I collected a number of MPS over a couple of years. Most held vacuum, some did not. I measured inductance vs. vacuum on those that I could, but then took all of them apart (except one brand new one).

The is a lot of variety in the diaphrams, probably because they get replaced when virtually every MPS is rebuilt. The photo below shows four diaphrams. I'll follow with descriptions and observations...

Click to view attachment

#1- copper, 2 pleats. This came from a rebuilt MPS that was in a pond or river for some time. There was actually sand in it, along with tiny aquatic snail shells of some sort, and the copper was pretty much green. This diaphram was ruptured. The workmanship is very good, and the alloy is idential to stock (see chart below). The threaded bushing looks like stock in design and attachment.

#2- copper, 3 pleats. This is a stock diaphram from a riveted MPS. It is ruptured.

#3- brass, 2 pleats. This is from a rebuilt MPS. I have three of these diaphrams, all similar. This MPS was freshly rebuilt in a rebuilder's box. Looked like new with fresh paint and plastic cap on vacuum port, but it leaked slightly. You can see why when you look at the ripples in that flange. The O.D. looks like it was cut out by hand with tin snips, and the threaded bushing was taken from a stock diaphram and soldered by hand into place. At the bottom in the picture, you can see that the flange is pretty smooth- that's where I tapped it out with a machinist's hammer on an anvil. I have no doubt that the leakage was from around the O.D. of the diaphram, and that tapping it out would probably fix it. This material (brass, see chart below) is stiffer and thicker than any of the rest. It would add quite a bit of spring tension to the mass-spring-damper system. In general, I rate the workmanship on this as "crappy", though maybe you could get a running car out of it.

#4- stainless steel, 3 pleats. This one is a bit of an enigma. It is identical to stock except that it is made from stainless (see chart below). The workmanship is perfect. It is from a rebuilt MPS. Interestingly, it is the MOST COMPLIANT of all of them, while most steel ones are reported to be stiffer. The other part of the enigma- the aneroid cells from this MPS are also stainless- same alloy. My suspicion is that this is a late Bosch rebuilt. Who else would make stainless cells, because the cells don't fail very often, so there are lots of spares available out there, and the cells are pretty complicated to make...


*** EDITED *** Materials. I measured alloy composition at work using an X-Ray Fluorescence analyzer. This machine is very precise, but it has limits to the range of elements that it can detect. Unfortunately, it cannot detect Beryllium (Be), and it is likely that the stock (at least) diaphram contains Be to harden and strengthen it. You can see a couple of things here though- the stainless diaphram and stainless cells are of exactly the same composition- nickel-chromium stainless steel. The nickel explains why they are slightly magnetic, as many stainless alloys are not. ***

Click to view attachment

Conclusions (really opinions) - The diaphram was put in there (early VW D-jets did not have one) to provide altitude compensation and to soften transition from leaner (high vacuum) to richer (low vacuum) regions. Early D-Jets had a separate unit with a diaphram and a switch to inform the ECU to richen the mixture at low vacuum. Cost reduction may have been a third reason- eliminating the separate unit, wiring, vacuum hose, etc. Anyway, this switch was either on or off, no soft transition. The MPS had only 2 aneroid cells and no diaphram, and its inductance curve was essentially a straight line from 0" to 25". There was no mixture compensation for altitude with this arrangement.

I'm thinking that the lower the stiffness of the diaphram, the more consistency in the setup and responsiveness, while both of these objectives are met. By maximizing compliance of the diaphram, the springs acting in the system are mainly the coil spring and the leaf springs that act to locate the armature.

My stainless diaphram is the most compliant, but there is another feature of steel (if I remember correctly) that adds to the argument that this is a late Bosch design- steel has a much higher Youngs modulus than copper. The higher the Youngs modulus, the greater the fatigue resistance, and the vastly most common failure mode of the MPS is fatigue failure. Could this have been a Bosch attempt to solve a reliability problem, even as the technology was being superceded by more modern ones? Since the cells are also subject to fatigue, would they have switched them over at the same time?

