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Tips For Starting Up A Rebuilt Engine With Sniper Efi

Discussion in 'Early CJ5 and CJ6 Tech' started by truckee4x4, Oct 9, 2021.

  1. Oct 28, 2021
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor 2021 Sponsor 2020 Sponsor

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    You have to know what the computer is doing with the trigger signal to say anything about this. You could use the tach signal if the computer were time-averaging the tach signal over more than two pulses (ala Megasquirt). If the computer looks at the the time between pulses, that goes back and forth between two values, neither of which are correct for the speed of an even fire six cylinder engine.

    Certainly if your computer can be programmed to accept a certain number of VR triggers per rotation, there is advantage to more up to a point. On a purely signal-to-noise basis, averaging a noisy signal (your pulses) reduces the effect of the noise by the root of the sample increase. So comparing 3 pulses to 36, the noise will be reduced by 1 - sqrt(3/36) = 71%. This may or may not be significant, depending on the strength and accuracy of your VR pulse signal. At some point, I'd expect the notches are so close together that the VR pulses are degraded.
     
    Last edited: Oct 28, 2021
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  2. Oct 28, 2021
    truckee4x4

    truckee4x4 Grant Kaye 2022 Sponsor 2021 Sponsor 2020 Sponsor

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    Cheers Ed thanks. That was my initial impression but I am still earning about all of this so I'm not quite confident enough to make any bold statements about what I think is happening.

    BTW here are the Holley directions for their generic trigger wheel:
    hly-556-125.pdf (summitracing.com)
     
    Last edited: Oct 28, 2021
  3. Oct 28, 2021
    Steve's 70-5

    Steve's 70-5 Active Member 2020 Sponsor

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    On my FiTech EFI, for the v-6 engine you programmed in 3
     
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  4. Oct 28, 2021
    skipilot

    skipilot New Member

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    Truckee, in the Holley instructions you posted it refers to crank “speed and position”. As I understand it (admittedly in a limited way since I have not deeply explored this system) the Sniper has the ability to control timing with the proper distributor, hence the need for accurate position data. Since you are only controlling fueling, all you should need is speed data and the 3 trigger concept others have used should suffice. It is the odd-fire nature of the engine that requires you to come up with the trigger system at all. If it was an even fire, the tach signal (3 evenly spaced per crank rotation) would work just fine. Now if you’re thinking about eventually having it control timing, that would be cool but a lot more complicated. I like your jumping into and documenting your Sniper install. It will be a valuable thread for others.

    Tim
     
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  5. Oct 28, 2021
    truckee4x4

    truckee4x4 Grant Kaye 2022 Sponsor 2021 Sponsor 2020 Sponsor

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    Thanks Tim. (You can call me Grant, that’s my first name….).
     
  6. Oct 28, 2021
    Jw60

    Jw60 Member: Club Foot Dad Club. 2022 Sponsor 2021 Sponsor 2020 Sponsor

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    I like the trigger wheel approach but as I understand the resolution of the trigger only needs to be as fast as the pcm can make use of it.
    I've primarily focused on the 4.3 and it only went to a crank trigger when the computer processing speed increased from the 1990s tbi to later mpi is when it gained the crank trigger then it went to even higher resolution on later v8s. This resolution is of high value with ignition control. but even on fuel only it will be better than 3 nodes or ignition pulses from the distributor as the engine speed may change rapidly due to load input and output forces from the driveline. we aren't really pushing the limits of the computer at 5k rpm but i would want to find a solid signal so mud and such on the pickup isn't a drivability concern
     
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  7. Oct 28, 2021
    Norcal69

    Norcal69 Out of the box thinker 2022 Sponsor 2021 Sponsor 2020 Sponsor

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    As long as you can input the number of cylinders and number of teeth on the wheel it seems like a good way to go.
     
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  8. Dec 12, 2021
    truckee4x4

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    OK I took the pulley off and had a lightbulb moment - why not just reproduce the spacer disk between the balancer and the pulley?

    CAAE8142-F875-4EDA-976E-3A41EF77DC32.jpeg

    I measured it and drew up a sensor disc to take its place.

    Went over to roundhouse to laser cut a wooden prototype to check the fitment but someone had the laser booked all day so I didn’t get a chance to make one. I might skip that and cut one on the CNC plasma tomorrow out of some scrap 14 gauge, and see how it looks and then make the sensor bracket as well. Then I can fiddle with the designs to make sure I have the right clearance, and then get the actual disc laser cut in steel from sendcutsend.com, and cut the sensor bracket from aluminum on our CNC.
    B8FCDE8C-064B-4898-819A-CD400B03BC4B.jpeg

    Gut check - can anyone think of a reason why this won’t work out in terms of balance or other issues?
     
    Last edited: Dec 12, 2021
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  9. Dec 12, 2021
    Jw60

    Jw60 Member: Club Foot Dad Club. 2022 Sponsor 2021 Sponsor 2020 Sponsor

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    If you are worried about balance due to a Master tooth or something I would just take some meat out of the wheel halfway out and whatever math works out to be equivalent (2x but don't hold me on math)
     
  10. Dec 12, 2021
    truckee4x4

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    Good idea. I’ll probably add a bunch of evenly distributed holes to cut down on the weight.
     
