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Thread: Hight Fuel Consumption. Cannot Find the cause (6MPS)

  1. Default Hight Fuel Consumption. Cannot Find the cause (6MPS)

    Hi all.

    Some of you may have seen me trying to diagnose poor consumption on my 07-6MPS in MPSTorque

    I've got no Mods, apart from VARX mufflers and a BOV.
    I had my consumption averaging 12.5-13.5 so a little high, then one week it just shot up to 16.5 and has remained like that.
    I drive quite normal, with the rare push.
    I think it's running rich because the back of my car gets really dirty really fast (Though it is white so hard to tell whats dirt and excess fuel)

    I've tried a lot of things, it's now back between 12.5-13.5 but I think it might go up again, additionally I've seen other 6MPS that have been modded getting better about 11.5

    Things I've tried / looked at.
    • No error codes thrown to ECU
    • Tyre Pressure (@38 PSI) - Tyres are less than 1500KM old, P-Zero Nero
    • Cleaned MAF Sensor, Air Filter clean (new)
    • Battery Reset to reset ECU
    • Checked LTFT , STFT, Fuel Pressure / Rail. All numbers verified by someone on MPSTorqe
    • Tightened Spring on BOV, set to Bypass mode.
    • Used Fuel Injector Cleaner (stuff you put in with Petrol)
    • Mechanic checked Spark Plugs, Injectors, Filters, etc.


    Ruling all that out people have suggested I check for boost leaks.

    Nothing is strange about driving the car, nothing feels weird no funny sounds, etc.

    Starting to become quite a mystery... any help would be great.

    Many Thanks

  2. #2
    Join Date
    Apr 2010
    Location
    Canberra
    Posts
    9,459

    Default

    How do you drive? Highway, stop/start?
    What was AFR/stft/ltft?

  3. #3

    Default

    My modded one gets about 9.5l
    Perhaps you should mods yours further :P

    Seriously though, if you have checked all those things, and there arnt issues, then i would look to question:

    Road quality you drive on. A poor quality road will result in a higher amount of friction and thus higher fuel use.

    Weight in the car. Are you carrying around a lot of weight? More weight = more fuel use.

    Drive style. Are you constantly stop starting? If so, more fuel use. This also goes for hilly driving. Are you going up and down hills a lot? Traveling up and down a hill will result in 30-50% more fuel use then going the dame distance on a straight road.

    Diff and transfer case friction. The more energy required to spin the cogs in your front and rear diffs will result in more fuel use. Perhaps an oil change is in order.

    Damage to the front of the car. Do you have any protrusions, cuts, dents etc on the front of the car? These might increase the air friction and wind resistance as you drive.

    Petrol quality. Are you running 98ron? I use bp ultimate in mine and always have. Poorer quality fuels will cause more usage.

    Shifting style. Do you shift too early or too late? Will cause more fuel use either way.

    That's all i can think of for now.
    wsDK_II
    Radiant Ebony Mazda MPS 6 (September-2007)
    My Ride: http://www.ozmpsclub.com/forum/membe...-services.html
    What is stock????

  4. Default

    Always use BP98, Driving is normal suburban city driving.
    Typical amount of hills and the like.

    The interesting thing here though is the fact that it changed so rapidly. 12.5-13 to then 16.5 after a new tank of petrol.
    In addition the back is a bit black which leads me to think it's rich burning, not just using more.

    Thanks for your suggestions

  5. #5
    Join Date
    Apr 2010
    Location
    Canberra
    Posts
    9,459

    Default

    Do you have logs/info on the stft/ltft and air fuel ratios?

  6. #6

    Default

    Dude apparently thermostat can cause this too.. how many mins from cold does ur car take to reach operating temp?

  7. Default

    I had a similar issue with my old Silvia, turned out to be a dead O2 sensor

  8. #8

    Default

    Might be your petrol or o2 sensor. I would see if anyone else who uses your petrol station has had any issues with fuel (google search or ask attendant)

  9. #9
    Join Date
    Nov 2008
    Location
    North side, Vic
    Age
    37
    Posts
    6,745

    Default

    Post up the ltft and stft and afr as Sam said, best place to start.