I am planning on assembling my own personal MPS using the stainless parts, and seeing how close I can tune it to my engine.

There are lots of other parts in the MPS that I've formed opinions about, but I'll hold off for now.

These are my own opinions, which may not be popular, so BLAST AWAY!!

(eye candy below)
Click to view attachment

Great Job! That is interesting information. If it can be shown than SS will work then maybe this will resolve the availability crisis concerning these MPS units.

Good work! It was always assumed it was BeCu, and it is still available, but expensive. Stainless would solve the cost issue for sure. I had sent a MPS to a freind of mine that does stamping, and for the small qty's the price was going to be over 100 bucks each. Everyone but capn balked at the price, but the dies are not free to build.

I just think it's awesome you can check materials that way. It's very cool.

The stainless story is still just a theory- I haven't proven it works as well as, much less better than, the stock. (But I think it will!) In the meantime, if you're looking to repro them, the pure copper may be a good bet. It should form better than the stainless, and it'll be a lot cheaper than BeCu alloy.

Photo below is my stainless diaphram with its mating stainless cell assembly-

Click to view attachment

"This came from a rebuilt MPS that was in a pond or river for some time. There was actually sand in it, along with tiny aquatic snail shells of some sort,"

THey just took it out and chucked it in the water

NIce work, great research thanks for sharing..

They gave it the "float test"?

(Must'a thought it was part of a single-Weber setup, perhaps...)

--DD

Of the MPS I have taken apart, I have only seen version 4 in what looks like solid copper. I know where there are several VW Type 3 MPS that are NOS that I was considering buying them for just the diaphram. I might get one just to take it apart.

Wow, really great info! With your permission and credit to you, can I use some of the photos and data on my MPS page (see link in sig)?

You mention the full-load diaphragm provides altitude compensation. This is only true under heavy and full-load conditions. The only MPS's that provided part-load altitude compensation were the 0 280 100 100 series that was used on the MB's. These units lacked the full-load diaphragm (full-load was sensed by the throttle switch) and had an altitude compensation cell that was connected to the atmosphere through a holow screw.

I agree with your observation that the lower the "stiffness", or spring constant of the diaphragm, the less effect it will have on the transition characteristic. For any material used, the thickness and pleat design will vary. Reliability and resistance to fatigue failure is also an important consideration in the material selection.

Crafting the aneroid cells out of a different material and/or a different pleat design would be tricky. The issue here is to identically duplicate the pressure vs. displacement characteristic of the OEM cells. It would interesting to compare the SS cells to the OEM cells for this characteristic.

Positioning of the full-load stop is also critical to defining the transition region, setting the proper full-load mixture, and reducing the mechanical stress on the full-load diaphragm. Bosch sets most MPS to a 2 in. Hg engagement, though I have seen some units set to 4 in. Hg.

Again, great stuff, thanks for sharing it with us.

This information is great.This is what I've often wondered about...If another diaphragm were created, it would have to be made with consideration for temperature, thickness, flexibility, pleat design, etc...Basically all the things you've mentioned. Jim you are on the right track!

On the data and photos- you're welcome to them, with one caveat. We're using beryllium in a project at work, and one of the characteristics is that it is transparent to X-rays. So I need to verify that our XRF is capable of detecting Be in alloys. If not, those numbers may not be right. I'm travelling until the end of the week, so it'll be Friday before I can get with the lab guy. We have other means of measuring alloys that I can pursue that don't use X-Rays. The brass and stainless alloys should be correct.... Sorry to everyone if my info was premature. I'll be sure to confirm or correct it shortly.

That makes sense about the full load only altitude compensation. The diaphram has to lift off the stop for any compensation to occur.... makes sense. I have a 0 280 100 120 MPS from a Cosworth Vega that is like the MB MPS you described... but then it is, as you said, part of the 100 series... Interesting that Chevrolet licensed the technology directly from Bendix, not Bosch, but all the comonents are Bosch.

