Why Dual Plug on 10.3 C/R?
 

Hopefully someone can help?

I see that the Euro Carrera was a single plug at 10.3 C/R. Why do we need to make them dual plug when using 10.3 C/R pistons to rebuild a 3.0?

Is North American gas that bad?

THANKS!

Twin plug
 

Motronic for one thing, fuel quality is another
Mike Bruns

^^^ I disagree... 10.3:1 would be fine with single plug. Just run premium gas.

Hi Brad! Good to hear from you. Have a look at what these guys say. Would any of this be different due to better gas in Canada? Is Cali. gas that bad??


I just found this;

I'd revise that and say that trying to justify twin-plugging is like trying to justify seat belts.

Take a look at Steve Weiner's web site for info.

Be conservative. Cut the compression a tad & twin plug ANY big bore motor with a rel. high comp. or hp goal. That is what I did.

As fuel gets worse over the next several years, you'll be glad you did it. You will be GLAD you left a few hp on the able and left a few $$ on the table.

You'll be glad b/c your motor will run just fine, thank you. While others are cursing the low quality fuel or are rebuilding the motor. Also, the motor will "feel" better right now.

When you push the leading edge it often turns into the Bleeding Edge.

From Rwebb



Also, from Steve at Rennsport;

Twin-ignition is the ultimate upgrade for any 911 or 914/6 that isn’t equipped with this system. Although not particularly inexpensive to do, it does pay big dividends in the drivability, throttle response, octane requirements, and power. The degree of power improvement is related to the static compression ratio. Engines with less than 10:1 can expect a smaller power increase than ones that are above 10:1.

and from the same web page;

Compression ratios on Porsche engines above 9.7:1 require twin-ignition to enjoy the most benefit from the compression increase. Bore sizes 98mm and larger should also have twin-ignition due to the burn time required for complete combustion in these big cylinders.

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One cannot run 10.3:1 on pump gas without taking out a lot of ignition timing and that just kills throttle response and power.

The original premise that Euro Carrera was 10.3 is wrong. Actual compression ratio for Mahle pistons is about .5 lower than advertised. So actual Euro compression ratio is around 9.8.

-Andy

twin plug
 

We have tested twin plug 3.0 and larger engines with 9.5 and up CR, all made more power and the response and driveability was much better, the simple combo of a 3.0 with 40mm carbs and 9.5 with 964 cams made 10 more HP with twin plug vs. single on our engine dyno. all testing was done with premium street fuel.

Mike Bruns

This is the an amazing source of information.

Brad394, we will talk soon over a pint of beer. Hope you and family are good.


Thanks!