Anyone reactivate EGR for better mpg?

I don't know what my EGR setting is at - Last I knew it was turned down as far as it would allow with VagCom, but that was over 2 years ago. Once I removed the EGR and had Rocketchip tuning installed I never looked at it again. I'll try and check it sometime this weekend and report back.

As far as mileage goes - my lifetime average over ~65K miles is ~54 MPG. The best ever that I referred to in post 56 was 75 MPG. (this is also in my signature) That was with the modifications listed in that post.

Hey you should set it back to stock and see if you notice any changes in mpg or power for that matter.

I am completely talking out my behind here.. but just some things I was thinking abotu reading this thread...

Doesn't a working EGR also theoretically increase compression, by introducing spent gasses which are not as compressible as fresh air? Also pre-heats the "air" charge, which in turn makes me wonder how that wouldn't make it predetonate, which perhaps to counter that possiblity they had to alter the fuel curve a bit.

Also - if you think about why internal combustion engines still suck for economy is heat-loss (due to many things... friction, combustion, etc...) in theory if you are re-using the Exhaust Gasses, perhaps that heat (albeit small) is not lost and therefore has to contain energy?

Again - just thinking outloud cuz I can...

I reset mine to stock too. This thread convinced me to try it. Car ('01) was in the shop having the IP resealed ##%^. Independent auto in Phoenix has done 20 with apparent success. I also had the fuel filter replaced. I wonder why I didn't notice the power go away! The car is certainly more powerful now & pulling nicely (especially noticeable in 2nd & 3rd) Of course the other changes done may have had some influence, but the quantity and timing looked just right. I'm hoping what people report on fuel economy is also true. Meanwhile, whee!

I would like to reactivate this thread for better economy!
Are there any other threads on this topic that are worth reading?

I have the EGR blocked off with a plate.
I have the VAG-COM adaptation with no other ECU mods.
I've adapted IQ at idle to 3.8, I will doublecheck this before and after the EGR mod.
I have the MAF twisted so that the readings at idle don't trigger the CEL.

This thread has finally convinced me to set the adaptation back to stock. It may cause the CEL to come back, in which case I would have to twist the MAF a little more to get readings down closer to requested again. Should be interesting. I will try and post graphs in my MAF Twist thread...

From the papers I've read, EGR can play a role on fuel economy, but whether it helps or is detrimental depends on operating conditions.

At light loads, increased EGR rate AND advanced timing to compensate for the increased ignition delay will lower fuel consumption, a little. However, at high loads EGR is detrimental to FE. FYI, I adapted mine for max EGR rate.

idioteque said:

I am completely talking out my behind here.. but just some things I was thinking abotu reading this thread...

Doesn't a working EGR also theoretically increase compression, by introducing spent gasses which are not as compressible as fresh air? Also pre-heats the "air" charge, which in turn makes me wonder how that wouldn't make it predetonate, which perhaps to counter that possiblity they had to alter the fuel curve a bit.

Also - if you think about why internal combustion engines still suck for economy is heat-loss (due to many things... friction, combustion, etc...) in theory if you are re-using the Exhaust Gasses, perhaps that heat (albeit small) is not lost and therefore has to contain energy?

Again - just thinking outloud cuz I can...

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Not enough to be significant in a diesel. In a gas engine, YES, it increases the compression ratio by increasing manifold pressure, not because exhaust gas is less compressible. It also decreases the required octane index by slowing flame front speed due to lower oxygen content.

In a diesel, it only decreases flame temperature. It can increase soot, hence the original perceived good of reducing EGR. But since the adaptation to reduce EGR also retards timing, the benefit is minimal.

I have set mine back to stock, noting a slightly better performance.

Keith_J said:

Not enough to be significant in a diesel. In a gas engine, YES, it increases the compression ratio by increasing manifold pressure, not because exhaust gas is less compressible. It also decreases the required octane index by slowing flame front speed due to lower oxygen content.

