My daily driver 2000 LM7 5.3 has EGR, and I'm thinking about taking it off. I've heard this can improve HP a little, since the EGR puts burnt fumes (and less Oxygen) back into the intake, which makes sense. But... he also said normal gas mileage will be hurt because it will use more fuel to combine with the increase in "burnable" air it's taking in.

What are you guys experiencing, who have deleted their EGR systems, with mileage changes? Thanks.

 

I deleteted it but may be putting it back on as mpg did go down..I just couldnt bare the thought of nasty exhaust in my PRC heads ot TBSS intake...stays much cleaner with egr deleted and a pcv catchcan..

 

I have not heard of EGR having an affect on fuel economy, and figure that if it did, tuning should cure it. EGR will help decrease cylinder temps though, which may allow you to get more HP by leaving it installed since cooler cylinder temps = more ignition timing is possible. Once you install a bigger cam with more overlap, it will have a natural EGR effect, and bring your dynamic compression ratio down, which may negate the "need" for EGR. GM deleted on their own when they found other methods to lower cylinder temps without the need for EGR.

 

Since an EGR system is only active during high manifold vacuum such as when cruising and isnt operating when at WOT, it doesnt affect WOT performance.

I have heard that it does affect fuel economy because it injects an inert gas into the engine in effect reducing the amount of a/f mix the engine needs.

Most EGR vehciles have their own EGR timing tables.


My 97 certainly lost some mileage when I dropped EGR.

peace
Hog

 

Mine stayed the same 15.5

 

I totally disregarded that the EGR is not operational at WOT, so it will not allow for timing adjustments like I mentioned above, good call Hog.

This is the first time that I've even considered EGR's affect on fuel economy though, yet it does make sense. Still, I believe that if EGR is deleted and accounted for with tuning software, the lost mileage should be able to be retrieved.

 

Once upon a time I was reading up on EGR and it was talking about part throttle and cruise cylinder fill and how it relates to compression. Basically it was saying that due to the high vacuum that the air/fuel mixture that is going into the cylinder under those conditions is at a lower density and then once compressed you effectively have less mixture in the cylinder, lowering compression. It was saying that if done right the exhaust gas would take the place of nothing and help ensure that what little air/fuel was in the cylinder was still compressed optimally. Basically filler.

This was quite a long time ago, so I apologize if I butchered that. Not sure how much of an effect it has.

 

The reading that I've done says that the main mileage improvement with EGR comes from reduced throttling loss. If that is true, there can't be a big increase in mileage.

 

not to hi jack but my ive never seen my fuel milage above 12 mpg in my 99 think maybe its egr issue

 

If memory serves right, guys over on FSC with OBS trucks seem to lose 1-2 mpg when they delete the EGR. IIRC the theory behind it is the recirculated exhaust gas is very low on oxygen and takes the place of normal air in the cylinders.

Since you have less oxygen in the cylinders you require less fuel, therefore you save a slight amount of fuel at idle and light throttle applications where the EGR is active.