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Join Date: Jan 2001
Location: Phoenix, AZ
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Sample D-Jet Characterization Plots for '74 2.0L FI Setup

I recently acquired a very old D-Jetronic tester (EFI Analyzer) that measures injector pulse width data and can simulate the trigger contact points, permitting complete simulation of the D-Jet system. By using a load signal on the MPS by pumping it to preset manifold vacuum levels, the entire operating characteristic of the system can be derived. Below are some examples of the data.

Here are URL's to three plots of injection pulse width vs. engine speed, as a function of manifold vacuum (engine load). All the data were taken on my 2.0L ECU and MPS, both are '74 parts (0 280 000 043 ECU and 0 280 100 043 MPS). My ECU is a NOS unit I bought last year, and my MPS is a Bret rebuild from last year.

The first URL is at simulated normal engine operating temperature (~100 C), the second is a cold start (engine temp 20 C), the last is a cold-cold start (- 10 C). Sorry for the size (slow loading) and rough quality of the images, I'll post clearer ones later:

The missing data on the last two graphs is due to a limitation of the pulse width meter in the EFI Analyzer - can't handle high products of engine speed and injection pulse widths. Note that to get all the data for all of these plots took me about 5 minutes with the EFI Analyzer.

The first graph is very similar to the Bosch characterization data (which is for a completely different 6-cyl engine) that is shown in my ECU web page:

Click on the "Circuit Block Analysis" section, and scroll down to the analysis of the Engine Speed Correction block. At the bottom you'll see two graphs similar to the first graph above, one by Randy Montellato, the other from the Bosch Technical Journal article on D-Jetronic. Good verification of the data.

The other two URL's above show the dramatic increase in injection time for a cold and cold-cold motor.

Do not assume these graphs are calibration data for the particular ECU and MPS combo I describe. From data I've seen, I suspect my MPS is calibrated somewhat low at full-load. I'll publish better data later.

Last edited by pbanders; 03-19-2002 at 10:06 PM..
Old 03-19-2002, 10:02 PM
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