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Go Back   TDIClub Forums > VW TDI Discussion Areas > Dieselgate - VW Group Emission Scandal

Dieselgate - VW Group Emission Scandal Discussion around the VW Dieselgate Emissions scandal. Details and news updates can be viewed here: http://forums.tdiclub.com/showthread.php?goto=newpost&t=448336 This forum is a work in progress depending on requirements, usage, etc.

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Old July 11th, 2018, 06:48   #1
hiawan
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Default 2012 Jetta TDI Emission Fix - Not happy

I recently purchased a 2012 Jetta sedan TDI with DSG that has gone through the emission modification. The best I ever experienced is 40mpg on mostly highway commutes of over 60 miles.

I used to have a 2012 Passat TDI manual I would average 50-55mpg on my highway commutes. VW bought that back.

The Jetta is also much louder than I remember passat ever being. At 75mph the RPMs are around 2400.

Is my lower gas mileage a result of the emission fix?
Is because it's DSG vs. Manual?
I have 114k miles on the Jetta while the passat had 30k miles is this the reaseon?
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Old July 11th, 2018, 06:56   #2
showdown 42
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I would guess it is the manual,which is geared lower to give you more MPGs and the fix is know to cost some , Not sure it should be that big a difference. I got mid 30's to 40 on highway with my 2009 JSW Jetta DSG..
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Old July 11th, 2018, 07:52   #3
hiawan
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Quote:
Originally Posted by showdown 42 View Post
I would guess it is the manual,which is geared lower to give you more MPGs and the fix is know to cost some , Not sure it should be that big a difference. I got mid 30's to 40 on highway with my 2009 JSW Jetta DSG..
That is about what I'm getting currently. Are the Passat DSG's geared similarly to the Jetta?
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Old July 11th, 2018, 13:14   #4
93celicaconv
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Quote:
Originally Posted by hiawan View Post
That is about what I'm getting currently. Are the Passat DSG's geared similarly to the Jetta?
From what fragmented data I could find, the Passat DSG & Jetta DSG transaxles have the same gear ratios and axle ratios, resulting in the same 2.31 final drive ratio. But factory tire sizes/diameters are different.

For the Jetta DSG, the 205/55-16 tire diameter is 24.8" and has 836 revs/mile, resulting in an engine speed of 1931 RPM @ 60 MPH.

For the Passat DSG, the 235/45-18 tire (for the SEL) or 215/55-17 (for the SE) tire both have a diameter of 26.5" and have 790 revs/mile, resulting in an engine speed of 1825 RPM @ 60 MPH.

I had a 2010 Jetta TDI Cup Edition DSG with 225/40-18 tires that were 25.1" in diameter and had 831 revs/mile for a resulting engine speed of 1920 RPM @ 60 MPH, and I know my tach was at a higher RPM @ 60 MPH than my 2015 Passat TDI is at now.

How this translates into fuel economy, I'm not sure.
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Old July 11th, 2018, 19:25   #5
the_janitor
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Yes to first question. I'm getting about 10% less mileage since the fix on my 2011 Golf.

No to 2nd question. The DSG gearbox is supposed to have better mileage over a manual.

Perhaps your Jetta wasn't maintained as well as your Passat to question 3? Also from my observation Passats have better mileage overall compared to Golfs and Jettas.

RPM at 75 mph on my 2011 GOLF is around 2200. Yours seems a bit high.
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Old July 11th, 2018, 20:20   #6
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DSG gearing is a bit shorter than the manuals, and the mechanical losses between the two units should be very similar. DSGs tend to get slightly worse mileage, but it heavily depends on the driving conditions. In the city I'd expect the DSG to win unless the manual owner is very conservative, since the newer DSG software is really designed to penny pinch.
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Old July 12th, 2018, 04:40   #7
740GLE
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Originally Posted by the_janitor View Post

No to 2nd question. The DSG gearbox is supposed to have better mileage over a manual.

lies lies lies, stop regurgitating the EPA numbers, the DSG has way more loses than the 6MT due to the pump that's constantly holding pressure on the clutch packs, plus the added coolant loop.

Plus the gearing of a Gen2 Passat manual is about 2-300 RPM less than a Gen1 Jetta DSG. It's been proven time and time again on this site a 6MT will always beat a DSG at straight higway runs.

It wasn't until Gen3 did the DSG get nearly identical gearing as the 6MT, but you still can't get away from the losses of the DSG over a 6MT.

The only thing the Jetta will have of the Passat will be a slightly lower curb weight (2-400lbs?), but that should only really affect city mileage.

