c rotor hemi miss?

Discussion in 'PSI Superchargers Tech Questions' started by overkill69, May 6, 2014.

  1. overkill69

    overkill69 Member

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    I have a BAE 5 @129% with a c rotor that ran ok last season. I raised the compression from 9.8 to 11.2-1 and updated the cam . I also slightly modified the psi plate and averaged out the port nozzles keeping the same total area.I left the main jet the same from last year in the heat.
    I setup the mag like last year. Phased to 18 degrees on the mag trigger and set the crank trigger to 25 degrees total.
    At about 5000 rpm the engine hits a dead spot almost like a rev limiter or lean condition.It acts ok above that. I went into the 8973 and raised my launch rpm to 10k in case it was activating but no improvement.
    I welded on the car over the winter with everything unhooked but I wonder if that could corrupt an 8973 file?
    Next step is unhook the rev limit from the points box, then try it on the mag trigger.
    If ignition won't clean it up try richening the barrel valve? Its idles at .73 gpm where the rear burst panel just gets warm.

    Thanks for any thoughts
     
    #1
    overkill69, May 6, 2014
  2. Will Hanna

    Will Hanna We put the 'inside' in Top Alcohol
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    Damn..

    Damn son, you building a bomb? LOL

    I'm not one to tell you how to run your deal but I know you have said you are on a budget, and real high compression can be fast but it can also be unforgiving. The tireshake window will be a lot narrower too.

    That's a shit ton of compression with that much blower overdrive.

    If you have the burst panel just getting hot, you don't have enough fuel going through the hat, and in my opinion .73 gallon at idle is quite lean. You ever look at Frankie or Scruggs car at idle? They look like a fuel car...

    Just think about that. If you are getting the blower warm enough to heat the rear panel, you are pumping hot air in the intake. During the warm up I always feel the blower case between the case and rear cover on the bottom. You should feel no heat there. Ever.

    Can you post up a pic of your graph or email it to me at will.hanna@insidetopalcohol.com and we will see if it looks like ignition or something else.

    Generally component failures don't just miss at a certain rpm. It could be a programming issue or maybe the 8973 is doing something it shouldn't. You can unplug the 8973 chip and put a conventional rev chip in there.

    Are you sure it's not missing at higher rpm? Could be a points box or coil if it is doing that.
     
    #2
    Will Hanna, May 6, 2014
  3. overkill69

    overkill69 Member

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    This is still on the jacks. I'm not going to the track with an engine that wont take throttle clean.
    It was idling at 600 degrees avg. I've struggled with it blubbering and loading up so I run the BV as lean as possible.
    All the ignition just came back from Leahy for what that's worth.

    Actually the compression is 10.9 with staggered rods so some of them are .5 less. My plan is 9600 rpm redline, generous fuel and conservative timing and gear ratios.
     
    #3
    overkill69, May 6, 2014
  4. blownapex

    blownapex Member

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    mag

    i dont know what it will do but you had a chevy
    this is a hemi rotation mag
     
    #4
    blownapex, May 6, 2014
  5. overkill69

    overkill69 Member

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    lol. why didn't you mention that yesterday?
    It starts and runs ok. Just a weird spot in the response.
    Thanks for the help.
     
    #5
    overkill69, May 6, 2014
  6. Will Hanna

    Will Hanna We put the 'inside' in Top Alcohol
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    jackstands

    If it is misfiring on the jackstands, sounds like a pretty major ignition problem.

    The reason I say that we had something similar happen a few years ago on Chris Foster's FC. We trashed two motors. It would act like it was on a two step around 5000-6000 rpm. We changed crank triggers, changed degree wheels (thinking it was the magnet). Finally ran out of time and put it just on the mag. It didn't miss as bad, but it chunked the blower belt early each run we made and we eventually found several blackened rod journals.

    We obviously changed everything so it's hard to point a finger at any one component. Everything tested fine at Leahy's. The theory was maybe a bad plug wire was broadcasting a major RF signal and the crank trigger was a better 'antenna' than the mag trigger. New wires, trigger and retested ignition the next race and no more problems.

    As far as fuel system goes, the egt avg doesn't sound bad but I would still be concerned with the heat in the blower. Do you have 2 nozzles in the blower on checks and two full time? I would play with the fuel through the hat to get rid of that heat. It's not just a tune up issue, it will eventually cause problems with your blower.
     
    #6
    Will Hanna, May 6, 2014
  7. Will Hanna

    Will Hanna We put the 'inside' in Top Alcohol
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    outside of ignition

    Just out there I have seen the bv spool installed backwards but it would just about die when you brought it off idle.
     
    #7
    Will Hanna, May 6, 2014
  8. Mike Canter

    Mike Canter Top Dragster
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    Can you explain the statement that you said in your original post about leaving the main jet the same as last year in the heat. You mean you made all those changes to improve airflow and never changed the mainjet? Do you have a weather station and compute density altitude and change your main jet depending on the reading or are you just guessing the size of the main jet?
     
    #8
    Mike Canter, May 6, 2014
  9. overkill69

    overkill69 Member

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    The first hit will be an educated guess/rich and less than 330ft. Maybe not engineering logic but I figured fire it on the jacks and try to get a feel for how much things changed.I use a weather station and crude math once I have a decent baseline. If it produces an impressive baseline i'll probably buy a Davenport program and get more aggressive.
     
    #9
    overkill69, May 6, 2014
  10. Dale Finch

    Dale Finch Member

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    I can't imagine taking a guess at the main jet without knowing what the corrected altitude is and at least having a chart set up. A disaster waiting to happen.
    Dale
     
    #10
    Dale Finch, May 6, 2014
  11. overkill69

    overkill69 Member

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    ok... Next step is correct main jet for DA and richen a little to compensate for hardware changes.
    This was supposed to be a quick warmup, set timing and check for leaks before loading up. I always reset the main based on the conditions at the track.
    The only reason i'm here posting about it is I can't work on the car again until Saturday, so I figured i'd research in the downtime.
     
    #11
    overkill69, May 7, 2014
  12. overkill69

    overkill69 Member

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    fixed

    Reloaded a new tuneup in the 8973 and the car acts completely happy.
    When we get to the track I might try the old file again and see if the problem returns.
     
    #12
    overkill69, May 10, 2014
  13. Jason Bunker

    Jason Bunker Member

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    Good luck in Tulsa Mike. Hope to hear you guys run well. Ill be watching when I can.
    Talk with ya soon.
     
    #13
    Jason Bunker, May 11, 2014
  14. turbo69camaro

    turbo69camaro Member

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    3.83 new best guess you fould the miss lol
     
    #14
    turbo69camaro, May 18, 2014

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