Does using dual spark plugs per cylinder make any difference?

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SUMMARY

The discussion centers on the efficacy of dual spark plugs in a 180CC single-cylinder petrol engine, specifically in a motorcycle marketed with "twin spark technology." While some participants argue that dual spark plugs can enhance combustion efficiency and performance, particularly in larger engines, the consensus is that the benefits in smaller engines like the 180CC may be marginal and primarily aimed at emissions control. Historical references to dual spark plug systems in engines like the Chrysler Hemi and Bristol radial engines highlight their role in reliability and emissions reduction rather than significant performance gains.

PREREQUISITES
  • Understanding of combustion chamber design and flame propagation
  • Familiarity with engine performance metrics and efficiency
  • Knowledge of emissions regulations and their impact on engine design
  • Basic principles of spark ignition systems
NEXT STEPS
  • Research "Combustion chamber design in small engines" for insights on efficiency
  • Study "Emissions control technologies in automotive engines" to understand regulatory impacts
  • Explore "Dual ignition systems in aviation engines" for reliability and performance comparisons
  • Investigate "Impact of spark plug placement on combustion efficiency" for technical details
USEFUL FOR

Engine designers, automotive engineers, motorcycle manufacturers, and emissions compliance specialists will benefit from this discussion, particularly those focused on optimizing engine performance and meeting environmental standards.

  • #31
berkeman said:
So each of the magnetos feeds one set of spark plugs for redundancy? Interesting...
During WW2, the test before takeoff was to run the engine up to temperature and speed, then cut one magneto at the time to check the fall in RPM. A "magdrop" of more than say 150 RPM, cancelled the flight.

I have a double toggle switch panel somewhere here, labelled "Magnetos".
 
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  • #32
Flyboy said:
I haven't touched a radial since school three years ago...

Lol, I haven't touched a radial since A&P school. . . 50 years ago. ( 1973 )

.
 
  • #33
When I was about 14, I wandered into the local Euro-Sports-Auto sales lot. They had a red Ferrari with the hood up. I spent quite a few minutes looking at the engine. Counted the 12 spark plug wires. Eventually I asked the sales guy "why are there two spark plugs per cylinder?" -- annoyed, he told me "that's a twelve cylinder engine, kid."

Much later I had a hot-rodded HD sportster with dual plugs. As mentioned above, this does allow for less spark advance, a lot less.
 
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  • #34
I recall seeing Honda Odyssey many years ago with two plugs. (Not the car) It was only a single cylinder engine. Two stroke I would assume.
s-l400.jpg
 
  • #35
And according to eBay, here is one.
s-l1600.jpg
 
  • #36
Sometimes, the second "plug hole" is for a compression release. Seen on old Brit bikes, if they don't have a "valve lifter."
 
  • #37
Baluncore said:
During WW2, the test before takeoff was to run the engine up to temperature and speed, then cut one magneto at the time to check the fall in RPM. A "magdrop" of more than say 150 RPM, cancelled the flight.

I have a double toggle switch panel somewhere here, labelled "Magnetos".
Exactly right. Still done today on light piston planes, although it's more of a maintenance check every so often.
 
  • #38
gmax137 said:
Sometimes, the second "plug hole" is for a compression release. Seen on old Brit bikes, if they don't have a "valve lifter."
That could be but I do recall a plug in each hole and a wire on each. The Odyssey I used to ride only had one and I don't recall a comp release.
 
  • #39
Averagesupernova said:
That could be but

Sorry @Averagesupernova , my comment was not directed at your photo. More of a general comment.
 
  • #40
gmax137 said:
Sorry @Averagesupernova , my comment was not directed at your photo. More of a general comment.
Hey that's ok.
 
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