  11. Dec 13, 2021
    Fireball

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    This is awesome. It should work fine. It doesn't seem like you could be out of balance enough to cause any issues.
     
  12. Dec 13, 2021
    Fireball

    Fireball Well-Known Member 2022 Sponsor 2021 Sponsor 2020 Sponsor

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    Something tickled the back of my mind after posting that. It's not a spacer. It goes *inside* the pulley as a reinforcement:
    [​IMG]

    You can see the witness marks from the lock washers on your picture. Those wouldn't be there if it was sandwiched between the pulley and the damper.

    Note it's called "reinforcement" not "spacer": https://www.chicagomusclecarparts.com/products/copy-of-crank-pulley-v8-3-groove-ac-used-67-70-buick

    If you put it behind the pulley, your belt alignment will be off so your plan won't work without spacing the water pump pulley and alternator forward.
     
  13. Dec 13, 2021
    truckee4x4

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    Edit - nevermind I looked at the pulley and the disc and see how they fit - I installed them backwards with the disc between the pulley and the balancer. Dangit I thought this was an easy solution.

    Dug out some pics from before teardown and sure enough you are correct - pulley is against the face of he balancer:
    3SH76T4qRQ2+PPQrnoJ2Ww_thumb_2fed.jpg

    There's still room for a sensor disc but it will have to attach directly to the balancer via the ~1/2" holes that are already there around the outside. My balancer will need to be filed down as well as there are some lips around these holes. And - i have to re-paint it too - the POR-15 came off and/or pulled off the Green paint from the balancer. Can of worms!
    UNADJUSTEDNONRAW_thumb_858e.jpg
    Measuring the balancer accurately enough to get this to work will be a challenge. Both of the two spare balancers I have are not the same as the one on my engine....
     
    Last edited: Dec 13, 2021
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  14. Jan 4, 2022
    truckee4x4

    truckee4x4 Grant Kaye 2022 Sponsor 2021 Sponsor 2020 Sponsor

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    Ok wanted to post a progress update here. Thanks to members who sent their balancers to me, and also to me remembering what a transfer punch is for, I managed to FINALLY get the sensor wheel geometry designed properly for my balancer.

    16908FB9-729B-4284-8574-5F3EBFD2F0DA.jpeg
    I’m going to send out to sendcutsend.com down in Reno for a steel laser CNCed sensor wheel, and this weekend I’ll machine the sensor bracket from 1/4” 5056 aluminum at the Roundhouse.

    good step in the right direction. Will report back when I have all the final parts fitted up.
     
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  15. Jan 11, 2022
    truckee4x4

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    Parts came in, looks like it just might work! TBD if I will have to add a spacer to bump the sensor bracket out for more adjustability (or find a thinner jam nut).
    09C3AEE0-8BF6-4D04-9F83-C72DED37EEA9.jpeg
    3781EE8D-FF3E-4965-AE1F-C4B8B0F9A6A5.jpeg
    4CE05559-904B-46DB-A9D9-849C07A229F2.jpeg
     
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  16. Jan 11, 2022
    Rich M.

    Rich M. Shoe salesman

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    That is ufb cool! Following closely
     
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  17. Jan 11, 2022
    Jw60

    Jw60 Member: Club Foot Dad Club. 2022 Sponsor 2021 Sponsor 2020 Sponsor

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    I'ld put the bracket in a vice and bend the slotted ear out 10°or so before hunting for spacers and jam nuts.
     
  18. Jan 11, 2022
    truckee4x4

    truckee4x4 Grant Kaye 2022 Sponsor 2021 Sponsor 2020 Sponsor

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    I might just get lucky...the specs from Holley call for 40-80 thousandths between trigger teeth and sensor for optimum pickup. If anything I might make another bracket out of 1/4" 5052 instead of 1/8" as this one flexes easily. It was $4 so no big deal. Cost me $30 for both.

    Their laser CNC cutter left some slag that I have to clean off and the bolt holes aren’t perfectly round. See how this prototype goes and if it works well enough, great. If not then I can adjust the design and maybe try a water-jet cut trigger wheel. B039BCC7-A0AE-4F34-A718-64DAAD3E3D7B.jpeg
     
  19. Jan 11, 2022
    Fireball

    Fireball Well-Known Member 2022 Sponsor 2021 Sponsor 2020 Sponsor

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    Now you need to go into business selling them to forum members.
     
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  20. Jan 11, 2022
    truckee4x4

    truckee4x4 Grant Kaye 2022 Sponsor 2021 Sponsor 2020 Sponsor

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    Well let’s make sure that it works first! If so I’ll write up a thread with all the part numbers and directions and what not in case anyone’s interested.

    Some of the guys on the Holley forums thought a trigger wheel with three nodes would yield better results than one with 35...so this prototype might get modified with the belt sander.
     
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