twin spark plugs on 3.2s?
11-18-2003, 10:16 PM
#5
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One of those questions I've always been afraid to ask: Why is it a good thing? And why do you need it on engines over 3.2 liters? Does it just increase combustion efficiency, or is there another reason?
11-18-2003, 10:23 PM
#6
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The most common reason people twin plug is that it allows you to run higher compression (or boost) with with a given octane fuel.
To save Steve the trouble of retyping it.....
http://www.rennsportsystems.com/2a.html
Tom
To save Steve the trouble of retyping it.....
http://www.rennsportsystems.com/2a.html
Tom
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11-19-2003, 08:37 PM
#10
RL Technical Advisor
Hi Jack:
Its a matter of cost,....Turbo motors need twin-ignition as much, if not more than N/A ones.
The proper hardware is not cheap and certainly the heads must be machined, too. In most cases, we machine the heads for the lower plugs at valve job time, so that this can be done at a later time if necessary.
Its all about cylinder pressure whether its from static CR or boost pressure. Detonation is spontaneous ignition caused by excessive pressures for the fuels being used. Starting the flame front at 2 places in these hemispherical combustion chambers really helps prevent the pockets of fuel-air at the edges of the chamber from self-ignition.
Its a matter of cost,....Turbo motors need twin-ignition as much, if not more than N/A ones.
The proper hardware is not cheap and certainly the heads must be machined, too. In most cases, we machine the heads for the lower plugs at valve job time, so that this can be done at a later time if necessary.
Its all about cylinder pressure whether its from static CR or boost pressure. Detonation is spontaneous ignition caused by excessive pressures for the fuels being used. Starting the flame front at 2 places in these hemispherical combustion chambers really helps prevent the pockets of fuel-air at the edges of the chamber from self-ignition.
11-20-2003, 01:18 AM
#11
The reason the 3.6 has twin plugs and the 3.2 does not is because the 3.2 does not need them. While they would be helpful in any Porsche motor of any displacement, they are not as necessary as when the displacement goes to 3.5 or higher. While they do make it possible to run a higher compression, their true use in the later motors is to make it possible to get a decent spark. Since the spark plugs are not in the center of the combustion chambers of the flat six heads, once the displacement goes above around 3.5, the spark plugs start to become too offset in relationship to the centers. But by providing additional spark where the other spark plug would not reach as well, a better overall spark is achieved. A 3.6 needs twin plugs. There is just no other way. They are also very popular with 930s. Twin plugs really add to the reliability of the 930 under high boost.
11-20-2003, 02:29 AM
#12
Race Car
That's interesting, Steve. It makes sense to twin-plug a Turbo, and yet in all the upgrading talk I see with Turbo owners, I rarely see it on the lists. I see it all the time on 2.7 RS motors.
Maybe I just need to pay more attention at the next Porsche show I'm at that has some Turbos.
Maybe I just need to pay more attention at the next Porsche show I'm at that has some Turbos.
11-20-2003, 11:36 PM
#13
RL Technical Advisor
Jack:
Its a cost issue for people and in the case of Turbo's, the options are more limited. The cheap 3.6 dizzy will not fit and the options are an RSR conversion to the Turbo dizzy, or pair of crank-fire units.
Ed:
LOL,...3.2's need twin-ignition as much as the bigger bore 3.6 does.
Again, its a cost issue and I see many people talk themselves out of this being guided strictly by their wallet to justify this decision,...
Bottom line:
If one has a compression ratio at 10:1 or more regardless of engine size, one needs twin-ignition or the use of 100 octane race gas to prevent detonation. Needless to say, a Turbo's dynamic compression ratio will be well above 10:1 on-boost and they are no exception.
Its a cost issue for people and in the case of Turbo's, the options are more limited. The cheap 3.6 dizzy will not fit and the options are an RSR conversion to the Turbo dizzy, or pair of crank-fire units.
Ed:
LOL,...3.2's need twin-ignition as much as the bigger bore 3.6 does.
Again, its a cost issue and I see many people talk themselves out of this being guided strictly by their wallet to justify this decision,...
Bottom line:
If one has a compression ratio at 10:1 or more regardless of engine size, one needs twin-ignition or the use of 100 octane race gas to prevent detonation. Needless to say, a Turbo's dynamic compression ratio will be well above 10:1 on-boost and they are no exception.
11-21-2003, 02:08 AM
#15
Jack, as for not seeing as many twin plugs on turbos, I don't know. Maybe it is a West Coast thing. Back when I lived in South Florida, at least every other turbo was running twin plugs and crank fire. Tell you the truth, I saw a heck of a lot more turbos there than I do in the West. And yes, it is pretty hot too in South Florida. Hence, the twin plugs.