size I doubt you really shouldn't have too much trouble with head sealing as it's a pretty modest sized turbo. We really only started seeing issues once we stepped up past the 700-800 hp mark.

Thanks Andre at the min we have 510 and 530ftlb at around 31 psi of boost but as it’s a 2.3 this turbo runs out of flow at around 5700 and the torque dies off along with boost pressure so the goal is to run the race fuel and lower the boost to a maintainable level right through the Rev range and try keep the power and torque up from running leaner with more ign advance I will be trying to get as close to 10 degree at peak and run up to the high teens at maybe .800 or .820 does this seem a safe afr for sprint use