HEMI Technical Info

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Fuel/Clutch/Ignition Management

Fuel/Clutch/Ignition Management  
This is a summary of many different fuel management systems , the numbers are a little old school
 and may not represent current "BIG show" technology. 
  Idle Stage Hit 0 --> 1sec 1-->3 sec 3 ---> end
RPM 2600 2500 8500 8000 --> 7500 8200+
GPM 2.8 4 55-60 55-60 max of pump used 75+
PSI 50 120 350 350 400 500 +
Ign 55 55 52 50 ---> 35 50 60
cc/turn 5 6 44 25    
Idle: No Load, clutch in, slightly lean ( add heat to engine),  fuel pump (shutoff) partially closed, timing
     close to max., 
Stage: Small load (set by weight of base arm --(minus) force of base springs on clutch) clutch out, 
     Fuel pump full on, Idl pressure = max,
Hit: The fuel system total area is large ( fuel pump is larger the 50 gal and a slide valve is being used
      instead of jets - that can be controlled with timers) then an AJ or Enrichment valve must be used
     to cover the lean condition that is caused by the delay in pump rpm and the filling of the fuel lines.
1 sec: (depending on track conditions) retard timing 15-20 deg. to allow for tires to grow and control tire
     spin as clutch management starts to expose arms and add weight to clutch pack. Fuel  
      management starts to add fuel to compensate for drop in engine speed (and fuel pump - they are
      directly connected) caused by increasing load from clutch.
First part of run: Cannon moves adding load to engine, Engine RPM drops, fuel management adds
       fuel to engine to compensate  for RPM drop ( closing off jets or changing orifice size in a slide
      valve). ignition timing is slowly being advanced .
Lockup: after clutch locks up the engine starts to increase in RPM, and now we can reduce the fuel
      as the pump increases in speed. Open the jets back up if you used a jet style enrichment system
     or open a BDK valve (regulator), to bleed of the extra fuel.

Example of Fuel/timing 2004 1320' run

Example of Fuel/timing 2014 1000' run