Quote:
Originally Posted by puddleglum
But, my intent was not to suggest that we should wait till the coolant is warm before driving, just that we should use whatever means available to get the engine/drivetrain up to temp. and use the SG to monitor it.
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I don't disagree, I am just noting that, in this case, OBD-II is not particularly helpful. For example, we have ECT, which is a very crude indicator of actual head temp, and IAT, which is generally beyond our control.
Quote:
Originally Posted by puddleglum
Most new cars with heated O2 sensors will drop into closed loop very quickly, long before the engine is warm, so the Cl Lp guage doesn't seem of much value to me.
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I have to disagree, I think it is a very good indicator of what the ECU thinks is going on in the actual cyls. Remember, a heated O2 sensor is basically heating a small bit of zirconia, essentially a ceramic thimble or waffer, to, say, 750 degC.
The ECU won't even start heating the sensor until it is reasonably certain that moisture is cleared from the exhaust, because a droplet of water will shock cool the ceramic and dramatically shorten sensor life.
The same is true with unburnt fuel. When the engine is cold and intake air is cold, the points are generally out of temp range, which is surprisingly narrow, so there tend to be misfires. Also, when the intake air is very cold, you tend to get partial condensation from the charge. So the ECU waits until all indications are for flame front temps within range and normal valve action - ie, an engine top end that has achieved a suitable operating temp.
Another reason I am a big fan of knowing when you are OL is it is a spectacularly dirty, environmental wise, condition. Cat efficiency is narrow anyway, but when you dump rich, the cat floods with CO and efficiency basically drops to 0, sending out huge spikes of NOx, etc.
Something we are working on is a much more durable O2 sensor. The idea is that you don't have to wait to heat it up, but could start it heating when the door opens or the key goes in the ignition. This doesn't solve the air charge issue, but it helps solve the pig-rich-zero-cat-efficiency intervals.
-jjf