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[HD Street Performance]

From the Delphi website
Delphi Ionized Current Sensing Ignition Subsystem features direct in-cylinder measurement of combustion quality. It uses conventional spark plugs as "in cylinder" sensors for combustion quality. The Delphi ion sense ignition subsystem also offers more precise misfire detection (determined by combustion results instead of speed calculations) and more accurate knock detection (measured by combustion signal not engine vibration). In the ion sense ignition subsystem, the igniter, bias and buffer circuits are fully integrated and encapsulated in the coil as one unit. The ion sense ignition subsystem enables continued development of future functions..

[HILLSIDECYCLE.COM]

No one seems to talk about plug gap.  Back in my drag car racing days (oh so many years back) we ran very short gaps with good results...of course the ignition I used back then could fry a cat at 25 feet.  

I played around a little bit with gapping on my 103' and have found no seat of the pants differences.  I have to ask has anyone ever done dyno pulls on a vtwin to see results of varying gaps only/no other changes?   

Small difference in gap sizes will never be felt seat-o'-the-pants, but up on the dyno is where you'll see it.
Scott

[HD Street Performance]

Ion sensing, measuring the current flow in the post combustion
Change the spark plugs resistance from OEM by a brand change or the gap and risk the ion sensing system malfunctioning. This is street bike information. The ones with can bus or data bus or even the early Delphi ECU. Not applicable to racing.

[EZRIDN]

Small difference in gap sizes will never be felt seat-o'-the-pants, but up on the dyno is where you'll see it.
Scott

   
I know this is splitting hairs when it comes to street stuff...I simply asked the question if anyone dyno'd just for change in gap because I was curious about how this might affect a vtwin.  I remember spending dyno time trying to tweak every ounce of power we could get out of my SuperStock/SuperMod small blocks wherein cutting off a nano-second could make all the difference between a win or loss or the goal of setting a class national record.  The drag bike boys here should be able to relate to that.   

There was a question, how would the gap make a difference?...simple, the closer the gap the shorter the spark has to travel hence the quicker the combustion process starts.

Regardless, this all makes for good beer/bar conversations.   

 

[HILLSIDECYCLE.COM]

We were informed that information gleaned from drag racing does not pertain to this.................
Scott

[hrdtail78]

I haven't found any power difference in changing the gap from factory specs, but I have cured false knock on higher than stock compression builds by closing the gap.

The ION sensing in the Delphi ECM is pretty good, but like everything else in the Harley world.  It is set up to work with stock Harley stuff.

[HILLSIDECYCLE.COM]

Tighter gaps on the engines that carry more ccp than OEM seem to be what we've seen here.........
Scott

[GMR-PERFORMANCE]

To show what I was talking about , Here is a head that as you can see has had work done to it. If you had a bike as I listed with mods done head work , and a shop that has taken the material out of the chamber could leave the plug hanging into the combustion chamber. Carbon will build up on the plug and when you remove it can damage the threads on the way out.  Here is where a index washer would work very well. 

I have some other pictures of 100% stock heads that have almost no area there either due to poor casting. Another area where you might want to use a extra washer or index washer to pull the plug back some. This is easy to see when you remove the plug as to where the carbon is showing on the threads.

[hrdtail78]

I have shims in stock for that very reason.  I see the same as Steve.

[HILLSIDECYCLE.COM]

That IS the reason for shims that we stock here........and with the cast "lug" left in the chamber, flow testing has shown us a 4 cfm intake deficit, almost accross the board.

[GMR-PERFORMANCE]

Just pointing out what I was talking about nothing more.  Can you post up the flow comm data showing the increase on CFM .. As you stated its across the board ,..would be great to see that before and after.

[Ridgerunr]

Thanks for the photo GMR. 

[GMR-PERFORMANCE]

Sure thing, a picture is nice so others can see how the plug can stick out in the chamber.   

[RayG]

Thanks for the photo, I had not even given that a thought.  The next time I check the plugs I will check for buildup.  I'm not a wrench and my memory is often temporary at best but a photograph seems to do what it is intended for.  Anybody can say anything they want, right or wrong but proper documentation has the ability to separate the BS from the truth in some cases.  As my old boss would say if it's not in writing or documented it never happened!   Would like to see more documentation where it is helpful.

[HILLSIDECYCLE.COM]