mfi

[fricker]

I have just bought a 911 70E, and the engine is idling high but the idle varies it bounces up and down. I know I have a leaking #4 throttle body that has to be fixed before any other adjustments can be made. I found that I have a 70S mfi on the engine. Can the engine run normal with this type of pump on it?
Chris

[svandamme]

can't use S pump on E engine or vice versa, the mfi pump has a space cam that needs to match the camshafts on the engine

an E engine has a different power curve than an S engine , so realistically , they will run with a different pump , but the fuel delivery will not match the requirement for that engine... for a given rpm , the delivery will be either to high , or to low




this is for the 72-73 2.4 engines , but i guess it's similar for the 70-71 2.2 engines..


biggest difference is going to be higher revs where the S engine puts out more than the E, not sure if this can be covered with mfi tuning, i assume it can't

[Jim Richards]

I'm sure you run the S injection pump with a compromise setting. Maybe tune it to be about right at lower RPM's and a bit richer at higher RPM's. Also consider finding a 2.2E injection pump and then you can sell your S pump for a profit. Fixing your leak first is a good idea, as is fixing any other known problems with air/fuel/spark. Then follow the procedure detailed in Porsche's Check, Measure and Adjust manual for MFI. It's availble here on-line at http://www.scatliff.mb.ca/pelican/MFI_Check_Measure_Adjust.pdf
You might also check the rest of your MFI system to see if you have E components. One way to do this is to measure the stack & throttle bodies and compare to the information in this thread
MFI Induction Chart

[pwd72s]

I might add that once you get an MFI system working properly, it's heavenly...fantastic throttle response.

[jluetjen]

Fricker, Congratulations on buying the car that you discussed on your earlier MFI thread. I'm sure that it will work out well for you.

Yes, the E and S pumps are different, but near as I can find they are different in the map (3D-Space cam) which controls the volume of fuel injected each cycle at engine speeds <4000 RPM. Above 4000 RPM, I believe that the pumps are essentially pegged and the fuel volume is controlled by the "Part Throttle Adjustment". Given that that the S pump is only one "step" off from your "E" engine, it should be able to work acceptably well as long as there aren't other issues such as leaky throttle bodies.

As you work through CMA, I suspect that you might find that the temperature control for the MFI may not be right. But confirm everything else prior to that step in CMA is working before you start playing around with that. Here's a thread dealing with the theory of operation as well as servicing of the Thermostat. Does your engine even have a good hose running up to the thermostat???

[fricker]

Hey guys, thanks for the info. I will be taking off the stack to fix the leak in the #4 body. But as of right now I have to deal with a bigger problem which is that the gearbox is stuck in 4th gear and it won't come out.
Chris