ignition timing and A/f Options

[ncgalant]

Alright, lets get down to it. I'm looking for power. Given that, which is better, a little richer and more ignition timing, or leaner and less timing? Currently I'm working toward the latter, but want some input from some that run fast.

Also, which is better for spool, lean or rich. I can't get my pre-boost #s into the rich range. If I do a 3rd gear pull from 1500-6500. My O2s will read .08 until 3500 or so when they jump up to .8 and then .9 around 4000. My setup is working, but I want it to be the best it can be. I can post up my SAFC settings if you guys want too. Their F'd up.

[natedogg]

I don't know that there is any right or wrong way as long as what your doing is safely making power. In my mind and according to my buttometer, the more timing the better, but YMMV. The ECU will start pulling the timing on its own when it gets dangerous because it sees knock. If its not seeing the timing getting actively pulled during a run, the engine's probably not knocking (2G ecu guessing here).

There is a value stored in the ECU called the octane value. This value changes over time based on the amount of knock the car has seen over a long period of time. If this value is FF (highest value on the 8 bit hexadecimal scale), according to the ECU, the engine is running no knock over time and will give it the most possible timing at WOT, limited of course by the amount of airflow (load) that the ECU is registering. Conversely, if it is 00 (lowest value on the 8 bit hexadecimal scale) your ECU is going to give the engine the least possible timing, probably just enough to keep the car running. The other knock value is much more dynamic and affects the timing in realtime. This, of course, is what you see on the logger screen when the timing is pulled during a logger run.

The reason I can run 30 degrees of timing advance and 13.5:1 AFR and not fear that I'm going to destroy my engine (beside the rods being asked to handle too much power ) is because I'm not knocking. Even if I were, the ECU would help me out by pulling that timing away from me until I make the necessary adjustments. Running that high timing and that lean without knock tells me that my engine is using all the fuel available to it every combustion stroke to make as much power as it possibly can. Its efficient, safe power production.

We don't have direct control over the timing that our ECU gives us, unless we run a standalone ECM. The only thing we can do is fool the stock ECU by dampening the airflow signal to it with piggybacks like the SAFC or the MAFtranslator. This obviously will indirectly lead to more timing, but like I said before, if the ECU sees a lot of knock over time or even actively during a run its going to take that timing away from us anyway. I've seen it happen both ways. Marcus's car even when it wasn't knocking, would only max out at about 15 to 16 degrees of timing because his ECU's octane value was low from many knock happy runs. Whereas, my old fwd would max out around 20 to 21 degrees when not knocking because I didn't tune to allow as much knock over time and many runs. These were both nearly stock 14b setups.

This is my approach at tuning and it seems to be working pretty well for me. But, I know everyone does it their own way, so take it for what its worth. I just know its hella fun to be able to click a few switches, press a few buttons, or turn a knob to take a few tenths off your ET or make a few more hp on the dyno all while monitoring your engine's health with the logger.