Diesel EGR Defeat
 

I finally pulled the trigger and built my EGR defeat circuit, and installed it this weekend. I'm still tweaking the MAF output to reflect the amount of EGR flow the ECM needs to see in order to not trigger the CEL, but the hardware is now in place.

When I get it configured where I want, I will be doing ABA fuel mileage testing. I had hoped to use my Scangauge to calculate trip mileage, taking note of the following data to facilitate comparison between data sets:

Initial coolant temperature
Ambient air temperature
Miles traveled (will only be commute, with no deviations)
Average speed
Scangauge reported average MPG

Unfortunately the Scangauge doesn't like the new mod. The lack of EGR flow must be affecting how fuel use is reported. Typically on my a.m. commute I average 36mpg or so. With the EGR defeat in place, the Scangauge reported 56mpg on todays commute.

Something tells me my little device has not improved my mileage by 55%. Anyone have any ideas for the scangauge or other methods for documenting fuel mileage?

No baselines yet. I had my device miswired, and managed to borrow an oscilloscope to troubleshoot; it seems to be working properly now.

The first thing I have noticed is the engine warm-up is MUCH slower. I am usually up to temperature within 5 miles of driving my commute, but with EGR disabled it takes almost 10 miles of driving.

My baseline will have to involve plugging in the block heater. Obviously the EGR cooler does a considerable amount of preheating the coolant before the engine is warm. Maybe a judicious reroute of the exhaust through the cooler back into the exhaust (instead of the intake) is in order; this could ensure a fair FE baseline, but is a complex endeavor.

I think I have hit on the reason most people claim defeating the VW TDI EGR will reduce fuel economy.

Interesting.

I have the 2.0 L CR TDI in my Multivan and already had an issue with EGR (valve defective, had to be replaced with an attached EGR cooler. Was done under warranty, otherwise it would have been around 1k€ oO), so I went and looked if a delete was possible after warranty is up.

But: no way. This was possible in T4 Vans of your vintage, but the T5 (and especially the T5.2) are so wired that deleting the EGR leaves the engine in a non-operable condition. Or you would have to make up a complete ECU.

Furthermore, deleting the EGR seems to bring 2 benefits but also two big no-nos:

- less hassle & repairs
- more power when engine is warm

but:

- higher NOx emissions
- higher fuel consumption

For me, the decision goes in the direction 'keep EGR' (as if I had a choice...). I only wish my new valve will hold up for more kilometers than the previous one (35.000 km). They said they installed the all new & improved type of valve. Lets see.

so long,

tinduck

My engine didn't have an EGR cooler, but about a year ago I installed one from a newer (EURO 4) version. It's hard to tell whether warm-up times shortened, since at the same time I had a block heater installed, plus I added an upper grille block and engine insulation for the winter.
I read that the EGR valve on my engine doesn't open until the coolant reaches a certain temperature, probably to reduce the risk of condensation. Newer, more emissions-centered, versions may start EGRing earlier.

As for milage, I didn't notice any immediate changes, maybe because right after installing the EGR cooler we had a long and cold winter. This year's milage has improved, but I like to blame that on fine-tuning the nut behind the wheel:D

I don't know if the cooler helped NOx, since my inspection garage doesn't do emissions:(

I'm more familiar with larger diesel engines, but I've never, ever seen any data showing a fuel economy benefit from EGR in a diesel (with all the same engine settings otherwise). In some cases there can be a fuel economy benefit in a gasoline engine, but that's a separate discussion. The thing to watch out for is whether your change to the EGR affects the ECM in such a way that it reacts by changing other things (like timing). IMO, that's where people are probably seeing the fuel economy penalty--it's not directly from removing the EGR--it's from the ECM's reaction. Knowing what the ECM is going to do is a pretty complicated matter in modern ECMs. I know for diesel trucks there are a lot of sims, chips, & programers to remove EGR in such a way that the other engine settings are negatively affected. There are probably similar things out there for the TCI engine. You might want to look into them, but be forewarned that there's a lot of crap out there too.

