Anyone reactivate EGR for better mpg?

Ah... thanks. I'll check my IQ when I get home. I had 'raised' it previously from 3 to 5.6 to reduce smoke. I guess I'll have to adapt again to get back to where I want to be.

IQ Adaption will also throw off Scangauge almost for certain, FYI

Yeah. I figured that out.

I originally changed the IQ to raise the percieved idle consumption, and hopefully reduce the dramatic calibration difference between my commute (with some P&G) and roadtrip cruising. Commute was -12%, roadtrip was -25%.

For that, it actually worked wonders. (now only a couple percent different). And I got the benefit of smaller boost spikes and a more linear throttle response.

I've also not seen the typical winter drop in economy (check my fuelly), so I'm guessing that also had a very positive effect on economy.

Well... checked the IQ after I got home today. Even with the EGR disabled, the IQ remained where I set it a few months ago. 5.6 mg/st.

I'll leave it disabled for the time being and see what the next fillup shows me.

After reading most of this thread, I decided to put mine back to 32768 from 33768 last night. It's been on 33768 for a couple months I guess. It's definitely using the EGR now according to the MAF readings. This morning on my commute there was a very noticeable improvement in power and response. It seemed peppier than yesterday, like it has more torque at lower rpm and also seemed to run a little bit better.

I freely admit that my perceptions might have been poisoned by the expectations of all that stuff happening because it was pointed out in the thread.

A general thank you to everyone for their findings. I never would have thought about any of this otherwise.

JettaJoy said:

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.

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Well after setting mine back to the "modified" mode and running two full tanks of fuel, I'm right back to my normal 47 MPG average. With the EGR set at Stock values, I was getting 41 MPG over several tanks. To note, my area has also been out of the "Winter" blend of fuel for months also.

So where stock settings may have improved MPG for some, it doesn't for all I guess.....

Ran a tank of fuel with the EGR vacuum line pulled and plugged. The CEL came on, of course. There was a definite difference in drivability, however I did get a slight improvement in fuel mileage, for the same number of miles I needed about 0.3 gallons less.

I will try again, but next time the ECM will not know the EGR is disconnected, so hopeully I will not have the drivablility issue.

I have had my EGR line plugged for quite some time now on my 02 and I did it after Jeff tuned it with RC2.
The car has always run well and there was no intake clogging. The only problem was reduced MPG.
I will report back with any information I have after going back to somewhat stock EGR action.
Edit
Took the car out for a spin and noticed it was runing smother. Wonder if my Wife will notice?

The root issue this thread is talking about is not whether EGR is actually being applied physically but whether the adaptation value for the EGR channel has been modified off of 32768 in an effort to reduce the EGR flow. When this is done, it modifies other maps accordingly and reduced output and efficiency are noted. I hope this clarifies the issue.

jollyGreenGiant said:

The root issue this thread is talking about is not whether EGR is actually being applied physically but whether the adaptation value for the EGR channel has been modified off of 32768 in an effort to reduce the EGR flow. When this is done, it modifies other maps accordingly and reduced output and efficiency are noted. I hope this clarifies the issue.

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Very well put. When I put mine back to stock I noticed more power but as for mpg I stayed the same.

jollyGreenGiant said:

The root issue this thread is talking about is not whether EGR is actually being applied physically but whether the adaptation value for the EGR channel has been modified off of 32768 in an effort to reduce the EGR flow. When this is done, it modifies other maps accordingly and reduced output and efficiency are noted. I hope this clarifies the issue.

Click to expand...

Exactly. If the EGR is physically blocked and the MAF signal is modified, either via a diode drop, MAF-twist or some other means, there should be a gain in fuel mileage with no driveability issues. Or at least no mileage penalty without the intake plugging.

also keep in mind that if the EGR circuit is blocked off, there will higher exhaust manifold pressures in cases where the EGR valve would normally be open. This will increase fuel consumption (all else being equal) due to the engine having to pump 'harder' against the higher Exh Man Pressure.

Hi guys,

What is the figure used for the absolute max flow rate?. I've been playing with some settings and found that 33768 reduces the flow and affects the IQ/Timing/MAF during log runs.

