FI Question

[1bad914]

I finally started going thru my 74 2.0, I started checking all the FI stuff per Brad Anders wonderful site, the ECU is a 75 ECU, will this effect the way the car runs, I noticed the waveform count is different. Should I replace it?

Thanks,

[pbanders]

The '75-'76 ECU has a couple of differences from the '74 2.0 ECU. It has a different speed correction waveform, and it has a different circuit for overrun shutoff. My guess (nothing more) is that it will operate essentially the same as the earlier ECU.

[Jason Porter]

I've switched both ways, early to late, late to early. No problems. I've run 1.7 brains with 2.0's and vice-versa, no problems.

I could just be lucky, but then again, if I was lucky I woulda had a 6...

[pbanders]

As Jason says, there isn't much difference between the various D-Jet ECU's used on the 914. The major item that varies in D-Jet ECU's is the engine speed mixture correction curve, derived from the volumetric efficiency (VE) curve (pumping efficiency) of the motor. This correction is realized as a OR'ed set of waveform generators in the ECU and is custom to the particular motor. I would wager that the VE curve of the 1.7 and 2.0 motors is very similar, hence the interchangability. Other differences in the ECU's are in the overrun shut-off control, and in the hot starting circuits, both of which don't have much effect on general performance.