Sounds like the OP is seeing the worse of both scenarios, switched to a DSG and a slight hit with the emissions fix software.
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Old July 12th, 2018, 04:46   #8
93celicaconv
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Quote:
Originally Posted by Owain@malonetuning View Post
DSG gearing is a bit shorter than the manuals, and the mechanical losses between the two units should be very similar. DSGs tend to get slightly worse mileage, but it heavily depends on the driving conditions. In the city I'd expect the DSG to win unless the manual owner is very conservative, since the newer DSG software is really designed to penny pinch.
This is correct - final drive ratio difference between DSG & manual. On a 2012 Jetta TDI sedan, the DSG final drive ratio is 2.31:1 (based on an axle ratio of 3.04 and a DSG 6th gear ratio of 0.76). For the same car in a manual, the final drive ratio is 2.24:1 (based on axle ratio of 2.76 and a manual 6th gear ratio of 0.84). Not much of a difference, but the engine runs a tad slower at the same road speed with the manual vs. DSG.
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Old July 12th, 2018, 04:50   #9
93celicaconv
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Quote:
Originally Posted by 93celicaconv View Post
From what fragmented data I could find, the Passat DSG & Jetta DSG transaxles have the same gear ratios and axle ratios, resulting in the same 2.31 final drive ratio. But factory tire sizes/diameters are different.

For the Jetta DSG, the 205/55-16 tire diameter is 24.8" and has 836 revs/mile, resulting in an engine speed of 1931 RPM @ 60 MPH.

For the Passat DSG, the 235/45-18 tire (for the SEL) or 215/55-17 (for the SE) tire both have a diameter of 26.5" and have 790 revs/mile, resulting in an engine speed of 1825 RPM @ 60 MPH.

I had a 2010 Jetta TDI Cup Edition DSG with 225/40-18 tires that were 25.1" in diameter and had 831 revs/mile for a resulting engine speed of 1920 RPM @ 60 MPH, and I know my tach was at a higher RPM @ 60 MPH than my 2015 Passat TDI is at now.

How this translates into fuel economy, I'm not sure.
I must not have the right information on the gearing for the 2015 Passat TDI w/DSG. This morning, running 60 MPG, my vehicle tachometer was at 1600 RPM. I think the Jetta information is correct, but either my Passat tachometer is off or I don't have the correct 2015 Passat TDI w/DSG gearing info.
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Old July 12th, 2018, 06:10   #10
93celicaconv
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Quote:
Originally Posted by 93celicaconv View Post
From what fragmented data I could find, the Passat DSG & Jetta DSG transaxles have the same gear ratios and axle ratios, resulting in the same 2.31 final drive ratio. But factory tire sizes/diameters are different.

For the Jetta DSG, the 205/55-16 tire diameter is 24.8" and has 836 revs/mile, resulting in an engine speed of 1931 RPM @ 60 MPH.

For the Passat DSG, the 235/45-18 tire (for the SEL) or 215/55-17 (for the SE) tire both have a diameter of 26.5" and have 790 revs/mile, resulting in an engine speed of 1825 RPM @ 60 MPH.

I had a 2010 Jetta TDI Cup Edition DSG with 225/40-18 tires that were 25.1" in diameter and had 831 revs/mile for a resulting engine speed of 1920 RPM @ 60 MPH, and I know my tach was at a higher RPM @ 60 MPH than my 2015 Passat TDI is at now.

How this translates into fuel economy, I'm not sure.
I got better information now for the 2015 Passat TDI 2.0L 150 HP variant, as far as gearing is concerned. It actually has a DSG 6th gear ratio of 0.62. The 5-6 gear axle ratio is 3.33. The resulting final drive ratio is 2.0646 (0.62 x 3.33), not 2.31 as stated above for the 2015 Passat TDI. This gearing, with the 235/45-18 tires I have on my SEL Premium results in a calculated engine RPM of 1,631 RPM @ 60 MPH (I'm actually reading 1,600 RPM @ 60 MPH, which may be tachometer error, will need to get an ECM output of engine speed).

So at least for me, there was a fair amount of difference in engine speed between a 2010 Jetta TDI Cup Edition w/DSG and a 2015 Passat TDI w/DSG, and the calcs based on gearing data support that difference.

Again, have no idea how that translates into real world fuel economy differences though.
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Old July 12th, 2018, 06:25   #11
ZippyNH
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Quote:
Originally Posted by 93celicaconv View Post
I must not have the right information on the gearing for the 2015 Passat TDI w/DSG. This morning, running 60 MPG, my vehicle tachometer was at 1600 RPM. I think the Jetta information is correct, but either my Passat tachometer is off or I don't have the correct 2015 Passat TDI w/DSG gearing info.
2015 cars have not only a different engine, but different gearing to make use if the TQ band...it's much flatter on the 2015, and gearing is quite a bit lower with the DSG.
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Old July 12th, 2018, 18:18   #12
06bluebeetletdi
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13 beetle dsg 9,000 miles since fix (now has 70k) - mileage between 34-38.3 mpg before fix 35.8-42.1 (bought car with 9800 miles 10/14) 14 passat dsg 13,400 miles since fix (now has 63,400 miles) 34-43.3 mpg (i like remote start in winter). Purchased 9/17 at 50k. Had timing belt/water pump done at 52,591 due to water pump leaking coolant getting on belts, it had sat most of the time since 3/16 due to takata and then diesel buyback.
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