I measured several (maybe 6) aneroid cells sets using the same MPS, but with the diaphram locked. I set their inductance to a common value at the same vacuum, and then measured and plotted the curves. Their slopes are identical. I plotted them on the same axis, and they are as coincident as I can imagine. These 6 included a set from a 0 280 100 001 (early type 3, no diaphram, probably the simplest MPS out there) AND the stainless steel set.

So now I'm setting up to measure the vacuum/L curves for diaphrams alone. I sacrificed a set of perfectly good aneroid cells by cutting them open and filling them with gorilla glue to set them. I let them harden in my vise with the jaws set to original cell dimension (gorilla glue expands when it hardens, and would have pushed them open). First thing I found was that the cells ARE MANUFACTURED WITH PARTIAL VACUUM INSIDE!! As soon as my cutoff blade broke through, they expanded out and became flacid. Anyway, now that they're hardened up, I'm going to measure inductance curves, which will represent the response of the diaphrams alone.

I'm thinking that I can combine the diaphram and cell responses using superposition and get pretty close to what the finished MPS should be.... getting interesting.

That's good to know that replacements for the cells exist that accurately duplicate the OEM cells response to vacuum.



If you look at the Bosch MPS patent that's referenced at my site, they state that the cells are evacuated - i.e. under vacuum. I assume this was to eliminate issues with the reference pressure.

I'm back. I looked in to this, and unfortunately, I was right (the second time). XRF cannot measure elements with atomic numbers lower than about 12, and Be is 4. XRF is steadily improving its detection technology, but given that Be is transparent to X-rays, it'll probably never be able to detect it.

How it works (roughly)- an X-ray is beamed onto the sample, which excites the electrons in the atoms, so they move to a higher energy level. When the X-ray is stopped, they move back to their original level, and emit photons (light), at a frequency that is characteristic of the element(s). So if a material is transparent to X-ray, it doesn't get excited.

So I poked around at alternatives. EDX (or EDS) analysis is similar but uses a beam of electrons from a scanning electron microscope to add the energy instead of X-rays. Measurement is then similar. Looks like they can read down to atomic number 5- still not low enough for Be, but still a pretty simple test....

It may be enough to just detect presence of Be, if not the actual amount. That may be enough, since many BeCu alloys I've investigated only have maybe 3% Be, so just knowing its there may be enough to know what we'd be in for trying to reproduce it. Still checking...

So anyway, I want to delete the table in my original post- anyone know how I can go in and edit that post? I'd probably replace it with one that at least still shows the stainless and brass composition...

Sorry about the red herring, guys.

when you (the OP) view the post you will see, at the bottom-right of the post, a small box with edit options. 'Full' is just like the original composition page, with smileys and formatting widgets and such. 'Quick' is a basic text editor if you're just changing words around. Make your changes and click 'Complete Edit.'

Ta Da.

I used to do a lot of surface analysis when I worked in silicon microcontamination in the '80's and '90's. My guess is that there may be some simpler chemical tests you could use instead of surface analysis. I'll ask one of my old colleagues about this and see what he says.

I haven't heard back yet, but I did some poking around on the web. I had a dim memory of this earlier that I wasn't sure of, but it tuned out to be correct. If you're going to use surface analysis, you need an Auger Electron Spectroscopy (AES - also known as as SAM scopes) tool, which is sensitive to light elements.

Also seems like once we get a material and a design together, we could get a custom metal shop to pump out a run of them. Example:

http://www.peterforg.com/metal-stamping-services.html

Big issue I see with this diaphragm is getting the central threaded flange fabricated and pressed on. I assume this is a two-part assembly that's pressed into place.

From RustyWa years ago in a PM to me.


"You were correct....COPPER.
--------

Ok, did the marterial analysis on the OEM diaphram this morning using a Niton XL-II 800 handheld alloy analyzer.

