Improving mpg in Vw TDI

[UFO]

Originally Posted by COcyclist

Thanks Mario, I have been trying to find this out for myself due to problems with a U.S. EGR cooler recall. From what I can find it is better to leave the EGR intact for lowest fuel consumption.

This is another area where I intend to settle this once and for all, hopefully, at least on a VW TDI.

I participated with the people on lostkjs.com to build and use a device that mimicked the presence of a functioning EGR system on the Jeep Liberty CRD. The EGR valve and AFC valve were both disabled, and a circuit inserted into the MAF line to modify the air flow signal according to what the ECM requests. Mileage improved universally, reported as between 1 to 4 mpg increase on a baseline of mid-20s, for a 4% to 16% improvement.

I am building a similar circuit for the ALH TDI. Most people who disable the EGR on the TDI simply live with a CEL, or modify the EGR flow using the VDCS software, in both cases the ECM is aware of the lack, and may make fueling and advance changes to compensate and avoid emitting NOx. My device masks the absence, so the variable is only the lack of EGR to make mileage assessments.

I have disabled mine and driven with the CEL, and my mileage did suffer along with driveability.

[COcyclist]

Originally Posted by COcyclist

Thanks Mario, I have been trying to find this out for myself due to problems with a U.S. EGR cooler recall. From what I can find it is better to leave the EGR intact for lowest fuel consumption.

I guess I should have said "from what I can find FOR THE VW TDI it is better to leave the EGR intact...". Most people report what you have found UFO, that if you simply block off the EGR or disable it with VAG COM it confuses the computer and performance suffers. If anyone has a tune that optimizes ERG for fuel efficiency I would love to try it on my car. So far, I have not found that.

[oldbeaver]

Cocyclist and the Forum,

There is a link where you can find what you want:

Visit :

MANUAL DE PERFECTO AJUSTE DE LA EGR CON EL VAGCOM EN LOS TDI

It is in Spanish, though.

Oldbeaver

PD I may translate that for you.

[Arragonis]

Hang on, its not hard to clean ?

[NachtRitter]

Originally Posted by COcyclist

I guess I should have said "from what I can find FOR THE VW TDI it is better to leave the EGR intact...". Most people report what you have found UFO, that if you simply block off the EGR or disable it with VAG COM it confuses the computer and performance suffers. If anyone has a tune that optimizes ERG for fuel efficiency I would love to try it on my car. So far, I have not found that.

Check out this thread: http://ecomodder.com/forum/showthrea...eage-7358.html. Might have the info you are looking for...

[COcyclist]

Unfortunately, Daox's OP "increasing EGR flow for better mileage" is written concerning gas or "petrol" vehicles. Without a gas engine's throttle plate and high vacuum at light load, the diesel is a whole different animal. In post #40 of this thread there is a link to scientific testing of a diesel with varying rates of EGR. To summarize their findings: A diesel engine is most fuel efficient with zero EGR but NOx levels are high due to excess oxygen in the cylinder leading to high temperature combustion. With EGR, power output drops slightly but NOx is greatly reduced. So we diesel owners burn a wee bit more fuel to have less toxic tailpipe emissions.

FWIW, my 04 TDI with 60,000 miles shows almost NO intake or EGR valve clogging. I know this was a problem with earlier VW diesels, hopefully solved now with EGR coolers and low sulphur diesel.

[oldbeaver]

Originally Posted by Arragonis

Nope, this engine (the one in the Autospeed article) has all the air it needs already. Improving the flow in this case made no difference at all. Adding fuel (via the remap) added the power.

I have seen loads of postings on Skoda forums where people with my car (PD130) have fitted the PD160 intake and say things like "wow". But no A-B-A testing and no before / after dyno to back it up. The PD160 replica intake made as part of this article made no difference, in fact it went worse.

There is no agreed international calibration for the butt-o-meter

I agree. I have a Skoda Octavia of 2009, with a 1.9 TDI engine and DSG transmission. Air intake that comes standard is bigger than the PD160 some are reccommending. So it has all the air intake it needs. This car is giving me over 48 mpg for a full tank.
Exhaust pipes as 2.5" factory standard.
Mileage is very difficult to improve with this beauty.

As it has a built in computer that gives real time consumption (marginal and mean), I am seeking a mean of remap "something" that can improve mileage, by means of software or such. I already bought a VAG cable, but need help to proceed.

Any suggestions?

Oldbeaver

[Arragonis]

If you can, go for a custom remap as it will be made to suit your specific car and preferences. The remapper will plug in their own laptop to do the work. Careful though, VAG locked down some ECUs to prevent remapping. The remapper should also keep a copy of the 'before' map so you can go back when you wish.

[ConnClark]

Originally Posted by oldbeaver

I agree. I have a Skoda Octavia of 2009, with a 1.9 TDI engine and DSG transmission. Air intake that comes standard is bigger than the PD160 some are reccommending. So it has all the air intake it needs. This car is giving me over 48 mpg for a full tank.
Exhaust pipes as 2.5" factory standard.
Mileage is very difficult to improve with this beauty.

As it has a built in computer that gives real time consumption (marginal and mean), I am seeking a mean of remap "something" that can improve mileage, by means of software or such. I already bought a VAG cable, but need help to proceed.

Any suggestions?

Oldbeaver

Actually if you read part 4 of Julian's write up Browser Warning he states "A dyno run of the car prior to tuning showed a peak power of 77kW at the wheels – a surprisingly good performance given the slight loss in on-road acceleration recorded after the intake and exhaust mods, and also given that the factory claims 77kW at the flywheel. (On these Dyno Dynamics dynos there is typically a 25-30 per cent loss in peak power between the flywheel and rollers – losses caused by the transmission and the deflection of the tyres over the relatively small diameter rollers.)"

Later he also shows that before the remap the exhaust and intake mods did improve mileage.

5.6 litres/100km before mods
5.5 litres/100km after ( note the web page says 5.5 litres/10km but it is safe to say that is a typo)


Interestingly the article states that the ECU has a torque limiting map. this is something I have never heard of in an ECU.

[dremd]

Torque limiting maps are pretty common on tuned turbo diesels.
Basically you limit fueling (and boost) to the max torque you think your driveline can handle.