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  • crank only sensor/sequential injection

    hi folks, i been doing some thinking on the ve head swap thing and i am curious if its possible to save some money (and in my case packaging issues) by changing the motor to a crank angle sensor for timing and doing away with the cam angle sensor completely. (I think it should be possible to get a little more accurate spark timing with a crank sensor too, no?)

    additionally, i would like sequential injection. normally the cam angle sensor would tell you which phase you are in to determine when to fire the injectors in sequential mode. but if you are crank only then you don't have this input.

    this leads me to my question: is it possible to use following heuristic to determine cam phase:

    fire injector and keep track of crank acceleration for the first 90 degrees. save this value. then fire the injector again on the next cycle and do same calculation. whichever injection event lead to the highest crank acceleration is the correct one. now you can switch to sequential injection.

    the reasoning behind this: (at idle) spraying on the back side of a closed intake valve will result in a worse burn than spraying into an open valve. this results in a lower crank acceleration which we can measure.

    will this work? i'm concerned spraying onto the backside of a closed, but hot intake valve will give ambiguous results and the ecu won't be able to turn on sequential injection reliably. (if you designed your fuel system assuming sequential injection, this could be a bad thing).

  • #2
    Cam sensor gives you better timing than crank simply because it spins at 1/2 the speed, therefor the same wheel/sensor would give 2x the accuracy when mounted to the cam,

    You could use a hall effect sensor mounted over a cam lobe to trigger engine phase,

    Or you could use the CAS from a "20V" motor like everyone else, unless you are putting this motor somewhere other than a S-Chassis engine bay you have no tighter packaging concerns than the next (or last) guy,

    Remember KISS

    FWIW people have written code to determine engine phase based on Crank trigger wheel rate of acceleration, but there's really no need (or advantage) to going down that road

    Is there a nissan engine that doesn't use sequential injection that I m unaware of? I can't imagine why you'd settle for less (unless you are married to a MS system)

    It just donned on me you are the guy with a SR powered miata with MS...

    I'm not gonna delete this post even though it's almost entirely pointless now

    I am SKULLWORKS

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    • #3
      appreciate the feedback. yes, i'm the freak with a sr20 miata, and i'm still fiddling with building my MS. sr20's have full sequential injection? i'm surprised to hear that for a 80's design. thats pretty cool.

      i don't think i understand the reasoning for the cs being 2x accuracy

      i would appreciate any references you have to existing systems which use crank acceleration. i just wanted the peace of mind to assemble parts without having the spectre something like this in the back of my mind:

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      • #4
        well now that I think about it again you are correct that the sensor would actually have higher resolution on the crank because it has 2x the reference points per engine cycle...

        I still feel phasing could be achieved by referencing a cam lobe with a hall effect sensor

        or make a cover for the CAS and place a sensor back there with a dowel sticking out of the end of the cam or something...

        I can't find the crank rate of accel stuff it was on the diy-efi.org mailing list a couple-5 years ago,

        I was under the impression that the MS only had 2 inj. drivers and had to fire batch?

        I'm strictly assuming the SR20 had sequential injection from the factory...but I can't reason having 4 coil drive circuits and only 2 injector drive circuits
        I am SKULLWORKS

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        • #5
          All Nissan ECUs from that time period are sequential injection. I think even CAs were.

          I think pretty much every import engine was there by then, and every domestic engine by the mid 90s (not sure why they lagged on some engines).

          MS3 or whatever it's called will do sequential injection, but it's pretty pricey. Very close to used AEM EMS territory.
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