Proper EGR delete

[paraplan]

I'm looking to delete EGR from my 2007 Mazda CX-7. However I'm not satisfied with just physically deleting the EGR and masking the CEL code, I want a real delete with proper ECU re-tune that restores the MPGs and deals with lean mixtures. Does anyone have a map for this or know how to do it?
Thanks!

[mituc]

Deleting the EGR will simply affect the fuel economy just because the chemistry going on inside the engine will be different.
To counteract this you can increase the closed loop timing but it may not work as well as if you had the EGR.

[Steve @ VersaTune]

The only benefit of EGR delete is a cleaner intake. EGR generally increases low load cruising fuel economy.

[Kay2thePea]

question about this @Steve @ VersaTune - is the reason that EGR increases low load cruising fuel economy simply because the exhaust gases that it puts into the cylinders basically takes up some of the room in the cylinder and effectively reduces the "effective displacement" of each cylinder while EGR is active, and thus the ECU injects less fuel as there is less air being brought into the cylinders?

If that's how it works, then I guess there isn't really a viable alternate way to increase fuel economy at low load cruise while deleting EGR to help keep the intake valves and combustion chambers cleaner? I'm trying to ponder on this but I can't really come up with a very good idea. Maybe if one just happened to own a nitrogen concentrator and one filled nitrogen cylinders from atmospheric air, and injected that nitrogen at low load cruise in lieu of having an EGR...?

On second thought, that would probably dramatically increase nitrogen oxides and dioxides being emitted from the engine, so probably not all that great of an option. Maybe an Argon concentrator instead

Any idea how much EGR increases fuel economy at low load cruise? Do you think it's actually worth the trade off? I mean, if overall you're saving something like 0.5 or 1 liter per 100km, that's a pretty alright savings (5-10%), and in that case it really would add up to a decent enough savings that it would easily cover walnut blasting every 40 or 50k km. But if you're only saving like 0.5% or something, and it's really just used by manufacturers as one of a number of very small mileage improvements that add up to enough to keep them from being penalized for higher pollution than allowed, then it's almost certainly well worth deleting.

If it's not worth deleting, is it worth pulling apart and cleaning the valve and possibly tubing every x km? I just know i've heard of EGR systems getting clogged up and not working right and causing people issues on some engines, but don't know if our engine is likely to have that kind of issue?

[mituc]

question about this @Steve @ VersaTune - is the reason that EGR increases low load cruising fuel economy simply because the exhaust gases that it puts into the cylinders basically takes up some of the room in the cylinder and effectively reduces the "effective displacement" of each cylinder while EGR is active, and thus the ECU injects less fuel as there is less air being brought into the cylinders?

Yes, it's all about mechanical labor.
Introducing a relatively inert gas into the combustion chamber, with the right amount of fuel and air for a complete combustion event, will heat that gas up making it expand along with the bi-products of the combustion. Basically it's that raise in cylinder pressure which drives the piston down and makes power (mechanical labor which translates into torque which translates into power).
Basically from a combustion perspective this is a similar principle like the lean burn.

If that's how it works, then I guess there isn't really a viable alternate way to increase fuel economy at low load cruise while deleting EGR to help keep the intake valves and combustion chambers cleaner?

Yes, there is, I'm basically implementing this approach in all the tunes I make.
However, it's not as efficient as having a functional EGR, or if you push things that far you will run into low load or tip-in response issues while pushing the NOx production even further.

The valves will not be kept much cleaner if you remove the EGR. The EGR is only one side of the issue, and most likely the smallest of the two issues.
If you want to keep the valves cleaner for much longer then install catch cans on both breather lines of the engine. If you want to keep them clean for ever then add any sort of auxiliary fueling, PI, or WMI.
As for the combustion chamber cleanliness it's all in the tune and the quality of the fuel you're using. Remember you basically burn 10-15 full tanks of fuel before you collect like 250-500ml of fluids from your catchcans (on a healthy engine at least, during summer). Also the piston cleans itself up if the temperatures and fuel mixtures are right, so those, say, 500ml of schmutz (which is usually like 20-40% oil and the rest is water and fuel) are nothing compared to the 10 tanks of fuel. You gum up the engine by idling it in total on 25% of the fuel in a full tank (say, bumper to bumper traffic and city driving mostly) than with all those 500ml of catchcan captured fluid ran through the engine at the same time.

So unless you are forced to (aftermarket intake manifold) or run into clearance issues with a huge turbo or a top-mount setup (on which I'm sure you'd not care about low load/cruising fuel economy which only come into discussion on street builds) I would not rush into removing the EGR.

Any idea how much EGR increases fuel economy at low load cruise? Do you think it's actually worth the trade off? I mean, if overall you're saving something like 0.5 or 1 liter per 100km, that's a pretty alright savings (5-10%)

When I blocked my EGR off once (was trying to diagnose something else) I saw the fuel economy moving from 13l/100 to about 16.5-16.7 in a certain kind of driving (qualifying mode) and in normal cruising and light city traffic from about 12.5-13l/10 to about 15.
I still cannot explain the huge jump in fuel consumption during hard driving (which of course also contains partial throttle driving) since the EGR is supposed to be mostly closed in those situations and I did not log the EGR duty cycle but the fuel consumption came back after removing the EGR block-off plate.