Ok, I am kinda confused here.... What i am seeing does not agree with what i have read.... But what i have been told doesnt seem to fit my case either...
what i read in a nutshell... plug gap is a good thing... you want as much as you can afford to run without spark blow out or misfire. The factory gap is a good starting point, but is just a guidline, you can squeeze more power by finding what works best for your engine, not just sticking with what is suggested for your whole generation of vehicles. The larger the gap, the larger the jump the spark makes, which gives more exposure and ignition from the same amount of juice. So slowly increase your gap till notice misfire or blow out, then close it in a little, and you will be good to go. (higher compression and/or boost increase likelyhood of blow out.. so high output engines may not be able to gap as large as a NA engine can)
what i am told.... Keep your gap small on boosted cars... stock gap is 50, but with boost you dont want any higher than 40... Typically a 30 or so is best.
What i am seeing... I have LOTS of boost... 17psi at times... and i have been running TR6's with 50 gap... no blow out, no misfires... (at least not with my trusty MSD DIS-2 box running... without its added juice i do get some blow out under high psi's.) But just today i regapped to 45... and just with such a tiny change, i can feel more power in my butt dyno... i mean like a noticable difference.... i could tell it was more peppy before i even left my driveway. I plan to drop the gap again to like 40 or so in the next day or 2... see what that does...
But why does what i am seeing directly contrast what the books tell me... they say "big gap = more power" but i find there is noticably more power as my gap gets smaller. And why is it i can get away with 50 or more gap with no blow out even with my boost levels? It sounds like most people cant even get close to this on much lower boost setups...
So does anyone know what the real deal is on gaps?
I would like some facts and inforamtion... "how and why" not just "well this is what i use, and it seems to work"
Has anyone else tinkered or experimented with their gaps? or different types of plugs... If so would you mind sharing your results?
Strap it to a dyno and confirm your suspicions.
I had to gap mine down to .030" to prevent high RPM misfire.
you have msd, thats y at 50 gap, no blow out. in school we had this really cool display of msd versus stock. msd is so much more powerful that stock, and msd will fire through paper, lol its pretty cool. but with a smaller gap, you have a fatter spark, which is what you want, the wider the gap just exposes more spark, but thinks the spark out. you want a fat, hot spark, which is also why iridium tipped plugs are junk.
horsepower is the force that determines at what speed you hit the wall, torque is the force that determines how far you take the wall with you after you hit it.
See, i heard that the actual spark itself is like a lightning bolt... (and i think i was shown proof as well)
it isnt a matter of how much material there is for the spark to jump from/to... if you have 2 big old-school flat electrodes... the big plank style ground electrode and a big cylindrical center electrode... it doesn't mean that you will have a much WIDER spark.... the spark will still be the same size "lightning bolt" but it will just choose the path of least resistance to jump across... larger elctrodes just give the spark more choices of where to jump.... but also provide alot more material to block the spark from the mixture, which is really the whole point anyway, to get that spark to light as much mixture as it can at once.
Most lightning doesnt cover the entire sky and contact the entire ground.. it just makes one concentrated bolt that jumps from a spot in the sky to a spot on the ground. and each bolt jumps to/from a different spot each time. Same with a old school fat electrode plug.
The newer style plugs try to "control" the actual arc or "lightning bolt".... Iridiums do to their high temperature materials can use a tiny thin center electrode that acts like a lighting rod on top of a building... saying "lightning hit me, over here, look nice easy jump for you!" and since they know where the spark will be jumping to, they also can tell where it will be jumping from so they can also shave down the size of the ground electrode. This way the spark has more of a dedicated and controlled "path" it follows, and alot less material blocking the spark from the fuel mix.
Multi-electrode and splitfire style plugs use a similar theory, trying to control the spark path, and expose more spark to the mixture. But instead of using smaller electrodes, the alter the placement and quantity of electrodes.
A split fire plug forks the ground electrode removing the material directly above the center electrode, so that the spark has to jump to one side or the other. This forces more of the spark to be visible to the cylinder (which is usually directly behind the usual placement of the ground electrode). basically the mixture doesn't need to ignite and then burn around the electrode, the flame front can just travel straight into the rest of the cylinder.
Multi-electrodes do the exact same thing... but instead of one forked electrode, they will have 2, 3, or 4 side electrodes... all of which fall short of the center electrode, keeping it exposed to the cylinder, and forcing the spark to jump diagonally to any ONE of the electrodes. and once again, keeping the spark exposed to the cylinder as to keep the flame front traveling in a straight line towards the bulk of the fuel, with fewer obstructions.
NO SPARK PLUG creates multiple simultaneous sparks. if you have platinum +4's it doesn't mean you will get 4 sparks each jumping to a different electrode each time. the spark will always take the SINGLE path of least resistance. 4 electrodes just give it a better selection to choose from to find the least resistance thus offering the best arc and spark quality.
This is the THEORY behind spark plug design and function....
