Twin plug /4, ROI? Options

[r_towle]

Has anyone done testing to understand the Net difference between single and twin plug on a /4?

[gereed75]

Aha, great to hear from some one that’s been there done that. Thanks Bill.

The comments are right in line with what you see in the aircraft world where your engine is fairly well instrumented - a CHT and an EGT on each cylinder and the ability to turn one set of plugs on or off. Twin plugging enables less advanced timing while still getting complete burn, less advance means lower combustion peak pressures, lower peak pressures mean lower CHT’s and more torque ( the piston is not fighting an early combustion event while still traveling up towards TDC) and there is better combustion even in the shorter time available because of the two flame fronts.

How much better will certainly depend on lots of variables, but the more compression and the bigger the chamber the more advantage to be gained.

Worth it on a small, low compression four?? Dunno but More worth it on a bigger high compression motor, just as Bill found out.

BTW, awesome build thread linked and very informative info from Jake, that guy knows his shit! Miss him around here