At idle-stock EGR: VCDS 32768

Engine speed MAF (specified) MAF (actual) EGR duty cycle
rpm-specified-actual-duty cyle
903 260 498.8 4.8
903 260 495.4 4.8

at idle-adapted EGR: VCDS 33768

Engine speed MAF (specified) MAF (actual) EGR duty cycle
903 360 488.8 4.8
903 360 498.8 4.8


during accel runs-stock EGR: VCDS 32768
2226 690 718.2 54.6
2835 850 847.9 4.8
3381 530 555.3 4.8
2184 240 372.4 84.5
2415 635 611.8 51
2625 500 571.9 75.7


during accel runs-adapted EGR: VCDS 33768
2079 595 588.5 48.6
2100 510 495.4 49.8
2100 440 442.2 54.6
2058 330 322.5 71.3
1806 320 322.5 67.3


I'm looking at running my mk3 at the following specs:

-IQ sitting at 4.2 with .205 Smog nozzles installed
-Timing sitting at +2.2 Degrees advanced in adaptation (basic is set at the blue line @ 92*C/coolant temps 62*C fuel temps)
-*want to achieve max EGR flow rate to enhance fe*

I've got full logs, if anyone is interested in browsing them or need additional info.

-thanks

I have had my egr reactivated for the past 50k. Today I removed the egr to check on soot buildup, since I reactivated after the introduction of ULSD. I was amazed at the condition of the egr and intake- virtually no buildup at all, just an oily residue. Thank god ULSD.

I dreamed my egr had been deleted by a guru, and that my miles per gallon and performance were not affected in any negative way, and that my car had not begun to clog up again and slow down like it did before said deletion may have occured. Then, I woke up and found this thread. Based on my dream, I'd vote for letting the sleeping dog lie.

jollyGreenGiant said:

VAG-COM adaptation for EGR plays with things like IQ and timing along with EGR, I never had any luck with reduced EGR adaptation, it effected too many other things for my liking and I too received a 3-4 mpg drop in mileage with it adapted on it's lowest setting along with a similar drop in torque. There's better ways to handle the EGR than through the adaptation method on the rotary pump TDI's IMO.

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I could be wrong, but it appears that reduced EGR adaptation must be followed with advanced timing adaptation to offset the retard of combustion. I've played a bit, but still learning, so i turned it back to stock calibrations.

When i first got this TDI, EGR hose was detached from the valve. Mileage was around 900km per tank. So i plugged it back in and mileage went up a slight bit, to around 950km per tank with the same non-vented fueling /driving conditions. This was measured briefly with 17' low profile wheels.

honda_vtec2 said:

I could be wrong, but it appears that reduced EGR adaptation must be followed with advanced timing adaptation to offset the retard of combustion. I've played a bit, but still learning, so i turned it back to stock calibrations.

When i first got this TDI, EGR hose was detached from the valve. Mileage was around 900km per tank. So i plugged it back in and mileage went up a slight bit, to around 950km per tank with the same non-vented fueling /driving conditions. This was measured briefly with 17' low profile wheels.

Click to expand...

The real question is, does raising the EGR adaptation to the highest value ( max EGR ), increase IQ and timing parameters and thus fuel economy? A scientific analysis on default and max settings with a couple tanks of carefully logged consumption along with some full load logs of 004,003,011 with default and max values may shed some light on the subject. Any volunteers?

This time of the year is bad to be doing this kind of thing also, the weather at least in my neck of the woods is too variable.

jollyGreenGiant said:

The real question is, does raising the EGR adaptation to the highest value ( max EGR ), increase IQ and timing parameters and thus fuel economy? A scientific analysis on default and max settings with a couple tanks of carefully logged consumption along with some full load logs of 004,003,011 with default and max values may shed some light on the subject. Any volunteers?

This time of the year is bad to be doing this kind of thing also, the weather at least in my neck of the woods is too variable.

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I'd volunteer, but the weather up here is fluctuating a lot to get good results. If this thread is still going come spring. I'm in. The last time i played with the EGR settings on the car. It didn't drive as nice, so i went back to stock. I took a small drive around the block and didn't even get to the point of starting logging. I'm not sure if this is due to an intake build up of soot. Last time i measured about 1-2mm or oily stuff around the EGR valve.

