Since the advent of the “OTTO CYCLE” . 4 Stroke internal combustion engines has relied on the Spark Plug to initiate the process of Igniting the air/fuel mixture. A lot has been improve on the engines, from overhead cams to variable valve timing, from points and condenser to the new electronic ignition with a crank trigger.
So what has change on the Spark Plugs? Not much! It is still basically the same configuration, with an improvement in the materials that make them different from each other. They still have a gap that has to be jumped from the collapsing field in the coil to create a spark for ignition to be successful.
Iridium,Copper,Fine Wire,V-Power and Platinum to name a few…
Since our subject is about High Performance or Racing here is our focus…In a car that is constantly being raced, I don’t see the sense into putting a 100k type spark plugs on your car and expect it to perform “100% for a 100K miles or kilometers, and leave it there cause its supposed to last that long…
It about makes as much sense to say you have a Brake and Rotor Combination that’s good for a million miles! So you don’t have to worry about it on the next 5 years- when you race every week-end or when you can escape from the wife/Girl Friend(s) to go Racing Cars not Skirts…
I have run all Types of Fancy High Tech Spark Plugs. The Main difference is “They Idle much better and smoother”.
Did I see a difference in Power or Speed? a big NONE!
What Happened here? A spark big enough to initiate combustion will self immolate most of the combustible mixture in the chamber! It does not know if it was with an Iridium or Platinum. A certain minimum is required to combust the mixture and when it meets that criteria its all done and over it by itself.
Many Moons ago i tested 2 different ignition systems to know what is true and what is a commercial. My car was a street oriented Race Car. I proceeded to install a set of Points and a condenser from a Company named “Accel”. This is a Factory Ignition with an aftermarket Points, cap, and rotor. The Ignition timing was set to be all in by 4500 RPMs “Stock” !
I ran about 12.50’s all day at the track with no hint of miss-fire or ignition problems as i ran with a new set of spark plugs gap at .035.
Next week-end I re-curve the ignition timing to be all in at 2500 RPMs and proceeded to the Race Track. Result? I ran straight to the 11.90’s with a point type Ignition!!! This is great…now Electronic Time!!!
I installed an Electronic Distributor with a “Big Yellow Coil”. and an Ignition box. To keep it a sense of fair play the ignition was all in by 4500 RPMs like the stock set-up. this to compare apples to apples.
Off i went to the track and proceeded to run the SAME! wat the **
As i suspected all along, it is the IGNITION CURVE not the Ignition that makes a Racing Distributor. Racers that have done this for a long time know about this, and i just want confirmation for my crazy head.
I proceeded to adjust the curve on this Racing Distributor to come in at 2500 RPMs and it ran as i expected 11.90s…I spent money.
There is a distinct change in the engine however, Now it idles smoother and seems to be more responsive, must be that giant yellow coil! lol
Many years later now I’m in the World of 16.5 compression ratios, nitrous, turbos, and blowers. Ignition systems are now more advance and it still relies on the Trusty Spark Plug! It is like going to War with the latest Cannon in your M-1 tank and use ‘Civil War Iron Cannonballs for shells, but now its made of Platinum and Iridium!!!
We haven’t found a better replacement for our trusty Spark Plug.
But now we have multiple Spark Discharge Ignition and bigger gaps and much better wires or coils on plugs. All this is a far improvement from the points.
However on extreme Ignition requirements like Turbo’s or High Compression Ratios we somehow go back in reverse to make ignition possible in the “Dense Environment of Boost and High Compression”.
When we are modifying our engines more and more the trend is into bigger and larger spark plug gaps and bigger wires and distributor caps to prevent spark “Crossover”. This is the way it is done and that is correct.
However in the “Extreme Racing” environment we are now going in REVERSE as far as Spark Plug Gaps! The Spark Plug regardless of the Material used has to have a closer Gap to prevent Ignition “Blow-Out or Flame Out”. It is a closer gap of .028 or less that is employed to enable the spark to jump the gap! If left at the high performance gaps of .045 to .055+ the Spark will cross-over at the cap or to the next wire as it follows the path of least resistance.
Very High Compression or Boost Levels must run a smaller gap or your not going to complete your runs. All this Ignition systems require this to be the norm. This is a lot less than a stock Gap in your Honda or Chevy. There is absolutely no loss in Horsepower with this smaller gaps. So don’t be afraid to experiment closing it down till the “Ignition Miss” goes away….
SPARK PLUG HEAT RANGE:
There are two things that are mysterious and more of a “Black Art” in Racing. Cylinder Head Porting and the Art of reading Spark Plugs!
I have a lot of experience in cylinder porting as a lot of you probably are, But with Flow Benches used every year by engine builders like me, we have come to certain conclusion of what works. However with the advent of the “Wet Flow Bench” technology all is out the window and back to zero as to what really works!
