Plug gaps - Don't be afraid to close them.
 

Ok, so I realize there may be one other person on this board who runs the same ignition as me but...

My car has been running ok-ish at 10#. I stumbled on a major breakthrough that found a hidden 100hp which was good. Once that barrier was clear I decided to go for more boost.

First attempt - oops a little too far. Pegged my 20psi gauge and have no idea how much it actually made.

Got it down to the 12ish area. Felt a little stronger but had a mild hesitation. Tried 17ish and it was breaking up all over the place. My first thought was detonation :eek:.

I was running a .035 plug gap and the Mustang guys (ford ignition here) suggested I go all the way down to .020. I thought that was crazy.

Runs just as smooth as it ever did under normal conditions and pulls great all the way up. Drove it to work today and saw 15psi several times. Now I need to schedule a couple of dyno pulls so I can find out exactly how much timing the motor likes and then max out the little 70. I'm still thinking 18psi will be about my happy point.

Butt dyno approves.

Hmm. Maybe I need to try this. I tried getting tuned a few weeks back and mine breaks up bad a lil over 4500rpm when it hits like 13psi. What plugs are you running? I have the tr6's gapped at .032

was that the chunk of pipe in the hot side?...:o


I closed mine up to .28 a while ago and it helped out a little....i still have a little break up when i run more then 13psi

maybe i will swap in another set of plugs and close them up to .20..just to give it a go

Yep. Some turbo Buick guys did a detailed dyno test on this a while back. They gained power every time they reduced the gap.

Why does this help? Does it reduce the chance of the spark getting "blown out"?

I'm closing mine up to 20. I went to the track last night and when I shifted early (roughly 10psi, 5800 RPM shift light) the car ran great! When I up'ed the shift point to 6000 (13psi) it was breaking up like crazy. Had to be blowing out the spark.

V=IR

So, I=V/R

V is set by the primary voltage and the coil.
R is the resistance of the wires, plus the resistance of the gap.

If you half the gap, then you half the resistance. This can double amperage, which doubles the wattage, equating to more spark energy.

Of course, if you reduced the gap to zero, you wouldn't even have a spark, so you can't extrapolate it to zero gap.

I am not an engineer, but I understand the above. But how does spark energy correlate to output horsepower?

I am under the impression that the spark either ignites the fuel, or it doesn't. There are obvious power implications to changing in the ignition timing, but the rest isn't making sense for me.

I don't see how high RPM misses and roughness are explained by insufficient spark energy. -- I thought it was caused by the fuel not getting ignited at all, usually due to a shortcoming or failure of the ignition system (which is apparently common in FI motors, but I don't have any experience messing with ignitions on FI motors).

Likewise, I don't see how more power is explained by more spark energy either.

I'm eager to learn, if anyone is willing and able to explain.

I suspect that reducing it to near zero (say, 0.001") would also not be effective. I expect that there is a point of diminishing returns, and I would guess that 0.020 is getting pretty close.

So would there be any negative effects on running a smaller gap? for example .020?

.020 seems like overkill. I have run .040 with a delteq and also with my latest opti+msdbtm setup and have never had any problem with missing in the higher rpms at 15psi. A large plug gap is good for the lower rpms for better combustion efficiency.

I don't know much about your EDIS8 Ford ignition system. Is it considered a pretty weak sparking system? :)

Hmm, typed a reply but I guess I didn't post it :(

Sweet thunder is a bad choice in mufflers for a turbo. Couldn't make more than 10psi, all I did was take it off and I pegged my 20psi guage. Wish I would have been logging to know just how high I got it.

The edis is not all that weak, but I am running coils with probably 200k miles on them. Not really fair to compare a stock ignition with years of wear on it to an aftermarket setup with ls1 coils (I think thats what they are). The plugs I checked were actually opened up to .038-.040. Perhaps some systems will do that but read on any turbo forums and thats not typical. Too there are too many factors to simply say mine should work because yours does. Compression, turbulence, temps, shape of chambers.. blah blah. .030 probably would have been fine for me, I just decided to try the extreme. Like any setup I can always buy better coils, and add ignition boxes, etc.

A larger spark will have an easier time lighting the whole air/fuel charge, but if you can't burn it at all thats far worse. The smaller gap is easier to spark.

I'm not going past 15psi until I get to the dyno for some timing tuning. Everytime I get some little thing worked out I am more and more impressed. Its finally starting to feel like what I had origionally expected.

Thanks for all the replies, didn't expect this to get any, just sharing an experience.

I usually run .020 in my turbo cars.

I tried the recommended .032 and that did not seem to work. When I dropped my blower out for my turbo, I was planning on new plugs, wires and closing the gap to at least .028 if not .025.

I'm glad to hear that you saw an improvement.

I think it has to do with how much of the air/fuel is ignited initially when the spark occurs. Having a high energy spark is next best thing to dual spark plugs or an efficient chamber shape.

Mike

I forgot I can run multi spark on this setup,, I need to read into. Basically sparks 2x instead of once.

As in waste spark?