Yes, warm up time will be longer without an EGR cooler. The block heater is a good way to go (even with EGR). Another thing would be to block off more of the grill. That doesn't really help initial warm up mich becasue the thermostat is closed, but your required cooling load under warm conditions will be decreased so you no longer need as much radiator.

I also started another thread recently to deal with this using an exhasut heat exchanger:
http://ecomodder.com/forum/showthrea...art-19607.html

Many at Fred's TDI Page. TDIClub.com. VW TDI Enthusiast Community have tried this.
The only positive is a slight top end gain.
One (don't remember who) drives long enough to eliminate the warm up issue.

Why are you wanting to delete it ? Intake/intercooler restriction/crud ?
Changing the PCV to vent into a can instead of the intake will nearly eliminate the intake crud. With no oil to stick to the EGR soot just goes right through.
YMMV

I don't remember where I read it (maybe here?), but in a diesel increasing EGR only works up to a certain point - first it reduces NOx without compromising performance, but then everything starts to fall apart.

Exactly!

I believe this is what the OP is attempting to do: cut EGR while emulating sensor readings for the ECU's sake to make it think everything is OK. I wonder what the effect will be? Since the ECU will think that the intake air is partially emissions, the fuel dosage/timing will be changed accordingly, compared to an intake charge of clean air.

I have done extensive searching and reading on Fred's site. No one has done due diligence in demonstrating fuel mileage changes with EGR removal. This should involve imitating the conditions of EGR to the computer so it makes no changes in how it fuels the engine -- when the CEL is lit, the ECM will retard the timing to avoid the creation of NOx and mileage will decrease.

To answer your question, I want to convince myself removing EGR improves engine efficiency. I hypothesize it will, and I want to demonstrate it in fact, with as much control over the experiment as I can get.

And secondarily, to keep the intake from clogging. Many on Fred's site make the claim the newer diesel fuels will keep this from happening. I pulled my intake and cleaned it two years ago, and it was a mess. I may do it again in the spring and see if there is appreciable buildup. I am not sure the new diesel fuels are any different in that regard. And I also don't believe you can remove enough of the oil in the intake to prevent the crud from sticking; if there is a fuel efficiency gain from removing EGR, that is the better solution for me.

EGR lowers the specific heat ratio of the combustion stroke gasses. This drops the efficiency of the diesel cycle.

you can see what sort of effect this has by changing g here

The Diesel Engine

(note just plug one nubmer in and the rest will be set to their defaults)

for pure air g would be equal to 1.4 . Typically combustion gases with excess air are about 1.35 . Combustion gases with no excess air are about 1.3 .

However adding EGR if employed in just the right amount at just the right amount for a specific fuel mass injected and a specific rpm can better approximate the idea diesel cycle. This will increase efficiency some. The trick is getting just that right amount.

Now days EGR is mainly just used for NOx control.

Bingo! there's your reason for FE getting worse by removing EGR.

EGR wil improve FE at the same NOx level, however, if all the other engine settings are the same, I have never, ever seen FE improve with EGR on a diesel.

This is the whole reason for the EGR vs SCR debate on diesels (see article here: http://fleetowner.com/management/feature/scr_egr_0701/). An engine with EGR has lower NOx emissions, but worse FE. SCR can clean up the NOx after it's left the engine, but not having to use EGR buys you FE. Of course SCR means you have to add DEF (diesel exhaust fluid).

If EGR improved diesel FE, SCR would have both DEF and worse FE, so there would be no point.

That is an interesting paper. I do wish they had provided enough excess air to burn the fuel completely even at higher levels of EGR; that would seem more fair. Of course, that might have adversely impacted the NOx production, I cannot divine the intent of the author in that regard. Then again, the test engine is not equipped with turbo, so extra air is hard to come by.

