changing from cam to crank angle sensor
 

hi i have a Motec M4 ecu and at the moment it is wired to the cam angle sensor. was thinking of changing to a crank sensor but not 100% on the wiring. anyone able to help on this?

is it really worth the trouble? would i be better off just leaving it as is?

What year miata? Some of the 1.8s have a crank trigger with pickup that you maybe to use the setup and get a trigger wheel made for it.

its in our race car. 1.8 flyin miata bottom end. was thinking i could use a standard crank sensor as my pulley has the 4 standard triggers.

It is easy. There are 4 wires at the own CAS connector. Two are power and ground, one is cam signal, one is crank signal. Just wire both nb sensors to power and ground, then run the cam signal to the cam signal wire on the oem harness and the crank signal to the crank signal wire. you cannot use the 96-97 sensor. The crank sensor you need comes from the 99-05.



The motec should be able to accept a custom 12 tooth trigger pattern too. Our 12 tooth wheel is a huge improvement over the factory 4 tooth wheel.

Brilliant thanks for the help. So do I have to run both cam and crank or can I just use the crank? Is it really worth the change? How quickly could I get one of your trigger wheels in the uk?

The M4 is actually a very dated ECU, circa 1995, and very limited. I installed and tuned an M2R on a RX-7 last year, and I swear I will never touch another non-MS ECU again.

Tuning under DOS anyone?

If you want to run sequential fuel or spark, and you do, a cam sensor ie required.

not really. got it for next to nothing.

may be an old ecu but easily capable of doing anything i need it to do.

would i have to use the NB sensor on the cam or could i leave the NA one in the back of the head? cant really use NB sensor as i have vernier cam pulleys with no pickup. what about a longer bolt in one of the vernier adjustment bolts with a sensor reading from that?

Assuming your ECU can be configured to understand the resultant pattern (I have no idea how the Motec's trigger inputs are defined) then yes, you can absolutely run an NA CAS with an NB-style crankplate.

The CMP output of the NA's CAS is kind of odd. It outputs two pulses per cam revolution, one long and one short. In the original NA configuration (using both outputs of the CAS), one of the CMP pulses was high for the entire duration of one of the CKP pulses (both leading and trailing edge), whereas the other CMP pulse was high for the leading edge of a CKP pulse but low for the trailing edge. It's a bizzare configuration, and the only explanation for it I can imagine is that it would reduce cranking time at engine startup, by giving the ECU two opportunities for sync capture per cam revolution rather than just one.

oh rite i see, thanks for the explanation. very interesting and very complicated. think it would be far more simple to use a sensor on the cam pulley in that case. is it even worth doing as it is working perfectly fine as it is? how much ign slop would normally be lost by changing setup?

If you're just wanting a single pulse off the cam to go with a new crank sensor, you can very easily modify either version of the cam sensor to produce the single pulse.