    Sent from my D6503 using Tapatalk

  10. Default

    9.5!?!
    9.5 is what I get on the highway.
    I tend to average 12.5 with mostly city driving using 98RON and a Cobb AP stage 1 98 OTS tune (no other mods).
    @wsDKII Did your car always average 9.5? is that mostly highway driving on level roads?
    If adding mods to my car will reduce my consumption to 9.5 then I would consider doing it.
    @89jase - Though it probably wont account for your instantaneous change in consumption I would definetely check tyre pressure as being a few psi down on your tyres will increase consumption by about 10%.

    Did the increase in consumption happen after a fill up? I have had bad consumption runs before which i suspect have been due to crap fuel

    Quote Originally Posted by wsDKII View Post
    My modded one gets about 9.5l
    Perhaps you should mods yours further :P

    Seriously though, if you have checked all those things, and there arnt issues, then i would look to question:

    Road quality you drive on. A poor quality road will result in a higher amount of friction and thus higher fuel use.

    Weight in the car. Are you carrying around a lot of weight? More weight = more fuel use.

    Drive style. Are you constantly stop starting? If so, more fuel use. This also goes for hilly driving. Are you going up and down hills a lot? Traveling up and down a hill will result in 30-50% more fuel use then going the dame distance on a straight road.

    Diff and transfer case friction. The more energy required to spin the cogs in your front and rear diffs will result in more fuel use. Perhaps an oil change is in order.

    Damage to the front of the car. Do you have any protrusions, cuts, dents etc on the front of the car? These might increase the air friction and wind resistance as you drive.

    Petrol quality. Are you running 98ron? I use bp ultimate in mine and always have. Poorer quality fuels will cause more usage.

    Shifting style. Do you shift too early or too late? Will cause more fuel use either way.

    That's all i can think of for now.

  11. #11

    Default

    Quote Originally Posted by discodave View Post
    9.5!?!
    9.5 is what I get on the highway.
    I tend to average 12.5 with mostly city driving using 98RON and a Cobb AP stage 1 98 OTS tune (no other mods).
    @wsDKII Did your car always average 9.5? is that mostly highway driving on level roads?
    If adding mods to my car will reduce my consumption to 9.5 then I would consider doing it.
    My driving is about 40% city and 60% highway. When i got the car in Sep 2013, it was averaging 11.5l/100km. I soon sorted that out with a modded air intake (Corksport SRI + TIP), and a stage 1 tune via the COBB.
    Important to note also, that it is my driving style that helps. I will usually go about 65 in a 60 zone for example, so i can be in 5th gear. Where it is safe to do so, i will coast in neutral, and am adept at not speeding up to a red light

    I'm currently getting a etune by @Rayd, so when we are happy with that ill post up official kW and L/100km figures so you can get an idea.

    check out my build in my sig for more details on everything
    wsDK_II
    Radiant Ebony Mazda MPS 6 (September-2007)
    My Ride: http://www.ozmpsclub.com/forum/membe...-services.html
    What is stock????

  12. #12
    Join Date
    May 2009
    Location
    Bathurst
    Age
    42
    Posts
    1,930

    Default

    What everyone else is getting isn't important here.
    His Driving style shouldn't be questioned as he says it hasn't changed.
    So obviously its a mechanical problem.

    Going on what OP has tried already, I would, post logs as mentioned, run the car nearly out of fuel and go to a completely different servo. If you use BP, go to a Shell or a Caltex or United for example.
    Then if that does nothing, get a boost leak test, then if that shows nothing, have a look at the O2 Sensors.
    Start with the simple and cheap options first.
    2013 Ford Focus ST - Performance Blue, Cobb AP

    Gone 2006 3 MPS Sports - True Red, Koni FSD shocks, in dash OEM look Ebay GPS/DVD, Hypertech, RX8 Rims

  13. Default

    Check your tyre pressures. Low tyre pressures increase rolling resistance.

  14. #14

    Default

    Quote Originally Posted by adz35 View Post
    Check your tyre pressures. Low tyre pressures increase rolling resistance.
    As simple as that sounds, it can have a huge effect on consumption... our run-about-rolla drinks like a sailor if the tyre pressures are out of wack

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