EGR what we know?

[Pat]

I had my EGR valve turned off by my Predator tuner a few days ago, mainly because other people do. I don't have any idea what EGR does or how it affects the engine.
While discussing this "Tune" with a mechanic friend he related the importance of the EGR valve and how different manufacturers use this device in emmissions control, cooling control, detonation contol, cylinder temp control and so on.
I just nodded my head like I understood. But the jest of the matter is that turning off your EGR is bad. For short drag strip runs he felt the engine would be unaffected. I'm turning mine back on until I learn more about this little but important mechanism. Comments?????

[Constable]

All that is true. PLUS: If the EGR is shut, you'll probably burn the cats out of your car within a few months. Very pricey.

[RF Overlord]

Pat, everything your mechanic friend said is correct. It's not a good idea to turn the EGR off...

EGR= Exhaust Gas Recirculation...it recirculates a small amount of exhaust back into the intake manifold...

[Krytin]

In the past, Ford has used the EGR to dilute the intake charge making it a little less volatile. This had the effect of allowing more total timing w/out detonation - something like 60 degress full advance! At least that's how it worked in '78. I have no idea how the tune is set up in our cars.

[duhtroll]

I have to have the EGR module replaced in mine. Good thing I read this. I was told "yeah, perfectly safe to drive - no problems" while I wait for parts.

I'm not driving anywhere unnecessary for a couple.

Gotta love this board.

-A

[metroplex]

Here's the deal:

EGR in the old 70s and 80s Fords with the 302/351 intake manifold will coke the engine oil that touches the EGR passageway that runs under the carb plenum.

EGR does recirculate the exhaust gas, but right into your intake charge.

Keeping EGR on reduces NOx significantly and increases gas mileage slightly. If you want to pass emissions, DO NOT TURN OFF EGR. Your NOx will be sky high, sort of like a faulty EGR or choosing the wrong orifice adapters on the older EGRs.

EGR is not active when idling or going WOT. EGR is only active when cruising up to about 3000 RPM.

In order to properly disable EGR, you will need to turn it off in the PCM, plug the exhaust port for the EGR pipe, and block off the EGR hole in the upper intake elbow. The "everyone does it" mentality is indeed prevalent among the Mustang owners, but that does not mean it is right.

I suppose if you wanted a cooler air charge at cruising, you could physically disable EGR to prevent hot exhaust gas from flowing into your combustion chambers. The PCM controls the EGR transducer which controls the vacuum for the EGR valve itself.

But disabling EGR by itself will not destroy your other components. Your exhaust will not "burn up" due to disabling EGR assuming you disabled it properly and blocked off all opened holes/ports.

[Warpath]

I'll add that EGR (and other additives such as water injection) lower the combustion flame temperature. Anything that is added that does not burn absorbs some of the energy created from burning air/fuel (i.e. energy is used to increase additive temp instead of flame temp). Therefore, flame temp goes down. When flame temp goes down, the chances of preignition/detonation go down as well. Therefore, timing can be increased. The disadvantage of adding EGR is that it takes the place of air/fuel and decreases the total amount of energy production possible. Sometimes timing can make up some or all of that loss plus the added benefit of improved emmisions outweigh not having it. In order to get the full benefit of deleting EGR, you need a retune to take advantage of the additional air/fuel and to make sure timing doesn't cause preignition/detonation.

I've heard someplace that the ECU monitors cat temp and, if it gets too high, it will add more fuel to cool them off. I don't know what vehicles and when it was implemented and I'd expect a code to be thrown. But, the point is that an MM may protect its cats.

Deleting EGR is not very popular amoungst the Mustang crowd - at least what I've seen.

[fastblackmerc]

I've heard someplace that the ECU monitors cat temp and, if it gets too high, it will add more fuel to cool them off. I don't know what vehicles and when it was implemented and I'd expect a code to be thrown. But, the point is that an MM may protect its cats.

Deleting EGR is not very popular amoungst the Mustang crowd - at least what I've seen.
I thought that if you richened the A/F mixture, more unburnt fuel would cause the cats to work harder making them hotter? Had a cat "cherry-red" once because a plug wire was disconnected.

[Warpath]

I'm not sure how it works. I know running lean increases exhaust gas temp which would cook the cats. So, running rich would lower exhaust temperature. I know running too rich can clog the cats. I've never heard of running too rich increasing cat temp. You may have burnt up your cat because without a plug wire, the engine was dumping unburnt fuel into the cat. It would burn inside the cat and increase temp.