My ASE Master Certified shop teacher today (in my advanced class, we were discussing OBD II stuff and egr valves came up)...he said that removing that egr, or if its faulty, will raise the exhaust temps and will cause detonation under light throttle. I know this true because I ready it straight out of the study book for the ASE tests, but on a rotary, why doesnt this happend? And why remove, unless you had plans to rid of the vacuum harness completely? And IF removed..how come detonation wont occur under the conditions described on the piston motor?

 

usally on our cars the EGR goes bad because 1. its very old and 2. its sitting right on top of a hot *** engine crammed under a lot of stuff...and anyway on the S5 they removed it anyway....
I don't know about the detonation though???
let the experts explain that part!!

 

ima waitin...hehe.

yeah my buddies tII engine didnt have the egr...

 

On modern cars (with piston engines),
the risk of detonation is high when the engine management systems asks for EGR flow but doesn't get it (due to a faulty valve).

This is because the ECU must take into account the EGR flow into his calculations for spark advance and injection duration.

If EGR flow is high (high-speed cruising), then the ECU is supposed to advance the spark and reduce fuel injection duration to account for the large amount of exhaust gases coming into the chambers.

As you can easily see, severe detonation may occur if the EGR is faulty and there is actually no exhaust gases coming in.

Now, if the ECU does not take into account the actual EGR flow (no advance and/or injection duration change), having a faulty valve may still lead to detonation but I think there is much less risk.

As for the rotary engine,
I don't know why it is not such a problem but that's an interesting question.

Hugues -

 

other input?

 

I have my EGR removed. no problems at all. Rotary engines have more or less a built in EGR mechanism, so the valve is not necessary.

I also live in a state where emissions are required and I passed the NOX test 0.43 out of 1.5 max!

It's worth it to remove if it's its old because eventually it will cause a vacuum leak. It isnt needed at ALL so just give yourself peace of mind and block it off

 

On the RX-7, removing the EGR will have no damaging consequences. The rotary has a large "natural EGR". As I recall, the 89+ cars don't even have the EGR valve (though I could be wrong).

 

thanks alot!