I always thought and lets say knew out of experience that the more rich the mixture the cooler the combustion chamber temp, but the hotter the exhaust gas temp, measured lets say at the manifold and vice versa.
SO how can cat overtemp which dumps more fuel COOL the cats and not do the total opposite??
i think i know what your talking about. but i understand it as
advance timing = lower egt
retard timing = increased egt. good for turbos
increase/rich fuel = lower egt
lean = hot = higher egt.
i think you may be right though as i have read that somewhere, but cant remember.
if your mixture is too rich on turbo cars the excess fuel combusts in the turbo housing causing egt's to sky rocket and make spool times non exsistent..
i think i know what your talking about. but i understand it as
advance timing = lower egt
retard timing = increased egt. good for turbos
increase/rich fuel = lower egt
lean = hot = higher egt.
i think you may be right though as i have read that somewhere, but cant remember.
if your mixture is too rich on turbo cars the excess fuel combusts in the turbo housing causing egt's to sky rocket and make spool times non exsistent..
-Carl
exactly, no doubt about the timing part, however the fuel mixture part seems to confuse me.
On my turbo car, when I had a vaccum leak, the ECU was pulling timing, and the car was idling at -3 degrees, the turbos were spooling at idle
the cats are combustion chambers. more unburned fuel that gets to them, the hotter they will burn, hence the overtemp problem.
That's not entirely correct. Catalytic converters are basically oxygen storage and release beds. Oxidation and reduction. They strip CO of the oxygen, plus store any left over oxygen, and recombine it with HC to form CO2 and H2O.
They use the fuel trim swing "rich lean rich lean rich lean" to store excess oxygen when the A/F ratio is on the lean side (numerically above 14.7:1 for petrol), and release it when it's below. When the mixture is on the low side of stoich, the cat goes into reduction mode, and reduces NOx at the expense of oxidation of CO and HC.
When a car is in PE, it effectively shuts down the cats because they cannot process the mixture at the rate it's flowing through the bed. It takes a few seconds, but it can actually be seen in the narrow band O2 sensors. You just have to look at your upstream and downstream voltage. Under WOT after a couple seconds, the voltage will be nearly identical, hence no O2 storage and release.
As for COT protection, my best guess is it temporarily turns them off. You're not dousing them with raw fuel, more like just running an overly rich mixture through.
Does anybody have a chart showing at what temps the ecu starts dumping more fuel? Or is there just a set temp limit that will set off the protection. On the road my a/f at wot is 12.8, on the dyno after 2 pulls my a/f was 10.9. I believe it was due to the COTP.
Does anybody have a chart showing at what temps the ecu starts dumping more fuel? Or is there just a set temp limit that will set off the protection. On the road my a/f at wot is 12.8, on the dyno after 2 pulls my a/f was 10.9. I believe it was due to the COTP.
the usual cot overtemp enrichment is 1.21, so thats 12.8/1.21 = 10.6 seems like that is indeed ur problem.
Corvette Store
cat overtemp, this doesnt make sense to me