I made three different scans of the sample piece I got from Geoff. The readings were as follows:

#1 - 99.78% Cu
#2 - 99.20% Cu
#3 - 99.39% Cu

No berillium. Supposedly anything between 98%-100% copper is considered pure.

The remainder of the 100% reading was a spattering of Al, Si Br, Phos Brz."


The stamping of the copper pleat isn't too hard to setup but as you say the two part center is. I looked at making a stamp with a machinist friend and it wasn't expensive. Coming up with the center part is and blocked my efforts.

My tests on units with steel diaphrams were they aren't as responsive and tend to make the car jerky in real world driving.

Great info, thanks. Though it's pure Cu, CuBe might be better, as it has much better fatigue resistance. Might not be as flexible, though.

I wonder if the 2-part flange stamping is a common part type?

I can source Cu-Be sheet from a friend in The Netherlands in fairly small quantities if you want some. For this I would need the alloy percentages.

I can't commit to do anything on MPS's myself now as I am leaving for Suriname for 6 mos next month. I do have a ton (50+) junk MPS's and parts laying around that I would love to have diaphrams for at some point. I'll take a diaphram with me to have a machinist make a stamp in Suriname (cheap).

As easy as it would be to make it from pure copper I have a hard time believing it is only coppper. Cu is such a soft metal and it work hardens very quickly.

This from the internet showing how little beryllium is sometimes used in its alloy form:

"The most popular alloys of beryllium at the present time are those with copper metal. Copper-beryllium alloys contain about 2 percent beryllium. They conduct heat and electricity almost as well as pure copper but are stronger, harder, and more resistant to fatigue (wearing out) and corrosion (rusting). These alloys are used in circuit boards, radar, computers, home appliances, aerospace applications, automatic systems in factories, automobiles, aircraft landing systems, oil and gas drilling equipment, and heavy machinery.

and...

Health effects
Beryllium is a very toxic metal. It is especially dangerous in powder form. The effects of inhaling beryllium powder can be acute or chronic. Acute effects are those that occur very quickly as the result of large exposures. Chronic effects are those that occur over very long periods of time as the result of much smaller exposures. Acute effects of inhaling beryllium powder include pneumonia-like symptoms that can result in death in a short time. Chronic effects include diseases of the respiratory system (throat and lungs), such as bronchitis and lung cancer.


Read more: http://www.chemistryexplained.com/elements...0f4XtvMtO"

I also looked into have the two piece center fitting fabbed at one time. I found the press-fit clamping ring at McMaster Carr, its a stock item. The inner-threaded fixture should not be hard at all for a machist with a lathe, and its may be possible to simply cut off the clamping washer from existing diaphrams with a dremel and reuse them with a new clamping ring - have not tried it though. The two-piece fixture would need to be pressed together, presumably on an arbor press.

And this which shows that some mfrs make BeCu with as little as .15% Be by weight.

Jeff's right, pure Cu is very soft. Ever hear of the Bronze Age? Think of Be as an improvement over Sn.

The Niton XL-800 is also an X-ray fluroescence instrument. Here's an excerpt from a DOE test of the XL-800 dated April 2000:

Click to view attachment

Note that chlorine is 17 on the periodic table!! That's higher than aluminum (13). AND BERYLLIUM IS 4!! The detection technology is called "proportional count". Newer technology is available now, using "silicon pin diode" detectors. As I understand it, the issue is signal-to-noise ratio. The lower atomic number elements may register, but their peak is lost in noise. The newer technology improves the SN ratio and they become visible. The Thermo-Fischer Scientific unit I tested my samples on (in November '08 BTW) using the newer technology can differentiate down to atomic number 12 (magnesium). There's yet a newer technology that can go lower, but it's moot for beryllium, because it's invisible to X-rays.

So sorry to say, I think we both fell into the same pit. XRF is a fantastic technology, but it's blind to Be.