The paper's conclusions seem simple enough given the data, and that's why I want to demonstrate a measurable fuel efficiency gain on the TDI. This same type of EGR defeat has been done for the US model of the Jeep Liberty CRD (Cherokee in Europe), and although my wife drives one, I have not tested its fuel efficiency. Others who installed that circuit claim a 10% improvement in mileage, but it is undocumented.

I can believe it makes a significant difference though, as for some reason the US model CRD controls a huge amount of EGR. I pulled the MAP sensor when I first bought it, and with 30k miles it was completely encrusted with oil/EGR accretion. That Jeep had EGR defeat installed around 45k miles, and now has 95k miles. Probably time to check the MAP sensor again, although when it gets gunked up, engine operation is noticeably affected.

Many on Freds site don't get CELs as they defeated the EGR through software. They still get nasty intakes.
My 94' doesn't send crankcase vapors through the intake, light coating of powder. It ran for years on regular "high sulpher" diesel.

Again YMMV

Where is the blowby routed? Every diesel I've seen vents the crankcase to the intake. Not that I'm familiar with a lot of engines, just the TDI, the VM Motori CRD and the Mercedes OM617 engines....

Same with PSA's HDi turbodiesels.

The messy and not real good for the enviroment answer is to pull the hose and put a filter end on it. Most race shops have them. Looks like a pod filter but onlt abouy an inch or so in diameter.

The better way is to route it to a small catch can then to the mini pod. This keeps the oil from dripping all over.

I guess you could put a few screens in the catch can and route the now dry vapors to the intake for emission reasons ?
Most diesel heads are anal about clean air to prevent turbo pitting yet will send droplets of oil into it ? Never really understood that.

Why don't they keep the EGR valve somewhere under the hood, but not connected to the exhaust or intake ?
I.e. working, but not functional, so it won't throw fault codes.

There's usually no EGR flow measurement, or is there ?

In some cases that can be done, but it depends on the sophistication of the fault detection software. Some ECM's probably just look to see if the valve is moving, others look at intake pressure, intake temp, exhaust pressure, etc. and see if it's consistent with the amount of EGR it thinks it's sending.

In some cases there's a deltaP sensor in the EGR loop that's used to estimate EGR flow. In some cases EGR flow is estimated based on a MAF sensor (fresh air flow) - total charge flow (estimated from speed, IMP, & IMT).

In some cases it has a "primary" estimate based on one set of measurements, and a "secondary" estimate based on another set of measurements. The primary estimate is used for controls, but if the secondary estimate isn't within a certain amount of the primary, it trips a fault code.

It all depends on how the software is set up.

While not a diesel my 99 maxima had a CEl with a code for egr flow volume. The supply tube from the exhaust was plugged. Cleaned the tube and cleared the code, no further codes.
No reason why a US emissions spec diesel would not have the same OBD2 code as a 12 year old Maxima.

regards
Mech

I read somewhere that a small amount of oil getting thrown at the turbo with the intake air will help lubricate it. On the other hand, every turbodiesel I've seen has the whole intake track "sweating" oil, so I doubt that this amount is small, or that it doesn't effect emissions.

How are you mitigating the increased NOX production now that the EGR is disabled?

He isn't.

If you keep NOx at the same level, FE will be worse without EGR, because you'll have to change something else like retarding timing.

We had that conversation already, in another thread. This thread is mostly about testing fuel economy by removing EGR, changing nothing else. Instrumentation with the SG is unfortunately problematic, so ABA testing is going to take a while, especially in winter where my biodiesel ratios, ambient temperatures and warm up time vary.

However, if I can verify my defeat circuit emulates the lack of EGR accurately, perhaps the SG can be used as a guideline. I'll have to see, right now I still get an occasional P0402 code, so I need to hook up the VAG COM to see if the expected MAF is too high or too low over the operating range.

