[urq] EFI + MAC-14 maxing ataround 5k RPM

[Stephen Redford]

------------------ Ben , you can get Megasquirt with Spark,  Why the hybred combo?  It sounds like spark might be the issue and maybe the Mac 14 is the reason .    Just a guess.       Stephen Redford  '85Urq with Megasquirt and still in the shop !!!     :)))

  ----- Original Message ----- 
  From: Ben Swann<mailto:benswann at verizon.net> 
  To: urq at audifans.com<mailto:urq at audifans.com> ; quattro at audifans.com<mailto:quattro at audifans.com> 
  Cc: 'Ben Swann'<mailto:benswann at verizon.net> 
  Sent: Tuesday, October 23, 2007 6:41 AM
  Subject: [urq] EFI + MAC-14 maxing ataround 5k RPM


  I think it is safe to rule out fuel delivery as a problem with my EFI'd engine now that
  I have replaced fuel pump and assured getting good fuel delivery at all times.  So back
  to the problem.  I think the ignition is dropping out at around 5000RPM, but at a loss
  on how to verify it and how to fix it.  To review, the engine is completely rebuilt MC-1
  with NF head being fed by Megasuirt V2.2 fuel injection through 42 lb injectors - need
  to verify as these are Lucas Bluetops, and might be 36#.  

  For ignition I am using the MAC-14 with dual knock sensors.  I have the car tuned fairly
  well by now in the below 5000 RPM range, and the engine runs great and pulls hard until
  it hits about 5000 RPM.  It doesn't matter what load and engine can be free-revving and
  still reaches about a maximum of 5000 RPM.  If I gun the engine briefly, the tach will
  hit 6K or so, but gradually increasing RPM it will go to about 5300 RPM and seem like it
  is hitting a rev limiter.  Holding the throttle open, the engine bounces - the RPM
  oscillates between like 4800 and 5400.  Occasionally I have seen 6000 RPM and holding,
  but not able to maintain that result.

  Things that can be automatically ruled out:
  Fuel pump relay - this does not apply, as I am providing continuous power to the fuel
  pump with a direct feed of #10 wire direct to the pump - relayed of course, but always
  on with ignition.  Once I get engine tuned, I'll enable cutout relay circuit - that can
  actually be done through MS.

  Fuel delivery - I have set at 45 PSI and it maintains good pressure with regulated flow.
  There is a pressure port on the regulator that can vary fuel pressure about +/- 5 PSI
  depending upon load/manifold pressure.  I see not reason to suspect there is inadequate
  fuel flow or pressure in the rail.

  There are no codes from the MAC-14.  Most of the fuel injection portion has been
  disabled and only providing power to O2 Heater at this time.  MAC-14 is being used
  mainly for ignition only.

  I swapped coils and it made no difference.

  I pulled wires one by one and no one cylinder deviates differently from the others  I
  will check plugs and do compression test - again.  When I installed the engine, I had
  even compression on all cylinders - consistant with a new engine.  Cap and Rotor are
  new.  Engine now has about 2000 miles on it and still running on the break-in oil.

  It does not make sense that it is EFI since the cutout happens regardless of how the
  engine is being driven or not - the cutout occurs at around 5000 RPM even just opening
  the throttle without any engine load.  If it were fuel, I'd think it would happen only
  under load.  Possibly the injectors are maxing out, but this does not make sense, as it
  should not take much fuel to rev the engine without a load. I also don't notice any lean
  condition when the problem occurs - seeing like a 12:1 on the O2 guage.   Still I won't
  rule out fuel injectors, but ..

  I think there is some reason the ignition is dropping out - like not enough current to
  the coil when the engine hits around 5000 RPM.  There is of course the long run from the
  battery located under the seat.  I ran an additiona #6 wire to a jumper post located
  near the coil and then runs down to the starter.  Although the engine cranks faster when
  starting, the RPM limit problem is still there.  

  I'm wondering if the coil is not saturating, and not enough current is available at
  higher RPMs.  Why this would happen on this car and not on a 200?  

  It doesn't make sense - this balanced engine should be good for well over 7000 RPM.  I'm
  going to post on some other forums - Megasuirt and MotorGeek, but this seems more like
  an ignition problem where the MAC-14 is  providing the ignition.  Maybe installing a
  capacitor or battery up front to test.I'm looking for ideas.

  Ben
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