----------------------------------------------------------------------------------------

Meanwhile, back to the stainless steel idea. I ran some tests over the weekend on my copper and my stainless diaphrams (#1 and #4 in previous pics). I measured inductance vs. vacuum, but with the aneroid cells locked (filled with gorilla glue, clamped at nominal thickness during cure. Photo later tonight). I wanted to see the incremental effect of the enrichment diaphram alone. I had previously tested cells with the diaphram locked, and saw that they were amazingly linear from 0" to about 22", across several sets of cells of wide vintage, including the one stainless set. (post that chart later)

So the two conditions were:

first test, called SS-
1. outer screw set flush with bushing on cell side of diaphram (set before assembly)
2. inner screw set to an inductance of .85H at high vacuum (seated diaphram)
3. full load stop set to inductance of 1.00H at 0" vacuum.

This setting maxes the bias of the diaphram towards the cells, with a total travel of 0.15H. (0.15H is kinda arbitrary, but not far off from Mr. Anders's 0.12H typical travel- I think. Can't find the reference in his MPS Bible at the moment, but I think it's 0.12H)

second test, SS+
1. inner screw set to inductance = 1.00 at 0", full load stop removed for this test
2. outer screw set to inductance = .85H at high vacuum (careful not to turn the inner screw while setting.)

This biases the diaphram position away from the cells as far as possible, but still with the same 0.15H travel.

The two curves represent the adjustment limits of the stainless steel diaphram.

A picture's worth 10000 words:
Click to view attachment

Comments
1. SS- curve looks like it blends smoothly with the 1.00 upper limit. It really doesn't. If I had the resolution to do 4.5" or even 4.25" it would crash abruptly into the limit.
2. That's quite a range, in both slope and vacuum at which the diaphram begins to lift off the stop. Quite an opportunity for careful tuning if you really got good at this.

Oh, and here's the copper (diaphram #1, from the bottom of the lake) range.... I call it Cu-2P (copper- 2 pleat)-
Click to view attachment

Note that in Cu-2P+ the diaphram starts to lift off the stop at 7", then stalls at 6", and then resumes a fairly smooth transition the rest of the way to 1.00H. I reran these points several times, and it repeated the same. I suspect that there is a point where the 2 pleat diaphram resists strain, which allows stress to build up, until it pops past that point and then behaves itself. This only occurs for Cu-2P+ because the entire test range for Cu-2P- is beyond this point.

I still want to test the brass diaphram (#3 in picture). I may get a chance yet tonight, but I'll probably post the chart tomorrow.... Like I said, this is getting interesting!

That's enough for now. I've got to drill some holes in my frozen lawn and put reflectors along my driveway. Big storm coming tomorrow.

yeah but, Eric's testing showed no Be just Al,bronze, etc in trace amounts. You tell me the alloy mix and I should be able to get it. He deals in airplane metals..

Quick update. I did the crappy brass characterization. Not surprisingly (I guess), it only had about 0.16H of total travel- when I set the outer screw flush with the bushing in diaphram on the cell side, and then set the inner screw to 0.85H at high vacuum (diaphram seated), I only had about 1.01H at 0". So basically there is no adjustment range the way I'm testing. This is almost certainly because of its stiffness. At least it has a pretty smooth transition.

In reality, assuming I need to get 0.12H of contribution out of the diaphram, there would be a little adjustment.... Anyway here's the curve-

Click to view attachment

Next step, I plotted a curve of a cell, without effect of diaphram. This was easy, I just snugged the full load stop down, pinning the diaphram between full load and idle stops.

I've plotted a lot of cells (SS below), and they are almost perfectly coincident, cell to cell. But none tail up at high vacuum due to their expansion being limited by the limit arms?? Gotta figure this one out...

Click to view attachment

Note that my inductance meter is NOT calibrated to a known standard, so it may be different from one that any of you guys use. It's repeatable though, so for what I'm trying to do, it's working fine and was very reasonably priced.

Gotta go to work. My last plots superimpose the cell curve and the diaphram curves. I'm looking for most range of adjustment and smooth transition for each diaphram type, and it's looking like the stainless one is going to be it. Of course, I don't have a stock copper w/ 3 pleats that isn't ruptured to test for comparison...