UFO,

I don't know how your doing your circuit but I think your going to have some troubles. EGR is usually set based on the O2 sensor reading. When the ECU computer senses data from the O2 sensor it will adjust timing and such to try and meet emissions.

To really know how to trick it you need the source code.

Good luck

The newer CRs I believe have an O2 sensor but the VEs do not.

Adjusting the expected value will probably be necessary.

Jason is correct, there is no O2 sensor. There may be a MAF output dependence on either the engine load or operating temperature, or both. Since the EGR is not modulated with a throttle, I believe the window the ECM expects is wide enough to neglect those effects, if I adjust the appropriate base amount.

I believe you need to adjust Adaptation block 3.
Bump it up 900-1000 so your reported quantity is at or just below 370.

The guys running the 6.7 L Cummins in Dodge PU's have found unplugging the EGR will provide from 1.5 to 2.5 increase in MPG. You do get a CEL light, but some are using a programmer to fool the ECM and get rid of the CEL.

The trucks warm up real slow in the winter.

My Best to You!

I have modified the circuit and verified it with VAG-COM that is is not setting the CEL. I left the MAF target at 270, where it has always been (I can't adjust it anyway, my VAG-COM is not registered.) To partially offset the loss of EGR warm-up, I installed a grille block.

I also have a 2-tank baseline (more or less) with the EGR connected using mostly pump diesel. The grille block opening is a bit too small, I peaked 215 coolant temperature on my morning drive, so I cut it out a bit more - it's just cardboard for now. I intend to keep the grille block for the portion of the mileage test when I reconnect the EGR.

Your not saying the EGR is just on off control right? I'm pretty sure the N-18 controls the EGR actuator and modulates it's position hence EGR flow rate right?



..

Right, the N18 alone controls the EGR flow. What I am saying is there is no intake throttle to help regulate the flow, like on PD VWs, or my Jeep Liberty CRD.

What I have learned since I wrote that is the EGR level is only checked at idle, so it is irrelevant what the MAF response to EGR is at any other engine condition. At the time I did not have enough output range in my circuit to make the ECU happy. My freeware VAG-COM has been invaluable.

So the N-18 duty cycle is not changed at all other than idle? I've never hooked up a LED to see if it pulses on an off. If it does change duty cycle than the vacuum applied to the EGR valve would change and EGR flow would also change.



..

No, EGR is active all the times the ECM deems it necessary. It is only tested at idle.

The EGR is modulated with the duty cycle of the N18, I've seen it on an oscilloscope.

i do not think so
 

EGR reduces NOx by decreasing combustion temperature, which has the side effect of decreasing thermal efficiency. By disabling that system, I am increasing the engine's ability to extract work from the fuel. THAT'S the theory, and I hope to have some measure of data to support it soon. To which "theory" are you referring?

It's only used to shut off the engine, it is not used as part of the EGR system
The freeware version IS the actual VW tool. Not sure what you mean.
Why not? And who is doing that? I use the VAG-COM to validate the performance of my mod.
Indeed, it might reduce your fuel costs, your carbon footprint, your emissions, increase your fuel mileage, your engine reliability. Don't do it.

Honestly, if you are going to criticize what I am doing, at least bring some facts or data.

no
 

The ALH engines do not have particle traps, and so there is no purging.

Regular diesel fuel also leaves behind deposits in the intake; based on the discussions on the TDI forum, I am not the only one that has removed the ALH intake and found there is only a dime-sized hole remaining due to all the soot deposits from non-biodiesel use. Whether bio-diesel also causes this or not, I would still want to check the intake every time I have to change the timing belt.

Carbon clogging of turbo vanes can also happen with regular diesel; this is not a unique problem for bio-diesel. The cause is driving like a grandma, not the fuel. And the stock VNT-15 on the ALH is less prone to clogging than earlier turbos. Solution to this problem is to drive the car like I stole it on occasion.

Can't speak for the glow plugs; haven't read about these kinds of issues on the TDI forum and haven't had the problem. Of course that doesn't mean there isn't such a problem, just that I haven't seen anything about it.

