It seems the 2.0 liter Volvo MPS has one critical difference.
the lack of a diaphram for the adjuster screw.

The result, as far as I can tell, is the full load setting will result in a bit leaner running setup if left alone.

Basically what I can figure is the adjuster diaphram is compensating for atmospheric conditions only for the aircooled full load circuit and for nothing else.
The screw moves and thus allows more movement of the inner diaphrams that really control the results.
So, if used, I think (and I will test this) that the car could be made to run a bit richer in the part load circuit to ensure the proper settings for WOT or full load.

If I am correct, its a far more tunable setup and it has no diaphram that will fail.

So, has anyone tried one? With good/bad results?

Rich

The MPS for the Cosworth Vega (also D-jet) used the same design variation. As did some (all?) Mercedes. I picked up a Cosworth Vega MPS, and mapped it. It's basically a straight line- as you'd expect, since it relies on the cells only to vary inductance with manifold pressure. The Bosch manual states that the diaphram in this type of MPS is used to compensate for altitude.

Below is my mapping of various MPSs that I own. They're virtually the same at higher vacuums, and differ in when and at what slope they diverge from that line as vacuum drops. The Vega MPS never diverges. (The bottom line- "long nose 019"- obviously has a ruptured cell. Someday I'll take it apart and confirm this.)

As far as using it, I think you'd have to richen too much at overrun and idle to get up where you need it at transition and WOT. In the Vega, the fuel pressure regulator was modulated by manifold vacuum, which helps move it in the right direction, but I imagine that the profile hard wired into the computer is necessary to finish the job.


Click to view attachment

Effect of a manifold pressure modulated fuel pressure regulator on Cosworth Vega MPS. The inductance doesn't change with fuel pressure, but the mixture does, so I showed it as if the inductance does change. This is just calculated, not measured, so it is very approximate, but not too far off I think.

The 40 psi would be set with the manifold pressure chamber open to ambient. Once set, it would then be connected to the air box.
Click to view attachment

Does your Volvo MPS look like this? The end where the adjustment screw sits is covered by a black plastic cap....
Click to view attachment

Hmmm, I've taken apart a couple of Volvo MPSs (though not sure from what make/model) and they were pretty well identical to a 914 MPS. I pulled out the diaphragm from the Volvo MPS and used it in my 914 MPS, in fact.

Seen a simular MPS in a Jag XJS. Are any of the parts transferable for
rebuilding?