I'll post those last plots tonight...

Jim

Yesterday during lunch, we tried to press apart a diaphram hub. One of the guys machined some custom blocking, and we set it up in a hydraulic press. Well, at 3500 pounds, it finally began to yield. Unfortunately, it was the hub that was yielding, not the presumed press-fit. (I used one of my crudely made brass aftermarket diaphrams.)

So we sectioned it. Take a look....

Click to view attachment
As you can see, there are three parts. The hub, the diaphram, and a locking ring. There is a ridge on the hub that retains the lock ring. The lock ring is continuous around the diameter of the hub, as is the ridge.

All I can think of is that they chilled the hub/diaphram, heated the ring, and then assembled them. As they equalized in temperature, the ring tightened down on the diaphram due to the champher on the underside of the ridge on the hub (arrow). I determine the alloy next week using XRF, so I can figure out temperatures involved. Back of the envelope calculation says they needed a temperature difference of 5000 degrees or so to clear a 1/64" ridge if it's standard steel, which would have melted everything.... or else I need a new envelope.

You can see the distortion in the hub from our attempts to press it apart.

did the ring seem hard yet gummy when you cut it? A company I used to work for invented shape memory alloys, in fact even invented shrink tubing. The alloy was frozen in LN, then was stretched using a tapered arbor. Once it came up to temp, it would be back in it's original shape. These were and probably still are used on all the composite aircraft for the hydraulic systems. Guess if you have a hydraulic leak with a composite airframe, you get paper mache.

Very cool testing your doing BTW.

To my untrained eye it appears that the flange of the hub that retains the lock ring might have been swaged in place. This technique would have been in keeping with mass-production (i.e. low-cost) quantities and readily available with late-'60's tooling.

Memory-effect metals and cryogenic techniques were known then, but were considered 'aerospace-level' technology - not economy-car stuff...

I think yer making this too hard.

I agree with the swaging technique.

Smack a really hard fastener into a soft material with the right tools and I gurantee the soft material will flow in place.

I've used a nut type fastener called a Pem Nut since the 70's. You drill a precision hole in aluminum, insert the Pem Nut and smack the crap out of it with a BF hammer. It swages the aluminum into the recess in the nut and holds everything in place. While not identical, the 914 part might use a similar technique with a Euro fastener.

Pem works on mild steel if the steel is softer than the Pem fastener. Pems come in nuts, studs, etc,

Attached are two pics of one type of a flush mount nut. One is shown inserted, and the second pic shows the optional swaging tooling...

We used the BFH technique or with some types, used the screw to pull the nut into place.

Pems might work for a new diaphragm.

Great stuff here. I'll bet ya'll will have it figured out in no time.

That's a great idea. I've also used PEMs. I'll be checking the material alloys this week at work, maybe tomorrow, and if the ring is softer than the hug, this is probably how they did it. Of course, for a repro, this could be how to do it regardless.

Great stuff, a few comments. One, the design of the adjustment flange is rather complex. Not only do you need it to be retained in the diaphragm, but you also need to supply a precise, smooth recess where the O-ring seal on the outer screw can slide, and maintain vacuum integrity during adjustment. From reviewing the Bosch patents, I can see that early on they tried to make "fixed" flanges without the outer screw adjuster, but apparently they found too much variation in the settings.

One more thing is that a low-effort way of getting what we want might be to work directly with a rebuilder, who has already done the tooling for the flange and the mounting process. Getting them to adopt a different diaphram material or design that gives better characteristics would be in their interests, and they could have a new market in selling diaphragms for something like $50 a pop. I think SLITS knows who picked up all of the stuff from Bret when they sold the business.

I think they make the PEM's out of the stuff that they use for the hinges of hell.

No matter how hard they are hit, the other stuff deforms- not the PEM.

