I really don't understand EGR. I have been told that an EGR duty cycle of over 75% is in error. I had a code 32 yesterday, and today TTS reads that my EGR duty cycle is 100%. Without fully understanding EGR, this data is useless to me. All I know is that it allow exhaust gas to be recirculated into the intake. To what purpose and effect? I have no idea. Anyone?

------------------
408cid 1985 Corvette
http://www.mojosgarage.com

 

They introduce exhaust back into the engine as a way to lower combustion chamber temps. and reduce the generation of NOX (leads to smog formation).

Engines to a certain degree are self egr'ing since the intakes and exhuasts overlap and exhuast by it's having backpressure will slightly dilute the incoming charge. Adding more cam, can in effect add too much egr when using the EGR valve's stock settings.
Yes, you can have a 100% EGR duty cycle. At 100% DC you might be diluting the intake charge 10% at low RPM.

 

Thanks Grumpy!

From a tuning perspective, how much egr is too much? I do have a bigger cam than stock, but not by too much. It's only thrown a code 32 once, and that was yesterday before it started dropping a cylinder! Personally, I think the cylinder dropping has more to do with wiring than anything. I think one of my injector harnesses may have come loose. The car is also notorious for ignition problems. I tell you, it doesn't *want* to run!

 

I don't do diagnostics by mail, so can't and won't say on what you have going on with that.
On the EGR is a matter of what your wanting to do.
In theory, there should be no HP loses by running it, and mileage should be better with it enabled. Trouble is in the real world I've seen neither. If you really want to tinker then start low and watch you TPS per MPH. Less being better, or if higher then must accompany lower PWs, and equal *cruise performance*