The lowdown on EGR

[MaineShark]

Actually, that's a request.

EGR tends to be a murky subject. On the one hand, dumping exhaust gasses into the intake sends shivers through the spines of many gearheads. On the other, emissions aside, EGR may help reduce detonation, allowing more agressive compression ratios and timing.

Can anyone clear this up?

I'm considering a new intake, and many performance intakes are not available with EGR. If it really is beneficial, I'll look closer at the intakes which do have EGR provisions (or into modifying one that doesn't). If the benefit is small, I won't worry about it.

Joe

 

[Stallion]

Don't you need to pass emissions, Joe? I know in NJ, I need to pass emissions on post-'74 cars.

 

[matchframe]

I don't think there is much benefit from EGR other than emmisions, but it can't hurt either. If you have to deal with emmisions testing in Maine I would definately look into getting the intake w/ EGR provisions. Where I live, when the car is 25 years old or older, no emmisions tesing required, so I am ditching mine. Just my personal preference.

Bill

 

[Stallion]

Even so, his '79 isn't 25 years old.

 

[matchframe]

Mine is, thats why I am ditching the EGR. :cool

 

[c4c5specialist]

Hi there,
EGR or exhaust gas recirculation is a means of reducing oxides of nitrogen emissions from your engine, other than the catalytic converter that is on your car.
Basically, here is the theory.
Combustion temperatures above a certain threshold produce this gas. The threshold is about 2500 degrees F.
This temperature will occur when fresh air, and fuel are burned.
Now, in order to reduce this temperature, exhaust gas is introduced. This takes the place of some of the fresh air. If there is less oxygen to assist in the burning of the fuel, then the temperature will not be as hot. Thus, below the 2500F threshold, little oxides of nitrogen is produced, so that the converter can clean up the rest.
Yes, it will reduce some power, due to less air producing power.
However, these engines are engineered to run better with EGR, than without.
Allthebest, c4c5

 

[MaineShark]

I ain't worried about emissions. We don't have a sniffer test, and no one enforces the visual inspection.

I'm just curious about what ways EGR might actually help performance by reducing detonation...

Or is it a case where the EGR lets you run a slightly more agressive compression ratio, which gives you a little more power, but ends up costing you a lot of power?

Basically, where is the balance? Is it a good thing, or a bad thing?

Joe

 

[Jack]

Here in SC we don't have sniffer nor visual either ... no inspection/testing at all ... yet. As a result, I've never heard of anyone looking for optimal power-performance that runs EGR. Everyone I know of around here picks CR via piston / comb cham volume/gasket thickness ... with cam also considered.

AFAIK, airplane motors don't have EGR ... power-performance is especially important here too.

For a lotta years, a lotta very smart and experienced GM engineers & techs did not employ EGR to enhance power-performance ... EGR was added only when needed to help reduce emissions-meet emissions mandates. AFAIK ... same applies to all makes.

AFAIK, EGR desireable only when originality/ emissions statutes/ compatibility with other emissions devices / a personal sense of eco-responsibility is at issue.
JACK:gap

 

[MaineShark]

So, it sounds like the EGR is going bye-bye...

Joe

 

[BlackNBlue95]

BTW I dunno if it was mentioned or not EGR is not active at idle or Wide Open Throttle.. so it really doesn't effect performance when your mashing the peddle.. so why remove it? it helps cool combustion temps and helps save gas under cruising conditions... So other then the weight which is probably less then a pound there should be no performance reduction from it.

-Rick

 

[MaineShark]

Yeah, but many performance manifolds don't have EGR provisions, so if I want to keep it, I'd be dramatically limiting my choices. If I happen to find a manifold that I like, which has EGR, I'll keep it around. But I'm not going to look at that, when choosing.

Joe

 

[KANE]

You can.... if you are really good.... cut out the old portion off another manifold and TIG it in. I have seen that done before!

 

[c4c5specialist]

Hi there,
The best reason, in certain instances, is that you can increase ignition timing based on compression.
This increase on ignition timing will increase power, without the fear of detonation, commonly found on high compression engines.
An example, if I may, is my 84 Monte Carlo SS.
406 CID, Edelbrock Performer intake, cam, and heads.
Now, EGR is there.
Compression is about 10.3 to 1. This would lead to horrible detonation, and a 12 degree reduction in timing under lead in throttle below 50%.
The EGR, which is fully functional, added 15.7 ft lbs of torque at 2400 rpm up to 25.4 ft lbs at 3800 rpm, at 50% throttle angle.
Horsepower was up 10 at 2400 and 17 at 3800.
With the EGR disabled, knock retard was up, and power lost.
There are always reasons to EGR, knock retard and power.
The key is to understand where and when in the powerband it is most effective, and to utilize it.
As Blackblue has eluded, the EGR will never function at WOT, as power enrichment will take this out of the equation. Carbs have the power circuit, and injected vehicles have the power enrichment capabilities.
So, with that, just a little info on how and why of EGR.
Allthebest, c4c5

 

[MaineShark]

Hmm... so we have arguments both for and against EGR.

I think what I'm going to have to do is to remove and plug the EGR hose and port, and see what happens. If I don't get pinging, I'll say "bye-bye." If I do get pinging, I'll have to figure a way to keep the EGR functional.

Joe