///// What are your MPGs WITH Performance Mods .... IF driving conservatively ? /////

Andyinchville1

Veteran Member
Joined
Apr 7, 2016
Location
Virginia
TDI
2003 Jetta TDI wagon, 5 sp, 226K miles
Hi All,

Most people on this site modify their cars for better performance and that often means more power.... sometimes LOTS more but who can blame them? ....I've been bitten by the bug too! ;-)

Anyways, it seems that these same cars can have their MPG's stay the same OR actually go UP when driven conservatively(when compared to stock ....my assumption is better / fewer pumping losses due to better flowing exhausts, intakes , turbos etc and better optimization of fuel injection via larger injectors , advanced timing etc...).

I am hoping to see if there is a correlation (and I'm pretty sure there is) between performance mods and an increased MPG's when driven "normally" or at least the same as stock in order to see MPG increases or decreases for similar driving.

I am wondering also..... at what point do mods go so far as to negatively affect mileage ? Like maybe an injector gets so big that fuel just dribbles out as opposed to proper atomization etc..

I would like to see how far one can go modding before it results in worse fuel economy if driven conservatively.....(maybe "normally" and not hot rodding around)

To start ,

My car is modified per my signature and I get MPGs per the fuelly link in my signature.

I probably drive slower than most (typically 62 to 66 mph regardless of speed on the highway just to be able to keep speeds at a relative constant over many miles .and because I drive at night when deer are out) .

My MPG's have gone up from stock considerably...

Before any mods, I was typically 46 to 48 mpgs highway

A big MPG boost came from the Tune / Pump / injectors ( I did the 11 mm pump / injectors at the same time since my pump stopped working (at about 315K miles) ... the tune was done before the pump / injectors but I'd have to look for the records on that ) ... got me closer to 50 - 52 MPG and sometimes a tiny little bit past it).

Somewhere in here I upgraded tire size to 205 70R 15 then again to 205 75 R15 for more overdrive effect ... this helped alot ... in direct correlation to the increased diameter! .... a "free" mod if you need tires anyways. Somewhere in here 3" exhaust was added .... This got me into the 52 to 54 mpg range.

My last round of mods (BRM intake , upgraded SMIC, 3 Bar MAP) has pushed me up to tanks in the 54-56 MPG range ... I am thinking there is more to be gotten because I am not as modded nearly as much as many on this site..

What kind of highway MPGs are you getting and what are your mods? (also , what were you getting before your mods?)

Thanks in advance for any and all help.

Andrew
 

JohnTF

Well-known member
Joined
Feb 23, 2009
Location
St. Paul , MN.
TDI
2003 Jetta 1.9 AT Wagon
Too early for me to add much , but adding to the base - because I just started , bought about 2 1/2 weeks ago with 228,000 miles , 1st top off after about couple hundred miles with under car cover removed [ remember auto trans ] about 32 mpg , trans filter & fluid top-off [ was about 1 1/2 liters low ] , put the after-market aluminum bottom & side plates replaced - got about 34 mpg .
Having a hard cold start [ and after sitting overnight ] issue , the glow plug only come on with unplugging coolant sensor - then starts much easier , but a little ruff for a moment .
Also timing about 42-44 , little retarded .
Tires 205/65/15 low maybe 10,000 on tires Michelins .

A few yrs. ago I heard of someone in southern MN getting about 80 mpg ???

Have to keep in mind [ having the math & data ] how much BTU's are in fuel and - work needed to move car , as an example some of the wives-tales I heard 150 + mpg from carburetor & other stories , the off the top of head figures for BTU etc. / along with a car with specific weight & wind resistance , getting around 75 mpg , is a very ruff max ?
 

