I spent some of my remaining vacation time with a new Chris Foley MPS diaphragm kit today. A week ago I installed the kit in a core MPS and it seemed to work well but I didnt have time to test it fully before a trip out of town. Got home and put it through its paces today. I compared it with 2 NOS and 2 other known good, used, unopened MPS's that I own as well as other data I have collected from others, to calibrate it. Interestingly, each MPS is factory sealed, with original factory settings. While the calibrations are slightly different between them they each work perfectly on my bone stock 50KMI 74 2.0L. The MPS with the new diaphram kit was road tested and put through its paces, in all load settings, testing idle, hills, highway, WOT, deceleration, and the transitions between all RPMs. It behaved perfectly, as anticipated. I don't have an exhaust gas analyzer or other sophisticated equipment or instrumentation so that is a caveat. YMMV. I then reopened the MPS to inspect the diaphragm and saw no visible damage or other indication of failure, distress or unusual wear. Chris has done a exceptional job with these diaphragm kits, they appear to match factory specifications and performance in every respect, and the kits also include 3 new gaskets to prevent air leaks.

Mounting the kit is easy enough, but there are two challenges in rebuilding them and in determining costs:

1.) Cleaning up the outer cases of cores may take alot of effort, or not, depending on the condition of the specific core. Most of the dozen or so cores I have are going to take some effort to make nice, I may need to look into getting a buffer. Cleaning and detailing the MPS case could easily take more effort than just getting it functional again.

2.) The bigger issue is in detemining the exactly correct calibration for a specific engine, which to a large extent depends on that engines particular mechanical, fuel injection and ignition systems (and their components) characteristics and conditions, including wear and state of tune. A factory stock new engine is easier to get right than modified or worn engines, at least using the calibrations we know about. Brad Anders mentions this on his site, to the extent that each MPS may have been adjusted specifically to the exact equipment used on each specific car and its specific nuances, most likely using exhaust gas analyzer equipment to perfectly tune it. I can get these close to what I understand to be 'factory calibration' using the inductance meter, but it needs to be emphasized that each MPS may need more refined calibration using an exhaust gas analyzer by a mechanic if its not spot on for your car.

One way that the calibration could be correct for a particular car, is if the known good MPS from your current car is sent along with the core and then the calibration could be matched exactly, especially if the MPS has been previously recalibrated.

I have calbration specs for the 1970-73 1.7L, 1973 2.0L, 1974-76 2.0L and 2056, using the LCR inductance meter.

I think I'll determine a fixed cost to install a new diaphragm kit and calibrate an MPS to known settings, and leave the case cleaning for its owner. I will also just put a dot of epoxy to hold the outer screw in place, not a full embedment, to make it easier for others to access the adjustment screws if necessary

Does this seem like an acceptable approach for now?

I've been using trial and error to adjust the MPS on my cars. It would be nice to have you calibrate the units I've already rebuilt.

Good to hear these are working out. Mine got delivered last week, I have an LCR55, and a wideband setups on my cars, but we also have a ton of salt on the roads at the moment so more data will have to wait till spring.

Hi Jeff Bowlsey,

I would like to be one of your early clients to have my MPS rebuilt with a Tangerine Racing's diaphragm kit if your offering the service?? Say, yes & I'll gather up my MPS stuff along with a complete motor specification write-up and send it to you.

Give me an approximate budget price $___ and I'll be a happy client.

BTW: My 914 is in winter storage so it will be spring road tested. I know my NOS MPS runs lean at idle and need tweeking.

Tom
1974, 914-4 2.0 Liter D-Jet F.I. with a few modifications like, Euro Pistons, Len/Raby new heads, Raby #9550 cam, lightened flywheel & crank, w/blueprint/balanced machine work. Close to stock with a few updates.

Jeff, thank you so much for doing this for us. You are the best!

I've got one I should be receiving any time now. It's possible that at some point I might need some calibration services if I can't get things figured out.

Jeff,

Just thinking out loud here.

Considering today's technology, are there any methods or basic processes we can use to measure an existing car's condition or setup, at a low-level cost? Applying 1 or 2 paths only, for simplicity sake, establishing a baseline setup for every given car.

Maybe listing the details required for each engine and the associated metrics in a menu format. Obviously, simplicity is key for many car owners, but if a wideband o2 measurement is a minimum requirement for preliminary measurements, then that can be part of a Process #1 menu or similar. If a set of simpler and inexpensive gauges can be loaned out from a FLAPS or purchased on the low cost side from Radio Shack or similar, that would be Process #2 or similar. These processes could be used, enhanced or separate path determined by a professional shop or restorer. But it would be a critical step for any owner who cannot have their car on premises when someone restores an Most for their car.

Lastly, it would provide all the guys who may offer this service a way to do so with known parameters to begin with as well as lowering costs for all involved, if not a baseline based on newer tools and techniques.

Dave B.

Hell, I would be happy if my kit had come with instructions.

The instructions are still under construction.
In the meantime, PB Anders' website covers everything pretty well.

You might consider using something a little less permanent, such as nail polish.

A little off topic, but how would one know if the MPS is leaky? The reason I asked is cause I tried calibrating a spare MPS with the MPS in my car and found to my suprise the one in my car wouldn't hold vacuum. I have a cheap LCR meter from Amazon and none of my inductance numbers are consistant with B. Anders'.

How would the car perform if the MPS was leaking? I installed my spare but have noticed little difference. I still need to order a wide band O2 sensor to calibrate it.

Received my unit yesterday and it looks terrific, but I too hope instructions will be forthcoming?

Dave, Anders site discusses the MPS function and calibrations in good detail. He does not describe the entire process needed to rebuild them but gives most of what is needed. The LCR inductance meter is what the calibrations are based on, but the best way to calibrate the MPS, especially for an engine with wear or modifications, is using an exhaust gas analyzer.

The MPS leaks if the diaphragm or seals on the MPS case leak air. Use a vacuum pump like a MighytVac on the input port and see if leak down occurs. Thats the way its done. See Anders site. If it leaks, the resulting fuel mixture is rich.

The correct inductance meter for calibrations is an LCR-55 Wavetek. Not sure what other 'LCR' meter you may have.

I found this out recently as I determined my extremely poor running condition could be due to a faulty MPS. I was driving home from a tech inspection and the engine ran VERY badly; it would run but I feathered the throttle all the way home as I felt it would stall if I had to let it idle, and all the time thought I wouldn't make it home. I removed the plugs and they were jet black. I thought the gas gauge needle was moving like the minute hand of a clock! After I got home, and felt like looking at "ole unreliable", I removed the plugs and observed what I described above. I initially thought clogged or crimped fuel line, poor valve adjustment (having just done it and driving on it for the first time; thought maybe the adjustment slipped), then related the black rich running spark plugs to the MPS and checked the vacuum on the MPS and it didn't hold a vacuum. I am reinstalling an -043 spare MPS and the decel valve. I am interested in the service of installing a Foley diaphragm and set up...

My kit has been sitting on the shelf for the winter, and I forgot about this thread.

Jeff - did you come up with a price?