Are MFI engines really THAT hard to keep on top of?
 

Asking for a friend - grin. There seems to be a fair amount of hand wringing over keeping them in tune and lack of resources/shops that support them.

I believe some ‘72 and ‘73 used them and of course the famed RS.

Can I get an education (please) on the pro and cons of this set up?

Thanks!

Mine is not hard to keep on top of.

Just pay attention to what the car is doing and, if anything abnormal, fix it right away.

I am only the third owner, so no one has messed with it during my tenure (1979 - ).

I drove it cross-country in 2005 with no problems - other than a points adjustment outside of Odessa, TX.

The altitude adjustment module did it's job over the Colorado Divide - actually I-40 in NM.
(I caught up with all the cars that had been passing me all day while they were doing 85-95, and passed them on the climb to the top (7,295 ft) as I was at a steady 75 mph.)

I do all my own maintenance and for me, it took about three months of fiddling around to really understand how all the components and control adjustments interact. Once you get the throttle bodies and pump in spec, linkages setup per the manual, and idle/part throttle mixture right with a meter, there isn't much you have to do to keep it running well. Keep filters, plugs, and timing always in spec.

Pros? For me, it's a lot more fun -- power and throttle response -- to drive than a car with carbs. So far, a lot less tweaking and cleaning than old Webers too.

Thanks for the responses – I’m not sure if this is a fair comparison but I am familiar with Bmw 2002faq I eyes and once it’s set up properly they tend to stay set up properly, is that a fair comparison and expectation I have with these as well?

Start with a rebuilt MFI pump and make the throttle bodies are tight and flowing evenly.

Change oil every 2000 miles and use a conventional oil.

Keep all the valves adjusted and points everything set correctly like dwell and ignition timing. MFI can't compensate for changes in engine condition.

Check the injectors for flow and spray pattern.

MFI is far less finicky than carburetors as long as you start with a good setup and properly maintain the car.

Prepare yourself for many opinions.

Been living with one for about ten years. No real issues to report once I got it into spec. I baselined it first, even using the correct plugs which most everyone will say are too cold. Set the fuel mix on the rich side but still in factory spec. Oil smells good, never gassy. I do avoid starting it unless I plan on getting it fully up to temp. I do like to run 100:1 synthetic two stroke oil as I think modern fuel has lost some lubricity. Driven it up to 14,000 feet and the altitude compensation worked well. Even better than later Motronic as it’s variable adjustment vs a one time switch to a different map in DME.

It’s Rube Goldberg for sure. But all the info is out there and if you come from a multi carb background it’s doable.

As others have stated the MFI is very reliable. Makes a sports car a race car as it did in 1973 Daytona 24 hours overall winner.
Never touched the MFI in the 1972-T but had to have the 72-S MFI rebuilt because I let the car sit for over two years, a big mistake.

Thanks for all of the responses.

I'm in my 20th year and approaching the 200,000 mile mark of MFI ownership. My first motor was the 2.4 "T" spec that came in my '72 "T", my second is the hot rod high compression twin plugged 3.0 that is currently in the car. I've described it at length on this forum as the years have gone by. It's going to roll over 100,000 miles before the end of this year. Where does the time (and mileage) go?

I have had literally zero issues with either system. My son is still running that 2.4 in his '68 912, and he has had no issues of any kind. We have found it to be an incredibly reliable, robust system.

Starting from a baseline of a good, solid, working pump and throttle bodies, there really isn't anything that will go out of adjustment all on its own. Keep the ball cups and pivots on the linkages well lubricated and really, there is nothing to wear and go out of speck. Make sure when you set up the throttle plates that none ride on the throttle body bores, that they all rest on the stop screws, and there is nothing to wear there, either.

Maybe one of the reasons we have had such good luck is that we simply never let them sit for extended periods. Nothing has time to dry out, varnish up, or the ethanol enriched gas doesn't have time to evaporate and leave its blasted residue behind. Maybe it's more of a "use it or lose it" situation with this system than it is with others - there are certainly places that are exposed to gasoline that you don't want to see dried out, like the injectors and pump cylinders/pistons.

