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TDI Fuel Economy Discussions about increasing the fuel economy of your TDI engine. Non TDI related postings will be moved or removed.

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Old August 12th, 2017, 18:05   #1
walterwood
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Default 2 mile/gal projected loss of fuel economy with "modification" of 2009 Jetta why?

Subj: 2 mile/gal projected loss of fuel economy with "modification" of 2009 Jetta why?
related Subj: "modification" vs "buyback" 2009 Jetta TDI Sportwagon

I just received a "recall" package describing the "modification" for my 2009 Jetta TDI Sportwagon located here in California. The package describes the proposed "modification" as reducing fuel economy by 2 miles/gallon and I'd be interested in any engineering assessments about what exactly the "modification" fix does that reduces fuel economy and performance.

Also of interest although not directly related to fuel economy, VWcourtsettlement.com is reporting they will pay $21,136.73 if I return it on 4/2/2018 or if I do the "modification" on that same date a payment of $6011.73 but the "modification" is described as reducing fuel economy by an estimated 2 miles per gallon and also effecting engine noise and performance. I'm considering 4/2/2018 because that is the month the registration will be due along with a CA required "smog test" that I am presuming would be failed without the "modification." An earlier "modification" or "buyback" date 8/26/2017 results in a smaller restitution payment of $5906.73 for "modification" and $20506.73 for "buyback." So it seems like it is better to delay until shortly before the required "smog" test.
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Old August 12th, 2017, 21:53   #2
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My understanding is that part of the fix is a bigger nitrogen oxide storage converter, and that the fixed software will refresh that converter more often, by injecting extra fuel to reduce the stored nitrogen oxide to nitrogen. So the car uses more fuel than before to put out less NOx, at the price of putting out more CO2. You pick your poison (or rather, the EPA picked it for you).
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Old August 13th, 2017, 03:31   #3
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I don't think anyone will know for sure the cause of the FE loss until cars are fixed and folks get to see the hardware and software changes. But I bet the loss is from fueling map changes, retarded timing to reduce NOx, and more after combustion dosing to improve the operation of the DPF and Cat. But that's my guess. Honestly, I don't think the number is that significant. Again, we'll know better once some fixed cars are out there accumulating miles.
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Old August 21st, 2017, 14:20   #4
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So you're going to turn in your TDI, Then you buy a gas burner which gets less Mpg and then you b i t c h about the worse Mpg.
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Old August 25th, 2017, 09:14   #5
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MY 2014 JSW got the VW fix last week. So far I've put about 400 miles on the car since the fix and can safely say that it has not lost any power and actually feels like it has more grunt in the mid range. I have the 6 sp manual transmission and drive pretty aggressively and I'm more than pleased with the results of the fix. I don't know yet if I've lost any mileage, but if so it's minimal. Certainly not enough to worry about, and since I'm going to have a Malone tune reinstalled my mileage should go back up where it was.
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Old August 25th, 2017, 19:39   #6
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Wish I had an eight year old car I could sell for $21K. Hard to believe.
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Old August 26th, 2017, 14:10   #7
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What is a "Malone tune" and why does it improve TDI mileage?

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Originally Posted by skromfols View Post
MY 2014 JSW got the VW fix last week. So far I've put about 400 miles on the car since the fix and can safely say that it has not lost any power and actually feels like it has more grunt in the mid range. I have the 6 sp manual transmission and drive pretty aggressively and I'm more than pleased with the results of the fix. I don't know yet if I've lost any mileage, but if so it's minimal. Certainly not enough to worry about, and since I'm going to have a Malone tune reinstalled my mileage should go back up where it was.
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Old August 26th, 2017, 22:37   #8
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Here is their link:

http://malonetuning.com/
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Old August 27th, 2017, 16:27   #9
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Default Malone Tune options compatible with the emmissions fix?

Which of the "Malone" tune kits will you install? The website describes three, the "MT1756 220 hp max" being one, but others with 250 hp max, and 280 hp max. Does increasing "hp max" improve fuel economy even with gentle conservative driving habits?


