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Air/fuel meter running lean after warm up

Discussion in '4 Stroke Turbos/Supercharger' started by Alen Dean, Mar 12, 2018.

  1. Alen Dean

    Alen Dean Newbie

    Messages:
    8
    Location:
    Rothesay NB
    Country:
    Canada
    Snowmobile:
    2006 Apex GT
    I have no experience with superchargers. I bought a 2006 Apex GT used with the kit (4000mi). My apex GT seems to run fine until 1/2 tank of fuel then it seems to lean out. Stage II MPI supercharger kit, 290 HP cold air intake and BOV, Power commander autotune ECU, low compression piston and rods, 12 PSI boost? sea level or 1000' elevation at times. I have been running 91 octane and I have tried Torco boost with the 91 and didn't seem to do anything different on the A/F gauge. It starts good and idles fine. Otherwise seems to run fine. no pinging sounds and tons of power. Top end in this thing is incredible. I have yet to find the WOT on this thing but my question is: When the A/F meter goes past lean should I be concerned? Is it the octane? Can it be tuned with auto tune? Is it the warm weather? Any help would be appreciated.
     
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  3. MrSled

    MrSled Administrator Staff Member Admin Moderator VIP Member

    Messages:
    17,117
    Location:
    Schofield, WI
    Country:
    USA
    Snowmobile:
    2017 Sidewinder
    I need more info on when it goes lean and what are the number, Throttle position and RPMs? how much boost are we talking?
     
  4. Alen Dean

    Alen Dean Newbie

    Messages:
    8
    Location:
    Rothesay NB
    Country:
    Canada
    Snowmobile:
    2006 Apex GT
    I am going out tomorrow and it will be colder and I will let you know what the numbers are. Last weekend it was running lean at idle and any throttle was off the meter after several miles of riding. It still performed well although I didn't push it. last weekend anything over 1000 rpm and maybe 5 psi boost.
     
  5. MrSled

    MrSled Administrator Staff Member Admin Moderator VIP Member

    Messages:
    17,117
    Location:
    Schofield, WI
    Country:
    USA
    Snowmobile:
    2017 Sidewinder
    Make sure you have a good sensor.
     
  6. Alen Dean

    Alen Dean Newbie

    Messages:
    8
    Location:
    Rothesay NB
    Country:
    Canada
    Snowmobile:
    2006 Apex GT
    Where is the sensor? Is it on the air box? There is a bosch sensor on the side of that. I found a bad idler wheel behind the oil tank. Would that do it?
     
  7. MrSled

    MrSled Administrator Staff Member Admin Moderator VIP Member

    Messages:
    17,117
    Location:
    Schofield, WI
    Country:
    USA
    Snowmobile:
    2017 Sidewinder
    Bad wheel, no..lol, I am talking about the Bosch 02 Sensor, make sure you are getting accurate reading. When they go bad they will read all over the place. What brand gauge are you using?
     
  8. hlmrx1

    hlmrx1 TY 4 Stroke Guru

    Messages:
    974
    Location:
    Manitoba
    Like Mr. Sled said, what are the numbers? I have a turbo kit and 2 AFR gauges, one seems to read lean at idle and at slow speeds down the trail, around 13 and up, where as the other gauge reads more decent numbers, in the 12's. Extra fuel does not come on until there is 2-3lbs of boost and as soon as it does I see the AFR come down into the 11's. I was told that stock Apex's run lean like that. I'm not worried about the high numbers at idle or at slow speeds, but when I mash the throttle I want to see those numbers in the mid to low 11's.
     
    MrSled likes this.
  9. Alen Dean

    Alen Dean Newbie

    Messages:
    8
    Location:
    Rothesay NB
    Country:
    Canada
    Snowmobile:
    2006 Apex GT
    My AFR gauge is an old school light meter (2005). It reads rich at 5 o-clock, stoich. at 12 and lean at 7 o-clock . I do not have another gauge. I did notice that the wires are connected with crimps which are not a good connection. Perhaps an updated gauge is needed. Any suggestions on what the most accurate brand is? I put about 80 miles on it yesterday and today and still the same. Once warmed up the gauge leans out right off the scale on the gauge. No lights or meter readings with any throttle position and at an idle. Shut it down, let it cool off for 30 mins and when started up again it shows normal readings. @hlmrx1 the engine is not stock - low compression pistons and rods.
     
