Can anyone explain this answer? I don’t get it:
Could Be Right | Car Talk
I think it is based on 30 year old “new” cars.
Back in the 90s coil packs with 2 leads was common especially GM. A 6 cylinder would have 3 coils with 2 spark plug leads. Both leads would fire at the same time. One in a cylinder under compression and a “wasted spark” in the cylinder in the exhaust stroke.
Coil on plug systems used on nearly every modern car don’t have a waste spark so don’t fire every revolution.
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The Puzzler also ignores the existence of platinum and iridium spark plugs not available in the 1960s as well as the elimination of leaded fuel. Both lengthen the plug lives a ton!
I remember spark plug cleaning machines sitting on the benches of nearly every service center.
Good points. It also fails to mention that the wasted spark fires at significantly reduced voltage because of the lower cylinder pressure at a few degrees BTDC exhaust vs. a few degrees BTDC compression.
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Thank you MM, I just read the answer. Puzzler had me puzzled.
My first job was at a gas station, we had a spark plug cleaner, never used, people would come in for tune-up, oil change, and new coolant before winter started.
I’m thinking some of the early Honda 4-cylinder motorcycles used two coils, like that. I should remember, I had one, but that was 40+ years ago…
edit- yep, here’s one of the coils for the CB550K, two sparks plug leads:
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Older single cylinder gas engines that used a magneto, like a Briggs & Stratton lawn mower also had “Wasted Spark”, The spark plug fired every revolution.
My 1985 Ironhead Harley Davidson has one coil and it fires both spark plugs at the same time… It is called a dual fire ignition system (also called a wasted spark setup). Both spark plugs fire at the same time while one cylinder is on its Combustion stroke and the other cylinder is on its exhaust stroke.
When I worked in a couple of Mobile stations in the 50s we used to remove, clean and regap peoples spark plugs at 5000 miles for 25 cents a plug and replace them at 10000 miles for $1.25. WE used the sprk plug cleaner a lot!