Rising Edge vs Falling Edge

[Raymond_B]

Which one is which?

[billr]

I think the first if "falling" and the second is "rising". You want to trigger on that zero-crossing that goes abruptly from peak-to-peak.

[racingmini_mtl]

The problem is that it depends on which input circuit you're using and how you connect the sensor. What you want to do is to check the input at the CPU and see what the signal looks like. You need to see which edge of the 0-5V signal (rising or falling) correspond to fast zero-crossing of the raw input signal (the one you show).

The fast zero-crossing is the one that has a consistent and precise location. However without seeing the signal at the CPU related to that raw signal, it is impossible to know if you need to use rising or falling because that depends on how you measure the raw signal, how you connect the sensor to the ECU, and which input circuit you are using. Some combinations will invert the signal at the CPU and others won't.

Jean

[billr]

Well, I'm rather confused now. I'll have to sleep on it...

[Raymond_B]

This signal will go to the MS3X cam input. It's being generated by a 2 wire Ford VR cam sensor.


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[Raymond_B]

Unless anyone disagrees I am going to connect the sensor with its output as shown in the 2nd pic and choose rising. I am probably being OCD about this, but I've got a lot of money in this build and when I fire it up initially I do not want to be messing around with wiring. I just want to get it started and to break it in.

[billr]

Before you "fire" it you should be checking the spark timing at cranking, and can check the tooth log at the same time. How much money is "a lot"? If you want to avoid a chance of prolonged cranking to get this sorted out, take the crank wheel off and set it up on spindle so you can play with settings endlessly without teasing the engine. A setup like that is a bit of a bother to construct, but can be used again-and-again if you continue to play with engines in the future.

[Raymond_B]

Before you "fire" it you should be checking the spark timing at cranking, and can check the tooth log at the same time. How much money is "a lot"? If you want to avoid a chance of prolonged cranking to get this sorted out, take the crank wheel off and set it up on spindle so you can play with settings endlessly without teasing the engine. A setup like that is a bit of a bother to construct, but can be used again-and-again if you continue to play with engines in the future.

Will definitely spin it over a few times for testing before starting after I get the oil pressure up. I've got at least 12k in the engine, which I consider a lot for me... It's the cam sensor that is VR and that's what I was spinning over with a drill to log the above pics, the crank is a Cherry hall sensor so I feel OK on it since it came with good documentation.

[billr]

Do you have a missing-tooth crank wheel? Start this up as wasted-spark/COP, avoid CMP issues until the engine has had some run time.

PS: Hall sensors can be just as troublesome as VR, don't take any short-cuts in checking the CKP sensing...

[Raymond_B]

Do you have a missing-tooth crank wheel? Start this up as wasted-spark/COP, avoid CMP issues until the engine has had some run time.

PS: Hall sensors can be just as troublesome as VR, don't take any short-cuts in checking the CKP sensing...

Yes, It has a 36-1 wheel. Interesting, OK I will read up on that. Thank you.

[Raymond_B]

Anyone else have thoughts on which one is which?