Spark Plug Gap

Tony · #1 07-02-2007, 11:30 PM

Just wanting to see if you guys have any ideas. Just finally changed the spark plugs on the z6 in the race car(I haven't even checked them when I installed the motor). Here was the interesting part....they were factory recommended NJKs...but they were all gapped at .080. Any ideas why someone would gap them that high?

I don't believe anything has been done to this motor other than the Header and Intake that I put on.

Just trying to see if anyone can think of a reasoning behind this, or if the person who installed them was just an idiot.

YZ125rider21 · #2 07-03-2007, 03:46 PM

I had spark plugs go from .042 to around that from spraying nitrous...which was fouling the plugs a lot...stock motor and not doing nothing I wouldnt know for your thing.

Christ · #3 07-03-2007, 08:28 PM

possibly stupid here... but I seem to remember something about gapping your sparkplugs way too open to help burn excess fuel in the chambers.. dunno if it's true or not, but I"ve heard it.. which means that I'm sure someone has done it, and probably not actually tested the theory.. just applied some redneck logic, and figured, "I heard it... and even tho I can't make any sense of it left or right, it MUST BE TRUE"... this is how engines get blown.. if you can't find a reason that they should be that open, close the new ones back up to stock spec

Tony · #4 07-04-2007, 06:12 AM

Yea, see thats what I was thinking...and don't worry, the new ones are back at .044.

Now I think I gotta replace the water pump on it...thing was running at 230, spiked to 260, then came back down to 230 and the radiator was still cold. Can't be thermostat because it doesn't have one.

Oh the joys of race cars when your broke.

Christ · #5 07-09-2007, 11:19 PM

oh I wasn't worried, I've been on here long enough to know that you have at least half a brain

unfortunately, I DO know the joys of trying to run a race car that was street legal w/o money for repairs when they're necessary... you tend to baby it a lil more than if you had the money to replace parts left and right... and on the plus side of all that, you learn how to make OEM parts work in the best manner they can, all in the effort to save a buck... just b/c your car isn't working right at the moment, don't be disheartened.. just fix what you can, and rig what you can't... keep "plugging" along.. no pun intended

PS, if you're replacing the water pump, might as well replace the timing belt while you're in there.. that way you can't have it break on you going down the street and lose your entire engine... all b/c of a piece of rubber...

Tony · #6 07-10-2007, 12:07 AM

Well it wasn't the water pump...it was me being an idiot, lol. Still strange though because what it was, I did when I first got the car going and it is just now causing problems. After one busy weekend, with me barely making it to the track in time to race(thanks to a friend bringing my car to the track and changing the front wheels out). I raced my qualifying race(6 laps) and the car got to 230. Over the week my dad found out that one of my fans was pushing air instead of pulling. I didn't have time to fix it before the heat race, so I just went with it. Flipped the 2 wires around to get it pulling air and during the main race(15 laps) it never got past 190, so I think that problem is fixed. I just assumed I had those wires right because it was a blue and black wire...apparently the black one wasn't the ground, lol.

And yes, racing on a budget, you MAKE things work. I'm amazed I don't have axle problems because of the angle everything is in there at. On the 5th gens, in order to correctly do a auto-manual swap, you need to either fab up a mount, or buy an after-market mount. I did neither and just lengthened the linkage. First couple axles I had did pop a bearing out, but once I changed those, haven't had a problem other than one boot finally got a hole in it.

drmatrix · #7 07-10-2007, 12:24 AM

Spark plug gap is determined by the output of the ignition system and compression ratio. The more kv's the wider the gap and the higher the compression the shorter the gap. It's still a guesing game when it comes to racing. Don't be afraid to experiment and good luck

Christ · #8 07-15-2007, 04:29 PM

Quote:

Originally Posted by drmatrix

Spark plug gap is determined by the output of the ignition system and compression ratio. The more kv's the wider the gap and the higher the compression the shorter the gap. It's still a guesing game when it comes to racing. Don't be afraid to experiment and good luck

This is primarily common sense... if you have high comp ratio, you'll quench the spark if there's too much gap.. if you have a high tension ignition system, you don't want the gap too short, else you'll burn plugs up... basically, need time for the spark to cool properly to the correct temp before it ignites fuel/air mix.

I had found a decent calculator at one point for this.... that used comp ratio and ignition tension and a few other points to give you a basic range that you should be starting in, adjusting from there.

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