But i was hoping to get some discussion on practical application and real world results and comparisons of different plugs in different situations.
mitdr774 wrote:
I had to gap mine down to .030" to prevent high RPM misfire.
i also had to gap mine down to .030 to prevent high RPM misfires. i was misfiring with a gap of .044 on the stock ignition system. if you have MSD you probably wont have to worry about that, so gap them to what you feel are the best results
12.33 @ 111.67 mph [Oct 2009]
Dyno'd on 08/02/09 - Mustang Dyno:
327.6 WHP 333.6 WTQ [10.1 AFR]
I am kind of confused as to what you are asking here?
Since you have a msd ignition it is no wonder you don't need such a small gap to prevent mis-fires. As already stated get on a dyno and experiment. In the end it does not matter what Joe Blow said worked under xyz conditions just what works for you and your setup.
FORGET GIRLS GONE WILD WE HAVE GOVERNMENT SPENDING GONE WILD!
my last post was in responce to 02 silver cavys comment on
"you want a fat, hot spark, which is also why iridium tipped plugs are junk."
where i believe he was implying that you want a big wide electrode, not the tiny lil iridium ones. I was just explaining the concept for future readers.
In general I was asking for some people to share their knowledge and research and experience with different plugs and gaps and how they worked for what setup.
I would love to get on a dyno... but those cost money.... and i am trying to tweak all i can before i get there, so i can just polish it up a bit once im on the dyno.
I was just confused as to why books are saying "use all the gap you can get" but people are telling me "nah you want a tiny lil gap" but my findings up till lately have not gone along with the warnings i recieved. but now realizing that most people arent talking about a full MSD ignition like i have.... So i guess the rules dont apply to me here... HAHAHAHA... well i was at 50some... and she ran great.... the other day gapped them down to 45 and she ran REALLY GREAT... i just finished gapping them down to an even 30... but havent taken her for a drive just yet.... so i will post up what i find soon.
Heres the deal....
Lets start with N/A. When the plug jumps the spark gap, its jumping lets say .050" of AIR. remember, you started at just under 1 atmosphere, then compressed it to 9.5:1 ratio of where it started. So, generally speaking, you now have about 9 1/2 atmospheres -or140psi) in your cylendar. That means MUCH more air is densly populating the gap. It will take on order of around 25,000 volts of electricity to jump this gap.
Ok, now lets talk about F/I. You say your running 17PSI. thats 17PSI on top of 1 atomosphere, which is adding another 14.7PSI. so all total, you have 31.7PSI of air pressure when you start. Then compress that to 9.5:1 ratio, you end up with 301.15 PSI. So, you can see that just becuase your gap has not yet been changed, that now with a much higher pressure in there, meaning more air molecules populating the gap, its really like the gap has been opened up alot more. The voltage to jump this gap is going to have to be ALOT higher. If you do nothing, you will have blowout. Meaning its just too much gap, requiring too much voltage , and it just cant do it. this results in a misfire.
What to do about it...
Start closing it up. When you close your gap, you will reduce the amount of voltage it takes to make the jump. Coils can do alot these days, but still, if your not using a MSD box, you HAVE to reduce your gap to a level that is in agreement with what your coils can develope.
If you add a MSD box, they work a little different than your factory setup. Of couse, you get Multiple Spark Discharge at anything below 3K RPMs. But after that you go to single fire mode, simply becuase there is not enough time to spark more than once. It takes time to charge between shots, and the faster your engine goes, the shorter those charge times much take. Around 3K its a losing battle and they turn that feature off. Another thing the MSD or any other aftermarket ignition controller does is it uses a much higher primary coil voltage. Remember a stock coil will use 12vdc on its primary. The MSD box will use its internal DC-DC power supply to create around 550VDC to use to fire the primary of the coil. This results in SIGNIFICANTLY higher secondary voltages. These higher voltages will allow you to use a larger gap. And a larger gap is ALWAYS prefered becuase it will cuase a better light-off.
If you dont want to add a MSD unit, you can also try aftermarket coils. These coils will have different turns ratios, which will allow them to create higher voltages from the same 12vdc that the stock coils use. A combination of this method and smaller gaps should do most people just fine.
M90'd Built LGO-15 PSI
http://webstarts.com/quadper4mance
one other thing... when you close your gap, you are effectively advancing your timing. When you open it up, you will be retarding your timing. Keep that in mind if you have ignition map tuning abilities, and this also explains butt dyno changes.
M90'd Built LGO-15 PSI
http://webstarts.com/quadper4mance
but that advance and retard, can't be measured by degrees..... Its true, but a bad analogy.
Chris
'02 Z-24 Supercharged
13.7 @102.45 MPH Third Place, 2007 GMSC Bash SOLD AS OF 01MAR08
Quote:
If so would you mind sharing your results?
where are yours? post up some graphs with numbers to prove it.
if you wanna take tuning seriously you should remember that the butt dyno ain't worth the sh!t that comes out of it.
Nice!
Chris
'02 Z-24 Supercharged
13.7 @102.45 MPH Third Place, 2007 GMSC Bash SOLD AS OF 01MAR08
on my cav i was to be gapped at .065 i'm currently gapped at .052 10lbs of boost consistantly do get up to 12 at times
JBO since July 30, 2001