My car is currently set with the following, so i'm not sure if i'm a candidate:

1Z engine
ALH pump
stock dsla 150p 706 injectors .170
basic timing 53/127
iq 2.8
timing adaptation 33000 (+2.9 degrees advanced)
14 inch wheels with 185-70 14 (33 psi all around)

I would put timing right on blue, removed any adaptations and test. Does that sound right for stock settings.

Test scenerio

Fill tank to brim (vented)
log a test run roughly 110km at around 3am, when there is limited traffic on the hwy with cruise set at 100kph, rpms roughly sitting at 2163. Stop, refill tank to brim (vented) adjust settings to whatever EGR adaptations. Continue test. Then measure, graph, log whatever fuel was used during the 2 scenerios. I don't think i can do a full tank test.

That's the idea, i think, correct me if i'm off.

EGR = BSFC Penalty

Ladies and Gents;

Before you go out and do some home brewed testing... It may be worth doing some research first. As a mechanical engineer specializing in diesel enignes this question is quite easy for me to answer. In general, EGR almost always comes with a BSFC (brake specific fuel consumption) penalty. One of the reasons for running EGR is to lower NOx but engineers always walk the fine line of the NOx VS PM (particulate matter) tradeoff. However, you have to remember that the lack of EGR creates higher temperature combustion, more NOx (since it is formed during high temperature combustion,) higher turbo temps (which can lead to lower efficiencies,) higher EGT's and so on. In the SAE (Society of Automotive Engineers) publication "Diesel Emissions and their Controls" written by Dr. Majewski and Dr. Khair a very specific example of this principle is detailed. A study on the effect of EGR versus injection timing retard was performed on a heavy duty diesel since both of those situations can be used to reduce NOx. The baseline BSFC was .396 lb/bhp-hr and NOx was as high as 3.976 g/bhp-hr. Utilizing timing retard the engine used .449 lb/bhp-hr but NOx was lowered to 2.804 g/bhp-hr. Finally EGR was used and bsfc came in at .405 lb/bhp-hr (a 2.3% increase over baseline) and NOx was lowered to 2.757 g/bhp-hr. Therefore as I stated earlier and the example demonstrates, EGR almost always comes with a BSFC penalty.

-Nick

Nick - Welcome to the club and thanks for the reference information.

Stick around - I'm sure there's many more questions that will be quite easy for you to answer

does anyone know what the vacuum should be on the EGR? suction wise?

viersam@gmail.com said:

does anyone know what the vacuum should be on the EGR? suction wise?

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You should have about 28 in/hg at the vacuum supply to the EGR solenoid and depending on the solenoid's duty cycle you will have a percentage of that reaching the EGR, 50% duty cycle would be about 14 in/hg and so on.

thanks! as you can probably tell in a vacuum idiot maybe you could help me with something else too? I just got my first TDI about a month ago and have had more than my share of problems. The guy i bought it from said the intake was clean. It wasn't. I just removed my EGR and intake and saw that the EGR cooler is clogged almost completely. I am going to solvent soak it and then boil it to remove the carbon build up but I was wondering about blocking out the EGR? how is this done? what are the negative effects? The forums talk about lower mileage but only 1 or 2 mpg? wouldn't having less carbon particles in your engine and not clogging your intake out weigh this?

My first post, so please be kind, and I am not a native speaker

And sorry for resurrecting a decade old thread (trying to catch up as a new member and it was on the first page)

Egr and pure water injection always decreases fuel economy (increases BSFC).
Have a look at this paper where they performed a lot of tests and in all of them the fuel consumption increases with egr (and with water injection).

So in my very humble and quasi-ignorant opinion, if you see a decrease in FE with the egr deleted, then it is very highly likely it is a tuning issue.

(NOX emissions go up dramatically with egr delete, NOX is some nasty stuff according to some people)


The reason for fuel economy dropping could be alternative maps preventing you from creating nitrous oxide emissions.

Link:
https://www.researchgate.net/public...d_NOx_Emissions_and_Specific_Fuel_Consumption