MFI rod lenghts

[Zithlord]

I need the measurements for these rods:


•pump to rack rod length
•the two rack to throttle body rods lengths, (unequal lenghts?)


Should the rod be measured like the picture shows?

The whole MFI system has been to Supertec, and I think the rack to pump rod is pre-set from them. If so the picture below is incorrect. The four rods on the throttle bodies are also pre-set and installed. When I install the rod from the pump to the rack, then I install the two rods from bodies to rack. I used this advice:


You don't really need the protractors, either. With all of the throttles on their stops and the pump to rack rod length spot on, adjust the two rack to throttle body rods until they snap on without moving anything. That's the poor man's correlation. There was actually a Porsche bulletin released in the early '70's allowing for this method in the absence of the protractors.

Following the above the two rods from the rack to the throttle bodies ended up being unequal length, is this correct?

Finally I installed the rod for the accelerator linkage, any advice on length on that rod?


Thanks
John

[mobius911]

Hi,

The number above is for cm, not mm. The 11.4 cm, or 114 mm length is straight out of the check, measure, adjust MFI manual. Definitely download a PDF of that. I believe there is a link to it from the technical page here.

The manual recommends measuring the end-to-end length and then subtracting the outside diameter of one cup. "If the rod does not have the proper length, it must be corrected to 114 +/- 0.2 mm."

You do want the rods that actuate the throttle bodies reasonably close, but the manual says they must be within 5 mm. If the difference is greater, you can adjust the "left activating lever" in relation to the cross bar.


Hope this helps.

Jeff

[Zithlord]

Thanks jeff, the 11,4mm was a typo by me, it should have read 114mm. I have the CMA, and reading your answer confirms the drawing, it should be 114mm center to center(or the lenght of the rod subracted the ball)

Anyone have a measure for the acelerator rod lenght?

John

[edmayo]

John, as you already know, the pump rod length is the starting point, and the only measured length. The procedure is to disconnect ALL rods from the cross bar, then attach the 114 mm pump rod to the cross bar, then adjust the two throttle body to cross bar rods to just snap on without any pretension, with throttle plates at their stops, then adjust bell crank to cross bar linkage rod to snap on without any pretension. Then adjust all remaining linkage and throttle pedal stop so that you will have full throttle just as the pedal hits the floorboard stop. When MFI first came out Porsche called for a fairly elaborate protractor adjustment for the throttle links, that was later superseded to the method described above.

[jcge]

Ed - that's the most simple explanation of the topic I've ever seen...bravo.
John

[Zithlord]

Very good explanation Ed!

John

[bliebler]

I re-opened this thread after I discovered that my socket caps have a flat spot machined on the ends. The end of my caps are not spherical or rounded therefore the method in the manual(measure end to end length then subtract diameter of one)will not apply. I assume that my caps are not orig as previous owner had throttle bodies and all my linkage caps replaced. Or did the orig caps from the Factory have these flat spots machined to give a better measurement? If not these flat spots will throw off this measurement by as much as 2mm. Does anyone have orig socket caps to compare? Has anyone else noticed this? This makes center to center measurement a pain as the cups oppose each other and it's hard to eyeball the centers.

Brian

[gled49]

Yes the new ball sockets have little flats on the ends, I have just left a visible gap at each end with the proper measurement and don't believe you will have any issues. Gordon

[Flieger]

If you are willing to do some fabrication you could take some angle (90 degree) Aluminum and measure out the correct center to center length, then thread 2 holes at the ends of that line using a center punch to keep the pilot drill from walking, then get some ball studs that fit your sockets on your go/no-go tool, and adjust until the sockets click on. Then you can take a new measurement end to end and find out how it differs from the factory spec when you take the center to center + one diameter. That way you know how much material the flats took off and you can adjust all the other linkages on the car, using this 'corrected' spec.

[72targa]

Check, Measure and Adjust article in Documents here:

http://www.pelicanparts.com/techarti...MFI/TipMFI.htm