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Old 07-09-2006, 12:37 AM   #1
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I know this ain't the army and our cars are not quite tanks, so bear with me.

My dad was in the Army in the 50'*. He was in 2nd Armored. The tanks they commanded had V12 engines in them. He said they had 24 spark plugs.

My question is this why 2 plugs per cylinder?? I asked him and he couldn't answer either. i'm hoping someone here will be able to shed some light on this for me and my dad.

Thanks,

Tim
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Old 07-09-2006, 01:32 AM   #2
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i've read somewhere also P51 mustangs (the 435 MPH single seater war planes of the WWII era) had twin plug per cylinder rolls royce supercharged V12'* if memory serves me right.

Methinks it'd be something with detonation of the fuel, maybe more HP? Not completely sure, but a hunch.
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Old 07-09-2006, 02:34 AM   #3
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Here'* the reason that Alfa-Romeo used it in theirs....

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The two sparks help create a larger flamefront ensuring less unburnt fuel in the exhaust as well as a higher thermodynamic efficiency.
It could also have had to do with reliability. If one fails, there'* a backup.
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Old 07-09-2006, 02:40 AM   #4
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The dual plug configuration was used as a back up in the event one ignition system failed. In the early days, many military vehciles shared some of the concepts and design of their airborne counterparts. They also had dual magnetos for the same reason. Modern jet engines have a dual ignitor system for redundancy. They run an ignitor system with jet fuel. Jet fuel is considered sort of a high octane diesel fuel.
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Old 07-09-2006, 01:30 PM   #5
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The Ford 2.3L 4 banger used 2 per cylinder back in the day. But if memory serves they didn't fire at the same time...one fired after compression, the other during exhaust evacuation to burn off unburned fuel. *I think*
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Old 07-09-2006, 04:01 PM   #6
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Quote:
Originally Posted by sandrock
The Ford 2.3L 4 banger used 2 per cylinder back in the day. But if memory serves they didn't fire at the same time...one fired after compression, the other during exhaust evacuation to burn off unburned fuel. *I think*
I HAVE ONE OF THOSES RANGERS!!!! 8 spark plugs on a 4 banger scared the guy at jiffy lube!
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Old 07-09-2006, 05:42 PM   #7
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The new Hemi'* have 16 spark plugs. My neighbor changed his and said it was the worst spark plug change he ever did. He had to literally remove 20% of the underhood components to get to most of them.
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Old 07-09-2006, 07:13 PM   #8
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Quote:
The Ford 2.3L 4 banger used 2 per cylinder back in the day. But if memory serves they didn't fire at the same time...one fired after compression, the other during exhaust evacuation to burn off unburned fuel.
You are correct...the same reason why they used the dual plugs in the Mazda Rotary engines. In the early Mazda Rotary engines, you can pull the two lower spark plug wires from the cap and plug them directly to the two coils, remove the cap and rotor and the engine will run.

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I HAVE ONE OF THOSES RANGERS!!!! 8 spark plugs on a 4 banger scared the guy at jiffy lube!
Be real...what would you expect from a Jiffy Lube Tech????
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Old 07-09-2006, 07:43 PM   #9
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I have to beleive that with ~1000 cubic inches the dual plugs primary function was to produce a better burn and the secondary purpose was ignition redundancy.
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Old 07-09-2006, 08:31 PM   #10
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Quote:
Originally Posted by popatim
I have to beleive that with ~1000 cubic inches the dual plugs primary function was to produce a better burn and the secondary purpose was ignition redundancy.
Either reason was reason enough for the military, yet both are important for the crewmember'* survival.
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