MFI used systems, are people actually doing anything with them?

[RWebb]

Originally Posted by BK911

I think the "10 extra hp" comes from the Porsche hp figures for the euro 2.4T with zeniths vrs the US 2.4T with MFI.

hmmmm...

[RWebb]

Originally Posted by Eagledriver

While carbs have the accelerator injector, they do a poor job of getting the proper mixture during transient throttle movements. There is always too much or too little fuel depending on throttle position or movement. ...

- this sounds like a time lag effect from something...

[Matt Smith]

I like Milt's answer the best. To add,

MFI is a loud, angry, exciting system that is hard to make work and deserves no place on a road car.

To most this is awful. To some, this is good. I am one of the some.

[davidbir]

Nobody has mentioned the power absorbed by the MFI pump--perhaps Mark can address that?

[haycait911]

Originally Posted by davidbir

Nobody has mentioned the power absorbed by the MFI pump--perhaps Mark can address that?

it can't be much. you can easily spin the pulley on the pump with two fingers.

[Matt Smith]

yeah, but try that at a few thousands revs!

Edit, or whatever magnitude actual rotation speed is above finger speed

[PropellerHead]

Originally Posted by haycait911

it can't be much. you can easily spin the pulley on the pump with two fingers.

On a bench or while actually compressing fuel to operating pressure?
The cog belt can't transfer a lot of power, can't imagine it would be more than a few Hp.

[356RS]

I use a 1 1/2hp 220 volt motor to spin the pumps. Testing a modified 2.0S 005 pump @4000 pump RPM @80 degree throttle delivering 68ml/1000 strokes the 4000 target RPM on the display drops to 3990 + - 3. All other tests below 3500 RPM @ WOT the RPM display is rock solid on the target setting. So I would assume 1 HP loss at max from the pump.

[davidbir]

Thanks Mark-that is much less than I would have thought!

[911st]

Originally Posted by BK911

I think the "10 extra hp" comes from the Porsche hp figures for the euro 2.4T with zeniths vrs the US 2.4T with MFI.

Also:

1967/8 911S on Webber's quotes at 160hp.

1969 911S on MFI at 170hp.

All were the same bassic long block spec's.


Still, I would be surprised if the difference was exactly 10hp.

[RWebb]

the MFI pump is also very heavy - not surprising as it was designed for diesel tractors

that was one reason I went with carbs on my motor

some one should link this thread to the others on MFI pump; one thread has a pic of an ad or poster for them

[YTNUKLR]

I am definitely doing things with used MFI systems...yes they are not cheap to get going...$6k+ fresh/rebuilt and ready to go for a performance, 911S/RS/RSR system is not uncommon. However, the performance is very good, tune-ability is decent if you use a "factory" combination (or talk to Mark Jung) and most of all it "feels" correct for the vintage cars...something you cannot get with EFI, despite its improvements in many areas.

There is nothing else quite like MFI. For most, the cost of doing EFI is similar or more than MFI. And carbs will severely detract from the value of a car that originally had MFI. CIS-not even in the same universe unless you are optimizing the car for stop-and-go traffic..

[boba]

While the performance advantage of MFI will stay open to debate, you either buy it or you do not, I do.

But more to the point it is period correct, and if your car came with MFI it should be there to realize max value. In my opinion the loss of value on a car without its original MFI is much greater than the potential $6K cost to replace it. I have and will in the future pass on cars missing their MFI, and I know others who have as well.

If you car is not original, a hot rod, a track car set it up as you please. But to go back to the original question, why, because it affects value.

BTW if in good shape and set correctly it will give great service over a long period of time. Most problems relate to worn parts or ham fisted ill informed trying to tune.

[jstobo]

The 67/68 S had smaller valves and less compression than the 69S (same cams). So how much difference was due to a different engine design vs fuel injection? Only the Shadow knows.

[911st]

Forgot the valve thing. Thought the compression was the same. Good catch.

[356RS]

Well I am and can't get enough of them. I'm in the process of putting together an RSR hybrid pump. Early Mercedes regulator with RSR vent and better baro cell location mounted on a 2.4 Alum pump body. Narrow space cams from the 2.0/2.2 can be used and a few experiments with some early Mercedes space cams will be done also.

[BURN-BROS]

Great work Mark!

[356RS]

Aaron, Your RSR front cover would work very well with this pump.

[mpeastend]

These are worth real money now? I've had the full system off of a '72 E or S (will have to check) for more than 25 years and forgot about it until now. It was a dream motor that was stillborn...I went 3.8. The motor was mated to a sportomatic but that really doesn't matter. What's a used system worth? (spoken as if I'm unknowingly sitting on the Hope diamond).

[RWebb]

Mark - build one out of Ti & Mg - just for fun