Replace MFI with Webers?

[FranksPlace2]

I am looking for a 70 - 73 Targa close to original. Two cars I looked at ( 1 T & 1 S)had replaced the Bosch MFI with Weber carburators. Is the common? Are there problems with Bosch MFI?

[pwd72s]

The biggest problem with Bosch MFI is that some mechanics didn't know how to tune it. Also that it was cheaper to replace with webers than to rebuild a worn MFI system. I suspect that in the cars you're looking at, the PO's opted for the "cheap" route. Which would make me also wonder about the rest of the car's service history...

[jkeyzer]

I think this is common. When I was shopping around last summer it looked like a lot of the MFI cars had been converted to Webers. One had been converted shortly after being purchased in the early 70s! I personally wanted an engine that still had MFI and I was able to find one pretty easily.

One disadvantage to keeping MFI on the car is that if you want to rebuild from a T to an E or S or play any other games with the engine, you have to replace or rebuild the MFI system to the new engine specs. This includes the injection pump and throttle bodies and also affects your choice of heads, cams, p/c's, etc. The MFI pump has a contoured cam inside it that is specific to the engine it was designed for (ie. 2.4T) and I have heard that you can't mix and match very well.

I have a stock 2.4T motor with no displacement upgrades planned in the near future so for now I am ok.

I think the MFI system (if working properly) buys you more than a few HP and slightly better gas mileage. This is good. The downside is that chances are in the end you will understand the system much better than your mechanic...

[Tyson Schmidt]

MFI is definitely better. Especially if you're going for originality.
10 more HP. (The carbed European 2.4T was 130hp versus 140 for the U.S. MFI 2.4T) Better cold start and running characteristics. Better mileage.

That said, Webers are more adaptable to future engine mods. They have very slightly better low to mid-range throttle response. (Due to the accelerator pumps and the venturis.) But have poorer top-end performance. (Due to the venturis choking effect, which actually helps the bottom end performance)

Which is better is entirely dependant on what is important to you.

Oh, one more thing. MFI is very stinky at the smog check. To get them to run well, they like to be at about 7-8% CO at cruise. Oddly, Webers are cleaner in this department. Webers, however, are stinkier in regards to fuel smell in the cabin.

[my72911t/rs]

My car came with mfi and now with all my changes Im starting to love it. A lot of mechanics I talk to say they are the only ones around who know how to make it run right? I would rather spend the money and know I made it run right and how to fix if I had too..

[Bobboloo]

You forgot one thing Tyson. MFI sounds killer when your on the cams say around 4500 RPM's.
By the way there is a really nice 72"E Targa on Ebay. It appears very original. It has the MFI. It is missing the original bumper which should be a real S style bumper. It may have been repainted as well, because the stickers are missing from the rear frame cross member. It also appears to have a MSD ignition. The dash looks original too. Nice interior. Aftermarket radio though. If I didn't already have two 72'T 911's I would diffenently snatch that one up pending a PPI. If I had my pick of any 911 Targa it would be a 72'E. I would even prefer it over a 72'S Targa. If it was a coupe I wanted by all means the S. I side note: The 72'E Targa is actually fairly rare. There were only 861 made.
The car on ebay is also in my favorite color for an early Targa. Maroon.
If by chance you'd want to buy that car I would gladly trade you my 72T's.

Bobby

[FranksPlace2]

I appreciate all the comments. Looks like either MFI or Webers work if you know what you are doing. I'm not fanatic about original but I would prefer MFI.

I saw the E on Ebay; I think Kruse is the "agent".
Seems hard to get a pre purchase inspection or at least see it. I try to avoid spending that much money without knowing what I'm buying.

[T Bird]

About Webers being the cheap solution-- I did the conversion in 1987. The Weber package from PMO cost $950 then. If I recall correctly, that was about twice as much as it would have cost to have the MFI pump rebuilt.

Some people love the MFI system. In my experience, it was nearly impossible to adjust HC. Over time, the pump also leaked fuel internally and diluted the engine oil, resulting in a worn engine and a rebuild. I have never regretted the change to Webers. I have found them to be easy to adjust and very forgiving.

[RoninLB]

IMHO..it's a carb eat carb fuel world