2002_auto_tdi

Veteran Member
Joined
Aug 3, 2020
Location
Virginia
TDI
03 5spd wagon and 02 01m sedan
Hi All,

Most people on this site modify their cars for better performance and that often means more power.... sometimes LOTS more but who can blame them? ....I've been bitten by the bug too! ;-)

Anyways, it seems that these same cars can have their MPG's stay the same OR actually go UP when driven conservatively(when compared to stock ....my assumption is better / fewer pumping losses due to better flowing exhausts, intakes , turbos etc and better optimization of fuel injection via larger injectors , advanced timing etc...).

I am hoping to see if there is a correlation (and I'm pretty sure there is) between performance mods and an increased MPG's when driven "normally" or at least the same as stock in order to see MPG increases or decreases for similar driving.

I am wondering also..... at what point do mods go so far as to negatively affect mileage ? Like maybe an injector gets so big that fuel just dribbles out as opposed to proper atomization etc..

I would like to see how far one can go modding before it results in worse fuel economy if driven conservatively.....(maybe "normally" and not hot rodding around)

To start ,

My car is modified per my signature and I get MPGs per the fuelly link in my signature.

I probably drive slower than most (typically 62 to 66 mph regardless of speed on the highway just to be able to keep speeds at a relative constant over many miles .and because I drive at night when deer are out) .

My MPG's have gone up from stock considerably...

Before any mods, I was typically 46 to 48 mpgs highway

A big MPG boost came from the Tune / Pump / injectors ( I did the 11 mm pump / injectors at the same time since my pump stopped working (at about 315K miles) ... the tune was done before the pump / injectors but I'd have to look for the records on that ) ... got me closer to 50 - 52 MPG and sometimes a tiny little bit past it).

Somewhere in here I upgraded tire size to 205 70R 15 then again to 205 75 R15 for more overdrive effect ... this helped alot ... in direct correlation to the increased diameter! .... a "free" mod if you need tires anyways. Somewhere in here 3" exhaust was added .... This got me into the 52 to 54 mpg range.

My last round of mods (BRM intake , upgraded SMIC, 3 Bar MAP) has pushed me up to tanks in the 54-56 MPG range ... I am thinking there is more to be gotten because I am not as modded nearly as much as many on this site..

What kind of highway MPGs are you getting and what are your mods? (also , what were you getting before your mods?)

Thanks in advance for any and all help.

Andrew
Great post.
 

burpod

teh stallionz!!1
Joined
Nov 27, 2004
Location
cape cod, ma
TDI
82 rabbit vnt ahu, 98 jetta vnt ahu, 05 parts car, 88 scirocco.. :/
my mk3 jetta, previously with: vnt 17/22, pp764s, 11mm alh pump, fmic with 2" tubing pd130 intake no egr no asv, no AC, 26psi requested tune, facet inline "lift pump", stock block and stock head. 195/65/15 tires (8% larger circumference which checks out according to gps measurements) + .681 5th gear CTN trans.

with non-winter fuel i would routinely get 55+ mpg on tanks where it was majority of miles on the highway and keeping speeds generally around 65-75 actual (taking into account the larger tires) and not beating on it too much, just the occasional italian tune up. more aggressive driving and more suburban driving i could sometimes see as low as 45.

since then, and i never got a chance to get any good readings, i installed .260 injectors and a real mk4 lift pump. now, since my timing belt slip it's getting forged rods, asv pistons, ported head with stage3 colt cam stiffer valve springs and 1856 turbo. also re-installing AC. i will be very bummed if i see much of a mileage drop. i don't think i will if driven normally. can't wait to finish getting it back together and broken in :)
 

GlowBugTDI

Veteran Member
Joined
Jul 20, 2018
Location
Cambridge, MN
TDI
2001 Beetle GLS TDI (BIODSL). Glow Bug TDI (sold)
27mpg...

