MFI query

[Porschekid962]

Is it possible to use a 009 or 010 MFI and intake system on a 3.2 litre engine? What kind of mods are required and how much should I expect to pay? Would it be wiser to keep the engine 3.0 for the use of the MFI?

[Wayne 962]

As far as I know, there was never a 3.2 MFI system made for the 911 engine (maybe something for the 935, but I don't know off the top of my head). There was a 3.0 MFI system used on the 911SCRS, but they only made a handful of those cars, and these parts are rarer than rare (I've actually never seen any of these 911SCRS at any events - Monterey, Rennsport, etc. - just pictures of them in books).

Anyways, you could probably use the 1969 Magnesium 'S' stacks (hard to find) and possibly bore them out to increase the diameter. Use that with a modified pump, and it should work. Note that your pistons and cams are designed to be used with the Motronic system and as such, you won't get more HP out of the MFI without changing these.

The question is why you would want to do this though (and why no one has done this already) - even with a properly functioning MFI system, you won't get the same performance and gas mileage that you can get out of an engine management system. Now, the Bosch Motronic system is good, but it's designed for street use, and as such uses relatively mild cams and pistons designed to match. To really build a 3.2 MFI motor, you'd have to change out your camshafts for something more along the 'S' profile, with pistons to match.

Using the 30+ year old MFI system may look cool in the engine compartment, but for the same cost or even cheaper, you can probably run a TEC-3 engine management system with the hotter cams, a bump in compression from "taller" pistons, and twin plugs. A 3.2 setup like this should make almost (or more) HP than a stock 3.6 (which is limited by emissions controls and the generally mild 964 cams). The engine I'm building is a short-stroke 3.2 with 10.5 pistons, mod-S cams, and turbo heads, and I to get about 270 HP out of it, give or take.

Good question though - hope this helps...

-Wayne

[Porschekid962]

thanks wayne, sounds like we ar building similar engines. my starting point is a 78 sc engine and yes i plan on changing the pistons to higher compression, cams to something hotter and twin plugging it. my reason for wanting to switch to mfi is one, the cis wont support the changes i am planning to make and two it looks awesome and is something neater than carbs. as far as ignition i plan to use the HPX crank fired system but i was trying to shy away from the full blown setup with the tec 3. at that point it is almost easier (according to tyson) to retrofit a 3.2 dme and burn a custom chip for it.