So, yeah, in our experience, there is nothing to be afraid of. We've had great luck with it.

Pioneers like Jeff have ushered in a new era of MFI enlightenment. You can read back in some of Jeff's old threads as various contributors put the pieces together and came to an understanding of how the pump itself works. Jeff himself came to better understanding as he delved deeper and deeper into the pump and various adjustments.

It's fascinating stuff to read - and got me hooked. It's been pretty much downhill from there, but I'm now the proud creator of a 3.2SS MFI Monster and I wouldn't do a single thing differently.

Whatever it is you are considering, DO IT!!! Take the time to understand the parts of it and how they work, GET A WIDEBAND O2 Sensor/gauge, make sure your ignition is up to snuff, and dive in!

OK- done. I've got a '71 2.8 MFI in my garage, but it's a Mercedes. What resources do you recommend I consult to understand pump adjustment, et al?

I had to do some Mercedes Bosch fuel injection work years ago. Some of their forums are really informative containing a lot of factory documents.

For starters try, https://www.sl113.org/forums/index.php?topic=1824.0.

Oh man I got excited there for about a 1/4 of a second!!

Mercedes are simpler with only one throttle valve.

Nope

Chris

73 911 E

Check Measure Adjust - and it will hold tune a good long while and give you 5-10 more hp than carbs, not to mention no float bowl issues in hard corners

con: it's heavy - originally designed for diesels

EFI is the ultimate but not a period correct solution

The trouble is always the "people" .. those guys who cannot resist fiddling and "improving". It was the same with SU carbs back when British sports cars were numerous, and then Datsun Z's ... some guy somewhere couldn't resist getting out his screwdriver ...

I've not had an MFI Porsche but I spent many years with very-similar Alfa's. When I was young, I too was that guy, tweaking, adjusting the first GTV I had. After that was sold and I realized I needed another, the second GTV required a full rehab of the F.I. So, as advised above, I had the pump overhauled then had the linkage set by the best guy in Philly (shout out to Vince at Nick Falcone's Sportscars). He set it up while I watched but chastised (threatened?) me NOT TO SCREW WITH IT. When I sold the car twenty year later, haing never touched it, the system still ran perfectly.

Or in other words, "what everyone else here said".

John

All I can tell you is my Porsche factory trained employer found the MFI systems so problematic we were replacing the MFI systems with webers all the time. Back then a complete weber set up was @ $1,500. 1970'-80's AND we threw the MFI systems in the scrap metal pile! I know hard to believe...

Good morning. Can I go back in time and take all of those removed MFI systems off your hands? Oh, and while we’re at it, I’ll take a bunch of 912s for $5000 and some good 911s for $10k please.

Hope you’re having a good morning.

My 73S is MFI, of course. When I bought the car in 2005 I had my shop baseline everything including the MFI. In 2016 I noticed my mileage was dropping a bit so I asked my shop to check the MFI, which they did and made a few adjustments. That’s been it; 16 years of near flawless performance with only one adjustment to the system in all that time. YMMV but its a pretty bulletproof set up when dialed in. Nick

That's exactly what I did. I picked up several of those "problematic" systems back in the day. For free. All fully functional. All completely out of adjustment and totally screwed up by some "factory trained" mechanics. One of them has been running trouble-free on my 3.0 for fifteen years and darn near 100,000 miles.

Owned mine since '13 never had to do anything to the mfi.

An AFR meter makes all the difference between now and then. It takes all the guess work out. Start with a CMA (Check, Measure and Adjust) to make sure you are at the right starting point and adjust from there. Really not difficult once you know what the adjustment do (and there are only a few).

Chris
73 911 E

I think all of the add ons and bandaids that were on the pumps, esp the decel system, caused some quirky drivability issues back in the day, and I think more with the Ts than the E and S. Maybe because we saw more Ts or maybe their lower compression was a hinderance. Carbs were the easy, economical way to go then. Saw an invoice for my 72 from 1995 when I had a 2.7 RS space cam installed. Other than a couple of belts and pulleys, never a hiccup. No decel system on it. Bob