In a diesel, it only decreases flame temperature. It can increase soot, hence the original perceived good of reducing EGR. But since the adaptation to reduce EGR also retards timing, the benefit is minimal.

I have set mine back to stock, noting a slightly better performance.

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What about stepping up your timing slightly to compensate for the EGR turned off?

SBAtdijetta said:

What about stepping up your timing slightly to compensate for the EGR turned off?

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That would probably work... but I think that 95 percent of people who have done the EGR adaptation are probably not comfortable with mechanically adjusting pump timing (me included).

SBAtdijetta said:

What about stepping up your timing slightly to compensate for the EGR turned off?

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Recently I helped a local member do some work on his NB 180K miles. We cleaned the intake (1/4" buildup), blocked egr, reduced egr w/ adaptation and advanced timing in VCDS to 3 BTDC. Mechanical timing was between middle and top. Also replaced stock injectors w/ sprint520, no injector servicing. From what he's told me sounds like about +2mpg vs. prior to servicing.

It's a funny coincidence, about a week ago i put the original Alligator tune back in my ECU (via Q-loader) this tune did not have the EGR delete (as per my request to Marc at mikrotuning). The car is super smooth at low RPM and crusing to a stop in high gear. My EGR is set to stock adaptation. I'll report back after a tank or so.

SBAtdijetta said:

What about stepping up your timing slightly to compensate for the EGR turned off?

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Well, it might work but remember, the ECU has enough authority to adjust timing to whatever it needs as long as basic timing is within the red lines. But with it far off the chart, the engine might have starting issues.

I set EGR adaptation back to stock and had to up the IQ because the engine was running rough when cold. But that is 20 F cold so you folks in S. TX might not have this issue. Car does warm faster.

I had a brain fart....small DPF pre EGR cooler. One of them electrically recharged units should work.

EGR adaptation throws off ScangaugeII calibration but that is OKAY

After putting my EGR adaptation back to stock the ScangaugeII immediately started reporting worse instantaneous fuel economy. I figured that the calibration had been "thrown off" so I filled up without changing the calibration, then on the next fillup I found the calibration had to be changed from -10% to -20% (the scangauge was over reporting initially) I did another fillup and the Scanguage reported 10 Litres vs 9.7L on the pump (pretty damn close) and I was very happy that the calibration was confirmed because I think fuel economy was up between 5 and 10 percent last tank, (I know, I'm getting lazy by not doing it on paper.)

p.s. forgot to mention IQ at idle did not change: 3.4

SBAtdijetta said:

What about stepping up your timing slightly to compensate for the EGR turned off?

Click to expand...

I didn't keep my EGR defeated for long. I noted a 2mpg loss, and no real change in smoke, so I ditched it after 3 tanks.

A few years later, when Ollie did my timing belt, he set my mechanical timing at the top end of the graph, which did help it start a little faster (Although I never had any real issue with starting)

I started driving more for economy as well, and my economy shot up from the low 40's to the high 40's.

Recently (and coinsidentally, right at the switchover to winter fuel) I made a few IQ and Adaptation Timing changes that were partially for economy, and partially to try to minimize the Scangauge errors between my daily commute and roadtrips.

I raised the IQ to around 5.6, which I believe makes the most difference in soot, as throttle tip-in is much, much more gentle, and I don't ever spike over 17psi. It also made the scan gauge much more stable over different types of driving. My adjustment has been rock solid within 0.1% the last 3 tanks, whereas it had been jumping all over the place before that.

I also set the adaptation timing to add 2.5 degrees more advance. The car is stock, so I'm likely adding less stress than a chiptune does.

Whether it helped with power, I don't know, or really care, since I really like the result. Typically, I'll lose 4-5 mpg over the winter due to both temperature and winter fuel. This year, (see my fuely) I've lost nothing, and have maintained roughly 51mpg, even through the recent spell of temperatures in the teens.

I'm looking forward to seeing what happens as spring catches hold, and the Kerosene gets out of the fuel.

