EI on top plugs

glenn654 · #1 10-25-2009, 05:41 PM

Why are the top plugs used for EI rather than the bottom which have a greater tendency to foul. Using the hotter stronger spark of the EI would seem to be better on the bottom plugs to me, but I have little real knowledge of electronic ignition.

Someone please enlighten me.......

Glenn Wilkinson

Mel · #2 10-25-2009, 05:43 PM

People who put the EI on the top plugs do it for simplicity.
If you have a choice, it's better to have it on the lower plugs.

dedgemon · #3 10-25-2009, 08:00 PM

Klaus recommends putting it on top. Best ask him why!

jclark · #4 10-25-2009, 09:13 PM

Quote:

Originally Posted by glenn654

Why are the top plugs used for EI rather than the bottom which have a greater tendency to foul. Using the hotter stronger spark of the EI would seem to be better on the bottom plugs to me, but I have little real knowledge of electronic ignition.

Someone please enlighten me.......

Glenn Wilkinson

The "Jeff Rose"/ElectroAir Systems recommend using the BOTTOM plugs.

So ... it varies. There is no single approach although I think Klaus (Lightspeed) recommended the top.

James

LifeofReiley · #5 10-25-2009, 09:52 PM

Ease of service on the top and with the spark these EI's put out, good fuel burn for sure... with proper leaning the bottom plugs stay very clean.

andrew phillips · #6 10-26-2009, 02:20 PM

I may be wrong but I don't think it is actually the quality of the spark that keeps the plug clean it is the quality of the combustion of the air/fuel mixture. If you have good combustion then the entire cylinder head area will be clean including the spark plug. Weaker spark plugs, like those on the magneto, produce a lower intensity spark which may cause a less complete burn and leave deposits behind which ultimately clog the plug. Even a good plug in an engine that is timed badly, runs too righ or has a lot of oil leaks may become fouled no matter how intense the spark is.

zilik · #7 10-26-2009, 02:50 PM

I, being of the lazy type, chose to run the the same plugs as the mag did. I could see no reason for rerouting plug wires from the remaining mag so I left them alone. So my EI runs the top plugs on one side and the bottom plugs on the other.

rvmills · #8 10-26-2009, 11:17 PM

I previously had a LSE Plasma I on my -6, and they did/do recommend running them on the top plugs. I asked them why once (after thinking about the bottom plug fouling issue) but didn't get much traction on the Q. I do know that making short runs from the ignition coils (often mounted on top of the engine or on the firewall) to the plugs is a desireable state, so perhaps its just easier to do on top.

I recently installed a new Electroair system, and asked Mike there about using the top plugs, as I didn't want to change out my mag harness. Mike said it would be no problem, and it has run very well so far.

One thought I had was that it is recommended (from my install manual) that the EI spark plug wires not be run closer than 1/4" apart, and maybe that is easier to accomplish topside too (it was for me anyway).

Just another $0.02

Cheers,
Bob

G3i Ignition · #9 10-29-2009, 05:45 PM

Glenn,
I agree with Klaus on the top plugs as my first choice because of the air/fuel ratio based on stock injector location and/or air/fuel mixture characteristics for the carbureted engines. Top plug is in the best location for the first crisp ignition event.
Since my G3i system runs all the plugs on EI I only have to give my insight on the 1/2 EI system based on conventional magneto drop rpm on run-up. Previously before developing the G3i system, on my supercharged IO-540. My left mag fired all the bottom plugs and the right all top (still with EI), The fuel injectors face upward on this engine. Mag drop @ 2000 was always 15 rpm more on the right over the left. If I had my mixture a little to the richer side, the right mag drop was 20 to 25 more than the left. I know my fuel set-up is not your typical stock set-up, but has shown mag drop that my lower plugs were in a more correct "power" air/fuel ratio. However with the stock position injector facing down, this keeps the top plug in a more combustible "power" air/fuel mixture. I'm curious, if any other bottom/top L/R mag set-ups out there and their mag drops on this theory?
Thomas Shpakow
G3i