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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 March 20th, 2011, 07:36   #16
rprice704
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i know someone on here has tryed making the car lighter . Carbon fiber hood removing seats or anything like that . Just curious im new so if this is covered already forgive me
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Old March 20th, 2011, 07:51   #17
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Quote:
Originally Posted by Nich View Post
I disagree 1-2 mpg differences are huge. .2 and .8 mpg differences are stistically insignificant and could easly be caused by weather, temp, wind changes. I am guesing that your mpg difference after changing stations is based off the pump inaccuracies. Pumps are allowed to be a certain percentage off. Someone said up to 12%
No the pumps cannot be off by 12%. I am sure there is some acceptable tolerance but it has to be orders of magnitude lower than this. Pumps are checked by the state to ensure accuracy and prevent fraud by the service stations. Perhaps the stat would be something more like 0.12%.

12% off would be 1 gallon off for every 8 gallons...I'd avoid that service station!
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Old March 20th, 2011, 08:41   #18
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I use to work for a meter reading service for water and natural gas . The meter manufacturing company that also makes meters for gas / diesel pumps and other things told us there are safe guards on all meters were even if they are bad they read in the customer favor with age they read slower so when you call your utilty wanting a meter change because of high bills your screwing yourself . Diesel /gas meters are calibrated regularly but they only slow down advantage customer.

Last edited by rprice704; March 20th, 2011 at 08:43.
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Old August 4th, 2011, 11:56   #19
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I agree with the though on a lower road speed over the 50 miles. seeing if the 10mph will actually make a big diffirence in milage.
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Old August 5th, 2011, 05:12   #20
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Has anybody monitored the effect of AFR on economy? What would be the effect of slightly increased/decreased boost (can simply be done with small resistor mod on the MAP sensor).

There are two things to be considered here:
Lower boost => less energy required to create it => economy
Higher boost => more complete combustion => economy

I suppose there is balance between these two, but I'm wandering if someone has some information about it .

Also what is the effect of pushing the injector pump (on the Bosch rotor pump engines) to advance?

What should be considered here is that if the advance is too much in some cases the required advance will not be achieved and instead the injection will be advanced and this should lead to economy in some cases. But if it is advanced too much the effect will be negative.

Last edited by brum; August 5th, 2011 at 05:24.
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Old August 5th, 2011, 05:27   #21
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brum, you're right... the AFR (lambda) ratio is one of the more important factors in economy and power production. Another important factor is fuel injection timing. Bumping the timing forward in adaptation (not a physical modification) will increase peak cylinder pressures, power, and efficiency. You can do that on the MKIII, right?

I know a guy in Sweeden whose nickname is "brum". In Sweedish, brum is the sound a bear makes.
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Old August 5th, 2011, 05:37   #22
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Brum, I just saw your edit...

Physically pushing the pump forward will only advance timing for starting the car. The physical location of the pump timing sets a window of available timing advances.

You need VCDS to change the dynamic timing across the entire fuel map. This is done through the adaptation channel. It is "not recommended". (However, many people have done the modification with success.

I've undone my timing advance mod for now until I get a boost gauge and an EGT gauge. Also, because peak cylinder pressures increase I'm definitely going to be ordering some ARP head studs before I advance timing with all my extra fuel and future air modifications.

Ideally, the tuner will set your timing perfectly for your hardware across the map. Every physical change you can make will alter the ideal tune. (unfortunately)

Ideal AFR (or lambda) is 1.35-1.5
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Old August 5th, 2011, 06:10   #23
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The problem here in Bulgaria is that not many (at least I don't know single one) with cylinder pressure measuring equipment. And for large nozzles (and updated pump) it can't hardly be done without this.

I have an idea of doing this myself (my ecu software is modified by me), but I need time and suitable Beru PSG for this .

Regarding the injection pump advance - yes, you only change the injection for the small IQs (for instance up to 15mg IQ), but this is mostly where you are cruising. So mechanical advance can produce better results than the dynamic change across the whole map.

