MFI synchronizing throttles PLEASE HELP!!!

Stormy · 11-04-2009, 07:03 AM

Dear MFI specialists,

For the synchronization of the idle screws, throttle stops and throttle linkages I wanted to hook up my synchronisation tool, comprising 6 (vacuum) pressure sensors; in fact MAP-sensors.
On all engines with separate throttle bodies I worked on before, there are drillings to connect the hoses for the instrument.

However, at first glance I couldn't find these drillings on this 911 MFI engine. In fact I noticed that some (four?) throttle bodies do have a casting, in whitch I could probably drill and tap such a measuring point.

So my questions are: (2.4l MFI engine '72)

- does this engine has (six) vacuum measuring point, that I overlooked??
- or can those six measuring point be drilled at some safe place on the TB's, or the intake port??
- is there an alternative?? (not being the use of six airflow sensors)

The only alternative I can think of is to make six 8mm thick plates (including M4vacuum conmnenctions) that I mount under the TB's. But this is a rather expensive solution.

PS the rest of the MFI system is perfectly clear to me.

Thanks in advance for any help!!

Ton

whalebird · 11-06-2009, 06:51 PM

Do you have all of the throttle plates set and secured. This is no simple matter and requires special tools from the factory. I hope you didn't fiddle with all the connecting linkages between throttles, they are specifically set and should be left alone. There is bypass screws on each venturi that is used to set the flow with a good old fashioned air meter. Pretty simple really. One of the biggest concerns is that for the MFI to really work correctly, the engine it's bolted to has to be in good shape. The MFI is sensitive to variations in compression and valve sealing. Then the MFI pump needs to be in good shape (few originals are) and timed correctly. There is a special notch on the crank pulley that is used to set pump timing. Then you have to set the mixtures (idle is done, well, at idle), the part and full throttle requires the use of a four gas analizer(CO meter) while driving with specific throttle angles at specific RPMs. More special tools. This is not a conventional system by todays standards, but is probably one of the best thing going on a air cooled motor for performance and reliability. If you can't get the pump to lean out it needs rebuilding, also the throttles should be rebuilt by one of the few people who know how to and have the equipment.
Good luck, a MFI 911 is the one of the best set ups...all the good of carbs with all the good of injection - unreal throttle responce when set right.

whalebird · 11-06-2009, 06:53 PM

Oh. Welcome to rennlist. You came to the right place

Stormy · 11-07-2009, 06:31 AM

Thanks for your elaborate answer, good tips and your warm welcome,

However: you did not answer my question (sorry) and I'm not sure if you have this specific knowledge I'm looking for (sorry about that, again)

First of all I'm familiar or very experienced with fuel injection systems, and I have tools like wide band lambda sensors (multiple) CO tester, vacuum synchroniser etc.

So I'd like to synchronise (at least check) the TB's on a car that has been incorrectly adjusted. Maybe the linkages were untouced and OK, but I need to check.
I don't have what you call a simple airflow meter, that's why I like to use the vacuum tool.

Since I couldn't find the (six) vacuum testpoints, I thought I make them myself, and just was curious if I'm the only one who had this idea. Looking at the TB's I think it's not so hard to make these connections.

Thanks anyway for your help, and thanks anyway for responding!!!!

whalebird · 11-07-2009, 10:41 AM

I would not reccomend drilling anything into the throttle-bodies. They are synchronized individually using a carb synchronizer available most anywhere. Just use your vacuum synchronizer on top of the stacks. I think that permanantly attaching MAP sensors to each throttle is a waste of time - if all you want to do is check the balance of each throttle. They do not have vacuum test points.
Be aware that the condition of the motor is critical. Checking the MFI should start with a compression and leakdown test. If there is any issues here or with cam timing you will not get an accurate adjustment. I think if you google search for Porsche MFI you will find a wealth of info. I belive Pelican forums have a lengthy thread on MFI. Also If you want the best info, read the factory service manuals before you touch anything on the system. You will not be able to make any adjustments with out the proper tools.
Good luck

HarryD · 11-08-2009, 04:58 AM

MFI is not EFI and has it's own unique quirks. Befroe you go messing with it, be sure you know exactly what you are doing and why. There are literally hudreds of posts on here, Pelican Parts BBS (http://forums.pelicanparts.com), and the Early 911 S Registry BBS (http://www.early911sregistry.org/forum/index.php) on the topic.

Most of the ones that actually help you will tell to to obtain, read and follow "Check, Measure, and Adjust" (http://www.pelicanparts.com/techarti...ure_adjust.zip) to get your MFI top notch.

HarryD · 11-08-2009, 05:01 AM

Quote:

Originally Posted by Stormy

Thanks for your elaborate answer, good tips and your warm welcome,

However: you did not answer my question (sorry) and I'm not sure if you have this specific knowledge I'm looking for (sorry about that, again)

First of all I'm familiar or very experienced with fuel injection systems, and I have tools like wide band lambda sensors (multiple) CO tester, vacuum synchroniser etc.

So I'd like to synchronise (at least check) the TB's on a car that has been incorrectly adjusted. Maybe the linkages were untouced and OK, but I need to check.
I don't have what you call a simple airflow meter, that's why I like to use the vacuum tool.

Since I couldn't find the (six) vacuum testpoints, I thought I make them myself, and just was curious if I'm the only one who had this idea. Looking at the TB's I think it's not so hard to make these connections.

Thanks anyway for your help, and thanks anyway for responding!!!!

