2015 Golf TDI sets new US mileage record - 81.17 mpg

prothe

Active member
Joined
Dec 22, 2008
Location
Charlotte, NC
TDI
99 Golf
I would bet money that the 81mpg car had a special ECU that was tuned for fuel economy and wouldn't pass EPA's emissions tests. For the last 5-10 years, diesel engines have had a really hard time meeting emissions guidelines, so the cars that we drive are tuned to meet the emissions standards. Remember when Mercedes and VW had to team up in a joint venture to meet emissions? If you advance ignition, you get NOX, if you retard ignition you get particulates. I think the ECU's in these cars were tuned for 100% fuel efficiency for some publicity. With common rail technology you can do incredible things, but what is sold today is a necessary compromise of emissions, noise and fuel economy. So I bet these test cars were loud and stinky, but were able to get 81 mpg. It's sad that we don't have the option to do the same to our cars.
 

Lightflyer1

Top Post Dawg
Joined
Sep 13, 2005
Location
Round Rock, Texas
TDI
2015 Beetle tdi dsg
I would say you are completely wrong. It wouldn't mean much if anything if it weren't a stock production car anyone could own.
 

prothe

Active member
Joined
Dec 22, 2008
Location
Charlotte, NC
TDI
99 Golf
Lightflyer1, I see you are driving a 2013 Passat TDI. I assume that it has a trip computer that shows your MPG in real time. Are you ever getting 78 MPG on a flat surface like hypermiler Wayne Gerdes got? Can you (or anyone) with a trip computer, enlighten me on what the max MPG you see on a flat surface at steady state?

78MPG for a Passat seems to good to be true.
 

atc98002

Veteran Member
Joined
Nov 24, 2006
Location
Auburn WA
TDI
2014 Passat TDI SEL Premium (sold back), 2009 Jetta (sold back), 80 Rabbit diesel (long gone)
Lightflyer1, I see you are driving a 2013 Passat TDI. I assume that it has a trip computer that shows your MPG in real time. Are you ever getting 78 MPG on a flat surface like hypermiler Wayne Gerdes got? Can you (or anyone) with a trip computer, enlighten me on what the max MPG you see on a flat surface at steady state?

78MPG for a Passat seems to good to be true.
The real time MPG is worthless for anything other than what is happening at that instant. Yes, I see in excess of 70MPG while steady state at 40MPH, but it can be influenced greatly by little things like the road slope (may look level but isn't really), wind, road surface, temperature, AC use, etc. I've been on the freeway doing 70MPH and see over 80MPG, but that's because the "flat" road really isn't.

From the factory, the MFI display is optimistic, to the order of 2-3 MPG average. It would say my tank was 42MPG and the real, calculated MPG was 39. I've tweaked mine with VCDS and is now slightly low.

Wayne uses techniques that aren't reasonable for anyone actually try to go somewhere. He keeps his average speed lower, lets speed bleed off while going uphill, and other things. His numbers are honest and accurate, but not really realistic. That said, you can certainly use his tricks more reasonably and improve your overall MPG.
 

prothe

Active member
Joined
Dec 22, 2008
Location
Charlotte, NC
TDI
99 Golf
Thanks guys. It just seems too good to be true. I could believe getting 50% better fuel economy than you guys, but he's getting double!
 

Lightflyer1

Top Post Dawg
Joined
Sep 13, 2005
Location
Round Rock, Texas
TDI
2015 Beetle tdi dsg
You misunderstood. It is possible to get that if you are a highly skilled eco driver like he is. Not the ordinary everyday driver though. His results are what is possible at the extreme edge of operating the car. I drive my car in a normal manner not trying for extreme mileage. On cruise on longer trips (400 miles or so) at 65 mph I can get in the low 50's. Someone with a manual trans and a ton of experience should be able to better that by a lot. Besides his results were certified. Do you think they were cheating?
 

993er

Veteran Member
Joined
Oct 10, 2013
Location
Canada
TDI
None
See post 5 and my previous post. Said the same thing.
I see...sorry, I can't read every post due to things I have to get done. :)

But as you, I am very happy to double the mileage of my Honda CR-V. Mind you it is a different car: pushing a box through the air, all wheel drive, etc. But it was damn reliable for the 15 years that I owned it.
 

The Turtle

Veteran Member
Joined
Jul 24, 2006
Location
rural Maryland
TDI
1996 B4 Passat wagon, SpeedTuning chip, 360,000+ miles, 1996 B4V, 306,000 miles on original engine
Cut to the chase

I've held off jumping in on the whole set of revelations this week, but for me, it boils down to a few things:

1. I know people on here who probably know the code in the ECUs at least as well as any VW tech.
2. I have a hard time believing the active tuner community never noticed anything on the "new" TDIs in SEVEN YEARS
3. If you have a polluting car, you have an inefficient car. I tell people, "even if your engine is just making excess noise, that energy spent making that noise is energy not spent getting you down the road."
4. If none of us had TDIs, imagine how much more gasoline we've had consumed over the years, with all the known levels of pollutants even the best of those kick out (never mind the pollution related to production of new vehicles versus the insane longevity many of us have seen with our existing cars)
5. Seems like the EU would have noticed something, given the much higher level of acceptance of diesel engines from ALL manufacturers in Europe compared to the smaller USA market.

I have done spoke now, I'll sit back and listen.

Turtle
224,000+ miles on my two TDIs in the last nine years
 

The Turtle

Veteran Member
Joined
Jul 24, 2006
Location
rural Maryland
TDI
1996 B4 Passat wagon, SpeedTuning chip, 360,000+ miles, 1996 B4V, 306,000 miles on original engine
81mpg?
Are they allowed to use draft vehicles? I would assume sitting behind a semi at 55mph for some portions of the trip would really help you get there.
Best mileage I ever got on my black diesel was 53mpg on the flat part of I-95 back in 2009 from Jacksonville up to Richmond drafting big trucks at 55-60mph, over a span of about 600 miles. Meaning, half a tank of fuel.
 

jerryn63

Well-known member
Joined
Oct 17, 2012
Location
Swansea, MA
TDI
2014 Beetle TDI
You hit it on the money.

Here's what I'm thinking. The NOx CAT get's too hot to work efficiently during DPF regen and takes some time to cool off to 300 degrees and start working well again. I need to setup dashcomm to monitor the CAT2 temp sensor and the temp sensor closer to the muffler. I'd like to catch a DPF regen to see if enough heat dissipates to where the exhaust is ~400F degrees. It might be cool enough to replace the muffler with a combo NOx CAT/muffler (maybe 3 CATS you really don't need a muffler anyway). Then if the 2.0 TDI has real low emissions advance the fuel infection to later in the power stroke, tune for more power and mpg. It would be an "ultimate in your face"!
 
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