Sprint Fuel Consumption Theory

Discussion in 'Sprint & Trophy' started by Duckadiledundee, Sep 15, 2020.

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  1. Duckadiledundee

    Duckadiledundee Peasant First Class
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    Jun 24, 2019
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    I've come up with a theory on why my fuel consumption is so high and need you guys to give me expert advice and such...
    In the old days we had a choke and if it was cold out you pulled out the choke and extra fuel was delivered, the engine warmed up and you pushed the choke back in..job done...

    Nowadays its all computer controlled and fuel injection and no choke..

    So is it possible that my bikes ECU thinks my bike is cold and stuck on initial start up mode where it throws extra fuel in all the time..This would explain my outrageous fuel consumption continuous smell of petrol and crappie mileage..

    If this is so what can I do???
    Also how can I prove or disprove my theory???

    I don't think it as a cold start sensor and think it may be a case of replacement ECU but as I understand that complicates things as you cant get them new and can't repair them...

    Cheers lads..
     
  2. Smilinjack

    Smilinjack Crème de la Crème

    Aug 14, 2016
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    I'm not sure a faulty sensor or ECU would cause the bike to smell of petrol, unless you can smell the unburnt fuel in the exhaust. Would quite likely enrich the mixture though. I had a VFR that did it when the wax fast idle unit went tits up and the engine ran really cool. I had a similar problem with my ZZR1200 when I trapped the main breather pipe after refitting the tank once. Guzzled gas, I had to ride across Spain at full throttle :p and fill up every 100 miles. :)
     
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  3. Rocker

    Rocker Elite Member
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    May 1, 2016
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    Did you get the throttle bodies balanced properly duck that'll make a big difference
     
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  4. Callumity

    Callumity Elite Member

    Feb 25, 2017
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    A code reader or program like TuneECU can read your ECU and identify error codes created by defective sensors that should inform fuel mapping. It is the price we pay for progress!
     
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  5. Georgez

    Georgez Member

    Nov 2, 2019
    50
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    Pacific North West
    "fuel smell" is real old school... leaky carburetors and such. Have the engine put under the scope and straighten out the trouble.
     
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  6. Old dumb arse

    Old dumb arse Senior Member

    Mar 28, 2020
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    Might want to check the spark plugs and gap. Occasional miss fires will increase fuel consumption.
     
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  7. Mof

    Mof New Member

    Aug 22, 2020
    1
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    Somerset, UK
    I assume this has been a problem since before the tank got 'overhauled' ?
    'Cold start sensor' = engine temp sensor, is the engine temp gauge showing sensible readings?
    Has the engine management light been on lately? As I understand it anything that causes the ECU to register an error code will also cause it to illuminate the management light - so if that hasn't been on there may not be any useful error codes to read if you connect up TuneECU.
    However, to some extent the ECU will re-calibrate over a few engine start/stop cycles and will stop registering a fault if it decides the system has become stable (I've had this happen in as little as two cycles). One thing that can cause the ECU to register an error and then resolve it is a slight change in the resistance across one of the 'critical' connections - it's done this to me when the fuel pump plug has reconnected 'differently' after I've had the tank off. If you've got a bad connection across the engine temp sensor that could cause the ECU to think the engine is running colder - but for that I'd expect the ECU to have thrown an error (management light on) but possibly to have 'resolved' it after a few start-stop cycles. And the engine temp gauge would probably not be getting out of 'cold'.
    Too many words :( - I guess the first line of attack is, are you smelling this at the back of the bike - in the exhaust - or up front when you're sitting on it??
     
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  8. Duckadiledundee

    Duckadiledundee Peasant First Class
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    Smell from exhaust and is unburnt fuel...
    No error codes on tune ecu..
    Not redone throttle bodies since putting the proper map backon it through tune ecu..
    Spark plugs at correct gap but are always black and sooty..
     
  9. Old dumb arse

    Old dumb arse Senior Member

    Mar 28, 2020
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    Black and sooty plugs bad. Check your air filter/air box for stoppages.
     
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  10. Duckadiledundee

    Duckadiledundee Peasant First Class
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    Oooh and I'm not sure how or even if this is relevant but after an oil and filter change my little oil level window looks lovely with clean clear oil but after only a couple of rides it thick black again...
     
  11. Duckadiledundee

    Duckadiledundee Peasant First Class
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    I think when I get the chance I will screenshot some readings on tune ECU from a cold start and later from when it as warmed up..stick em on here and see if you guys can tell what's going on..its all Egyptian hieroglyphics to me..:confused:
     
  12. Smilinjack

    Smilinjack Crème de la Crème

    Aug 14, 2016
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    Don't shoot me Dave, but what's your air filter, and associated plumbing, like?
    Oil goes black disappointingly quickly after a change, not sure that's an issue. If fuel was getting in the oil you'd be more likely to get engine noises for one thing. :)
     
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  13. Duckadiledundee

    Duckadiledundee Peasant First Class
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    Air filter is new from W.O.T...
    I did replace all the cracked IACV hoses with new tubing but wasn't OEM and I'm wondering if that's a bit too soft and collapsing in on itself although it shouldn't do...
     
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  14. Callumity

    Callumity Elite Member

    Feb 25, 2017
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    I read that as Wide Open Throttle!

    Sometimes electronics need more electronics I.e. a rolling road re-tune. It is pure guesswork without a full history of all deviations from OEM and diagnostic confirmation of fitted sensors.
     
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  15. alfie

    alfie Getting older but still going for it
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    Jan 27, 2018
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    You tend to see an increase in the oil level if fuel is getting in the oil.

    Alfie
     
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  16. Aidan

    Aidan Well-Known Member

    Dec 31, 2018
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    Essex
    I have a 2016 Sprint and often got a whiff of fuel in the garage after putting it to bed after a run. Did service and air filter was in pretty poor shape (even after a year), so maybe that was it. Still get a little smell, but maybe they run a bit rich? New plugs and old ones were perfect biscuit colour. Have TuneECU and TBs all balanced perfectly. Stock exhaust and map. Oh, and the oil does start to discolour almost immediately after an oil change (however, nowt as bad as my Mercedes diesel which makes treacle out of the oil every year).
     
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  17. stinger

    stinger Senior Member

    Nov 28, 2017
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    Just my thought, my Sprint was idling a bit rough, someone said to me your bike smells of petrol. Me with my enhanced sense of smell didnt notice it. Anyway, a bit of investigation found the fuel pipe at the bottom of the tank was partially off, the fuel pipe clamp connector was damaged.
     
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  18. Duckadiledundee

    Duckadiledundee Peasant First Class
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    Mine is definitely unburnt fuel from the exhaust...ive had that tank on and off maybe fifty times checking different things...i know my bikes fuel tank plumbing intimately...oooer missus :p:joy::joy::joy:
     
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  19. ChrisJHuff

    ChrisJHuff Active Member

    Sep 2, 2020
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    #19 ChrisJHuff, Sep 21, 2020 at 1:37 PM
    Last edited: Sep 21, 2020 at 3:39 PM
    Just a thought - way out right field...right on the boundary line in fact so feel free to ignore and shoot down in flames... Fuel pressure regulator ??? or more likely the injectors... just ideas to try
     
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