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Thread: Tune Issues

  1. #1
    Swedish Viking Craigo's Avatar
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    Tune Issues

    I'm trying to figure out how I destroyed a couple of pistons last year....

    I have the Riva X-Charger Upgrade, the Riva RRFPR, Riva ECU and Bosch 50lb injectors. With my fuel pressure set to a static 42lbs (and the boost reference line hooked up) I was between 10.8 - 11.2 AFR at idle and 11.5 - 11.9 AFR at WOT depending on the temperature (according to my MTX-L guage). The day it blew up - I did notice an AFR spike of 12.7 just before the boost kicked in? According to my machinist - I ran lean which caused the ring ends to touch and destroy 2 of my pistons. I went with the Bosch 50lb injectors because I ride in mostly in 50 to 60 degree temperatures, and thought the extra flow would help to prevent catastrophic failure.

    To make a long story short... I've installed new pistons and am ready to fire up my ski. SO ... what should I check or what do I need to do differently in order to get my setup to run more reliably (without spending a billion dollars). And could my setup have gotten too hot in the RPM mid-range causing the failure?

    Thanks,

    Craigo
    Last edited by Craigo; 02-27-2013 at 04:45 PM.


  2. #2
    Doing any modding and tuning on any of these skis without the capability to datalog the motor is sketchy at best. I like the CMD/Wideband2/LCD-200 option but other choices are available out there.

    Andy

  3. #3
    Eastside Powersports Slow 91's Avatar
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    12.7 BEFORE you went into boost would not have caused the ski to run lean and blow up. 12.7 @ full throttle for a long period of time would cause deto.

  4. #4

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    I personally would be suspecting the AFR monitoring being correct. 42 lbs. fuel pressure w/ a finish of 54 at full boost on bosch 50's in 50 degree air temp and cool waters just sounds like a leaner condition than 11.5-11.9.

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  6. #5
    shrabber's Avatar
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    Well I had My buddy Go through the same thing He Had two Problems.. One To Me your Base Fuel Pressure at 42lbs Is to Low But at 11.9 Your spot On But when the Moon aligns Just as Him. He was Hit Or Miss. I ask Was fuel Pressure Regulator Are you Running? Secondally I think Your Injectors Being Bosch at 50lb are a bit Tall for your specs Hence your Base at 42. If you would want it to be More consistant You will Need to drop The Injector size IMO. I dont know If those reading mean that you ruined the engine because of it there are alot of variables as well.
    Last edited by shrabber; 02-27-2013 at 01:35 PM.

  7. #6
    imp0ster's Avatar
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    get your injectors flowed. all it takes is one pissing injector to destroy your engine

  8. #7
    boost junkie skidoochris's Avatar
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    riva race ecu.... timing?... knock working? if you deto the pistons (when lean) then knock is not working
    let me guess pump gas right ,bad combo pump gas and no knock control
    good afr dont mean shit with crap fuel
    my point, if you want reliability then you want knock control!

  9. #8
    Swedish Viking Craigo's Avatar
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    Lots of good info here! Thanks guys! ...

    *I think I can "data log" with the MTXL if I just plug my laptop into my ski while I'm riding and record the AFRs? Would that help to tune it ?

    *Also I thought that these engines had Knock Sensors? Is it likely that mine isn't working? There was no warning - replace sensor?

    *My injectors were purchased from the online store and were flow matched - plus it was 2 pistons that were damaged. I think my injectors are fine.

    *I'm assuming that there is a way to test my AFR sensor for accuracy? Wrong numbers? Maybe I need a new sensor?

    I'm running the Riva RRFPR.

    Hmmm...

  10. #9
    google MTXL "free air calibration"

  11. #10
    Swedish Viking Craigo's Avatar
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    Quote Originally Posted by whittlebeast View Post
    google MTXL "free air calibration"
    I know how to calibrate my MTXL. I just did that when my ski went together, and when I originally installed it last year.

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