forbiddenera

This may be a bit technical for some, but I'm curious.

We know the speed of the flame front after ignition is dependant on AFR. We know the theoretical best angle for the end of combustion to be 12-15ish degrees ATDC, where the force will have the best leverage on the crank.

The combustion window depending on AFR is about 19-29 degrees.

Some quoting this amazing ignition article,

Turbulent flame speeds can range from 1.35 to 2.2 m/sec. in a well-mixed combustion chamber using a stratified charge at various cylinder pressures.

0.89mm is the piston to head clearance for an integra
0.89 mm / 1,350 mm/sec. = 0.0006 sec. = 0.6 milliseconds
0.89 mm / 2,200 mm/sec. = 0.0004 sec. = 0.4 milliseconds

0.021 msec is 1 crankshaft degree at 8000rpm
0.6 msec / 0.021 msec / degree = 29 degrees
0.4 msec / 0.021 msec / degree = 19 degrees

Could we not, from a datalog, use logged AFR/RPM to calculate flame front speed / combustion window, subtract it from 12-15 ATDC and show the theoretical best time for ignition? Could even show the delta from actual used ignition.

So, at datalog row X, afr is 13.5, rpm is 8000, we have 19 degree window of combustion, we should spark at say 7 BTDC for theoretical max best torque?

Would an app for this be useful? Thought about coding it up.

forbiddenera

Ps, this is the article I quote and explains a lot about this..

One of the BEST Ignition Timing Writeups I have ever come across - Honda Forum : Honda and Acura Car Forums

rhd91integra

u got PM