I just check my AFR's using this method with fully warm engine.
Quote:
Proper AFR calibration is critical to performance and durability of the engine and it's components. The AFR defines the ratio of the amount of air consumed by the engine compared to the amount of fuel. The turbochargers increase the density of the air resulting in a denser mixture. The denser mixture raises the peak cylinder pressure, therefore increasing the probability of detonation. As the AFR is leaned out, the temperature of the burning gases increases, which also increases the probability of knock.
As a protective mechanism, the ECU is designed to make the AFR richer, reduce boost, and/or retard ignition timing to prevent catastrophic detonation, but also diminishing performance. These parameters need to be optimized to give the best performance with a margin of safety for the engine.
Rich versus lean, why lean makes more power but is more dangeros
A stoichiometric AFR has the correct amount of air and fuel to produce a chemically complete combustion event. For gasoline engines, the ratio is 14.7:1, which means 14.7 parts of air to one part of fuel. This ratio is dependent on fuel type-- for alcohol it is 6.4:1 and 14.5:1 for diesel.
Durametric reports lambda - a percentage of AFR based on the stoichiometric ratio. To report the proper AFR from Durametric, multiply the pre catalytic actual lambda by 14.7. For example, a lambda of 0.78 gives a AFR of 11.47:1 (0.78 * 14.7 = 11.47.)
In general, a lower AFR number contains less air than the stoichiometric AFR - hence the mixture is richer. A higher AFR number contains more air and therefore it is a leaner mixture.
For Example:
15.0:1 = Lean
14.7:1 = Stoichiometric
13.0:1 = Rich
A lean AFR results in higher temperatures when combustion occurs
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Bank 1 Idle 0.98 = 14.406 AFR @ 4k RPM 1.01 = 14.847 AFR
Bank 2 Idle 0.96 = 14.259 AFR @ 4k RPM 1.02 = 14.994 AFR
Not bad, a tune would help or the computer needs more miles put into it, less then 100 miles since the upgrade, but like I said, the tune will be done after my exhaust upgrades and I'll be changing over to the 987 MAF housing and larger pipping.