Duel Plug vs Single Plug

Are there any real benefits gained by having a duel plug head over a single plug head? If so, what are they or aren't they?

So the bike can run on just one plug with a duel plug design??

then why on earth did they put two plugs in the head???!!!!:gah:

So in that instance a duel fire coil would be better than a single fire coil?

not sure..some folks preferred a single fire

A little bit of info here is needed: on a high compression engine, dual plugs do burn the fuel mix faster for more power. On stock compression heads (9.2-1), it's a waste of time.

I have a Jeep with the Hemi engine. It's 350 c.i., compression is 11.2-1, output is 350 ponies and the heads are dual plugs per cylinder. And yes, they make a big difference.

Dual fire ignition is a coil that fires in both cylinders each time (wasted spark- no advantage). Spark plugs are fired twice as often and have half the life. Single fire ignition fires only in the cylinder that needs the spark.

BMW dual pluged the 1150 boxer motor to cure the lean surge they said the motor didn't have it was all imagination of the rider beemer beta testing again

olbill

Can you be a little more specific on this??

I will try when BMW introduced the 1100 motor some of the bikes surged so bad on part throttle they were almost unrideable so everybody got tuners of some sort and fatten them up and it cured the problem but the mileage went in the toilet.at that time i knew the factory rep he was very aware of the problem but the boys at BMW turned a blind eye to the problem. Then the 1150 came out and boom twin plugs after a year or two of them surging they said the problem was in the combustion chamber design and the flame path wasn't working properly so they twin pluged it and it was a runner most of the old air head racers twin pluged their motors also. but again good old BMW ignored that there was a problem.I hope this helps to explain it a little better.they also had some more inexcusable problems that the public sorted out for them.I got tired of the attitude of the dealers and after 9 beemers i got out. So far i very happy with my Harley's i had a few minor problems but they have been addressed and no B.S.
olbill

Ok, but it sounds like the major advantage for the dual plugs is for the higher compression engines. Ok, then why did HD start doing that when most of their engines are fairly low compression, (at least stock they are low CR)? At what CR is the dual plug really beneficial at??

I'm not an engineer but the older high end auto's of the past ran dual plugs my self i don't believe that compression ratio as much as combustion chamber design has much to do about dual plugs you can get cleaner burn and better A/F control and control high R.P.M. detonation two things you can't hear until it's too late. Besides it look's cool and it costs more to tune.

olbill

You need to own a beemer that has problems and you will really appreciate Harley "IF" you get a service writer that has their head on straight.

olbill

See post #9. What is your response to that?? Are the coils for dual plugs and ignitions about the same as those for single plug? Or are they "beefier," for lack of better term, by this I am referring to the output of the ignition and coil?