Quote:
Originally Posted by Steam Driver
I don’t consider myself an engine guru, but here’s my take on twin-plugging.
I don’t think for your engine the end justifies the means. The main reason Porsche twin-plugged the 964 was for emissions reasons, not power. This was because of the bore size of the engine. This also is one reason why aircraft piston engines are twin-plugged; without it combustion just doesn’t progress across the piston well-enough. The other reason is redundancy, of course. This isn’t a factor in the 911 of course. (One thing a lot of people don’t know is that the mags on an aircraft engines are not timed identically; I don’t know if the dual distributor does this or not but I doubt it.)
I have also had some experience with a BMW R100 engine that was twin-plugged. Looked cool, good bragging rights, but I didn’t notice any significant performance benefit.
So my bottom line it’s not worth the cost, additional complexity, and maintenance. But that’s just my opinion, and we all know about those!
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Well,.....I'd respectfully take a different tack here.
1) Twin-ignition has zero downsides (besides cost) and plenty of benefits that make it very worthwhile if one has the resources. More HP, more torque, reduced cylinder head temps, easier starting, and of course, reduced octane sensitivity. The latter may allow more timing depending on CR (remembering that twin-plug engines need 1/3 less total for complete combustion).
2) Porsche twin-ignition systems all fire both plugs simultaneously.
3) Porsche used twin-ignition for more power with the fuel grades of the day, using higher CR going back to the 4-cam Carrera engines. Emissions wasn't a consideration. 3.6 litre engines NEED twin-ignition to safely run high CR's with pump gasolines.