And brum here in Bulgaria is like buzzing sound, the one created by the beetles . So it has something common .
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Old August 5th, 2011, 06:13   #24
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Here's a great thread that discusses what happens with physical pump adjustments:

http://forums.tdiclub.com/showthread.php?t=240450

Quote:
Originally Posted by brum View Post
Regarding the injection pump advance - yes, you only change the injection for the small IQs (for instance up to 15mg IQ), but this is mostly where you are cruising. So mechanical advance can produce better results than the dynamic change across the whole map.

And brum here in Bulgaria is like buzzing sound, the one created by the beetles . So it has something common .
IQ is Injection Quantity, which is another variable that can be changed across the graph in VCDS.

Once the physical timing is set correctly, the adaptation mod is the next step to gaining mpg. Just check out the results of the guy that put an ALH in his Saturn. After bumping his adaptation timing forward 4 degrees or so, his MPG went to 70mpg+ and stayed there!

Last edited by manual_tranny; August 5th, 2011 at 06:19.
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Old August 5th, 2011, 06:31   #25
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Originally Posted by 1.9 TDI Awd View Post
I agree with the though on a lower road speed over the 50 miles. seeing if the 10mph will actually make a big diffirence in milage.
That's a no brainer. Slowing down 10 mph will make a significant impovement, more than anything else the OP's "mods". Aprox 5 mpg increase.
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Old August 5th, 2011, 10:06   #26
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Brad, I assume you are considering low rolling resistance tires. We've (Prius/Civic hybrid owners) noticed that when someone replaces their OEM LRR tires with a non-LRR tire their MPG drops fairly significantly to the tune of 3-6mpg. We've also noticed that when someone changes their OEM 15" wheel to a 17"-19" wheel the MPG also drops fairly significantly. TDI owners with 17" wheels may consider dropping down to a 15" wheel with LRR tires for a big boost in FE.

I regulalry swap between my 17" wheels with LRR Michelin Primacy MXM4s (215/45/17) tires to my 15" wheel with LRR Yokohama dB Super E-Spec tires (185/65/15) and my mpg goes from 46mpg to 55mpg. My commute consists of a 1200ft. elevation gain otherwise the numbers would be 50mpg (17s) and 58mpg (15s).

Just something to consider. I do not think the TDIs would be any different with respect to gains or losses due to tire choice.
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Old August 5th, 2011, 10:31   #27
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Quote:
Originally Posted by bfrinkus View Post
EGR kit by dieselgeek:
-mpg before 44.9
-mpg after 44.3
-conclusion, not a smart mod if for mpg. However, this is a well made kit that serves an important purpose. I recommend this kit.
If you lived north of the 40th parallel, you'd see quite a much larger hit to fuel economy from EGR delete. My before/after (2000 mile average by precisely calibrated scanguage) was 46.x/42.x(It's been a while) in winterat lattitude 45 on the left coast.

EGR delete has ZERO benefit anymore. If it makes you feel good then fine, but it is completely useless now that the intakes don't clog any more. The fuel has been cleaned up, and intake clogging hasn't been an issue for 4 years now.
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Old August 5th, 2011, 10:55   #28
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My 150K mile TDI used to be my grandfathers... and it was run exclusively on diesel supplied to a home tank. There has never been a reason to remove the intake, for the life of the car!
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Old August 5th, 2011, 16:55   #29
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hey so Ive been wondering, is this ''timing adaptation'' or advancing the timing. Is it possible on a BEW? I want to be able to get this car to the 50mpg+ zone just as my old ALH
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Old August 6th, 2011, 05:50   #30
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Quote:
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hey so Ive been wondering, is this ''timing adaptation'' or advancing the timing. Is it possible on a BEW? I want to be able to get this car to the 50mpg+ zone just as my old ALH
I'm not sure if the PD timing can be changed in adaptation (someone who knows will let you know), but regardless it will not get as good of mileage as your older ALH model due to design changes (tighter emissions, more power, heavier car, etc.) Timing changes in ALH models are easy and have w/o a doubt increased my mileage a bit.
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