1994-2002 [Subscribe to Daily Digest] |
Most N/A engines will run rich at WOT (wide open throttle). This helps avoid knocking and keeps temperatures down. Yes, this generates elevated CO levels, and the cat converter cannot do anything about it. As the mixture is rich, the cat converted does not have enough oxygen in the exhaust stream to work with. The first stage in the cat will convert NOx compounds into N2 and O2, but not under these conditions.
Turbo engines also run richer at WOT and for all levels of boost.
So when running rich, the O2 sensor does not resolve well when there is little free O2 to measure. So the systems go open loop, and are mapping rich against estimated mass flow.
Also, with WOT or near WOT the engine speeds and mass flows are changing so fast, that the O2 sensors might have a problem with time lag and not be useful for that reason as well.
When at moderate throttle conditions and steady state, the O2 sensor's signal is used to compute a correction factor which can be used to bring the O2 sensor's voltage level to the not lean, not rich balance point. I would think that these correction factors would be stored in a map, so that a different correction factor was available for different operating ranges.
The trionic also monitors the conditions in each cylinder and is, I believe, able to fiddle with mixture and timing differently for each cylinder.
But, all said and done, the DI/trionic engines do run their best with clean injectors and with plugs in good condition.
These systems are very adaptable and you don't need to worry about getting new ECU mapping when a new exaust system is fitted, (as with other makes).
The three wire O2 sensors will last well into the 100,000's of miles.
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