Need advice and parts to regulate MFI

[pszemia]

Hi, i finally got the high quality check-measure-repair manual from a very good user of this forum.

But before starting with everything, there are some tools i need.

Principaly i don't know how to do the leakege test, or if it is mandatory or i can skip it.

Then i don't have the protractor neither the CO2 meter.

I do have the synchrometer and 3 special tools i bought a kit for that (3 pieces)

so, i want to know if there is anybody who know where to buy those parts.

In the procedure section i understand almost everything except the terms BTDC ATDC and where to adjust those things and where to meter.

first that parts.

Thanks

[Grady Clay]

pszemia,
First I’ll start with the basics. We all had to learn this stuff.

BTDC = Before Top Dead Canter
ATDC = After Top Dead Center
Both usually refer to the compression stroke.
These terms are usually associated with ignition timing.

These terms don’t tell the whole story.
In fact they should be TDC Compression (BTDC & ATDC) and TDC Overlap.
A 4-stroke engine has 720º of rotation to consider.
The first 180º rotation is ‘intake’ with the piston going down.
The next 180º rotation is ‘compression’ with the piston coming up. Spark happens.
The next 180º rotation is ‘power’ with the combustion gasses pushing the piston down.
The final 180º rotation is ‘exhaust’ with the piston coming up expelling the exhaust gasses.

You do a static ‘cylinder leak test’ at TDC compression for each cylinder. This is where the piston is at the top (TDC) and both valves are closed, sealing the combustion chamber. This is a great test because it not only gives a quantitave number but you can identify the leak from the valves, head gasket or rings. This allows you to focus your repair efforts.

The ‘cranking compression test’ is a dynamic measurement. This gives you a clue to the gas (air) pumping of the engine. Not only does give clues with combustion chamber sealing but also cam tming and more.

The combination of both of these tests gives you the best analysis of your engine at reasonable cost and is easily done.


There is more to CMA than Porsche published. CMA considers you have been through the Bosch MFI training and are already an expert MFI technician. It also assumes your MFI is new - not likely. There is a lot on Pelican that fill in the blanks of that experience and deals with our geriatric MFI. That is what CMA2 is all about. Search Pelican.

Best,
Grady

[pszemia]

great explain

it's a shame i don't know how to do it

i will have to find hard to know how to make all those tests.

and, what about the CO2 meter??

[frogger]

I use a Gunson Gastester to check CO levels coming out of my exhaust. They are available for less than $200.



Where are you located? Perhaps someone nearby can work with you to check the MFI system.

[frogger]

You can probably get around having the factory protractor tools by just getting some one to measure the lengths of the key linkage components on their MFI systems and using that as a guide. Right now, I need to tweek mine, so I wouldn't use it as a guide if someone else can offer their linkage measurements. Good luck and I hope it all turns out great for you.

[pszemia]

thanks frogger..

the co2 meter, i think i will ask in a local shop if they have them.

And related to the protractro, it's very difficult to look someone who has mfi in tune, i live in Buenos Aires, Argentina. And all the porsche MFI are most converted to Weber Carbs

[frogger]

That's why the internet is so good. Ask here for help, and you will likely receive it.

Iwill try to remember to check mine this weekend and let you know what my linkage lengths are. I may need to tweek mine a bit more to make it run better, but whatever information I can provide you will at least give you a starting point to check against what you have.

Maybe someone else here can help, too?

[David E. Clark]

The protractors are now almost impossible to find and, if you somehow manage to find all three, the directions for their use that are outlined in the Check, Measure, Adjust manual are - I'll be kind - not easy to follow unless you were trained by the factory in the late 60's and you are, to quote Grady "already an expert MFI technician." In my opinion, this is why Porsche came out with the 28 April 1972 Product Information Circular "P250" which eliminates the need for the protractors and greatly simplifies the correlation procedures. From my experience, if you follow the directions and measurements in this circular exactly you will be fine without the use of the protractors. If you follow the links under my name you will find an enormous amount of useful MFI information. Good Luck!

[David E. Clark]

Originally Posted by pszemia

... Principaly i don't know how to do the leakege test, or if it is mandatory or i can skip it ...T

You should find all the information you need in either of these two links: Compression test vs. Cylinder leak down - How, why and what do they mean? and/or Diagnosing engine condition without disassembly.