MFI conversion Carrera 3.0
 

This thread http://forums.pelicanparts.com/porsche-911-technical-forum/593665-ultimate-3-0l-cis-mfi-conversion-thread-2.html refers to 2 approaches to CIS to MFI conversion with the principal difference for my purposes being that one uses a system configured to 2.7Rs specs and the other uses a mix of 2.4S parts (stacks, t/b's) and 2.4T parts (MFI pump with standard space cam).

My question - sure to be the first of many! - is as to the MFI pumps. I have 'spare' 2.4T and 69S 005 pumps available to use for this application along with 69S t/b's and stacks and I'm interested to know how thin that T pump might be at higher rpm given its original application. Second question is thoughts on how that S pump would be in standard trim for 50% more capacity in the engine?

I know there's lots more to think about but this is a fairly big starting question as the unused pump will be sold to help fund the rest of the required work - JE 9.5:1 pistons, S or 964 grind cams etc.

thanks in advance,
Mark

I'm just an MFI beginner here but...from what I know about the MFI system, it would be nigh on impossible to predict how either of those pumps would perform on an engine with a different displacement, compression, and cam profile from stock. Your better course may be to firm up the specs on the new engine and talk to someone like 356RS (Mark Jung) and have the pump upgraded to a custom space cam for your application.

You could almost fund ITB and electronic injection from the proceeds of selling the MFI stuff....

I'm playing with this right now..seehttp://forums.pelicanparts.com/911-engine-rebuilding-forum/858139-s-alive-first-build-creation.html

The T pump can supply the volume required but everything becomes a compromise as to drivability, fuel efficiency, AFR and so forth. I'm in the midst of trying to tune my pump and I have amazing throttle response and what I think is great performance above 4000rpm. This comes from heavy richening on the main rack (more fuel). However, from my reading, understanding and now realization this of course is at the effect of changing the AFR and performance at lower RPMs and later on the idle circuit. In the end you can only go so far to adapt a pump that was not designed for it purpose. This antique system can only go so far without having a new cam profiled.

I can't attest to the fuel delivery of a 69pump, but I somehow recall reading somewhere that it would not suffice for a 3L or greater creation.

I also believe that the T cam in the T pump is also the most forgiving for a bastardization attempt due to the more subtle profile used for drivability, etc.

Currently still having fun and have another T pump apart just to learn, but eventually for ease of mind and overall performance I think a new cam will be in order.

Thanks for the comment and I'll check your build thread.

Main reasons for wanting to run the S pump is that the car it will be going in is a 69S long parted from it's motor case but for which this is the original pump - and with all the original shroud, air box etc, the first glance look will say 69S engine....and I really like the MFI performance characteristics. :cool:

Cheers,
Mark

Hi Mark,

The 69S pump would be the starting point for me if I were to choose. The space cam inside the pump would be removed and a cheaper unit would be sourced to modify to the required spec.

I did a similar build for a 69E.

Cam choices would be MOD solex and Mod S(DC-30,DC-40) for the compression you want.