2.2L MFI Build Question
 

Our shop is building a 911ST clone and the donor car is a 1971 2.2L MFI 911.
Question is how far can we expand the displacement of this engine?
I'm thinking 2.5L would be a nice bump with high compression.

How big? You mean with mostly standard Porsche parts, I guess.

My recently retired, (and for sale), motor was a 2,5 based on a 2,2 T motor. It used 2,7 Mahle 90mm P&C and the stock 66 stroke crank. The heads and case had to be machined for the larger cylinders. The heads also had to be chamfered for the larger pistons. The cylinder seating surfaces get thin, but it did not cause any problems with my motor over two decades of use.

You could also install a 70mm (2,4 or 2,7) crank and rod set for a 2,7 displacement.

You could also, ( I assume) install overbored 2,7 cylinders and go up to ( I think) 2,8 or 2,9.

Yes. 2.4/2.7 crank and 1mm overbore. I think Henry at Supertec has done a ton of them.

Second question; what is the expansive capacity of the 2.2L MFI? Can it be adjusted to fuel 2.5L?

85mm on a 66mm crank is the original config for an ST (2.3L). Later STs ran 2.5L in both short (66mm) and long (70.4mm) stroke. The MFI pump and lines are fully capable of supporting over 3L in displacement with space cam swap.

Sent from my Nexus 6P using Tapatalk

Long stroke used 86.7mm pistons.

Sent from my Nexus 6P using Tapatalk

If you do short stroke the case will need to be machined to accept the big bore cylinders. Is the customer on with that?