VersaTune User Forum

Posted: **February 12th, 2017, 3:33 am**

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!

Posted: **February 13th, 2017, 3:20 pm**

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.

Posted: **February 15th, 2017, 12:53 am**

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

Posted: **June 30th, 2025, 3:10 am**

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?

Posted: **June 30th, 2025, 3:48 am**

Kay2thePea wrote: ↑June 30th, 2025, 3:10 am 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.

Kay2thePea wrote: ↑June 30th, 2025, 3:10 am 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.

Kay2thePea wrote: ↑June 30th, 2025, 3:10 am 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.

Posted: **July 2nd, 2025, 3:24 am**

mituc wrote: ↑June 30th, 2025, 3:48 am
Kay2thePea wrote: ↑June 30th, 2025, 3:10 am 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.

Kay2thePea wrote: ↑June 30th, 2025, 3:10 am 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.

Kay2thePea wrote: ↑June 30th, 2025, 3:10 am 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.

WOW! Thanks so much for such a detailed and clear answer here man!!! You really addressed every single question i had in great detail, very much appreciate it!

What do you think the reason is that EGR deletes seem to be something that many people do look at? and why do a number of companies bother making a block off plate/block kit? Is it actually intended for people who really do just need the clearance more than anything (it sounds like that's the case, but then because people who don't fully understand how these engines operate or how EGR operates on it, but who have heard plenty of stories of people on other vehicles, diesels in particular, that have all sorts of amazing gains after the EGR is removed, and these people think it makes sense to delete the EGR on their vehicle, and of course manufacturers of these delete kits aren't going to turn down a paying customer).

Crazy how much your fuel economy got worse when you deleted the EGR - good to know!

As for your tunes, you said that you try to implement the approach i mentioned in your tunes. can you clarify what you mean exactly, because i don't think you mean you are injecting an inert gas, so i'm guessing you're talking about leaning out your AFR at low load cruise, but that it needs to be done in a balanced way in order to ensure things don't get out of control and cause issues?

Would i be correct in thinking that the biggest issue with going too lean at low load is likely that when the throttle is increased while the car is cruising at low load, there will be a short period of time (called tip in?) where the engine is still running lean, but the engine load is increased a fair bit, and that this would potentially cause issues if it gets too far out of control?

As for increased NOx production, is that caused by going too lean? or too lean at too high of an engine load? if so, this is where the "balanced approach" would come into play?

would you be willing to elaborate on your AFR targets at lower loads, perhaps even share some logs or something? just wanting to get an idea of how lean you've found you can push things, at various loads, without having issues crop up. i imagine the data you've found for the CX7 engine would be a bit more useful to someone like me, since you're running WMI on your 3MPS, but the fact you've got a built engine and are running a different turbo makes me wonder if i would be asking for problems if i used your tune as any sort of guide for my own tunes, since my engine is stock with only a 3" intake.

thanks again for the great response, i appreciate it man!

Posted: **July 2nd, 2025, 9:50 am**

Kay2thePea wrote: ↑July 2nd, 2025, 3:24 am What do you think the reason is that EGR deletes seem to be something that many people do look at? and why do a number of companies bother making a block off plate/block kit?

An EGR delete kit is required in several cases. When you will be in one of those situations you will know.
Why do people do it while not even installing catch cans - ask them why they do that, probably for the same reason some of them still use 5w30 oils or use diesel truck engine oils in these 2.3DISI-T engines. Because "they've read it on a forum or group" and because it's different, while improper oils (and this is just an example) will lead to valve contamination and soot/gunk production a lot more than the EGR.
However, as I mentioned (I think), removing the EGR will help keeping the valves cleaner, but without catchcans you will only get less coloring on those deposits, and matt-black looks thicker than a translucid brown so the impression that removing the EGR helps a lot more than it actually is.

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