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CAS/CKP and tooth resolution

 
Old 02-06-2018, 05:07 PM
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Default CAS/CKP and tooth resolution

  • 91 chassis
  • 99 head with CAS in rear
  • 97 block with 4 tooth hub
  • MS3x
  1. Can I run the rear CAS in combination with a CKP for my toothed crank hub?
  2. If true, can I lead the CKP wire from the CAS to the CKP sensor? Then splice 12v and ground?
  3. What is the total resolution ms3x can handle? Is there a recommendation? 32?
Thanks.
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Old 02-06-2018, 05:26 PM
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1) No unless you have the magnetic-type CAS, in which case you can cut one of the two inner "teeth" to get sequential, and swap the front trigger for a 36-2 or other (the stock 4-tooth trigger is uneven and won't work this way).
2) Yes but you also need to use the 99+ cam sensor if you want to use the stock 4-tooth trigger wheel.
3) The MS3 can easily handle say a 60-2 crank wheel but you also need a single cam pulse from the CAS in this case - see 1).
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The “into to megasquirt thread” mentions that the MS3 basic has 5 inputs with built in pull up resistors - and I was just wondering why it would have so many, while the MS3Pro PnP has just 2 (with no pull ups?)
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Old 02-07-2018, 11:16 AM
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Thanks Rev,

This is not what I was hoping to hear, but it is understandable. I do not have the option to run the 99+ cam sensor, because my valve cover will not support it (protege valve cover).

If I am understanding you correctly - If I were to get a 36-2 tooth hub wheel, and cut two ears off my Magnetic CAS. I could run a trigger wheel CKP off my existing CAS wiring ?

Does it matter which pair of ears?
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Old 02-08-2018, 09:55 AM
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If using a 36-2 crank trigger and the NA CAS for a cam sensor, you'd need to modify the CAS so it supplies only one pulse per revolution. This could be done by cutting either the inner 2-tooth ring or the outer 4-tooth ring down to one tooth.
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Old 02-08-2018, 02:26 PM
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Why nit get 99/00 valve cover? Seems the easier thing to do then try to hodge podge other stuff together.
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Old 02-08-2018, 04:24 PM
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Originally Posted by shuiend View Post
Why nit get 99/00 valve cover? Seems the easier thing to do then try to hodge podge other stuff together.
Would I just run the wiring for both sensors from my existing CAS plug harness?

I thought Cam gears needed to be magnetic as well? Is there a special cam gear type for the 99?
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Old 02-09-2018, 09:42 AM
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yes you need the 99 cam gears, or any chinese-adjustable that are compatible with any NA/NB (except VVT).

https://www.miataturbo.net/general-m...m-gears-87595/

BTW it's not magnetic, it only has some "nubs" to stimulate the sensor. if you get chinese make sure they have the right height (distance from the sensor)
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Old 02-09-2018, 10:11 AM
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fwiw- I just drilled, tapped and screwed/threadlocked in a stud on an adjustable cam gear for the NB cam sensor. Ran several seasons of racing like that.
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Old 02-09-2018, 10:58 AM
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what loss of resolution or accuracy would there be running just NA CAS?
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