After reading Grumpy's most recent post on tuning a stocker it occured to me that EGR has no place in an underpowered highway heavy weight, BUT what about thirdgens and healthy v8's? I don't have enough experience with EGR (vortec heads) on my vehicle so what I suggest is only speculation. With a heavy truck with already not enough power, disabling egr would make more torque at a given rpm resulting in less tps. Enable EGR only kills power but couldn't this be a good thing with a lighter vehicle which requires less hp to cruise? Wouldn't this always be a case where EGR would save you some gas?
Or does EGR only affect emissions? What about the air pump and the thermac riser? I know there are lots of posts on these topics but I'm asking for opinions on everything, just a brief description of what you think helps or hurts milage etc.

 

On most applications, EGR just adds very warm exhaust fumes to the intake charge. Being already once reacted, you have to add more fuel, and increase the timing to reburn them.

Some will argue that in theory you then can operate at a larger throttle opening, and decrease the pumping loses. So far in several serious attempts at increasing MPG with EGR, I've never been able to see any gain. YMMV

EGR adds heat to the manifold, heat to the incoming air charge, and lowers the actual VE.
It does lower the peak combustion temperature.

MPG is in great part about the mechanics of the car. The rolling resistance is a huge part of it all. The basic engine design is also a fixed part of the equation.

Running a little learner then Stoich, min timing consistant with a given TPS at cruise value are what generally works for me.

That same tune you witnessed, on the GN, netted 25 MPG in 90dF temps, 90% humidity, at 75+ MPH. And was non EGR'd.

Not to mention that even when it's supposedly not able to work that it can, ie backpressure can open an EGR valve. So they can alter WOT performance in some apps.

 

Jon, I USE to be a strong advocate of the EGR system. I obtained impressive gains in gas mileage. And yes, it could handle great gobs of timing when the EGR was functioning. But, to be honest, I NEVER did equivalent tests with the EGR turned off.

I now have a Miniram on my car. The heads are better but the cam is currently stock (I want to do a "step by step" comparisions with just the Miniram and heads, and I'll do the cam later).

Unfortunately, I have had to deal with other issues in my personal life (like my health, and them buy the wife a house). But now that I have that dealt with those , I can again turn my attention to my car.

Once I get back into detail tuning of the car, I will let you know how much of a difference the lack of an EGR makes. I will attempt to run Highway Mode again and see the differences there also.

Personally, I would expect the new Miniram/head combo to get less gas mileage EVEN if I had an EGR. But I will get back to you with the differences. My all time best gas mileage was just under US 30 MPGs with the old TPI, stock heads and the EGR but it would consistently get 28-29.

Hopefully in a few months I will be able to tell you all the differences. My first observation is the car runs better/smoother with the new setup without the EGR. Not that my car previously ran bad - far from it. But it just seems to run a bit smoother with the new setup - and it is not fully tuned yet.

Let's just say that I am not rushing to make an EGR function with the Miniram at this point.