Optimum A/F Ratio for 30psi

[Huecool]

What's the leanest one should go at 30psi? I'm just dialing in my ride and it's running strong at 11.5:1. I've got a big air/water intercooler with intake temps 50F-70F through out the run. At 21 degree timing EGTs are still hot, 1500-1600F @ 8k rpm, with fuel burning out the collectors.

Best so far in the 1/8: 5.11/140 @ 3000lb (my 3nd full pass since putting this thing together, switched from carb/nitrous with consistant 5.50s)

390ci SVO V8
D3R ProCharger
FAST Sequential

Fred

 

[azgn]

I guess you can go as lean as you are brave

11.5 seems to work well with the TR's at high boost (30+) and 28* or so (EGT's 16-1700....so kinda on the edge.....)

 

[BoostKillsStres]

I would imagine your not using any kind of knock sensor and probably can't so careful plug reading is your best bet....tiny black specs on the procelain is the start of bad things going on inside but you probably already know that. I've looked over a FAST log from a 9 sec TR and it had a target of what looked like 11.5:1 and wasn't using a cooler such as yours.

HTH

 

[Huecool]

Yeah, I know a little about molten metal on the plugs

A buddy of mine with a *little bit* more HP than me runs around 12.3:1 at 40psi. But he has plenty of sponsorship and seems to end up rebuilding often....

I'll try to keep it conservative and just plan to make it to as many races as I can, even if I'm giving up some extra HP. That's the interesting thing about programmed blower cars compared to carbed nitrous. It's much easier to get greedy with the juice.

For now I'll leave the A/F alone and creep up on the timing keeping an eye on the EGTs and plugs.

Fred