MFI Butterfly Settings

[domtoni]

Perhaps someone out there has some wisdom in this area !!

The story goes like this:
- I put an Ansa 911 R exhaust system on my car (it is for sale) that has no heat riser for the MFI pump.
The system was installed by a local dealer in Chicago. He short cut the cold start solenoid, and I think adjusted the low and high fuel delivery settings on the pump, and short circuited some of the other electronics. I don't know the settings.

- When I got the car in the UK, I installed SSI heat exchangers, and the car ran much better.
My mate who got the car going after 15 years, adjusted the butterflys so they all opened simultanously. Prevously, someone had f...ed up the butterfly settings. The car ran better.

- I then gave the car to someone who I was lead to believe was an expert in setting the MFI. All of the rod settings were not to Porsche specs, and the car did not seem to run well at all. I now have the car being worked on by a local technical expert.

- The rod settings are now per Porsche spec. Only issue is the idle. It is at 1200 to 1400 rpm, which is 300 to 500 rpm above the factory spec of 900 rpm.
In their static state, the butterflies are open a few degrees (we don't have the protrators to measure the degrees), and the bleed screws are closed. The rod setting is at 114 mm as it is supposed to be.
The bleed screws should be open some turns and the butterflies closed completely.

- Logic tells me that we can just shut the butterflies, and open the bleed screws to the recommended spec, and the motor will probably run better than it does now. I think the butterflies will be then be in sync with the main pump.
No Porsche spec talks about how to set the butterflies in a default situation.

- Can anyone shed a bit of light on what to do here?


Thanks
_________________
domtoni
1969 911E

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[Zeke]

First of all, I think you have a handle on the understanding of what is needed. But, you should avail yourself of a publication called Check, Measure and Adjust by Bosch. There is a download on Pelicanparts.com.

But, yes, the air screws should be used for fine tuning the air flow thru the stacks to be all equal. So, to start, they must be open a little so you can go either way to equalize. You must reset the butterflies so they are as eqaul as possible and the car idles correctly. You will have to go back and forth a couple times between the idle mixture setting on the pump and the openings at the stops on the butterflies. This all assumes your part load adjustment is correct and the ignition system is spot on.

[domtoni]

Thanks Zeke for the info. I will give it a try !!!

Best from the UK on a rainy day !!!

Domtoni

[spydr32000]

You need to make sure every aspect of you tuning is correctly adjusted, tappets,timing,points,and compression should be good.Then be sure your linkages are correctly adjusted, making the correlation right between the pump and butterflies. To obtain correct adjustment and control of your idle, the butterflies must be closed, but not closing hard against the throttle housing. This will allow the air screws to be opened approx 2-2.5 turns from fully in. In this position your idle should be close to 900 rpm Then its just a matter of adjusting your mixture at idle, and with a little luck your done.
Regards Mike

[lisa_spyder]

Uh Mike?

Maybe a little "hi, I'm the hubby who drives the jazz blue 911 in lisa-spyder's signature" intro would have been good ! Nice for the guys on the board to know who you are so they know they can trust your info babe!

Fellas - you can trust his info...I promise - he's the other half of the Lisa/Mike circus at Spyder!

Cheers,

[Chuck Miller]

Welcome Mike

…was wonder'n when you'd make it on the board…

The more you contribute the more informed we'll be…

Cheers mate,

[spydr32000]

Chuck, I would have been on earlier, but have not had a chance. Lisa has it well covered most times! I have been watching with interest, also have been kept well up to date! (as you could imagine) Happy to contribute though.
Regards Mike

[Chuck Miller]

... yeah, I bet you've been kept informed...
Your other half is'a real pip...
This whole car deal is such'a fraternity (in the real sense of the word) that it's such a double pleasure to have not only a feminine view, but such a well informed passionate one...she'a pleasure - don't tell her this mate or she wont be able to get her cap on...

It's great to know that people that make thier living at this are look'n in and help'n us out...

Looking forward to more...
Cheers Mike,

[lisa_spyder]

Oh gee,

I'll be heading home now that I can finally see my desk at work...but how will my head ever fit through the doorway?

Cheers,

[domtoni]

Thanks Spyder3200.

Not bad to get tech info from an Ausi, by a Yank driving a Yank car in the UK.

Sounds like calibration is easy enough but I got to find the right guys to do it here.

At least I understand what needs to be done !!!

Best Regards
Domtoni