EGR Elimination
Racer
Joined: Oct 2011
Posts: 318
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From: NP Nebraska
Anyway, I have searched for spacers everywhere. I can find them for Corvettes but only listed up to fit in vettes up to '79. Is there some difference, other than those that differ in diameter, that would cause them to not fit all the C3 stock exhaust manifolds?
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From: Corsicana, Tx
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Thanks for bringing this useful topic back to the top!
I have not read such a concise clarification as given by Jim in #6
Only one question about the knocking: If the standard timing curve still is in operation, why should knocking become an issue? After all, the EGR operates That being the case, why then knocking? That does not happen at light loads? Or?
Also a nice explanation about the 'stream of exhaust gases through the inlet manifold casting, heating up the intake, by partially shutting off one of the exhaust pipes by means of the heat riser.
Cor
I have not read such a concise clarification as given by Jim in #6
Only one question about the knocking: If the standard timing curve still is in operation, why should knocking become an issue? After all, the EGR operates That being the case, why then knocking? That does not happen at light loads? Or?
Also a nice explanation about the 'stream of exhaust gases through the inlet manifold casting, heating up the intake, by partially shutting off one of the exhaust pipes by means of the heat riser.
Cor
The pinging will usually happen under those light throttle and *tip in* conditions. Since the original calibration of the timing curve included the EGR adding exhaust to dilute the mixture and lower cylinder temps...when we remove the EGR the cylinder will get a lot more full of good stuff that will actually burn and make power. In some cases the cylinder pressure gets a little high and you can get a ping. Not always though...those engines had such low compression they can usually do OK...just wanted to point it out in case it happened no one would freak out. If it does, we just recurve the distributor, or play with vacuum advance as needed. Usually more initial timing with less vacuum advance really wakes these engines up.
On the exhaust control valve..if you don't necessarily want headers and want to just remove the valve action, you can gut the flapper out of it and just use it as a spacer.
JIM
Racer
Joined: Oct 2011
Posts: 318
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From: NP Nebraska
On the exhaust control valve..if you don't necessarily want headers and want to just remove the valve action, you can gut the flapper out of it and just use it as a spacer.
Or you leave it in position, and lock it in the fully open position; remove the vac.line and or the control rod.
Cor
Or you leave it in position, and lock it in the fully open position; remove the vac.line and or the control rod.
Cor
Last edited by myko; Nov 28, 2011 at 12:20 PM.
Racer
Joined: Oct 2011
Posts: 318
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From: NP Nebraska
Another question on the topic.
I realize the purpose of the EGR is to decrease NO in the exhaust by recirculating exhaust into the intake. How does this affect gas mileage and fuel efficiency? It dilutes the mix so it can't help gas mileage unless the exhaust will still burn with some addition of power. I know that it doesn't affect power at WOT b/c the vacuum is lost and the valve is open but how does it affect mileage at highway/cruise speed?
Race Director
Joined: Jan 2000
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From: Corsicana, Tx
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EGR does not help fuel mileage at all. It takes up space in the cylinder that could be filled with a strong fuel mixture that will burn and push the piston down...even at part throttle.
JIM
JIM
Racer
Joined: Oct 2011
Posts: 318
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From: NP Nebraska
Right, so you have to keep the throttle down a little more to keep the same power being generated. I was just curious if you end up mixing more, less, or the same fuel with the exhaust to run at a steady speed. I was hoping for a real world example of someone who monitored gas mileage before and after removal? Or even a study from a tech school?
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Drifting
Joined: Aug 2009
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From: Enid Oklahoma
Right, so you have to keep the throttle down a little more to keep the same power being generated. I was just curious if you end up mixing more, less, or the same fuel with the exhaust to run at a steady speed. I was hoping for a real world example of someone who monitored gas mileage before and after removal? Or even a study from a tech school?
Drifting
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From: Lewisburg WV
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From: CORVETTE 77 385 C.I. TEXAS
Racer
Joined: Feb 2004
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From: Denville NJ
Resurrecting this old and good thread with question to those in the know.
When idling at operating temp is the EGR valve open or closed? At these same conditions is there a vacuum draw from the carb or only at higher RPMs.
After 20 yrs my 1976 can't seem to pass the NJ hydrocarbon emission test out of the blue.
Checking out all the normal culprits.
Thanks
When idling at operating temp is the EGR valve open or closed? At these same conditions is there a vacuum draw from the carb or only at higher RPMs.
After 20 yrs my 1976 can't seem to pass the NJ hydrocarbon emission test out of the blue.
Checking out all the normal culprits.
Thanks
Le Mans Master
Joined: Oct 2007
Posts: 7,445
Likes: 971
From: Tennessee/Rhode Island
Its not rocket science. Exhaust gases don't burn very easy since they are low in oxygen. The fact that they take up space that could be used for the good stuff makes the case that with out the gasses the mix is better. A better mix is more efficient. An engine that gets a good tune up gains power and mileage, same theory here. There is a line where to increase HP you sacrifice MPG, but in this small case you increase volumetric efficiency with the mixture and increase both power and MPG, but neither by a substantial amount.
Le Mans Master
Joined: Oct 2007
Posts: 7,445
Likes: 971
From: Tennessee/Rhode Island
Its not rocket science. Exhaust gases don't burn very easy since they are low in oxygen. The fact that they take up space that could be used for the good stuff makes the case that with out the gasses the mix is better. A better mix is more efficient. An engine that gets a good tune up gains power and mileage, same theory here. There is a line where to increase HP you sacrifice MPG, but in this small case you increase volumetric efficiency with the mixture and increase both power and MPG, but neither by a substantial amount.
Instructor
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From: Pensacola FL
Advanced
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From: Linköping
Burning Brakes
Joined: Mar 2014
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From: Crestline CA
I love the tree huggers who calim that an EGR valve is good for combustion, cools the incoming mixture, doesn't effect mileage, and certainly has no effect on power production....yea right....Its common sense and basics physics, both of which are often lacking. Get rid of the EGR valve unless you must have it for emissions inspection...then block it.
The EGR valve is truthfully a great device. Think about it, that simple device allow your engine have variable displacement and a variable compression ratio, pretty impressive for such a simple, reliable device.
Once you start to understand how a EGR actually works you begin the realize that on a otherwise stock engine there is no reason to remove it.
Drifting
Joined: Apr 2008
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From: Lewisburg WV