How many MPSs are "popped"? Options

[McMark]

I pretty much assume that every MPS I see is either broken or on its way out (diaphragm damage). I'm I right or wrong?

[lapuwali]

I went down this path partway with Brad Anders.

Making new diaphrams is, in fact, being done, but the replacements don't work exactly like the originals. I've heard a lot of dissatisfaction with the rebuilt units.

It's been suggested that all of the D-Jet MPSes are are the same internally, and only the sealed adjustments are what makes each one different (with a different part number). The MPS on my '69 VW looks exactly like the MPS sitting on the shelf for my '71 914, but the part numbers are different. Brad has done a lot of measuring, and it looks like the curves are all within the range of the adjusters, if I remember correctly. His site has a lot more detail on this.

As for a solid-state replacement: as Rich said, it's not that easy. Simulating an MPS perfectly electrically would be possible, but would require about 90% of the electronics of a Megasquirt to do it. The MPS really is the heart of the system, taking engine speed, temp, and manifold pressure and integrating the signals together to produce the pulses for the injectors. It's not just a MAP signal generator.

Over the next 10-15 years, I'd expect most 914s still on the road to be using some aftermarket EFI setup, replacing the D-Jet ECU and MPS with modern bits. Or they'll be switched to carbs. The only cars still using the stock system will be show cars.