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nokones
01-30-2018, 05:45 AM
A couple or three months ago, there was a discussion regarding voltage drops while starting or the engine might be kicking back. I believe the discussion may also include that most of the people experiencing the voltage drops and/or kickbacks were using the Holley HP EFI System. During the discussion, it was suggested that maybe the crank timing setting could be set too high that may be causing a kickback rather than a voltage drop. Also, this discussion included some may be experiencing actual voltage drops.

In any case, I am posting this because I also were experiencing possible kickbacks and/or voltage drops and I am using the Holley HP EFI System. I made sure that my grounds were good and also I have a second ground from the battery directly to the engine block along with a ground strap from the chassis to the engine block. The primary ground cable runs from the battery to the chassis and my battery was relocated to the back of the car, in my case, in the radio module compartment behind the passenger seat in my C4 Corvette.

Yesterday, I had the cranking timing setting set from 15 degrees to 5 degrees. After the setting was set to 5 degrees, so far, I haven't experienced any kickbacks or momentary drag in starting the car. I know that at this time of the year I won't be able to experience what I would normally experience in the summer time when everything is extremely hot and just coming off the autocross course and go and try to start the car a few minutes later until the weather gets warmer. But, so far, so good.

At this very moment, I do believe that my 15 degree cranking timing setting with a 12.25 compression built engine may have been the issue with the momentary drag in the starter. We will see when the weather gets warmer.

andrewb70
01-31-2018, 07:37 AM
With over 12:1 compression, I'm not surprised that it wasn't happy with 15 degrees cranking advance. Mine is set to 13 and I'm below 10:1. Fortunately, cranking timing is very simple to change with the Holley EFI systems. Glad it's working for you!

Andrew

nokones
02-01-2018, 05:27 AM
The guy that tunes my Holley HP EFI ran a data log on my cranking after he set the crank timing and the log showed that there were a couple of RPM spikes during the cranking before it fired up, one was up to about 900 RPMs and the other was about 600-700. He said that may be from the slop in the distributor gear and the cam because there is no drag on the distributor from not having an internal oil pump. I'm not sure that I can buy that theory. He said when the spike goes over the 500 RPM threshold than the computer will revert to the run timing setting which I believe is set at 30 degrees. He said when the computer sees the spike it doesn't know that it is just a spike or the engine is actually running or not.

Oh well, we'll see if this was an improvement when the weather gets hotter alter this year. I think it will be better now with the 5 degrees of crank timing and so far I like it.