  10. MrSled

    MrSled Administrator Staff Member Admin Moderator VIP Member

    Messages:
    17,117
    Location:
    Schofield, WI
    Country:
    USA
    Snowmobile:
    2017 Sidewinder
    I would get a new meter and O2 Sensor from Innovate.
     
  11. mbarryracing

    mbarryracing TY 4 Stroke God

    Messages:
    1,697
    Location:
    Springville NY
    Country:
    USA
    Snowmobile:
    2006 Yamaha Attak Turbo
    2015 SR Viper RTX-DX
    1996 Vmax 600XT
    Does it run fine when the gas tank is full, and the fuel is cool? I used to struggle with a similar issue of my Apex, inconsistent AFR and start running on the lean side after riding for a while. I would constantly be playing with the settings on my piggyback after the fuel level got down after riding and everything was hot.
    My problem was the fuel temperatures... The fuel in the gas tank gets hot after running for a while because the hot exhaust under the tunnel bakes the plastic gas tank and the fuel getting returned to the tank being heated through the fuel rail. Fuel gets heated and no way for the heat to get out...
    The fuel would actually boil in the bottom of my tank when low level...
    Fill with fresh cool fuel the sled would run awesome until started getting back below 1/2 tank and the fuel temps rise again...
    Happens on a stock sled but they aren't as sensitive to it as a boosted sled.
    My solution was ceramic heat shields and pads between the headers and tunnel, and tunnel and gas tank... fuel temps don't vary as much and the AFR's are more consistent.
    I agree your AFR gauge sounds sketchy, but the only concern for running lean is under load and boost. Cruising light throttle no concern with a turbo but SC is pushing boost based on RPM so not sure myself on the SC.
     
  12. Alen Dean

    Alen Dean Newbie

    Messages:
    8
    Location:
    Rothesay NB
    Country:
    Canada
    Snowmobile:
    2006 Apex GT
    @mbarryracing I agree with you 100% on the temperature theory. I get the best readings when tank is refilled. The only way to know for sure is to monitor the fuel temp in the tank. When starting out on a run it reads perfect at all rpm's - idling and under load at full boost. As I ride along it slowly progresses to run leaner until it's off the gauge. I'm surprised that the design of the exhaust in relation to the fuel tank location was not considered to have an effect on the fuel temp ultimately effecting the flash point. As far as sensors go there is one on the air box (bosch), and one on the exhaust but do they both feed the AFR gauge? Which one should I be concerned about?
     
  13. mbarryracing

    mbarryracing TY 4 Stroke God

    Messages:
    1,697
    Location:
    Springville NY
    Country:
    USA
    Snowmobile:
    2006 Yamaha Attak Turbo
    2015 SR Viper RTX-DX
    1996 Vmax 600XT
    3877-SENSOR.jpg Alen, I'm not sure what the sensor is on your airbox. It would have to be an IAT (Intake Air Temp) but maybe post a picture?
    The AFR is a Lambda sensor in the exhaust stream to measure the ratio amount of oxygen in the exhaust. Sensor should look like this.
     
  14. mbarryracing

    mbarryracing TY 4 Stroke God

    Messages:
    1,697
    Location:
    Springville NY
    Country:
    USA
    Snowmobile:
    2006 Yamaha Attak Turbo
    2015 SR Viper RTX-DX
    1996 Vmax 600XT
  15. Alen Dean

    Alen Dean Newbie

    Messages:
    8
    Location:
    Rothesay NB
    Country:
    Canada
    Snowmobile:
    2006 Apex GT
    20180319_203614[1].jpg
    @mbarryracing I have a sensor on my exhaust under the skid the same as the pic you posted above. Here is a pic of the one on my air box.
     
  16. mbarryracing

    mbarryracing TY 4 Stroke God

    Messages:
    1,697
    Location:
    Springville NY
    Country:
    USA
    Snowmobile:
    2006 Yamaha Attak Turbo
    2015 SR Viper RTX-DX
    1996 Vmax 600XT
    Alen,
    What you have in your picture is a MAP sensor (Manifold Absolute Pressure) reading boost pressure in the intake plenum. Or the BARO sensor that the Apex uses that they mounted in the intake. Apex uses one of each.
    Do you know what type of fuel controller you have for the SC kit? That Bosch sensor looks to be a 3 Bar MAP sensor likely used by whatever fuel controller they have for the SC...
     
    Last edited: Mar 20, 2018

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