This is what you need:

$55.80

http://www.pelicanparts.com/cgi-bin/...20Synchrometer

11-04-2009, 07:03 AM	#1
Stormy New User Join Date: Apr 2007 Location: Schiedam The Netherlands Posts: 2	MFI synchronizing throttles PLEASE HELP!!! Dear MFI specialists, For the synchronization of the idle screws, throttle stops and throttle linkages I wanted to hook up my synchronisation tool, comprising 6 (vacuum) pressure sensors; in fact MAP-sensors. On all engines with separate throttle bodies I worked on before, there are drillings to connect the hoses for the instrument. However, at first glance I couldn't find these drillings on this 911 MFI engine. In fact I noticed that some (four?) throttle bodies do have a casting, in whitch I could probably drill and tap such a measuring point. So my questions are: (2.4l MFI engine '72) - does this engine has (six) vacuum measuring point, that I overlooked?? - or can those six measuring point be drilled at some safe place on the TB's, or the intake port?? - is there an alternative?? (not being the use of six airflow sensors) The only alternative I can think of is to make six 8mm thick plates (including M4vacuum conmnenctions) that I mount under the TB's. But this is a rather expensive solution. PS the rest of the MFI system is perfectly clear to me. Thanks in advance for any help!! Ton Last edited by Stormy; 11-05-2009 at 08:47 AM.

11-08-2009, 04:58 AM	#6
HarryD Addict Rennlist Member Join Date: Oct 2001 Location: Sunny Oregon Posts: 872	MFI is not EFI and has it's own unique quirks. Befroe you go messing with it, be sure you know exactly what you are doing and why. There are literally hudreds of posts on here, Pelican Parts BBS (http://forums.pelicanparts.com), and the Early 911 S Registry BBS (http://www.early911sregistry.org/forum/index.php) on the topic. Most of the ones that actually help you will tell to to obtain, read and follow "Check, Measure, and Adjust" (http://www.pelicanparts.com/techarti...ure_adjust.zip) to get your MFI top notch. __________________ Harry '73.5 911T Red Targa for Fun Several Trusty Beaters for Work

11-06-2009, 06:51 PM	#2
whalebird Addict Rennlist Member Join Date: Nov 2004 Location: Blue Ridge Mountains NC. Posts: 1,422	Do you have all of the throttle plates set and secured. This is no simple matter and requires special tools from the factory. I hope you didn't fiddle with all the connecting linkages between throttles, they are specifically set and should be left alone. There is bypass screws on each venturi that is used to set the flow with a good old fashioned air meter. Pretty simple really. One of the biggest concerns is that for the MFI to really work correctly, the engine it's bolted to has to be in good shape. The MFI is sensitive to variations in compression and valve sealing. Then the MFI pump needs to be in good shape (few originals are) and timed correctly. There is a special notch on the crank pulley that is used to set pump timing. Then you have to set the mixtures (idle is done, well, at idle), the part and full throttle requires the use of a four gas analizer(CO meter) while driving with specific throttle angles at specific RPMs. More special tools. This is not a conventional system by todays standards, but is probably one of the best thing going on a air cooled motor for performance and reliability. If you can't get the pump to lean out it needs rebuilding, also the throttles should be rebuilt by one of the few people who know how to and have the equipment. Good luck, a MFI 911 is the one of the best set ups...all the good of carbs with all the good of injection - unreal throttle responce when set right.

11-06-2009, 06:53 PM	#3
whalebird Addict Rennlist Member Join Date: Nov 2004 Location: Blue Ridge Mountains NC. Posts: 1,422	Oh. Welcome to rennlist. You came to the right place

11-07-2009, 06:31 AM	#4
Stormy New User Join Date: Apr 2007 Location: Schiedam The Netherlands Posts: 2	Thanks for your elaborate answer, good tips and your warm welcome, However: you did not answer my question (sorry) and I'm not sure if you have this specific knowledge I'm looking for (sorry about that, again) First of all I'm familiar or very experienced with fuel injection systems, and I have tools like wide band lambda sensors (multiple) CO tester, vacuum synchroniser etc. So I'd like to synchronise (at least check) the TB's on a car that has been incorrectly adjusted. Maybe the linkages were untouced and OK, but I need to check. I don't have what you call a simple airflow meter, that's why I like to use the vacuum tool. Since I couldn't find the (six) vacuum testpoints, I thought I make them myself, and just was curious if I'm the only one who had this idea. Looking at the TB's I think it's not so hard to make these connections. Thanks anyway for your help, and thanks anyway for responding!!!!

11-07-2009, 10:41 AM	#5
whalebird Addict Rennlist Member Join Date: Nov 2004 Location: Blue Ridge Mountains NC. Posts: 1,422	I would not reccomend drilling anything into the throttle-bodies. They are synchronized individually using a carb synchronizer available most anywhere. Just use your vacuum synchronizer on top of the stacks. I think that permanantly attaching MAP sensors to each throttle is a waste of time - if all you want to do is check the balance of each throttle. They do not have vacuum test points. Be aware that the condition of the motor is critical. Checking the MFI should start with a compression and leakdown test. If there is any issues here or with cam timing you will not get an accurate adjustment. I think if you google search for Porsche MFI you will find a wealth of info. I belive Pelican forums have a lengthy thread on MFI. Also If you want the best info, read the factory service manuals before you touch anything on the system. You will not be able to make any adjustments with out the proper tools. Good luck