Need MPS's for Adjustment Method!!!

[pbanders]

Hi, some of you may know me for the mad scientist work I've been doing with the D-Jetronic system:

http://members.rennlist.com/pbanders/djetparts.htm
http://members.rennlist.com/pbanders/manifold_pressure_sensor.htm
http://members.rennlist.com/pbanders/ecu.htm

I've come up with what I think may be a fairly simple way to characterize and adjust the D-Jetronic manifold pressure sensor (MPS) by an electronic calibration method. The only test equipment required is either a Wavetek LCR55 ($190) meter or a Wavetek 27XT multimeter (as low as $30 on Ebay), and an Actron hand vacuum pump with gauge ($30 at your FLAPS).

The inductance of the secondary coil is measured over a vacuum range of 0 to 25 in. Hg. I've include a URL to a plot I took of the new rebuilt MPS in my 2.0L car:

http://members.rennlist.com/pbanders/MPSPlot.gif

The blue line with the diamonds is the actual measured response, and the violet line is a linear fit to the region from 6 to 17 in. Hg. Using procedures in my MPS document (URL at the top of this message), you adjust the part load and full load screws to obtain the same slope and intercept, and full-load delta at 0 in. Hg. The measurement takes less than 5 minutes.

I've tested two of the 043 units, and they have essentially identical characteristics. You can also use this procedure to document adjustments you have made to the MPS for increased displacement or other tuning.

Where I need YOUR help is in gathering some units to build the set of standard calibration curves. What I'm looking for is new or newly rebuilt MPS's with the following Bosch part numbers:

0 280 100 049 1970-1973 1.7L
0 280 100 043 1974-1976 2.0L
0 280 100 037 1973 2.0L (and 1.7L)

I really need the 049 and 037 units. Here's what I ask:

- contact me by email at pbanders@yahoo.com if you are interested in helping out
- ship your new or newly rebuilt MPS to me, insured for replacement
- I'll do a 5 minute, non-destructive inductance characterization
- I'll ship the MPS back to you the next day, insured, and will reimburse you for your shipping to me, and include a copy of the test results (similar to what you see at the URL above, including the linear fit data and full-load delta calculations)
- Your assistance will be acknowledged in the updated version of my MPS document that I'll create once I have the data set

I would like to have at least 3 of each type of MPS above to establish the characterization curves. If I get enough participation to satisfy this need, I'll let you know if I don't need any more units for testing.

Help out if you can. The MPS is the most critical sensor in the D-Jetronic system. Many have been tampered with, leaving owners no recourse but to drop upwards of $200 on a rebuilt or (gag) nearly $1000 on a new unit. A reliable and inexpensive calibration method can save a lot of money.

thanks,

Brad Anders

[pbanders]

[Dave at Pelican Parts]

I've gotta check what the boxes of spare parts hold. And see how many I can find. (Ditto those ECUs I owe you!! Did you ever get that one from Randy??)

--DD

------------------
Pelican Parts 914 Tech Support

A few pics of my car: http://www.pelicanparts.com/gallery/Dave_Darling

[pbanders]

Dave, thanks! Nope, haven't gotten any ECU yet. Jeff Bowlsby is sending me some MPS's of his to characterize.

If this technique works out, I'm going to re-write my over-the-top complex MPS web page and split it into two parts: "MPS for Eggheads" and "MPS for Wrenchheads", with the latter being more of a "how-to" document.

Brad Anders

[bowlsby]

Well Brad, sending you what I have:

043 (74-76 2.0L)

049 (70-73 1.7L)

The 037 (73 2.0L) is elusive!

[bowlsby]

An update. I sent Brad two factory sealed MPS units to non-destructively characterize. Brad checked them out and the data he provided is superb and extremely well done and presented. I will let him describe any global results as he confirms and verifies the results with other MPS units.

He was able to verify the calibration and operational function of my two MPS units. His results offer the hope of greater tuning potential through recalibration of the MPS.

I was surprised to see such little calibration difference between the two units...the difference must be very subtle between the manifold vacuum levels of a 1.7 v. 2.0L engines.

The calibration is so delicate between the 1.7L MPS and the 2.0L units, I would not recommend that anyone attempt to play with them, unless they have the proper analysis tools.

Send Brad more MPS to characterize!

[This message has been edited by bowlsby (edited 08-14-2001).]

[pbanders]

Thanks, Jeff. I'm still looking for new, nearly-new, or freshly-rebuilt 0 280 100 037, 043, and 049 MPS's.

The few I've tested so far verify a lot of things that I had suspected, but I need more units to make certain of the results. Here are some preliminary findings:

1. All of the aneroid cells seem to be the same, as they all have expansion rates within a very small window.
2. Calibration differences between the three MPS's used on 914's are significant, but small, and mostly affect full-load operation. That's why people have been able to use different MPS's than spec in their cars and get decent performance.
3. The linear range of operation is smaller than one might suspect. At high manifold vacuum levels (overrun), the armature in the MPS core begins to be pushed up tight against the spring stop at about 20 in. Hg. Transition to full-load operation begins at about 6 in. Hg, so you have about 14 in. Hg of linear range.
4. The transition to full-load operation begins at higher vacuum levels than one might suspect. It starts at about 6 in. Hg and ends at about 2 in. Hg when the diaphragm touches the full-load stop.

Assuming I get some more units, I should have a decent set of calibration curves ready in a couple of weeks.

Brad Anders

[bowlsby]

I am so pleased, I just had to share one of the reports Brad provided for those who are curious:




[This message has been edited by bowlsby (edited 08-14-2001).]

[GermexAmerican]

Do you offer testing service?