However on Spark Plugs it has basically stayed the same the last 100 years. So it baffles me that this art of reading plugs is still a mystery to a lot of people. I will try to simplify what works for me…
When you look at your spark plugs, when its been run combustion residue is evident in 2-3 turns of the spark plug threads. This will be one thing I look at.
When you increase compression ratio at least 2 points go to a “colder plug” from your baseline factory recommended heat range.
I basically run 1 range colder for the 2 points of compression increase.
Use a Spark Plug Reading tool with the lighted option. Use this to look at the center of the ceramic to spot black- grey dots as signs of detonation! BEWARE: Some manufacturers have this discoloration when you take the new plugs from the box! Check the condition before you start your testing….
If this Magnifying instrument is not available try to look at the center for the obvious if possible. If not, turn the plug on its side and look thru the plug opposite of a lighted lamp or anything bright and see if the center “electrode’s corners or tips are starting to round -off”.
This is evidence that you are “LEAN” and probably about to detonate/pre-ignite. The new plugs you just installed and run looks like it was there for the last 4 years and 40k miles where the center electrodes tips are rounded off and the gap consequently got bigger. The plugs sharp edges are starting to melt and rolls off.
Check the ground strap for the proper coloration as per information given by your manufacturer of your choice. Generally the color of the ground strap will start from the tip to halfway of the ground strap. A grey coloration of the spark plug ring is also something to look for. When this is the situation it is evidence of a correct heat range and an ideal or almost ideal Air/Fuel Ratio.
WARNING: When you use a given brand of spark plug, set your readings and get the proper coloration after your adjustments to timing and jetting, make absolutely sure you stay with this brand!
Another Spark Plug Manufacturer will show a different color or not show anything at all! I have watch numerous times individuals reading spark plugs and they will jack the timing one way and increase the jetting 3-4 steps with no obvious changes in spark plug color! Why? Because some do not read or are self cleaning through projected tips or other designs that are not for racing use…
Manufacturers have different Heat Ranges and some are narrow and some will span several ranges before you change to the next cold/hot plug. This is why they will color differently on a given engine….
Always Install New Spark Plugs when setting up…
When you do 2 or 3 FULL THROTTLE RUNS make sure on both runs you “CUT-OFF CLEAN ! by shutting off the ignition.
GET TOWED BACK TO THE PITS AND COOL DOWN AND AVOID “IDLING” YOUR RACE CAR.
GET TOWED BACK TO THE STARTING LINE. AND WHEN YOU MAKE THE LAST PASS CUT-OFF CLEAN AGAIN! AND GET TOWED BACK TO THE PITS !!!
NOW IS THE TIME TO PULL THE PLUGS AND READ IT.
The reason for this is the prolong drive back to the pits will discolor your readings.
WARNING: IF AND WHEN YOU CUT -OFF CLEAN AND THE ENGINE “SNEEZES OR BACK-FIRES” THROUGH THE INTAKE-, IT WILL NULLIFY YOUR PLUG READINGS…
INDEX YOUR SPARK PLUGS TO ORIENT THE GAP TOWARDS THE EXHAUST VALVE OR HAVE THE GAP FACING DOWN TOWARDS THE PISTON TOP WITH A SLIGHT TILT TO THE EXHAUST. MARK THE PLUG WITH A MARKER OR GET AN INDEXING TOOL. IF THE GAP IS INWARD TOWARDS THE HEAD CHAMBER INSTEAD OF THE TOP OF THE PISTON, THEN THE FLAME FRONT IS STARTING FROM THE WRONG DIRECTION….
MY OPINION ON THE DIFFERENT SPARK PLUGS AND MATERIALS USED IS “I KEEP IT SIMPLE AND BASIC”. A GOOD QUALITY SPARK PLUG WILL SUFFICE.
A SPARK THAT IS STRONG TO START THE COMBUSTION PROCESS IS ALL THAT IS NEEDED,COMBUSTION DOES NOT KNOW IF IT IS FROM A PLATINUM OR IRIDIUM ETC…
YOU CAN PROVE THIS THEORY WHEN YOU LOOK AT VERY HIGH BOOST OR NITROUS LEVELS ASSOCIATED WITH TODAY’S 2000 HORSEPOWER OR MORE ENGINES. IF THE BUILDER WILL ADMIT OR NOT WHAT HIS SPARK GAP IS? YOU WILL BE SURPRISED HOW SMALL IT IS…
THIS LENDS CREDENCE TO THE FACT THAT A SMALL SPARK IN A HIGHLY COMBUSTIBLE ENVIRONMENT WILL CREATE A COMBUSTION PROCESS…
Feel free to ask any questions below.