Awesome, thanks Lee.
64uS is a very narrow pulse, and although ford filters it I doubt any stock rev counter would be fast enough to respond to it. The FRST revcounter I tested only responds to pulses longer than roughly 400uS, but will occasionally 'tick' on the narrow pulse. The 64uS pulse vanishes as soon as there a flyback voltage from each coil so I guess that it is clean whilst the car is running. The IDM pulsing only on coil flyback pulse is useful for tracking misfires down too which is handy.
I don't think any ford ecu (EEC-IV on) used extra tach inputs other than crank/cam/PIP so i guess they are referring to using it as a rev counter driver. I've got some vague recollection of there being some tacho conditioner that plugs into the loom on some cars???? But that might just be rubbish.
Using only Pin10 to drive the tacho makes my life soooo much simpler, so thanks very much for the info
PS,
I think pin 2 and 11 being connected is probably a legacy thing, I suspect they had a pin left over on the EDIS4 unit so though fuck it, I'll use it for this.... I doubt the EDIS6/8 has the IDM output on more than one pin.
Originally Posted by
mentalasanything
Interesting, I read that as just the ECU gets its tach reading from the IDM. That document makes no reference to pin 11 other than in the Pinouts. It's interesting that you say pin 2 and 11 are connected together since the 64us pulse needs filtering, which would make the tach output dirty, not clean.
Browsing through so many other threads and guides, pin 2 is cut back on and FRST setup as its not used by OFAB and OFAC, apparently it's cut back from the factory on an FRST.
You're right about it not being easy to find this stuff out. But it seems that European Fords don't follow the same setup as the American Fords. I know I read that the FRST uses pin 10 and I'm sure the XR3i EFi and XR2i do too, I'll see if I can find it
Lee
