MoTeC Global Forum

Hi folks,
just taken my first REF/SYNC trace since connecting all the sensors to ECU. Both cam and crank are using magnetic Marelli SEN8D sensors and are connected to ECU +5V sensor feed.


SEEMS to be OK but just a bit concerned that the REF trace oscillates in amplitude..? Is this normal?

Also, both REF and SYNC voltage outputs seem a bit low?


Any comments or reassurance would be grateful..



TT

Your capture looks fine for such a low cranking speed. You are only cranking at about 128RPM so that's lower than typical. Are you sure your battery, starter and wiring are OK?
Anyway, the oscillation is because the crank slows down due to compression as the pistons approach TDC, once engine speed comes up that effect will flatten out. The low voltages is because the cranking RPM is slow, again that will improve with speed. It should be fine and allow the engine to start as is.

Now why are you connecting those to 5V? There is no offset in your capture to confirm that statement but the SEN8D is a VR sensor, it should only be connected to 0V and SYNC/REF pins as far as I know.

As AdamW said, and going by the traces, these are magnetic sensors and should not have +5V feed to them, they generate their own voltage signal and should only be connected to a 0V and Ref or Sig input.

The Sync trace is not that clean through the most important part of the trace, and that is where it crosses the 0V when going from high to low. This will lead to you having a lot of Sync errors as the Sync signal will not have a consistent position.





I would wire the sensors correctly, and then redo the capture first, and then, depending on what the capture shows, how to proceed.

Thanks for the reply's folks.....put's my mind at rest.

Silly me, my initial post says I wired them up to +5V which has been commented on. Just wanted to say that I did not do this and they are wired to 0V and SIG as per Motec M880 wiring diagram. .

Will get on with the rest of it now that I'm happy about the trace. The SYNC is a bolt on the Exh cam wheel. I filed the head to make it flat but I might remove it again and sand it down further to remove any imperfections.


TT