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Originally Posted by Claudius
Hi there
Long time no speak ... 
Regarding the ignition advance settings, while you're right in practice on lowly tuned cars, IMHO the "correct" ignition advance setting depends on a bit more than whether the car detonates or not.
You mentioned combustion chamber pressures. As you know, the more you advance the ignition, the leaner the fuel mixtures and the higher the boost, the higher the combustion chamber pressures.
All that to say that, even if you may well run 30 deg of timing in the high rev range at relatively low boost levels like the afore mentioned 1.2 bars relative, you will certainly make a few more hp, but also run much higher combustion chamber pressures and have less reliable an engine.
What's the 93 / 91 in the O2 column? Lambda values ie. 0.91 / 0.93 lambda ie. 13.4:1 or so AFR?! |
Hey Claudius,
About timing I was speaking in terms of tuning with an AFC and it's indirect effect on timing. If you actually have
control of your timing it is a different story
Best way to adjust timing in a system where you have direct control is to use a load bearing dyno, and adjust timing until you see torque start to drop off... that is for max power, and you can take all those settings and back it down 3 deg or so at each point for a daily drivable tune.
About the O2 reading they are talking about, that is the voltage being read from the stock O2 sensor. The sensor reads from 0 to 1 volt and is only really acurate at stoichiometric ratio so any reading from it should be taken with a grain of salt. Anything above .93 is really rich, below .90 is pretty lean (for WOT operation)... but unless you have had your car data loged while on a dyno with a wide band O2 sensor you never really know exactly what those voltages equate too.
Keith
