afr how

Discussion in 'PSI Superchargers Tech Questions' started by blownapex, Jun 20, 2020.

  1. blownapex

    blownapex Member

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    how is every body calculating or getting air fuel ratio
    screw blown promod hemi automatic race pack datalogger jetsize
    so once you get the plugs afr correct in high gear
    how are you getting afr with your fuel timers with no 0/2 sensors(mfi)
    my experience 02 will not work with mfi
    i helped a team this weekend and they just opened jets and didnt know till they tried it and they still didnt know early in the run if afr was to rich or lean early
    plugs seem to only read burn in high gear
    my thoughts are get fuel correct from .5 on then use timing graph to correct driveshaft gmeter et
    what are the ways to get boost to fuel correct in all the different rpms early in the run
    discuss
    thanks
     
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  2. Mike Canter

    Mike Canter Top Dragster
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    Tried 02 sensors and they are all over the place and did not produce usable data and did not last long. The 02 sensor data was worse in the first half of the run and did start to stable out in the second half but still not producing very useful data. People use Boost to Fuel or Fuel to Boost but that will only put you somewhere in the ballpark. It boils down to plug reading and watching performance indicators.
     
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  3. Templar Motorsports

    Templar Motorsports New Member

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    Is there any way to get a handle on it? Or can you not because of the constant variable load until you hit high gear?
     
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  4. aj481x

    aj481x Member

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    You knew Mike would say to read the plugs. Most people have found O2 readings to be erratic at best on blown applications, although they are great on NA particularly on a dyno.
     
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  5. Templar Motorsports

    Templar Motorsports New Member

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    Yes I did know. lol

    But it is really hard to get a reading on the plugs on the front half of the track
     
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  6. Mike Canter

    Mike Canter Top Dragster
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    When you say the front half are you meaning the 1/8th mile. If so we read them all the time at 1/8th mile.
     
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  7. Templar Motorsports

    Templar Motorsports New Member

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    Yes. Sorry I'm in the north west. Mostly 1/4 mile stuff here.
    But if you are setup (geared) for the 1/4, do you just do a full hit in each gear and shut off? Then read the plugs?
     
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  8. TOL

    TOL Active Member

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    Thanks Mike. I'm kind of curious about the whole O2 sensor thing. Appreciate your input.

    So you had no luck with UEGO readings? You were using heated UEGO's retracted so they were not penetrating into the main exhaust primary pipe and getting wetted/impinged by globs of unburnt fuel? Were they pre-heated before the run? Sorry for so many questions.

    Have others had any luck with O2 sensors in blown meth applications? Would be really curious to hear more. The timing of this discussion is perfect as I was planning to order some.
     
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  9. Mike Canter

    Mike Canter Top Dragster
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    Templar, yes you can do that but you don’t want the 1/8 mile readings too lean so you can’t get to the 1/4.

    TOL, had heated UEGOs. Did not turn them on until the motor was running because they were not retracted. Didn’t want to hit hot sensors with liquid fuel. They still didn’t last long and cost big bucks.
     
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