Hondata

Hi guys,

datalogging shows a stable idle but ignition timing fluctuates 4 degrees erratically.

Motor stars to misfire at WOT above 4000rpm. Everything checks out alright. So i'm guessing the distributor might be the culprit, any suggestions?

Could it be noise interference or a faulty crank or cylinder sync sensor in the distributor?

Attached is a datalog showing the erratic ignition at idle.

For this test i've sent the ignition timing at 25degrees for the entire idling region but ignition timing fluctuates very badly.

Trigger problem or noise?

It is because your battery voltage is changing from 13.2 to 14.3 volts at idle.

Hondata wrote:It is because your battery voltage is changing from 13.2 to 14.3 volts at idle.

Fixed the voltage problem. Changed alternator but ignition is still fluctuating at idle. What could be the problem?

It looks closed to normal. See ignition controlled idle in the help file. http://www.hondata.com/help/smanager/in ... meters.htm

It has not got much vacuum for the highish idle speed, so if you make tuning / mechanical changes which improve the idle quality then you'll find the ignition variation will go down. I'd suggest looking at cam timing first.

Hondata wrote:It looks closed to normal. See ignition controlled idle in the help file. http://www.hondata.com/help/smanager/in ... meters.htm

It has not got much vacuum for the highish idle speed, so if you make tuning / mechanical changes which improve the idle quality then you'll find the ignition variation will go down. I'd suggest looking at cam timing first.

This is a turbcharged B16a. Perhaps the high idle can be adjusted on the throttle body but if you look at the datalogs, the idling is pretty stable with very slight variation.

Moreover, the ignition map has been adjusted to the same numbers for the entire idling areas.

How could the ignition timing have so much variation on its own? I dont see why the camshaft timing would affect the way the ignition timing fluctuates so erratically.

The ignition is within normal range; but if you want to reduce the variation then see what will give you more vacuum at idle. If the compression is lower than stock then that would explain the lower idle vacuum, otherwise often the cam timing might not be correct.