Despite that possible problem, I am still very much in favor of bio-diesel and will put the highest bio-blend in that I can find (currently B20).

You are right however that bio-diesel is not good for later models of VW diesels (such as the 2011 you are talking about). I still hold out hope that future iterations of the VW diesels will 'play nice' with bio-diesel!

I have had swelled glow plugs before.
I think the best way to remove them is snap them off and fish them out through the injector hole.
If you have tiny injectors where this wont work you will have to pull the head off or live with 1 less functioning glowplug. On a 4 cylinder this might make cold starts pretty rough, on a V8 its not so bad.

EGR might be good for gas engines, but most of the diesel users who delete EGR report better fuel mileage.
If EGR was so great why aren't some of the latest gasoline engine generations using it?

EGR in a gas or diesel is full of soot. Soot is abrasive like dirt. Why would I want dirt going into my engine?

Layers of diesel exhaust soot and motor oil from the crank case vent does a pretty good job a clogging intakes with sludge. When I tore my diesel down the sluge in the intake ports was between 1/8 and 1/4 of an inch thick. It was caked on so thick I could have stuck birthday cake candles in it. It took over an hour in the parts washer for each head to get the ports cleaned out and that was after I pressure washed them with a 0 degree nozzle.

Now that its gotten colder lately my cold starts with B10 bio diesel involve a lot more white smoke. Next fill up will be with regular diesel. I have not been using bio diesel for very long so the mix sloshing around in the tank is some where around B5 to B8 mix.

The ALH engine(1999.5-2003) does have an anti shudder valve(ASV) which by the Liberty CRD guys and others is called throttle valve. The only time to my knowlege that it is active on the ALH is when you stop the engine. There is no demand for it to actuate during normal driving conditions. The EGR is forced in by the exhaust backpressure, and would need to over come whatever boost pressure the intake is seeing at the time. In the CRD realm, the throttle plate is most likely used to enhance EGR flow as you mention in a more active implementation-the ALH EGR is rather rudimentary.

..

EGR does reduce NOx. On a gas engine, there are some circumstances where EGR can improve FE due to reducted throttling losses. EGR on a diesel is a different story. I've worked with and tuned diesels for years (both EGR & non-EGR) and have never, ever, ever seen a scenario where adding EGR improved FE. EGR can often produce better fuel economy at the same NOx level, but just adding EGR will always reduce FE.

Not sure where you got the information that EGR doesn't operate at max power. I've seen lots of diesels where there's EGR all along the torque curve.

When made properly, biodiesel doesn't contain any more ash than traditional diesel fuel. The ASTM standard for traditional diesel fuel (ASTM D975) calls for ash <=0.01% mass. The ASTM standard for B5 & B20 (ASTM D7467)
also calls for ash <=0.01% mass. The spec is exactly the same for ash.

Of course, sometimes people use some crappy biodiesel that they made in their garage. Of course there can be problems there. But you'll have the same problems if you burn crappy conventional diesel fuel--but it's not a biodiesel thing.

If anything, biodiesel should extend the life of the particulate filter, because biodiesel typically produces about 10 times less particulate than conventional diesel fuel. Even B20 typically produces about 1/2 the soot than conventional diesel. Less soot produced means fewer regens, therefore more DPF life.

How is biodiesel going to leave deposits in your intake?! In a diesel the fuel is injected directly into the cylinder, not the intake. The only way anything from any fuel could get in your intake would be if you have EGR. Even then, it's after the fuel has been burned. What exactly are these supposed deposits? Most all the deposits that cause problems with VG's, glow plugs, etc. are primarily soot and, as I've already stated, biodiesel produces far less soot than conventional diesel.

Biodiesel is good, unless you are cold starting an IDI at 15'F.

Remove all doubt, for me I just delete the EGR.

I say just don't listen to non-diesel people on the subject of anything diesel related.