Senior Tech Team
Join Date: Apr 2012
Location: Yerington, Nevada
Re: Crank Trigger Question
The main reason today's engines use individual, sequential ignition systems is that fun word we all just LOVE....EMISSIONS. Varying the timing in the wrong way makes for more emissions output, with the problem of making less power.
It is all in emissions efficiency and fuel control. When we developed the first HEI's when I worked on that project at GM, the premise was to build an ignition that would need absolutely low maintenance, along with not changing the timing at all during that period, so emissions wold not be increased. So, we designed and developed the large HEI, to replace points systems that changed with every spark plug firing from wear on points rubbing blocks and condition of points contact faces.
If anyone has tinkered with a points distributor for enough to get frustrated with it, they know that when they go into setting the system, they find a dwell change, and the timing they left the system at, retarded. And, during the maintenance, simply resetting the dwell back to the original spec, which would have been done at the service before, brought the timing right back to where it was the last service. I see it all the time, dwell set to 30 degrees, timing set to proper degrees. 10K miles later, dwell is changed, as is timing. Simply returning the dwell to the original 30 degrees, brings the timing straight back to where it was last set, service interval previous.
Electronic ignitions were designed to NOT allow the tiimng spec to change as miles were driven, eliminating one facet of emissions levels increasing. Those electronic systems have evolved into help for our engines along the way, they help increase performance.
If you have an older car that still has a points distributor, you can have some fun learning, set the dwell and timing, then, leave the dwell meter connected, and use the Allen screw to change the dwell as the engine runs, record the timing changes on the balancer, then, bring the dwell back to the original spec. Amazing how a bit of dwell change, changes the entire engine performance by also changing the timing.