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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Powertrain and Drivetrain Discussions > N54 Turbo Engine / Drivetrain / Exhaust Modifications - 335i > Experiencing Bad MPG



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      05-14-2013, 12:54 PM   #1
BD_e92
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Experiencing Bad MPG

Hello everyone, so I am running the HPF gen 2 exhaust and bms dci right now as my only bolt ons and no tune yet.. I went from averaging about 17-19mpg with the HPF exhaust and now after installing the dci I'm down to about 14.5 mpg.. can anyone shed some light on if the dci could affect my mpg that drastically?
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      05-14-2013, 12:55 PM   #2
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Not related.
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      05-14-2013, 12:57 PM   #3
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Not related.
any advice as to what it could be?
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      05-14-2013, 12:58 PM   #4
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Quote:
Originally Posted by #teambimmer View Post
any advice as to what it could be?
Could be quite a bit of things. Are you stepping on the throttle more to hear that exhaust/intake? That would do it.
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      05-14-2013, 01:01 PM   #5
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Originally Posted by E90Company View Post
Could be quite a bit of things. Are you stepping on the throttle more to hear that exhaust/intake? That would do it.
lol definitely did that in the beginning and figured that was why it decreased significantly, but after my last fill up i reset the mpg in the vehicle info and drove normal for a week with very little hard acceleration and it averaged out to be about the same
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      05-14-2013, 01:08 PM   #6
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I average 18.9mpg and I drive mostly highway. Your mpg seems normal to me
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      05-14-2013, 01:10 PM   #7
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heavy foot... bets way to measure MPG is do it yourself. fill the tank and reset the trip counter.

drive around till it's less than half at least (or whenever, but the more the drive the more accurate the measurement would be).

Refill and divide the trip counter number by the # number of gallons it took to refill.

Also take it easy
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      05-14-2013, 03:35 PM   #8
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I found your problem...

Your foot is too HEAVY with the new intake and exhaust sounds.

My MPG average over the course of 20,000 miles was 21.0. Your drive habits can sway this number largely. I know a few N54 locals that get about 23-24 Average MPG and others who have a heavier foot with more city driving in the 17-18 range.
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      05-14-2013, 04:13 PM   #9
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Quote:
Originally Posted by Jeff@TopGearSolutions View Post
I found your problem...

Your foot is too HEAVY with the new intake and exhaust sounds.

My MPG average over the course of 20,000 miles was 21.0. Your drive habits can sway this number largely. I know a few N54 locals that get about 23-24 Average MPG and others who have a heavier foot with more city driving in the 17-18 range.
hahaha I definitely agree that sometimes my foot can be a bit heavy but like you said people with a heavier foot are around 17-18, that doesnt explain how I am as low as 14.5mpg.. Should I possibly change my spark plugs being I have 36k miles and they have never been changed?
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      05-14-2013, 04:33 PM   #10
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The n54 doesn't have a MAF sensor so there' really no explanation of why the DCI filters themselves would have any effect on your fuel economy.

Have you checked to make sure you didn't accidentally knock your charge pipe loose?

The charge pipe is in the general vacinity of the intake location and if you fought trying to get the DCI to fit, you might have knocked it loose. The MAP sensor is located on the charge pipe and if there's a leak, it could in theory cause a loss in performance/fuel economy (although you'd likely throw a code).

Aside from knocking something loose, there's really no other explanation I can think of aside from a change in your driving habits, bad gasoline, or a significant change in weather.
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      05-14-2013, 04:51 PM   #11
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Quote:
Originally Posted by #teambimmer View Post
hahaha I definitely agree that sometimes my foot can be a bit heavy but like you said people with a heavier foot are around 17-18, that doesnt explain how I am as low as 14.5mpg.. Should I possibly change my spark plugs being I have 36k miles and they have never been changed?
I know the Bronx a bit and I would imagine in local traffic that 14.5 with a heavy foot seems reasonable. This car under accel in traffic averages about 10-12 MPG in stop and go traffic.

How much highway do you do? I woudn't sweat anything. Most of the spark plugs changes at 25K are for vehicles with a tune. 50,000 would be for a non tuned vehicle. There is really nothing a cat back exhaust or a dual cone intake can do that would tell your ECU just to waste more gas and spit out more fuel.
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      05-14-2013, 04:55 PM   #12
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With 90% city driving I get 15mpg or so in my 1er.....so yea :/
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      05-14-2013, 04:55 PM   #13
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I averaged 23 over the last 1000 miles... heavy foot you have
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      05-14-2013, 05:02 PM   #14
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Quote:
Originally Posted by Jeff@TopGearSolutions View Post
I know the Bronx a bit and I would imagine in local traffic that 14.5 with a heavy foot seems reasonable. This car under accel in traffic averages about 10-12 MPG in stop and go traffic.

How much highway do you do? I woudn't sweat anything. Most of the spark plugs changes at 25K are for vehicles with a tune. 50,000 would be for a non tuned vehicle. There is really nothing a cat back exhaust or a dual cone intake can do that would tell your ECU just to waste more gas and spit out more fuel.
thanks for all the help, I appreciate your detailed responses
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      05-14-2013, 05:06 PM   #15
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This happened to me after I installed my intake - turns out it was my foot
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      05-14-2013, 05:31 PM   #16
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I am averaging 24.5 mpg and have gotten as high as 32 mpg on road trips.
I have intake,cat-back exhaust, Helix IC, Vishnu Procede and charge pipe.
I have 85k miles and this has been consistent through out that mileage.

14-15 mpg would bum me out.
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      05-15-2013, 06:31 AM   #17
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Daily driving 100 mile round trip, all highway I average 29.3 mpg... It is all in how you drive it.
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      05-15-2013, 08:15 AM   #18
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Quote:
Originally Posted by marv85 View Post
heavy foot... bets way to measure MPG is do it yourself. fill the tank and reset the trip counter.

drive around till it's less than half at least (or whenever, but the more the drive the more accurate the measurement would be).

Refill and divide the trip counter number by the # number of gallons it took to refill.

Also take it easy
+1
I thought I was getting 17 mpg (according to the car), after calculating myself I found that I'm actually getting 22.5 mpg.
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      05-16-2013, 04:23 AM   #19
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22 no ethanol.
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      05-16-2013, 11:56 AM   #20
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I've got a tune on top of what you've got and a moderately heavy foot getting 21.7 avg mpg... something is wrong with your foot or car!
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      05-16-2013, 12:24 PM   #21
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I drive mostly stop-and-go in suburbs. I've noticed my mileage avg dropping per model of BMW i have owned

325ci - 25 mpg
328xi - 24 mpg
135i - 18 mpg
335i - 19.4 mpg

Ok, so I have improved with my 335i over my 135i
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      05-16-2013, 02:05 PM   #22
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When I was getting MPG like that my plugs/coils were starting to go bad. Replaced em and getting like 21-25 now.


14-15 did really bum me out, especially after a few quick tanks.
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