Quote:
Originally Posted by greasemonkee
Are you sure about this? Haven't studied too much into the D15Z3 operation, but both engines have the wideband. An ecu must hear knock before it can retard timing and honda's knock boards (at least the OBD 1 versions) were the equivalent of silicon excrement. I find it difficult to believe any manufacturer would intentionally set a system up ignition and timing wise to operate at the mercy of the knock sensor which would need to hear detonation in order to maintain efficient fueling. Once detonation does occur, air/fuel readings (via the O2) will go lean and skew the fuel trim. If this were the operating principal, it is often difficult to achieve detonation at low manifold pressures. It would be likely that in the instance of leaner than stoich operation, if continued to be leaned out, flame speed would become increasingly slower until misfire would ultimately set in without a whisper of a knock. Besides that, all detonation isn't audible nor detectable by a piezoelectric device, there are levels of detonation - detectable or not, it still is a hindrance to power and economy.
This is theory, but stranger things have been known to happen in the real world with engineers.
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I could be wrong, and i haven't studied them either, but don't these lean burn engines all have LAF (Linear Air Fuel) Sensor systems? They can detect how lean the burn is, and then run at 16.0 AFR? If they ran much leaner then that the EPA would refuse to license it on account of the amount of NOx they would produce.