mods and effect on mpg

bfrinkus

Active member
Joined
Oct 13, 2010
Location
Watkinsville, GA
TDI
1997 Jetta TDI
I LOVE these forums, but have a beef with relative lack of data relating mods to fuel economy. I see a lot of "I did x and got about 10% mpg improvement!". Many claims are unrealistic and don't take into account all possible variables. Here's my approach to make a contribution to these forums:

-all mods are performed by me, but primary driver of the car (1997 jetta tdi sedan 5 spd manual) is my wife. She is not aware of what mods are made or when so this should eliminate placebo effect.
-all "fillups" are comprised of fuel ups of at least 8 gallons.
-all mpgs reported are 3 tank averages directly before/after mod. This should eliminate a one tank outlier where maybe the fuel tank doesn't get filled all the way to the top.
-all fuel ups are as consistent as possible in method.
-my wife's driving routine and habits are pretty dang consistent. She's no hypermiler, but consistently upshifts at 2000 rpm and drives at or 5 over the speed limit.
-I perform 1 mod at a time so as not to confuse results.
-car was purchased used with "high" miles of 216k. Car was dealer maintained and 100% unmodified when purchased.

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.

Switch from conventional motor oil to synthetic oil:
-mpg before 44.3
-mpg after 44.1
-again, if for mpg only, you're out of luck. There is lots of discussion on here about this topic. I think synthetic is great, read some other posts and see what you think.

Fuel quality: some companies clearly disclose diesel cetane, other companies won't let the cat out of the bag. I switched from bp (company publicly claims to sell diesel with cetane of 40) to QT (neither corporate nor stations can/will tell me what cetane they sell).
-mpg before (bp): 44.1
-mpg after (QT): 46.1
-WOW! I actually set 2 tank mpg records in this 3 tank span. This reinforces the importance of fuel quality on performance of our diesel engines. Again, there are some great posts telling what fuels are what quality. Take the time to find the best fuel in your area...as my experience shows, it may be worth a few miles a gallon!

I recently added MotorKote hyper lubricant to my engine. My gut tells me it's snake oil, but there's only 1 way to find out, huh? If there's anything ya'll want me to try, let me know! If it's cheap and not dangerous in my opinion, I'll do it. If it's expensive and you're willing to foot the bill, I'll do it.

More to come soon...

Best,
Brad
 

AndyBees

Top Post Dawg
Joined
May 27, 2003
Location
Southeast Kentucky
TDI
Silver 2003 Jetta TDI, Silver 2000 Jetta TDI (sold), '84 Vanagon with '02 ALH engine
Obviously, there is something going on with your TDI.....seems MPGs are low! The low MPGs could be related to the driving circumstances, i.e. mostly city and mixed vs on the road.

Statistics: I don't think a three tank usage after a mod will actually reflect the data you are looking for, unless the driving circumstances are the same as the previous three tanks..........and were all those tanks actually full...very important! Long term data is more reflective of any results, etc.

EGR mod: I do not have the Diesel Geek EGR, however, I did do the EGR mod via VCDS and the stats I maintain in Excel spreadsheet definitely showed a difference in MPGs. It is very reflective in the numbers as well as the MPG graph!

Oil: Why was conventional oil being used in the engine? I thought it was dealer maintained????? I seriously doubt that switching from the conventional oil to synthetic caused a MPG drop ....just no way!

Fuel: I have always purchased fuel where it is the cheapest...... really have not noticed a difference in the MPGs. I have burned QT diesel (my brother lives in Gainesville, GA ..QT stations there) and did not notice any difference........ lately I've been burning diesel fuel purchased from Kroger supermarket pumps...no noticeable difference.

Additives: I'll get beat over the head for this: In my opinion, most "additives" are snake oil....regardless of the product or name brand! I do not use additives of any kind, unless a very cold weather system is moving in. Then I add Power Service to aid in preventing the fuel from gelling!

I have over 236,000 miles of data in my Excel Speadsheet! The Mod I have done that achieved the best results was to slow my average speed! Of course, other good driving habits can improve fuel economy. Avoiding jack rabbit starts, stay out of drive-thru lines (McDs, Banking, etc.), avoid idling the engine, make the best use of coasting in gear (approaching a stop sign, red traffic light, etc.), draft when possible/appropriate/safe, empty the car of unnecessary junk (weight), keep a skid cover on the bottom of the engine (reduces drag), avoid speeds in excess of 70 mph, avoid driving in lower gear when the next higher will be more appropriate for the circumstances (driving around with the RPMs up unnecessarily), etc.

Back to my first statement: A determination should be made as to whether the car is achieving the best MPGs under the driving circumstances before doing any mods.......i.e., does it need attention to maintenance issues: engine timing, air filter, accumulated oil removed from the Intercooler, Intake manifold & EGR cleaned (probably packed with crud due to using the conventional engine oil), ...........fuel filter? Well, I seriously doubt a new fuel filter will improve MPGs.

