Tuning with a/f ratios

[FullAuto]

How much does the a/f ratio effect the dyno tune? I know that's pretty much everything you're going for. But if it's off, how much does correcting it give you in terms of rwhp/rwtq?

I made 2 dyno pulls Saturday. I took it to have a chip burned to correct my problems. The first pull, it went off the chart within 50rpm (Yes 50 not 500) and never came back on the chart. I think that's when it pretty much started registering. BTW, the chart read down to 10:1. And this wasn't an "off" reading. With my combo and the way it was driving, this was overly obvious.

Then the chip was burned. The 2nd pull, it took ~200rpm for it to go off the chart this time. The pull only lasted just over 600rpm though because the car got real loud and the a/f reader went crazy. They thought I had blown a head gasket. It turned out that I blew a 4" piece of header gasket out and #3 and #4 were basically open head. They wouldn't do any more pulls because the header gasket caused them to get non-accurate readings.

So I only got 2 pulls in and he couldn't make any more changes to the chip. I was told it would take several pulls to dial in the a/f ratio. On the 2nd pull it picked up a little rwhp and >15rwtq compared to the previous run's peak numbers and this was at a lower rpm when it was obviously rapidly climbing before it was shut down short.

Anyway, after all that, the numbers still weren't too bad considering... So what kind of gains in terms of actual numbers or percentages could be gained by getting the a/f dialed in. Leaner's Meaner, right?

[fanglemeister]

It varies widely. Max power tuning means taking the temperature of the fuel in the chambers right to the edge of self-igniting without actually getting there. If your compressed (93 octane) fuel is reaching @ 800 degrees or so before your sparkplug lights it off, you will get detonation. If you are running big boost, you are now adding 150 to 200 degrees to the ambient air temp being mixed with your fuel, so you have to inject extra fuel to help cool things down again.

In very general terms:

11.5:1 = rich limit best torque
12.5:1 = safe best power
13.2:1 = lean limit best torque
14.7:1 = stoichiometric (no O2 or fuel left after burning)

Adding boost will require more fuel to suppress detonation, unless you are running a very efficient intercooling system (and I see in your sig you have H20, so you may get away with mixtures very close to these). I have seen some high-boost (20+ psi) apps running mixtures way down around the 10.0:1 range to keep the headgaskets intact.

[FullAuto]

It made 14psi on the first pull and 13psi on the second pull when it was cut short.