Twin Plug engines

[Robbbyg]

Ok heres one, if its a stupid question weell

Anyway twin plugs, ive seen a few on 911 engines and am wondering is it an aftermarket option?

or not possible??

if it is possible is it worth it?

[boba]

Twin plug ignition has been used by the factory for race engines since at least the late '60. It was not used on a production street car until the 964.

It can be done to all pre-964 cars but is not cheap. Cost will vary depending in ignition system chosen.

It is not needed for most engines but comes into play when CR gets much over 9.8 or when pistons gets over 100mm. The need for twin pluging is to improve flame propagation. High compression pistons tend to have a high dome and the palcement of the plug one the top side of the head makes for a long travel. The second plug gives a second flame front from the bottom of the head.

While the twin plug configuration will gain small improvement by itself it is not worth the cost and effort unless you are making CR and displacement increases. Of course this leads to cams and flow and the slippery slope begins.

If you go high CR and big bore with todays gas it is needed or at the least good insurance.

Most of the performance gain comes from the higher CR and larger displacement which would not live without the twin plug.

Do a search for steve@rennsport for more detail on twin plug.