Looks like the factory design is a sandwitch of a hard PEM like fastener, the soft diaphragm placed onto the fastener, and a steel or aluminum washer that captures the diaphragm on the fastener. The washer does the deforming.

The particular one that I added above is a flush mount fastener and might require a sandwitch of a washer, the diaphragm, and a second washer on the other side of the diaphragm. That way, the soft diaphragm is pinched between the washers, and the washers do the deforming- not the diaphragm.

You guys are awesome for researching this...

Diaphram #3 in my original post is from a fresh Bret rebuild. It's the one I call "crappy brass", and it has no adjustment range, because it's so stiff. Their approach to mounting the diaphram maybe isn't so bad though. They cut the original diaphram back to where it's just a collar, and then soldered the replacement (with its oversize ID) onto the remnant of the original copper one. Quick and dirty, not very esthetically pleasing maybe, but maybe workable. It may work with a quality diaphram as well.

I have to photo the other side of my stainless diaphram and post it. I think it's assembled differently.... Later today....

OK. I took some more photos. These three are copper, stainless, copper. (presumably beryllium-copper).

Click to view attachment

Both copper use the same hub attachment design- the one I sectioned earlier. The stainless one is different. It is definitely swaged together (arrows) in 6 places.

Click to view attachment

Could it be possible that the 2-pleat copper type was a factory attempt at addressing the fatigue problem? Now I'm more strongly doubting the stainless being factory, because both the material and the hub design are different. Of course, if Bosch put engineering into design improvements, they wouldn't have necessarily stopped at diaphram material. And the stainless hub has another difference- it protrudes higher off the diaphram on the ambient side. This allows for more adjustment before the outer screw's o-ring exits the hub and starts leaking.....

Also, I peeled the lock ring off one section of the hub, and both the lock ring and the hub are definitely steel- they're magnetic. I'll find out what alloy later this week.

Click to view attachment

Picked up a -010 MPS this week, allegedly from a Volvo 142E, circa 1972. But it's got to be late 60s vintage, so I'm thinking it's probably from a P1800.

Click to view attachment

It's a long nose. These guys have a mechanical damper built into the snout, inside of the spring, which requires a longer snout to account for the extra piece. I'll post a photo later.

Also, note that there are four drilled holes in the diaphram end, instead of cast slots like every other one I've ever seen. Kinda hard to see in the photo. Two are visible at about 3 o'clock, one on the face and one on the side. The other two are maybe 45 degrees below that.

I profiled it, and then took it apart. It's a rebuilt, non-leaker, and sports yet a 5th diaphram type. The diaphram hub is idential to stock, which I'm now convinced is swaged as suggested by kwales.

Anyway, the diaphram is a copper alloy, and it has 3 pleats, but the pleats range in width from wide on the outside to narrow near the hub. I've dubbed this the "3 asymmetrical pleat" diaphram, and she's a beauty!!
Click to view attachment

I loaded the diaphram up into my test MPS, with its filled aneroid-
Click to view attachment

and profiled its adjustment range-
Click to view attachment

This is the widest adjustment range I've found yet. It beats out the stainless one, though not by much.

In case anyone is wondering what I'm going to do with this, well, first I want to see which diaphram material/design has the greatest adjustment range, and then I'm intend to try my own materials and see what I can come up with that is comparable, or better than stock. I'll make a die set to press diaphrams from, and I've reverse-engineered a hub that will close with a lock nut so I can try different materials.

On that note- I also picked up a -035 MPS- another Volvo, this one probably truly is from a 142E. It's short-nosed, original-riveted, and it doesn't leak. Tomorrow, I'm actually going to open it up (not for the squeemish, opening a non-leaking stock MPS!!!) so I can profile the stock copper diaphram to compare with all of these alternate designs.

Love this science stuff!

...or someone ...

Really amazing reading!!

I agree, amazing reading.

My question?? Has anyone thought about a simple solution??? Contact Bosch engineering and ask for the material composition or who their supplier was?? Now that MPS's are obsolete Bosch might release this info from their engineering files. Somebody at Bosch knows. Just a thought

I don't have any contacts, but maybe someone on the board knows someone???
How about George @ AA????

