Why Twin Plug?

[Alan Lindquist]

I've seen some nice motors on this bulletin board. A few weeks ago there was a gorgeous build by Rothsport, I think. It was a twin plug conversion of a special 3.0 liter motor.

I know that some of the 2.X liter racing motors had a twin plug set-up and the 964 went twin plug. I've seen some 3.0 and 3.2 modified with twin plug.

How much do you really gain for the expense and complexity? Is it about the redline performance or is there a gain across the torque and HP band?

[Steve@Rennsport]

Originally Posted by Alan Lindquist

I've seen some nice motors on this bulletin board. A few weeks ago there was a gorgeous build by Rothsport, I think. It was a twin plug conversion of a special 3.0 liter motor.

I know that some of the 2.X liter racing motors had a twin plug set-up and the 964 went twin plug. I've seen some 3.0 and 3.2 modified with twin plug.

How much do you really gain for the expense and complexity? Is it about the redline performance or is there a gain across the torque and HP band?

There are HP & torque gains across the whole RPM range as well as crisper throttle response. Further, cylinder head temps are reduced due to less total advance needed for complete combustion.

One also gains some detonation margins and the ability to use a higher compression ratio on pump gas, compared to single ignition.

Some further info is here: Welcome to Rennsport Systems, Porsche Performance Products for the 21st Century

[Bill Verburg]

it's all about managing the combustion process, and it is necessary all the time, sometimes more than others.

W/o twin plug cr must be lowered reducing torque & hp. w/ twin plug cr can be raised and more aggressive spark timing and fuel maps can be used raising hp & torque.

w/ twin plug the combustion is started at 2 sides of the combustion chamber at the same time, making the flame path half as long and also taking up half as much time to complete.

here's an illustration of a typical spark event from Bosch


and here is the timing of a combustion event, w/ twin plug you have 2xs the time to manage the event

[Bill Verburg]

Beat me again Steve

[cgarr]

And it looks

[Alan Lindquist]

Originally Posted by Steve@Rennsport

There are HP & torque gains across the whole RPM range as well as crisper throttle response. Further, cylinder head temps are reduced due to less total advance needed for complete combustion.

One also gains some detonation margins and the ability to use a higher compression ratio on pump gas, compared to single ignition.

Some further info is here: Welcome to Rennsport Systems, Porsche Performance Products for the 21st Century

Steve - thanks for the quick reply and I do apologize that I got the name wrong. I should have investigated first. That motor looked awesome. I'm dreaming of getting the same thing done some day.

[RWebb]

get the heads drilled when they are off - you can then do the distr. switch when you have some $$

[Joe Bob]

Higher compression/hp with lower octane crappy gas....