Hoping 50ish once i fix the problem.
You read my 450mi tank thread though so you know i got problems here lol.
 

scooperhsd

Top Post Dawg
Joined
Aug 19, 2003
Location
Kansas City KS
TDI
NB, 2000, RED(5 Speed conversion) 2015 Golf SE
At least as good as stock for MPG (45+ MPG on highway, 40-42 in KC city / suburban driving) when driven conservatively (with traffic). Stock sized tires (205/55 HR 16) at recommended pressure.
Mods - 5 speed manual (no special gears / stock final drive)
much larger Fuel injector Nozzles
RC2 (special - in light of fuel injector nozzles, it's pretty close to stock below 3000 RPM to minimize smoke)
3 inch exhaust
 

IndigoBlueWagon

TDIClub Enthusiast, Principal IDParts, Vendor , w/
Joined
Aug 16, 2004
Location
South of Boston
TDI
'97 Passat, '99.5 Golf, '02 Jetta Wagon, '15 GSW
Stock turbo, 11mm pump, PP357s, lift pump, RC3+, PD150 snorkel, airbox, and turbo inlet, 2" downpipe no cat, stock exhaust.

This is from a particularly good run of fill ups year before last:

Included a trip to WI and one to NC, I think.
 

Nevada_TDI

Top Post Dawg
Joined
Aug 17, 2008
Location
Reno, sort of...
TDI
2001 Jetta TDI
I drive moderately around town and I cannot seem to get my city average above 38 MPG, and I have not been able to get highway miles yet.
I have new .216 nozzles setup by Frank, and a 24 PSI conservative fuel tune. I have changed my IQ from 4.2 to 6.5 and felt no loss of power and a very slight haze at WOT. Timing is slightly advanced too.
What should I do next is my quandary. I see members here getting way better FE with similar hardware and tunes, and I cannot figure out how they do it.
 

scooperhsd

Top Post Dawg
Joined
Aug 19, 2003
Location
Kansas City KS
TDI
NB, 2000, RED(5 Speed conversion) 2015 Golf SE
I drive moderately around town and I cannot seem to get my city average above 38 MPG, and I have not been able to get highway miles yet.
I have new .216 nozzles setup by Frank, and a 24 PSI conservative fuel tune. I have changed my IQ from 4.2 to 6.5 and felt no loss of power and a very slight haze at WOT. Timing is slightly advanced too.
What should I do next is my quandary. I see members here getting way better FE with similar hardware and tunes, and I cannot figure out how they do it.
Automatic ? You're doing about as well as you can get.

5 speed manual ? Well - city driving is by nature not going to get the MPG of highway driving / mixed driving.
 

IndigoBlueWagon

TDIClub Enthusiast, Principal IDParts, Vendor , w/
Joined
Aug 16, 2004
Location
South of Boston
TDI
'97 Passat, '99.5 Golf, '02 Jetta Wagon, '15 GSW
I drive moderately around town and I cannot seem to get my city average above 38 MPG, and I have not been able to get highway miles yet.
I have new .216 nozzles setup by Frank, and a 24 PSI conservative fuel tune. I have changed my IQ from 4.2 to 6.5 and felt no loss of power and a very slight haze at WOT. Timing is slightly advanced too.
What should I do next is my quandary. I see members here getting way better FE with similar hardware and tunes, and I cannot figure out how they do it.
There's a TDI owner around here with a similar setup and similar FE. Like with is car, I think if your mileage is that low then something's wrong. Track days aside, I can think if two incidences where I've gotten less than 40 MPG in my wagon: once was driving to PA into a near hurricane, and one was driving across ND with the cruise set at 85 and the A/C on. Otherwise, regardless of mods, I've always gotten low 40s at worst, 50ish at best.
 

Nevada_TDI

Top Post Dawg
Joined
Aug 17, 2008
Location
Reno, sort of...
TDI
2001 Jetta TDI
IBW, thank you for your response. I have been pulling out what little hair I have left trying to figure out what the source of the problem is.
My tires are all at proper pressure...the only thing I have not done lately is checking the temperature of the brake rotors when get out of the car. I just checked the rotors, and they all in the middle 80's.
I will see if there is anything I missed; the cost of a new tune to gain 5 MPG would likely take years to recover, so I will check again.
 
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