Keep us posted!
 

bfrinkus

Active member
Joined
Oct 13, 2010
Location
Watkinsville, GA
TDI
1997 Jetta TDI
andybees, thx for input. To address your concerns:
-all maint up to date ie fresh filters, intake cleaned, snow screen cleaned, ecm parameters set within oem specs, etc. I also regularly check and maintain consistent tire pressures.
-wife's driving routine very consistent. 50 mile round trip daily commute at 60mph with no lights. Small amount of city driving. Fuel ups made in same manner to full each time, ventectomy performed before any mods.
-i agree...neither synthetic oil nor egr delete caused mileage drop. I think small drops or gains are likely statistically irrelevant.
-i also agree that driving style habits are biggest affect on mpg. However, i'm looking for mods to supplement improvements made by driving style.
-i have a theory that pirelli tires are robbing me of several mpgs. I won't know for sure until i swap tires.
-sounds like you have some good data! To all on forum, please share mods you made and thier effect on mpg if you have supportive data.
-most stations sell diesel with cetane of 40 which is why i believe you don't notice mpg difference between brands. However some stations ex: amoco branded BP is 47 cetane, sell higher quality fuel that i'm convinced provides better performance and mpg. Whether costlier fuel is cost effective or not is another question...
Thanks for input!
Brad
 

MikeMars

Veteran Member
Joined
Mar 6, 2008
Location
UK
TDI
Vento 1.9 TDi (retired), A4 1.9 TDi (rear end collision), VW Passat 1.9 TDi (retired), Audi A2 1.4 TDi
...
-i also agree that driving style habits are biggest affect on mpg. However, i'm looking for mods to supplement improvements made by driving style.
...
This is the problem - it is likely that the data you are generating is dominated by temperature&driving style, rather than reflecting the changes made by your modifications. These two variables dominate all others.
 

VWBeamer

Veteran Member
Joined
Jan 1, 2009
Location
GA
TDI
2004 Jetta Wagon
Did you get a re tune after the egr delete? I went from 38 to about 42 after Egr delete, tune and larger turbo.
 

UFO

Veteran Member
Joined
Jul 31, 2007
Location
A mile high
TDI
2001 Beetle
Unless you can undo the mod and repeat the results, differences of less than 1 or 2 mpg are typical tank to tank, and cannot be held as significant. Especially if you are not the driver and have no awareness of the driving conditions.
 

Nich

Veteran Member
Joined
Jul 17, 2009
Location
Pheonix, AZ
TDI
5 spd 03 Jetta TDI
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%
 

UFO

Veteran Member
Joined
Jul 31, 2007
Location
A mile high
TDI
2001 Beetle
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%
The term huge is subjective. It depends on how much variation there is in the conditions out of your control - traffic, driving conditions, habits, weather, and yes, pump variations. Normal pump variation is limited and tested to 6 cubic inches in 5 gallons -- that's 0.5%. 12% is either a lie or criminal.

Your typical fillup probably varies more depending on how full you fill your tank, so multiple tanks must be averaged to determine the success of a mod.
 

fastalan

Veteran Member
Joined
Jan 1, 2010
Location
Richmond BC
TDI
2010 Golf TDI Wagon
How about using slightly taller tires? Sure that should help. Same rotation, more distance traveled.
 

Souzafone

Veteran Member
Joined
Nov 4, 2004
Location
Freetown,Ma.
TDI
'99 Jetta A4, Whitish
While the car in question is a TDI, it is also worth noting that it's a Mk III. Also, temperature can be a huge variable, especially when using such small samples.
 

bfrinkus

Active member
Joined
Oct 13, 2010
Location
Watkinsville, GA
TDI
1997 Jetta TDI
Wow, loving the response to the thread!

To restate my goal with this little project, my hope is to identify mods that will supplement smart driving and debunk overstated claims of efficiency improvement. Please understand that my R and D budget is very small. With this in mind, i think i've done a fair job minimizing variables well enough to identify statstically relevant trends. I will take into account all suggestions. To address some of them:

-i will review and compare ambient temperature to tank mpg results to see if there is a positive correlation. I'll let you know what i find.
-wife's commute: she takes the same route every day at the same time each day. There is no traffic. Ever. Best commute ever. She drives at to 5mph over. Test track? No, but ya'll are going to have to trust me that it would be hard to create real world driving conditions with fewer variables.
-i have thought about screwing with tire circumference, but have not due to money as well as speedo recalibration issues. In related news, I hope to be installing .681 5th gear in the next few months here.
-re-tune after EGR delete? I don't even know what that is, but i'll look into it.
-fuel volume:i'm aware that the gov allows only minimal inaccuracies in dispensed fuel volumes. I have no way to check this and will have to trust that Uncle Sam is enforcing things.
-Souzafone, i'm newish to the tdi world and did not understand your comment. Would you be so kind to explain what you meant? Thank you!

