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What is the limitations og CIS, with no limitations on displacement?

If displacement was "unlimited", taking an SC engine and install a 993 crank, bigger cylinders/pistons, bigger valves, higher compression, bigger cams, etc, etc, what is then the limiting factor of the CIS system and fuel delivery? What is the biggest piston bore to work with with single plug? 98mm? 100mm?
If I ever buy an SC (I already have a Carrera), I would like to keep everything original on the outside of the engine, but do a lot of subtle modifications. Is 250Hp achievable? 300Hp? Just curious...

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Old 08-19-2017, 01:42 PM
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Single plug will "work" with any size bore, but it will not make the power a twin plug will. TP allows timing to be retarded minimizing cylinder pressure before TDC.
Old 08-20-2017, 04:52 AM
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In theory you could make it a 3,5 or 3,6 or I guess a 3,8 or who knows.

I read, a number of yeas ago, that someone was building a 3,5 to run with a CIS. You would want to run the large port style, I would assume.

Porsche used dual plugs when the CR was above 10 to 1 or the bore was at 100mm. So I'm guessing dual plugs would be in order.

As far as cams go, probably a 964 would be the way to go. You may be able to push that however.

Guys that turbo SCs will need to mod or replace the fuel distributor and upgrade the injectors and other parts of the fuel system.

The point of doing this would be to have a motor that would have passed smog inspections. Now with 3,6s being available with their much more advanced FI systems, CIS has lost its appeal.

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Last edited by Trackrash; 08-20-2017 at 12:12 PM..
Old 08-20-2017, 12:00 PM
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