MPS Characterization

[pbanders]

Some of you have used the LCR-based MPS characterization technique I described in my web pages below. I have some additional data for the 0 280 100 043 MPS, used on later 2.0L cars. I've acquired two NOS units, and also have a rebuilt unit in good condition. Below are data on all three units:

Conditions:
* Bench test in Phoenix, AZ: T = 65 deg F., altitude 1350 feet
* Three MPS's: "Rebuilt", "NOS #1", and "NOS #2"
* All three units are p/n 0 280 100 043
* Inductance testing: Wavetek LCR55 meter, 20H range
* All inductance readings across pins 8 and 10 (secondary)
* Injection pulse width measurements:
...*Tester: EFI Model 1401
...*ECU: NOS 0 280 100 043 unit
...*Air and head temp sensors: simulated to normal op temps
...*Engine speed: 2500 rpm (simulated)
...*Idle switch: open

Data: (sorry, hard to make a proper table here, I'm using ` to separate the data)

Vacuum (inHg) `Rebuilt (H, ms) ` NOS #1 (H, ms) ` NOS #2 (H,ms)
15 `````````` 0.72 , 2.9 ````` 0.70 , 3.0 `````` 0.72 , 2.9
4 ``````````` 1.18 , 6.6 ````` 1.16 , 7.0 `````` 1.23 , 7.3
0 ``````````` 1.37 , 8.4 ````` 1.32 , 8.9 `````` 1.33 , 8.4

As you can see, pretty good consisitency across all three units at high vacuum, and some variation in the part-load and full-load levels (4 and 0 inHg). In general, if you're using the values in the table in my article, you'll be very close if you're using the LCR method for calibration.

Note that the 0.5 ms difference between the two NOS units at full-load (0 inHg, or wide-open-throttle) is significant. From what I can tell, Bosch didn't calibrate these units all that consistently. What is interesting here to note is despite the 0.5 ms difference in actual injection time, the secondary inductance values vary by only 0.01H. The inductance method of calibration is an approximate method - if you want truly accurate calibrations, you need to build a simulator and measure the actual injection pulse widths.

I'll update my web page with this new data in the near future.

[pbanders]

One more piece of data - the correlation between the Acton vacuum guage I used and a Fluke PV350 (traceable to NBS) pressure sensor:

4 inHg Acton = 3.27 inHg PV350
15 inHg Acton = 14.95 inHg PV350