47Pilot
07-05-2008, 09:38
-Spark plug indexing and side gapping-
I thought I'd bring it up, i was explaining it to my roommate out here in afghanistan, he's a ford drag strip junkie.
Indexing the spark plug is the technique of aiming the side electrode towards the outside of the combustion chamber.
The concept is getting that pesky spark flame from the plug to perform at its best for burning fuel. First I'll start with indexing portion. If you picture the inside of a combustion chamber, the object of this is to point the spark towards the inside of the combustion chamber by pointing the side electrode towards the outside. This can be done with indexing spacers/washers, ask any automotive parts store or summit online. The kit comes with different sizes ie. 10mm 12mm 14mm. Mark your spark plug as follows so you know where that side electrode is:
http://www.heavyliftoffroad.com/ProjectPics/plugs.JPG
use trail and error to correctly aim the side electrode away from the center of the chamber by way of the black mark. Therefore giving you this on the inside of the combustion chamber:
http://www.heavyliftoffroad.com/ProjectPics/goodangle.JPG
the following is what you don't want, when the flame of the spark has to travel around the side post to ignite the center of the combustion chamber:
http://www.heavyliftoffroad.com/ProjectPics/badangle.JPG
With the side electrode pointing away from the center of the chamber as the spark ignites the flame will not have to travel around the post ignite the fuel cloud in the chamber.
SIDE GAPPING
Since the combustion chamber isn't perfectly flat the spark can use more help by making more room to travel.
Pictures explain alot, first picture is a stock spark plug obviously:
http://www.heavyliftoffroad.com/ProjectPics/img117.gif
Now we take this spark plug, not some fancy bosch 4+ or splitfire, but a regular Autolite, and shave back that top electrode to expose more area:
http://www.heavyliftoffroad.com/ProjectPics/img118.gif
Now this is what we get, the flame travels without restriction to fully ignite the combustion chamber:
http://www.heavyliftoffroad.com/ProjectPics/img119.gif
I've seen different numbers for different for different vehicles. Larger gain on larger horsepower engines. On average 2-5% hp/tq gain, 1-1.5mpg gain. Personally my jeep got 1+ mpg definitely and I never dynoed it so i got no hp/tq numbers. I've been working on the proficiency of my jeep not just horsepower. But this technique has been used by racers back to the 60s. Its a proven technique, google it and you'll see. Spark plug indexing and Spark plug side gapping.
I thought I'd bring it up, i was explaining it to my roommate out here in afghanistan, he's a ford drag strip junkie.
Indexing the spark plug is the technique of aiming the side electrode towards the outside of the combustion chamber.
The concept is getting that pesky spark flame from the plug to perform at its best for burning fuel. First I'll start with indexing portion. If you picture the inside of a combustion chamber, the object of this is to point the spark towards the inside of the combustion chamber by pointing the side electrode towards the outside. This can be done with indexing spacers/washers, ask any automotive parts store or summit online. The kit comes with different sizes ie. 10mm 12mm 14mm. Mark your spark plug as follows so you know where that side electrode is:
http://www.heavyliftoffroad.com/ProjectPics/plugs.JPG
use trail and error to correctly aim the side electrode away from the center of the chamber by way of the black mark. Therefore giving you this on the inside of the combustion chamber:
http://www.heavyliftoffroad.com/ProjectPics/goodangle.JPG
the following is what you don't want, when the flame of the spark has to travel around the side post to ignite the center of the combustion chamber:
http://www.heavyliftoffroad.com/ProjectPics/badangle.JPG
With the side electrode pointing away from the center of the chamber as the spark ignites the flame will not have to travel around the post ignite the fuel cloud in the chamber.
SIDE GAPPING
Since the combustion chamber isn't perfectly flat the spark can use more help by making more room to travel.
Pictures explain alot, first picture is a stock spark plug obviously:
http://www.heavyliftoffroad.com/ProjectPics/img117.gif
Now we take this spark plug, not some fancy bosch 4+ or splitfire, but a regular Autolite, and shave back that top electrode to expose more area:
http://www.heavyliftoffroad.com/ProjectPics/img118.gif
Now this is what we get, the flame travels without restriction to fully ignite the combustion chamber:
http://www.heavyliftoffroad.com/ProjectPics/img119.gif
I've seen different numbers for different for different vehicles. Larger gain on larger horsepower engines. On average 2-5% hp/tq gain, 1-1.5mpg gain. Personally my jeep got 1+ mpg definitely and I never dynoed it so i got no hp/tq numbers. I've been working on the proficiency of my jeep not just horsepower. But this technique has been used by racers back to the 60s. Its a proven technique, google it and you'll see. Spark plug indexing and Spark plug side gapping.