[Diy_efi] ignition timing variation

[Stewart Prince]

Does anyone have any information on "acceptable" variation of ignition 
timing?  We're getting about +/- 2 degrees of jitter on our home-built 
EFI system (Formula SAE).  By my calcs, 100 microseconds of error 
corresponds to 1.8 degrees of rotation at 3000 rpm, and 7.2 at 12,000 
rpm (assume constant angular velocity). I believe the students are using 
the time between the last two teeth on an 8-tooth wheel (crank mounted) 
to calculate engine speed.  Is it possible that some sort of averaging 
scheme should be used to account for the speed variation due to combustion?

-- 
STEWART PRINCE

PROFESSOR, MECHANICAL ENGINEERING

CALIFORNIA STATE UNIVERSITY, NORTHRIDGE





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