IGNITION PROJECT

[jac at wave.sheridan.wy.us]

In my system the rate of change in advance is limited by the 
response of the MAP sensor and one A/D conversion cycle.  The system 
clculates the advance for the ignition B just after loading the 
timer for ignition A. It is always 1/2 revolution behind the 
measured pressure.  This is pretty fast.  I expect that most systems 
would react as rapidly.  I doubt that the MAP has a time constant 
this short, no matter how fast the throttle is opened.

Consider an additional input indicating WOT + Nitro and program an 
exact advance if the input is present.

As a rev limiter it is effective to drop out all of the advance, but 
because my units go into airplanes, there is never a possibility of  
"clutch in - no load" situation.  Can you cut out the Nitro and 
advance and run rich with just air to limit revs?

 

-------------------------------------
john carroll
 jac at wave.sheridan.wy.us
 
---------------Original Message---------------
I'm currently working on a system similar to the one described in 
the
previous messages under the "Re:IGNITION PROJECT" subject heading. I
have a couple questions for anyone with some experience or knowledge 
in
this area.

1) Ignition advance on my controller will be compensated when a 
change
in temperature occurs. Should I sense coolant temperature or air
temperature? I know I have to reduce the amount of advance as the
temperature rises. Does anyone have a graph/equation for the rule of
thumb advance compensation versus temperature?

2) Should I bother with temperature compensation or just use the 
knock
sensor as the "feedback"? Then the uP could learn the change in 
advance
required and store it so after some running time it would look up 
the
compensation value.

3) What is the best method to reduce engine speed when a rev limiter 
is
utilized? Retarding the timing is one suggestion but is it fast 
enough
to protect an 500 HP engine revving 6000 RPM when a sudden big blast 
of
Nitrous Oxide is shot into it and the tires break loose? I think
removing the spark from every other cylinder would be a bad idea 
also (
cylinder wall wash among other things ). Any Ideas?


Any help or suggestions would be much appreciated!

Mark.


----------End of Original Message----------



-------------------------------------
john carroll
 jac at wave.sheridan.wy.us