Is it absolutely necessary to run dual spark plugs
Can you only fire one plug
Will the engine run properly
Is there a horsepower advantage to two vs one

dual plugs are mainly for emissions purposes.

The stock coils fire both at the same time, unless you're planning on aftermarket wires/coils?

I know there has been people run them on one plug, and even made good power(turbo). I believe they ran them off of a Microsquirt ECU and used an LS coil to fire the one plug. You have to add some hardware to fire the stock coils with that setup. Not a big deal but when your trying to do it as cheap as possible one plug works.

While I am sure one plug would work, I would think two plugs would give you better flame travel and allow you to run less timing.

I wanna know how you can fire two plugs at once off of one coil. Spark energy is supposed to follow the easiest path.

How can two plugs both be the easiest path.

Dual plugs are great in a boosted application.

"Dual ignition promotes engine efficiency by initiating twin flame fronts, giving faster and more complete burning and thereby increasing power".


Aviation piston engines have dual plugs; during the engine run up prior to flight it's SOP to switch off one set of plugs, this produces a noticeable reduction in RPM called a "mag drop".

I can understand dual mags firing two plugs at a time. What I can't understand is one mag or one coil firing two plugs at the same time.

each coil is actually a dual coil and has its own driver and control from the computer so one coil fires one plug

That makes more sense. TY.

The early 5.7 has a coil on one plug and a plug wire from a coil on the opposite side for the second plug. My understanding is the second spark is mostly wasted, firing on the backside of the power stroke. It's purpose is mostly EPA related.

There is apparently a kit to to fire both plugs together.

Kevin

Normally I'd never consider indexing plugs, but I wonder if your return would be greater considering the two plug setup.

Its called don't cross over the wires, just coil up the extra length and stick it in the hole next to the coil. Jacobs makes a short wire specifically for this, probably the "kit" you are thinking of butt it is very easy to do even with the stock wires.

Very little advantage unless you are trying to light off something hard to light off, lean mixtures, very high compression... Very small HP advantage, very small MPG advantage, very small emmissions advantage, add up all those small advantages and they figured it was worth while.

Very little advantage unless you are trying to light off something hard to light off, lean mixtures, very high compression... Very small HP advantage, very small MPG advantage, very small emmissions advantage, add up all those small advantages and they figured it was worth while.

Back in 2003 I asked one of the plant engineers (Ram truck plant) why they used the dual plugs and he said it was strictly for emissions.
When they had the crossover plug wires that one fired on the exhaust stroke is what he said.

They got rid of the plug wires after a few years and I believe they just used the computer to do the same thing.

There's some good and some bad info on this post. Dual plugs are useful in that starting the flame travel from two points burns the mixture quicker. This requires less ignition lead (timing) and does have a power increase associated.

All gen3 hemis fire both plugs in a given cylinder at the same time!!! I'm not sure where people are getting info that one fires during the exhaust but that is not true. 2003-2005 with the crazy spark plug wires use waste spark to fire the plug on a cylinder 360 degrees away. For instance, when #1 is firing, one plug gets lit by the #1 coil and the other plug gets lit by the waste spark off of #6 coil. In 2006 they went to a '2 coils in one box' design and went away from the bundle of plug wires.

The above is why using a short plug wire to hook the coil to both plugs on a 2003-2005 coil is IDIOTIC. You might as well just run one plug at that point because the second plug is doing absolutely nothing for your combustion. The engine will have close to the same power potential as properly firing both plugs but require more timing to do it.

Long story short. If you have an engine management system capable of firing both plugs, do it. If not, don't worry about it but know that your timing numbers will be higher than anything else you see posted online to make the engine happy. And the short spark plug jumper wires are pointless.

I just added the short wires from Taylor to clean up the engine. This is on a 2005 5.7 in my 64 wagon. I was surprised that the engine revs higher at startup than it did before the short wires. It settles into the same idle after startup. Any ideas for the higher revs on startup now?

There are several big power turbo builds running 1000+ hp using one plug.

Don't some of the heads up series add extra weight on 16 plug engines?

One plug fires 20 degrees btdc...the second fires 5 degrees atdc to clean up the nox emissions.

Years ago I owned a 426 Hemi out of a Modified Production Coronet. It had dual plug heads and I don't think emmisions was a concern on that engine.

This is incorrect. They fire at the same time.

Why would two plugs be needed for that? Just fire the same plug twice.

dwell time is too short

The class I race in adds 50lbs to dual plug applications. There are two or three people in the class running a 3rd gen Hemi and they claim it's unfair and would run the same with one plug BUT they haven't tried it yet. I would bet it changes their tuneup -both fuel and timing - and I'm betting power changes too. Just FYI, these are >2000hp engines on methanol.

Ive seen those, big RB Hemi's with dual distributors, dual plugs.

of course, I've also seen that on other applications, including a 1991 Ford Ranger 2.3L, which had two distributors and two plugs per cylinder on it's 4 cyl engine. Pretty sure that was for emissions, kinda like the new 5.7L Hemi...:)

JS