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Here is their link:

http://malonetuning.com/
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Old August 27th, 2017, 18:24   #10
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Which do you think is the best for someone who do long drives weekly?
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Old August 27th, 2017, 22:13   #11
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I don't think they promote their product for economy (fuel mileage). Some have reported gains and others not. If all you are looking for is economy I wouldn't buy.
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Old August 28th, 2017, 16:02   #12
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Quote:
Originally Posted by walterwood View Post
Which of the "Malone" tune kits will you install? The website describes three, the "MT1756 220 hp max" being one, but others with 250 hp max, and 280 hp max. Does increasing "hp max" improve fuel economy even with gentle conservative driving habits?
I think you might be on the wrong page, past stage 3, which is 180-190WHP, we list varying results http://malonetuning.com/ecu-tuning/a...tdi/20l-cr-tdi


Other than the VE platform we don't advertise fuel economy gains, without deleting emissions components for race use. With that said, the recent changes to injection mapping to reduce NOx would likely affect mileage, so I wouldn't be surprised to see 1-2 mpg restored from a tune. It's too early to tell and the results vary so much that it will be hard to get finite data. That's also assuming you can keep your foot out of it/drive the car identically. Of course, to make more power you have to burn more fuel, so driven harder the car will burn more fuel.

Most people drive their cars harder once tuned and don't notice a difference in mileage. When we're talking a 25%+ power gain in most cases that's worth every penny. If all you're concerned in is getting from A to B for as cheap as possible, the $500 would be better spent on fuel.
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Old August 29th, 2017, 10:51   #13
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Of course my experience with my 2002 Jetta TDI may be different to the newer TDI's.

But my car had the rotten 4 speed automatic and stepping on the accelerator was like stepping on a wet sponge. Any small hill the tranny would shift down.

First mod was to put in .205 injector nozzles instead of the factory [.155] nozzles. Big difference in get-up and go and even better Mpg since the
d a m n tranny didn't have to shift down so much. If I remember the .205 were factory in the 5 speed manuals.

Second mod was to get a tune done, now there was an even bigger difference and a Mpg improvement too.

Had it dynoed back then and the out put was 128hp up from 95hp and the torque was also quite bit higher at about 185lb, up from the original 155lb.

What the OP needs to know it is NOT the horsepower in the TDI, it is the TORQUE which makes the difference!!!

Gasser's develop their Hp at high Rpm's. Diesels get their almost maximum power at around 2,000 Rpm.

When all the VW fixes are done I'm getting the Malone tune and DSG tune.
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Last edited by Jetta_Pilot; August 29th, 2017 at 11:06.
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Old September 7th, 2017, 07:32   #14
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Default Mileage degradation

My coworker had his 2015 Jetta SW modified 2 weeks ago.
He drives his manual 6 speed like a man possessed to get every mile out of his tank of fuel. After the mod he is telling me that he's gone from the high 40's mpg to @37 mpg. That would be a helluva lot more than 2 mpg degradation. Neither of us are new to VW diesels.. We both had Rabbits in the 80's and picked up Jetta's some years later.. His 2009 TDI is still running strong with 390k on it!
I take my 2012 TDI SW in tomorrow for the "fix". I don't get the high 40's he sees but I do average @42 with the DSG so it'll be interesting to see how bad the mileage hit is on this unit.

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Old September 7th, 2017, 20:38   #15
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I've been examining the new software in some depth.

Probably the reason for the expected decline in MPG is due to much higher egr rates than before. There is also retarded timing at mid-low loads and *greatly* increased rail pressure at part load. Also, timing is retarded at some time compared with before.


So the way they got the nox "numbers" is by cranking up the egr. A lot. The problem with that, though, is increased soot production... thus the increase in rail pressure to offset the potential increased soot from egr.

Why didn't they do that in the first place, without all the dieselgate hoohah? Well, here's my thoughts on that. The engine noise is more "dieselly" with more noise and clatter under some conditions. Traditional TDI guys don't mind. (in fact we like it) But the mass mainstream camry buyer types that VW was trying to appeal to for increased market share would be more likely to wrinkle a nose at the sound of a clattery diesel.

SO there you have it.
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