Ignition: Skip Pulses

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Ignition: Skip Pulses

Postby goodysgotacuda » Wed Nov 15, 2017 6:26 pm

I am seeking a little quicker startup. I have a good start, but it always takes the same amount of revolutions to fire, hot, cold, add fuel, or not.

I cam across "Skip Pulses" which was set at 3. Does that mean the ECU will ignore up to 3 full revolutions before trying to fire?

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Re: Ignition: Skip Pulses

Postby elaw » Thu Nov 16, 2017 6:33 am

There are probably others here that are more knowledgeable, but I'm 90% sure the count under "skip pulses" applies to teeth on your crank trigger wheel. So in your case, you've got a wheel that's nominally 36 teeth, "skip" is set to 3, so the delay would be a little less than 1/10 revolution of the crank.

How long (in seconds) does your engine take to start?

Are you judging the # of revolutions by the noise the starter makes? This is going to sound a little silly but if you're going by the "rrr... rrr... rrr..." noise from the starter, each "rrr" usually represents one cylinder hitting compression stroke, not crank revolutions. So if you've got an 8-cylinder engine and it goes "rrr... rrr... rrr... rrr..." and fires, that's only 1 revolution of the crank.

If you post your tune (.msq) and a log file, we might be able to help more.
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Re: Ignition: Skip Pulses

Postby goodysgotacuda » Thu Nov 16, 2017 9:11 am

I’ll snag a log of it but I am going by the “Rrrr”. It would say it gets a full rev before trying to start.

My old carb/distributor engine would fire instantly when warm. Id like to get my efi to that point.


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Re: Ignition: Skip Pulses

Postby Dennis_Zx7r » Thu Nov 16, 2017 9:33 am

Don't know if this also fits for this wheel type, but the way I understand this is that for some wheels the MS seems to wait for full-rpm sync instead of starting in semi-sequential and then switching to sequential. I'm referring to this thread:
viewtopic.php?f=125&t=67660&p=514902&hilit=start+sequential#p514902
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Re: Ignition: Skip Pulses

Postby Spiffy » Sat Nov 18, 2017 8:24 am

This intrigues me too since it seems like after I switched from fuel only and batch fire to semi sequential and wasted cop the engine takes longer to start up...
I'm running the diyautotune 24-1-1triggerwheel that behaves like a 12-1

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Re: Ignition: Skip Pulses

Postby DaveEFI » Sat Nov 18, 2017 9:07 am

I noticed this too when changing from fuel only to EDIS. Takes quite a bit of churning to start, but when it does idles perfectly. I've played with the cranking pulse - which was OK with the distributor.
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Re: Ignition: Skip Pulses

Postby Tjabo » Sat Nov 25, 2017 4:24 pm

Did anyone try decreasing the skip pulses number yet to see if it noticeably speeds up starting?
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Re: Ignition: Skip Pulses

Postby elaw » Sat Nov 25, 2017 4:29 pm

I've done the opposite... I had mine set at 1 for a while but occasionally would get sync errors at startup. I changed it to 3 and noticed pretty much zero difference except the sync errors stopped.
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2012 Audi A4 quattro, desperately in need of tweaking

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Re: Ignition: Skip Pulses

Postby Tjabo » Sat Nov 25, 2017 4:32 pm

Very interesting, thank you!!
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