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I've been challanged with a bit of a problem, but let me first tell you on what engine it's happening.
5.7l LT1 Corvette V8 equipped with a Vortech supercharger and some cams.
The specs of the cams are attached.
Well, the customer wanted to pass emission testing and therefore purchased a pair of 400cpi ceramic catalytic converters for his car.
Basically from the dimensions, they should support around 350hp on a 3.0l engine, which per bank should be sufficient.
Exhaust is 76mm pipe diameter for each bank.
Anyways, I tried to dial in the idle areas in the ECU first, before heading over to the dyno bay.
Well, it turns out, that whatever I do within the software (wether it's ignition timing, fueling, injection angle, or idle rpm), soon after the car has started and warmed up, the cats start to glow really really red and hot.
I could make sense out of it, if unburnt fuel passes through the manifold and starts to ignite within the cat, BUT the EGT shortly after the exhaust ports is around 450-480°C.
The pipe just after the exhaust manifold is around 200°C (measured with an infrared sensor), and the cat itself has around 500-600°C and is red like an apple.
It's idling at around 800rpms and close to lambda 1.0. Actually it moves around within the range of 0.98 - 1.03.
What can be the cause of it?
I'm already thinking that the cam or cam timing might be off, causing injected fuel to pass unburnt through the opened exhaust valves.
Any ideas or thoughts on that?
what is your ignition advance at idle and what plugs are you using
Anything from 10 to 22 deg will make that happen. Although the car idles pretty unhappily at anything lower than 11 or 12 deg. ... you can feel that it wants more. I can see a difference in the exhaust manifold temperature, but the cats will always start to glow after a bit.
Plugs are NGK TR7IX
it's sorted ...kinda.
I talked to the cam manufacturer today and we talked about more detailed specs of that particular cam.
Well, with that Setup we wont have much luck running a cat, so I guess we'll have to trick somewhat :)