Surface Gap Plugs & MSD 44

I'm just curious as to whether people have tried non-standard plug designs with an MSD mag (12,20,44) ?........

What I mean is something other than the normal J-gap or side-gap plug.

A lot of the experimental electronic "plasma" ignitions use a sort-of surface gap plug design for better plasma discharge area/volume, which led me to wonder about such plugs together with the huge energy of a 44. The other side benefit would be no strap hanging in the wind which could potentially act like a glow plug.

Any thoughts or experiences? Would be interested to know either here or via PM.

 

First thing that comes to mind is that you can't adj. the gap, even a MSD 44 amp genarator need a .014 to.016 gap, pretty sure they are pre gaped to car manufactur, spec. gap. stick to the ngk's

 

What gap does everyone run on the NGK Plugs? .020 is what I was told.

 

plug gap

we run 15 and never had a prob

 

Those plugs may work fine in an engine with a closed loop electronic injection system and self monotoring ignition with a knock sensor but.... the "no strap hanging in the wind" isn't really a "benefit" when that stap is a good part of what you read in order to tune your engine.

P.S. I agree with Will .016 gap

 

I like the straps, but I don't have a computer...

EDB

 

Problem with using surface gap plugs with large (.030") built in gaps will be starting the motor. The high output mags like the 44 have very little output at cranking rpm. Once the engine is started a 44 will fire any practical plug gap.

 

Wil, I've done some magneto testing with a test bench I constructed, and I don't doubt what you are saying. My theory on what causes the misfire is energy escaping to ground by some other path other than the plug. When a high output mag is loaded on the bench with say 350psi (co2) at the plugs, the spark starts to jump inside the cap to ground. As the plug gaps are opened wider the jumping to ground starts at lower pressure. If we could do away with the cap and rotor we could better channel the energy to the plugs and thus fire larger gaps. In order to do this we would need 8 coils and a different points box plus a cam trigger ( the weight of the coils alone would make this impractical). The problem of misfire from high very cylinder pressure is at its worst with a supercharged alcohol drag race engine due to very high boost, high compression, and somewhat retarded timing. A blown nitro engine on the other hand has high boost but low compression and very advanced timing.

Bill

 

Very interesting post!

Supercharged meth, rich A/F ratios for cooling, high compression, high boost are bad enough by themselves, then to dynamically adjust the timing any significant amount and hope the spark gets to the correct terminal must be a real balancing act.

On your test bench, when the spark goes out, can you see where it is going if you turn out the lights? Down the outside of the ceramic of the plug perhaps, or strictly somewhere within the cap? Have you tested a MSD44 with ProCap?

I like your multi coil (CNP) idea, to get rid of the rotor/cap/wire issues. In fact, that's exactly what we are about to try ourselves under the PSI-C at 2:1 with meth. It should work but I guess we won't know for sure until we run it.

Would like to hear more about your findings on the test bench, and where the energy is "going" when the spark stops, and potential ways to stop that. Any reason why you chose CO2 rather than nitrogen for the pressure chamber?

 

Co2 is more of an insulating gas so I need less pressure for a greater load. Only problem with co2 is after a short time testing the plugs get fouled with carbon and need to be cleaned. When the spark stops at the plug I can hear the arcing in the cap. This is a mallory SM V or IV with an msd standard mag cap not the large unit. I will post a video asap so you can see the test.

 

Nitrogen

Bill,

Wouldn't nitrogen be better since it makes up ~78% of air? There is buckets of the stuff (many times more than anything else) in every cylinder when the spark plug fires (ironic considering it inhibits combustion), so it might give better test results? Also, it's not cold to use, and you won't have any build up to clean up.

Just curious.

Paul.

 

I'm sure by now that everyone running an MSD, have a ground strap from the heads to the coil, so the question is do you have one on your test bench?

 

I use co2 because with argon or nitrogen at the max pressure that is safe on my bench 375psi I cannot put out all the plugs. With co2 I can cause them to misfire before 300psi. The plug rack is grounded to the bench and the mag is also grounded to the bench coil neg is also grounded. I would not want to get hit by any stray voltage from one of these mags! When I first built the test bench I failed to ground the motor speed control properly and one stray spark killed it.