OkieRon

I have a just bought a 72T with MFI that needs a complete rebuild. The Porsche club guys say keep the MFI- more power, better fuel consumption, a great sound, and less maintainence once they are rebuilt (Jeepers- at least $800 to 1K)The wrench and others say change to Weber carb. They say Webers have less to go wrong even if you are constantly having to adjust carbs and clean the venturi. What's your vote folks and why?

Thom Fitzpatrick

MFI. Once it's set up correctly, you have no reason to putz with it, unlike carbs. It's also more efficient over a wider range of conditions.

Clark Griswald

10HP edge to the MFI. That should pretty much settle it.

Chris Campbell

I'd take a properly setup MFI system over anything except for a modern hi-perf EFI system such as Motec/Haltech etc. Those are of course extra cool, particularly for custom engine configs, because they are laptop-tunable.

911 Guy

I dont know what the HP difference is, but a properly set up pair of carbs "feels" like alot more HP than MFI. The throttle response is much different. I converted my 2.7L to carbs last year and love it. The carbs do require alot of tinkering though. If you dont like to work on cars, stay with the fuel injection.
Two thumbs up for dual Webers. They look, sound and drive better in my opinion.

Kurt V

As you have heard from the others, nothing beats the MFI for HP and response. By the way, what makes you think the MFI needs a rebuild? Very few MFI's actually need a rebuild, they just need to be adjusted correctly, something the average owner can do if they are patient and are willing to read the tech articles posted here: http://www.pelicanparts.com/techarti...MFI/TipMFI.htm

Kevin

Unless you like spending your Saturday mornings adjusting your carbs or replacing linkages, stick with your MFI, spend the money to get it right and leave it be.

Billy B

I think you need a new wrench.

This fellow is scared of the MFI or doesn't understand it. Find someone who does, it is a superior system. And sounds so sweet!

JPIII

I'd say....It depends.
If you have a full MFI system, by all means have it redone....if you can find someone to
not only redo it, but also, tune it. Don't let a complicated, 30 year old system scare you :-)
There are prolly 500 people in this country that can properly tune these things and, apparently, some are on this list, but do they live near you?

There is a learning curve for each system.
Hands on learnin' with assistance from some experienced hands makes the curve easier to handle.....humm, too many puns in one sentance. Sorry.

As for power:
Stick your head in the back of a few PCA, GT4,race cars. Hummm....EFI, for the well off, Webers for the poor folk. No wonder they're poor, the fools :-).

richard glickel.

Okie,

Carbs look great and sound beautiful. That said, fuel injection is still the way to go ... it's not even close.

Richard
'87 Carrera 3.6L

Steve Weiner-Rennsport Systems

Great thread!

I'd surely like to offer some perspectives of working on these things, racing different cars so equipped, and living with them since 1973,......

Everyone has a different opinion about which system they prefer and all are valid.

That said,.......All things being equal, a MFI-equipped engine will make slightly more top end power than its carbureted equivalent and the carbureted version will have slightly better mid-range torque and throttle response. Given the possible variations in MFI systems and current sizes of carbs that are now available, its really tough to side-by-side accurate comparisons. Its all a matter of preference & budget.

If an MFI system is in top shape and the engine underneath is, as well, then they really are neat. When they are worn or mis-adjusted, they are a real PITA and carbs will be better. The MFI system is very complex and has lots of parts that wear. They do require a level of expertise and knowledge base that is NOT growing.

Webers are also a real PITA if they are not installed and setup properly. These are VERY reliable when they get clean, pressure-regulated fuel and have perfect float levels. No MFI system has the throttle response of a well setup set of Webers in good shape. On all of the Weber's that I've setup in the past 26+ years, none of them have required constant fiddling. Only those that receive dirty fuel and improper float levels will cause grief. Weber's are VERY picky about these issues; far more than any domestic carburetor!

The vast majority of whatever bad rap that Weber's receive are owner-operation related. The "Peter Principle" is absolute here,...
We have built a lot of street & race engines using both systems and they both make big power. One of the most powerful 2.7's that I've even seen (325+ HP) uses 50 mm PMO's.

Lastly, EFI systems are also excellent IF properly mapped on a dyno but these are very expensive.

The best bang-for-the-buck lies with Webers/PMOs. Just make sure that either system is in excellent condition and setup properly.

Hope this helps somebody.

Howard

Okieron,

I think it really depends on whether your car is track only, track/street, or street only. MFI is more suitable for the stock 2.7, but if you plan to build it up and race it, the MFI will limit your potential HP goals. I chose carbs due to point restrictions in my class,if I had gone with a Motec EFI I would have been bumped to the next class. As far as "fiddling" with the Webers, I have built my last 2 race motors and once the initial tuning is complete, (which you would have to do with any fuel delivery system,Motec,MFI,or carbs) the tinkering is minimal. Webers have less parts to fail compared to the MFI, and carb parts are easily obtained. Try finding replacement parts for the MFI, you may find everything BUT the pump.
SO... my vote is this...stick with the MFI for a street car. If you want to build a club car and you want more HP, better low end response and a less complicated engine compartment you can troubleshoot easily, go with Webers or PMO's. If you want a fully competitive full blown race car, and you have the $$ for TWM throttle bodies, Motec EFI, maybe $7k, go for it, but I see lots of guys with their laptops trying to dial it in all the time at the track. (tinkering)lol
Good luck !

saint

My vote goed to the MFI. I call my webbers, "Depression injection."
Ask someone about starting a webber equipped car after the engine has been sitting for 10 min.

Anyhow, at the pressure the MFI injects the fuel at, It must be better for mixture formation
Thanks
Saint

JPIII

Actually, my car starts great after sitting for 10 minutes.....up to 24 hours.
I have the PMO insulator "blocks" and the carbs have the anti-perculation mod.

If I start if daily, it starts well. Let it sit for a 3-4 days or longer...ugh..2-3 minutes to get fire in all the holes.
Working on that.

Steve Weiner-Rennsport Systems

That one isn't too tough to cure either. As these carbs have no starting circuitry or chokes, as such, they completely rely on the accelerator pump outputs to provide a starting mixture.

I'd suggest confirming the pump outputs using the calibrated vial for that purpose and make sure that the float levels are perfect at 3.5 psi of fuel pressure.

Works great,....