MPS, I'm going to open one up- Test Results Options

[76-914]

Well, I tried the grease and two gaskets with good results but not acceptable, either. Leak down from 15"vac to 0" was a little over 2 min's duration. So. I stripped it down again and went back with contact cement with identical results.



As seen in this pic, the leak around the outer seal was cured, whether using the grease or the contact cement method.



Normally I would not assume but since I am not using this diaphragm I shall. In that the diaphragm ceased to leak around the outer seals and no other leaks were discovered, I'm assuming that "this particular" adjustment screw has allowed a small amount of leakage. I decided to put it in the car for S&G's. I wished that I had had some adjustment tools to tinker but I didn't. When at idle it was hunting (too lean?? TB & ECU adjustments had little or no effect). It appeared (and remember that this source is completely unqualified) to stumble thru 3500 rpm occasionally, which might be related to the flex of the brass plate. It started and ran so I would keep this as an emergency back up unit but I would not consider using it unless adjusted to spec.
In summary, I will say that I am no longer intimidated by these "black boxes" and that I feel comfortable with installing one of these diaphragms, should they become available from Tangerine Racing. I believe that myself as well as any other member can easily replace this diaphragm in < 2 hr's, first attempt. I can probably do one in <15 min's, now. (IMG:style_emoticons/default/beerchug.gif)
EDIT: A quick and shameless plug; Geoff (Bleyseng) adjusted my last one to spec's and I would use him again.

[ChrisFoley]

FYI 1psi equals almost 28" H2O.

[76-914]

FYI 1psi equals almost 28" H2O.

That's the gage on the comp that's reading 60psi. Test was only 1psi. I have a manometer for anything below that. Water never lies. (IMG:style_emoticons/default/biggrin.gif)

[SLITS]

FYI 1psi equals almost 28" H2O.

That's the gage on the comp that's reading 60psi. Test was only 1psi. I have a manometer for anything below that. Water never lies. (IMG:style_emoticons/default/biggrin.gif)

Yeh, but fish fornicate in it!!

[Bleyseng]

I have tried to run MPS with steel or brass diaphragms and they just don't give you the right response. The engine has no life or stumbles thru transitions but it will run.

Looks like you are having fun with this! nice job.

[ape914]

I have tried to run MPS with steel or brass diaphragms and they just don't give you the right response. The engine has no life or stumbles thru transitions but it will run.

Looks like you are having fun with this! nice job.

It is probably not so much a materials issue such as brass, vs. steel vs. copper vs..... as it is a design issue for the material selected. The properties of the stock diaphram could be replicated pretty well in any of these materials, with the correct convolution shapes, heat treatment, alloy content, and thickness of the material. The trick I think, would be in predicting the right design without a lot of trial and error.

[ChrisFoley]

It is probably not so much a materials issue such as brass, vs. steel vs. copper vs..... as it is a design issue for the material selected.

I think it is very much a materials issue.
The mechanical properties of beryllium copper make it uniquely suited for these diaphragms.
I'm sure its possible to create an assembly which approximates the output patterns of the inductive circuitry using a different diaphragm material.
However either the diaphragm would fail prematurely due to embrittlement, or the output signal would change over time due to creep of the material.

[ape914]

It is probably not so much a materials issue such as brass, vs. steel vs. copper vs..... as it is a design issue for the material selected.

I'm sure its possible to create an assembly which approximates the output patterns of the inductive circuitry using a different diaphragm material.

that is all I refered to, the response of the diaphram, not fatique life. Other materials can be used to replicate the response of a stock one. However fatigue life may not be good enough. by correct design, the fatigue life can be extended by minimizing the strain, which could be done with a different convultion pattern.

the best bet would be to exactly copy the original design, materials and shape.

[r_towle]

Has anyone considered the transition step where the diaphram always gets torn?
Seems a dremel to round over that edge and take the sharpness out of that transition may prolong the life of the diaphram ??

Yes? no?

Rich

[Bleyseng]

I think that all the stress is on that outer edge of the diaphragm no matter what you do or relieve. That is where the most movement occurs from what I can tell. The decel valve might helps reduce the slamming of the diaphragm under decel, lessening the hard pull of the vacuum. Under most driving conditions you are pull 4hgish in Partload, say at 35mph in 3rd gear. WOT or Ohg doesn't happen that much but everytime you are off the gas and are decelerating that engine pulls 15hg of vacuum.

[914_teener]

I think that all the stress is on that outer edge of the diaphragm no matter what you do or relieve. That is where the most movement occurs from what I can tell. The decel valve might helps reduce the slamming of the diaphragm under decel, lessening the hard pull of the vacuum. Under most driving conditions you are pull 4hgish in Partload, say at 35mph in 3rd gear. WOT or Ohg doesn't happen that much but everytime you are off the gas and are decelerating that engine pulls 15hg of vacuum.

(IMG:style_emoticons/default/agree.gif)

Gonna send Chris Foley some bucks....as long as it is based on the original design.