MFI related questions

[peter 911 TS]

Hi,

I have some questions regarding my 2.4E engine that still has the original MFI system.

Regarding the banjo bolt for feeding oil to the injection pump. My mechanic fitted the bolt so that the feeding and recieving holes of the banjo bolt assembly does NOT align at all (off by 45 degreess) - I asked him about it and he replied, "no problem, the pump will get the oil it needs"is this correct - does the banjo bolt ring play accomodate room enough for the oil supply? and isn't it best for minimizing wear if the holes align in any case?

Regarding enrichment, the guy twisted the enrichment at idle to be "4 clicks" leaner, and told me to watch the color inside the muffler outlet, if it goes dark grey it's ok, if it goes light grey it's too lean and care should be taken. Is this a safe procedure? don't want to burn holes in my pistons. So far I went 25 miles after the adjustement, and it went from black to dark grey in the exhaust tube -so seems ok.

Generally, is it ok to go about starting adjusting various bits and pieces in the MFI individually, or does everything need to be done at once?

Finally. Given the specific chracteristics of my "E" injection pump, at a given point of rebuild, is there any power/displacement upgrades (like 2.7 high compression) that can be done effectively matching the pump characteristics, i.e. NOT having to get the pump recalibrated at $$$$$ Here in Europe people say only Porsche factory does that and at a cost of approx. 15.000 USD -no thanks I say!

Thanks in advice for any qualified advice.
Peter

[304065]

By the banjo bolt you mean the bolt that goes through the oil line to the side of the pump. This threads into the case, and the oil pressure sender threads into it. But there is enough room around the bolt to allow oil to flow- it's not necessary to have the oulet holes in the bolt aligned with the line from the banjo fitting. Also, oil feed to the pump is VERY slight, so it's not like the pump will be oil starved or anything.

Looking at the exhaust pipe is not a reliable indicator of Air Fuel Ratio. Search here for "LM-1" to see the modern wideband oxygen sensor approach to tuning. Four clicks leaner is a lot for the idle adjustment, and the correct sequence is part load (main rack) first, THEN the idle, never the other way around. Search here for "check measure adjust" on the "ultimate MFI resources thread" for our collective wisdom on a sequenced, evidence-based approach to MFI tuning issues.

Adjusting "bits and pieces" is OK if the components are clearly defective, e.g. if your throttle microswitch doesn't work and everything else is fine, go ahead and fix that. But there's a sequence prescribed in CMA that MUST be followed so you avoid chasing your tail-- you DO NOT want to go fiddling with the mixture settings if you aren't absolutely certain that the air cleaner, plugs and timing are ok, for example. All is revealed in CMA>

Jeff Higgins was successfuly able to tune a 911T pump to work on his high-compression twin plug 3,0 engine, so I would say all things are possible without changing the space cam. That said, changing the space cam and recalibrating the pump IS what the factory did in the old days, and Gus at Pacific Fuel Injection can do that, he's in South San Francisco (search here for Gus Pfister-- are you getting the sense that we use the search feature a lot? ) Koller can do the mod in Europe, the factory wouldn't know what to do with an MFI pump if it were placed on a serving platter at Christmas dinner. . .

Good luck! You will find that Pelican is the largest repository of qualified MFI advice on the planet.

[Jim727]

Like John said:

1) CMA;
2) CMA;
3) CMA.

Check here: http://www.pelicanparts.com/techarticles/911_MFI/TipMFI.htm

I'm no wizard at MFI, being new to the cult and all that, but I have learned that you don't just go in and twiddle. Any adjustment to the MFI pump outside of the CMA procedure will either screw things up or try to compensate for something else.

Resource in your neighborhood:
http://www.koller.de/oldnew.pumpen,103_106,8861926021042695715237573666 3688.html

This is definitely T.H.E. place to find MFI smarts. John, Grady, Jeff, et. al. are a wealth of knowledge.

Jim