Holley HP EFI Coil Near Plug Spark Plug Gap

I have been running a .035 spark plug gap with the MSD ignition that was attached to my Holley HP EFI unit, and now have the (8) Holley Smart Coils...should I increase the spark plug gap now?

And if so, what gap should I go with? I have the CNP on both cars now, one on my 440 Wedge engine, and one on my 605 Gen II Hemi. I have 11.5:1 compression on the 440, and 11:1 on the Hemi.

Thank you for any suggestions.

Mark

I run 035 on my HP with the GM coils on my SB..
gust a little less compression

I would recommend .028 to .030.
Inductive spark and CD spark have to be looked at differently.
With inductive spark, the power that doesn’t get used during spark initiation gets discharged in duration.

Rick.. quick question.. what was the name of
the holley that I can ask a question
thanks.. this is a new puter and I didnt
transfer all that stuff
thanks

Im not understanding your question. I think some words are missing😯

Holley efi forum?

The Holley site on line that has the one guy
that answers most of the EFI questions.. you
have been on that site many times.. if you have
a problem he usually knows of it
thanks

Danny

I dont know the guys name but I want to ask
something on the HP unit
thanks

Danny is the guy that handles most of the questions there. Ijust posted there this morning regarding a post by andyf.

Can you give me the web site name.. I want to
do some reading on the HP

Thanks Mike for your response, however I am using the Holley Smart Coils, and they are supposed to be a hotter spark because of one Spark per cylinder. Right?

That is why I was asking about Gap size.

Mark

On the GM coils I run 1 spark per cyl.. I dont
know if the smart coils are hotter or not

https://forums.holley.com/forumdisplay.php?13-Holley-EFI

The smart coils are inductive. Typical high hp engines using them set plug gap @.018- .022.
Spark duration is the benefit.

This is a neat video of a spark trail. CDI first, then inductive added...
https://youtu.be/2GGIgXwSPdo

Hi Trendz, Watched the video...the MSD is the long duration spark, and the Inductive is the short spark.

So, they show the inductive first, then the MSD spark. Correct?

If the program in the HP is set for 4.5 MS of charge cycle for spark, would that not be much stronger of a spark?

Since the Holley Smart coils are not MSD (multiple spark discharge), then the video you show is immaterial. Right?

Besides the MSD unit is only MSD under a certain RPM?

Thank, Mark

I haven't looked at this issue much but it seems like the factory uses some fairly wide plug gaps on the newer CNP engines. In the range of 0.040 or so on a few engines that I looked at. Maybe it all depends on the engine and the ignition system?

Hi Andy, I am using 8 of the Holley Smart coils...that alone should give me very good spark, I think. Also, since there are 8 coils, each coil has a longer time period to charge and store energy per fire.

I Thought the LS engines spark plugs were set at .045, but that, might not be correct?

Mark

No just the opposite. The CDI is the short duration, high energy start. The inductive sparkis the long duration trail.
This is why MSD has multiple sparks below 3000 rpm. The short duration CDI spark would not burn up themixture fully at low rpms.

As far as plug gap, you can run it wide... but you end up with a much shorter spark duration doing so. The wider the gap, the more you stress the coil/ wires/ plugs.
The Ign1 coils are capable of burning holes through some spark plug insulators. Much better to take it easy on the hard parts and turn the energy into duration.

I would suggest lowering that 4.5 ms time below and above peak tq. In most engine conditions other than high load, 2ms would be sufficient and be easier on the coils.

I'll try it.. my plugs are out right now.. so its
a good time to try it

Rick, do I need to re-down load the V4 program
on my new puter or can I get it off the car
then save that.. I dont have it anywhere at the
present time
thanks

You can get the software from the Holley website free. I haven’t checked if there are software updates since you changed yours. There is usually software update notes that tell you what has changed, or things you need to be aware of. READ THIS CAREFULLY.

I set the dwell time at 4.5ms since that is what the Holley data sheet recommended for 1.5 hp/cubic inch. I can tighten up the plug gap and reduce the dwell time easy enough.

Ok got the new down load

Rick, The Holley Smart Coils also have a capacitor/condenser that charges, then gets discharged...so is that not a CDI? I always thought so.

The MSD has circutry that sends a pulse to the capacitor/capacitors that discharges multiple times, right?

I would think that having a fully charged single coil dedicated to each cylinder would discharge a hotter spark with a wider gap, and the MSD is a completely different animal altogether.

Where am I going wrong on this?

Does MSD make their own smart coils that do MSD like the larger units?

Mark

The holley dominator/ hp ecu is set up to be able to control the timing and the dwell of each coil directly. No external box/ amplifier.
Each coli will be powered by the cars charging system voltage. Call it 12 volts. Each coil has a smart circuit looking for a hi and a low signal. There are also some internal self presevering features like a clamping diode set around 18 volts if I remember correctly. This is the maximum voltage that they will handle.

A CDI ignition box sends about 400 volts to the coil, then uses the coil as an amplifier. CDI coils are much different and are not interchangeable with inductive coils. The dominator/ hp ECUs don't directly control the coil with CDI. The ecu just tells the ignition box when to fire.

CDI gives a very strong very short duration spark. Much stronger than an inductive set up. The problem is duration. You need multiple events with CDI to be sure that the mixture lights. At higher rpm, there isnt time to charge multiple times. You could get around this I guess, by putting 8 msd boxes in and having multiple sparks at much higher rpm.

Hi Rick,

Thank you for the explanation...MSD does make some MSD Smart coils, and I will also look into those as well. I read a few reviews, and most were very good.

BTW, my Corvette C6 PWM controllers that you set me up with are working out great on both cars, however I am leaning on replacing the 160* thermostats with 180*. It seems that the engines could use the extra heat for moisture control, and less sludge problems.

Thanks, Mark

I wouldn’t look any further. If you have the Holley coils(aka IGN1A), and you are running them directly from the ECU, you already have the best ignition for your application. The only step up would be some sort of all out magneto ignition.

It is my opinion that the benefits of CDI go away when the multiple spark drops out, and those benefits don’t return until over 9000+ rpm. The benefit being full, “adequate length” spark.

Both CDI and inductive have pluses and minuses. The rpm and hp range that most people operate their engines in would be best suited with a multi coil inductive set up. That’s just my opinion.

I have heard of reliability issues with the MSD individual coils. I think stock GM coils or IGN1A coils are the ticket for reliability and power.

This was an interesting thread, I am about the change plugs in my car and I will close the gap up some(I think they are at .40). I run the GM truck coils.