Tom

Great idea!! Other questions are whether the tooling still exists, would it be possible to arrange for one more run (maybe 500 pieces??), and if we could speak with someone who can shed some light on the design changes that Bosch made along the way... it's possible that more than one of these 5 diaphrams are original Bosch, just representing design evolution.

Anybody have any connections at Bosch?

(I'm having fun, though, so I'm going to pursue my trail further either way.)

Jim

It would be great if we could get Bosch to supply a run of replacement diaprhagms.

I might point out that even if a replacement diaphragm were available, that rebuilding and calibrating the MPS isn't a trival thing. Here are the steps as I see it:

1. Remove the epoxy from the full load stop - don't attempt to remove the full load stop yet.
2. Drill out the case rivets to remove the top.
3. Using a 3/8" tip flat screwdriver (filed to fit the slot tightly), drive the full-load stop through and out of the top half of the case. Don't try to back it out, as there is epoxy holding the threads. Heat and WD-40 will help this operation. You may want to break it loose before drilling out the case rivets first, as it may make it easier to secure the MPS.
4. Remove the old diaphragm and remove the adjuster assembly from it, reinstall in the new diaphragm to approximately the same depth. Use a vernier to set it exactly.
5. Clean out the interior of the MPS with contact cleaner.
6. Install the diaphragm. Assuming we don't have a supply of new gaskets, install the old gasket, and use a thin layer of heavy grease to seal it.
7. Tap the case and bore the top to accept screws to secure the top.
8. Install the top, leave the full-load stop out for now.
9. Using the tables on my MPS page (see my sig for links) and a Wavetek LCR55 meter, set the inner and outer adjusters as described on the page. Install the full-load stop as described on the page.
10. At this point, the MPS is approximately adjusted and should work. To properly optimize the adjustment, you'll need to set the part load and full load mixtures using a dynamometer and a gas analyzer. Suggested settings for stock 2.0L motors are part-load (i.e. 2500 rpm, low throttle angle) at a CO of 2.5% to 3.0%, and a full-load (i.e. 4000 rpm, wide-open throttle angle) at a CO of 4.5% to 5.0%.


To those out there who have done this before, please feel free to edit and correct this procedure as required.

FWIW, this is the correct contact info in Germany. I've had a little bit of luck in the past, perhaps someone else will do better than I did.

Robert Bosch GmbH
Gasoline Systems Division
P.O. Box 30 02 40
D-70442 Stuttgart
Telephone +49 711 811-0

FYI, are others aware of the Bosch Classic web shop on eBay?

http://stores.shop.ebay.de/Bosch-Klassik-T...g__W0QQ_armrsZ1


Not a lot of 914 parts, but some are there.

FWIW, I sent an email to the guy in Bosch Germany who was the press coordinator for the 40th anniversary of D-Jetronic to see if he can put us in touch with anyone at Bosch who might be able to help us out.

That's a great lead. Better than cold calls to Bosch.

OK, some images from that -010 Volvo MPS. First the coil, with damper.
Click to view attachment

Then a surprise- never seen one of these-
Click to view attachment
Click to view attachment

Any ideas what it could be for? I have an idea, but maybe someone knows for sure... Looks factory. Can't imagine a rebuilder tooling something like it.

Cleaning a couple of housings with special purpose MPS cleaner....
Click to view attachment

Nice clean housing. Not perfect, but not bad. You can see the vent holes I was talking about.
Click to view attachment

Also, took apart that other alleged Volvo 142E unit. The non-leaking, riveted, -035. Found the holy grail of diaphrams- a perfect stock piece-
Click to view attachment
I'll profile it later.... Almost time for 24.

Also found another of those plastic rings... Why do the two Volvo pieces have these? The cells fit inside, but it's a loose fit.... What're they for?

I have found a few in even the 914 MPSs. They are for holding the cells from flopping around.