I have had my egr disconnected for a few days now and no CEL and I just changed the EGR adaptation back to stock. I was getting 43-44 MPG combined city and wighway driving. I am filling up tomorrow and will watch the next few tanks to see if there is any improvements in MPG.

After I set the EGR adaptation back to stock and with the egr disconnected I got the CEL this morning on the way to work.

When I had EGR adaptation at the lowest setting I didn't get the CEL, now I will check the mileage and see what happens there.

The Jeep Liberty CRD must have a massive amount of EGR, as I gained mpg when I defeated it. I intend to test it out on my TDI next.

After reading this I want to change my setting back to stock and see if anything changes. The day I bought the car I changed the egr setting so I can't remember how if felt or ran the first day.

UFO said:

The Jeep Liberty CRD must have a massive amount of EGR, as I gained mpg when I defeated it. I intend to test it out on my TDI next.

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The theory here is that defeating the EGR with VCDS has a negative impact on MPG due to side effects on ECU parameters. Defeating EGR via tuning has not been linked to negative MPG.

Honeydew said:

The theory here is that defeating the EGR with VCDS has a negative impact on MPG due to side effects on ECU parameters. Defeating EGR via tuning has not been linked to negative MPG.

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It would be interesting to hear from some of the tuners on this subject.
It could be helpful to know what parameters are changed to increase fuel efficiency... could they be applied to a custom tune with or without EGR?
I bet if a tuner looked over the maps and shared with us, we could learn much.

I ran 446 miles friday and yesterday, all highway and with my egr set to stock my mpg was down from the previous tank, 42.4 MPGnow compared to 43.6. I will check the next fill up and see.

did another fill up, same pump and the MPG is still below the previous setup where I have the EGR set for off road use only, it is now 41.8 MPG.
Looks like I am changing it back.

OK. I drank the Kool-Aid and set mine back to stock.

Ran two full tanks on my regular commute route and mpg dropped from my normal 47 to 41.

Dragging out Vag-Com this evening to "remedy" the situation.....

Jettajoy and pfiermka, do you have the EGR deleted via block off plates or vacuum disconnection?

No, stock setup, fully functional EGR.

Yep, same as pfiermka. All stock. I even checked the EGR after I changed it back to make sure it was seating correctly.

Will see if I get back where I was and report.

I just pulled the vacuum line on my EGR (and plugged the line), new tank of fuel. No CEL (yet) either. In two weeks we'll if it makes a difference in my mileage.

2002 ALH. Disabled, then re-enabled a few years ago.

Yesterday afternoon, I re-disabled it with VAG.
I was curious about what the Scangauge would tell me.

Typically, I get between 53 and 58mpg on my morning drive.
This morning, the Scangauge reported 65mpg.

I guess I'll have to wait a bit to see if/how much it's screwed up my calibration.

I found that changing the EGR adaptation will throw off the calibration too. I think it was about 10 percent? It will probably take you two fillups to get it back since it sounds like you changed the adaptation mid tank?

Variant TDI said:

2002 ALH. Disabled, then re-enabled a few years ago.

Yesterday afternoon, I re-disabled it with VAG.
I was curious about what the Scangauge would tell me.

Typically, I get between 53 and 58mpg on my morning drive.
This morning, the Scangauge reported 65mpg.

I guess I'll have to wait a bit to see if/how much it's screwed up my calibration.

Click to expand...

Your calibration will be off and it's totally normal.

With VCDS, go look at your IQ, then go adapt the EGR, and come back looking at the IQ. Oh surprise, it has changed! EGR adaptation impact the IQ, which is directly used to calculate fuel economy.

When the EGR is adapted, the IQ varies in the same direction. So if you tune the EGR down to almost nothing, the IQ value will go down, which is reported on the scangauge as fuel economy going up.

But in fact, a lowed IQ just means you're injecting more fuel.

I remember in my mk3 when I had an every mod. At steady state I would turn the pot and the IQ would go way down, but the reported fuel consumption on the scangauge would skyrocket to stellar mpg, when in fact my actual fuel economy would be pretty much the same (while steady state driging on the highway)