I invite all others with data to share so we can learn from one another!

Best, Brad
 

Turbospool

Veteran Member
Joined
Sep 15, 2007
Location
Daleville Va
TDI
2001 White TDI Jetta, 280k, 2003 jetta 270k
Wow, loving the response to the thread!
To restate my goal with this little project, my hope is to identify mods that will supplement smart driving and debunk overstated claims of efficiency improvement. Please understand that my R and D budget is very small. With this in mind, i think i've done a fair job minimizing variables well enough to identify statstically relevant trends. I will take into account all suggestions. To address some of them:
-i will review and compare ambient temperature to tank mpg results to see if there is a positive correlation. I'll let you know what i find.
-wife's commute: she takes the same route every day at the same time each day. There is no traffic. Ever. Best commute ever. She drives at to 5mph over. Test track? No, but ya'll are going to have to trust me that it would be hard to create real world driving conditions with fewer variables.
-i have thought about screwing with tire circumference, but have not due to money as well as speedo recalibration issues. In related news, I hope to be installing .681 5th gear in the next few months here.
-re-tune after EGR delete? I don't even know what that is, but i'll look into it.
-fuel volume:i'm aware that the gov allows only minimal inaccuracies in dispensed fuel volumes. I have no way to check this and will have to trust that Uncle Sam is enforcing things.
-Souzafone, i'm newish to the tdi world and did not understand your comment. Would you be so kind to explain what you meant? Thank you!
I invite all others with data to share so we can learn from one another!
Best, Brad
Here's an idea for you to test ..... if the wife is willing?;) Have her drive 5 mph under the limit instead of over, leaving home 10 minutes or so earlier and enjoy the scenery. I guarantee a significant mpg change.:D

Second idea.... would your wife enjoy a scanguage 11 ? This would inspire the right foot mod. :D
 

rprice704

Member
Joined
Mar 15, 2011
Location
Bessemer City NC
TDI
2001 jetta 1.9 tdi
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
 

schultp

Veteran Member
Joined
Mar 11, 2008
Location
Michigan
TDI
2010 Jetta Sportwagen, 6sp manual
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!
 

rprice704

Member
Joined
Mar 15, 2011
Location
Bessemer City NC
TDI
2001 jetta 1.9 tdi
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.
 
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1.9 TDI Awd

Veteran Member
Joined
Nov 20, 2010
Location
Marquette, Michigan
TDI
2000 TDI Golf 5spd
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.
 

brum

Veteran Member
Joined
Nov 30, 2009
Location
Bulgaria
TDI
Passat B5, 1.9 TDI, AFN
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.
 
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manual_tranny

Smyth Performance- Intern
Joined
Jan 5, 2010
Location
New Bedford, MA
TDI
2001 Golf @182K; 2000 Jetta @290K
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. :D
 

manual_tranny

Smyth Performance- Intern
Joined
Jan 5, 2010
Location
New Bedford, MA
TDI
2001 Golf @182K; 2000 Jetta @290K
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
 

brum

Veteran Member
Joined
Nov 30, 2009
Location
Bulgaria
TDI
Passat B5, 1.9 TDI, AFN
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 :) .
 

manual_tranny

Smyth Performance- Intern
Joined
Jan 5, 2010
Location
New Bedford, MA
TDI
2001 Golf @182K; 2000 Jetta @290K
Here's a great thread that discusses what happens with physical pump adjustments:

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

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!
 
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F8L

Veteran Member
Joined
Jul 17, 2011
Location
Woodland, CA
TDI
2012 Prius Three w/Solar Roof
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.
 

nicklockard

Torque Dorque
Joined
Aug 15, 2004
Location
Arizona
TDI
SOLD 2010 Touareg Tdi w/factory Tow PCKG
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.
 

manual_tranny

Smyth Performance- Intern
Joined
Jan 5, 2010
Location
New Bedford, MA
TDI
2001 Golf @182K; 2000 Jetta @290K
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! :)
 

mx07gt

Veteran Member
Joined
Apr 9, 2009
Location
Eagle Pass, TX
TDI
B5 Passat TDI
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
 

jettawreck

Top Post Dawg
Joined
Aug 2, 2004
Location
Northern Minnesota-55744
TDI
2001 Jetta and 2003 Jetta
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.
 

mx07gt

Veteran Member
Joined
Apr 9, 2009
Location
Eagle Pass, TX
TDI
B5 Passat TDI
well my scangauge right now says im averaging 52.1mpg on the tank. im 200 miles in the tank so ill see how that goes.

the best ive gotten before was 46mpg. about 40city/60hwy
 
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