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Old 06-17-2019, 06:06 PM   #16
Austrianvespaguy
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My screenshot is of the composite log instead of the tooth log, so that's why it looks a little different. The red graph along the bottom is the de-sync counter. Next time I fire up the car I'll grab a tooth log for comparison, but basically it'll show the missing teeth section as being too tall of a bar and then only one too few short bars in between.
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Old 06-17-2019, 06:25 PM   #17
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Oh and to the OP, your graphs certainly look like your problem is not seeing the missing teeth gap properly (sorta opposite my problem), but for this the 18k (or 10k) resistor in series with the VR+ wire should be the first fix you try if you haven't already!
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Old 06-17-2019, 06:55 PM   #18
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Here's my tooth log. You can see the extra long gap in the middle that's then only followed by 57 instead of 58 teeth. Also, this problem seems to worsen as engine temperature increases, which I really can't explain. Revs fine to redline dead cold (though I don't like to do that!) Here it's about 190 and cutting out around 6000 RPM, and fully warm around 210 it cuts out at 4500-5000 RPM.
Hmm, attachment not working, so here's a link to the screenshot:
https://drive.google.com/open?id=1uC...Yogu-rwSgjyIWz
On a final note, is the small wave along the normal teeth just a bit of runout on the wheel itself?

Last edited by Austrianvespaguy; 06-17-2019 at 07:19 PM.
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Old 06-17-2019, 10:10 PM   #19
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I was under the impression that the resistor on the board was 25k, but after reviewing the schematics realized it was actually only 5k. I added a 10k resistor and that seems to have fixed the issue with the CPS.


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Old 06-18-2019, 04:11 AM   #20
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Good stuff! Glad we were able to get you're solved! Now if I can just figure out my issue. . .
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Old 06-18-2019, 06:57 AM   #21
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Quote:
Originally Posted by Austrianvespaguy View Post
Here's my tooth log. You can see the extra long gap in the middle that's then only followed by 57 instead of 58 teeth. Also, this problem seems to worsen as engine temperature increases, which I really can't explain. Revs fine to redline dead cold (though I don't like to do that!) Here it's about 190 and cutting out around 6000 RPM, and fully warm around 210 it cuts out at 4500-5000 RPM.
Hmm, attachment not working, so here's a link to the screenshot:
https://drive.google.com/open?id=1uC...Yogu-rwSgjyIWz
On a final note, is the small wave along the normal teeth just a bit of runout on the wheel itself?
Since yours is temperature dependent I would consider that it could be the toothed wheel itself. It is mounted on a rubber damper that degrades over time. When your car is running does it look like the toothed wheel has a lot of run out? Have you tried other/new CPS's? Have you ohm tested yours both at the sensor and at the 55 pin connector?
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Old 06-18-2019, 11:25 AM   #22
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Ah, I didn't realize it was mounted to the rubber part of the pulley, good call! I have checked it's resistance (575 ohms at the sensor connector) but I'll verify at the 55 pin connector also. My gap is pretty small, about 0.5mm and no I don't really see much runout, but I do see what I think is a very small amount in the tooth logger.
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Old 06-19-2019, 06:16 AM   #23
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Well a little more info for the general knowledge-base here; I'm using the DIYPNP board w/Microsquirt card, and it has TWO different VR signal conditioners on it. The Microsquirt uses a MAX9926 chip, and the DIYPNP board has an extra optional LM1815 chip. The MAX9926 wants the ~10k resistor on the input for noise reduction, and the LM1815 wants the ~18k ohm resistor on the input to lower the current that it needs to sink. I made the small mistake of installing the 18k resistor with the MAX9926 circuit, and I think it was blocking too much of the signal. Just switched down to the more proper 10k, and things are certainly improved. I'm not closing the book on this one just yet, only tested briefly and think I still dropped once or twice at redline, so might go with an even lower resistance, but looks like I'm on the path to improvement now!
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Old 06-19-2019, 11:25 AM   #24
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I HAVE SOLVED THIS FOR EVERYONE!!!
But the solution varies depending on exactly which Megasquirt setup/VR condition circuit you have, so make sure you understand this! @Malcolm206, as I understand it you're using MICROsquirt v3, and if that's correct, you are not done yet! So here's the rundown:

1.) If you are using an LM1815 chip for as your VR conditioner (found as an optional extra on some PCBs such as the DIYPNP), then you want the 18k resistor in series with the VR+ sensor wire (to limit the current that the IC needs to sink).

2.) If you are using MEGAsquirt 3.0 or 3.57, then you want the 10k resistor in series with the VR+ sensor wire (to filter out noise at higher RPMs).

3.) If you are using MICROsquirt, then you want a 10k SHUNT resistor that goes BETWEEN the VR+ and VR- sensor wires! (<- This really solved my problem and is the proper setup for the MAX9926 chip on the Microsquirt board)! See page 47 of the Microsquirt Maunal here!
http://www.msextra.com/doc/pdf/Micro...rdware-3.3.pdf

Malcolm and DigitalWave, I'd suggest you double check which VR condition circuit you are using; if you have the white Mirosquirt daughter card that looks like this:
http://www.microsquirtmodule.com/mic...V2.2_front.jpg

THEN YOU NEED THE SHUNT RESISTOR IN SOLUTION 3!!!
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Old 06-19-2019, 11:35 AM   #25
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There are a variety of resistors that will "work." I doubt this will solve everyone's problem, as there are a lot of reasons it could be happening.

FWIW once I replaced my CPS with a new metal one it fixed my issue. I can and have used a 10k, 18k, 20k, and 25k resistor and all of them worked fine with the new CPS. My MS is Microsquirt-based.
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Old 06-19-2019, 11:54 AM   #26
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So yes there are various combinations that can probably made to work, but I now completely understand these circuits and can assure you that using a single inline resistor with the Microsquirt VR conditioning circuit is just plain WRONG (even if it 'works'). The reason for this is the MAX9926 chip uses differential input, meaning that it's looking at BOTH the VR+ and VR- signals relative to each other and NOT relative to ground (aka single-ended input, which is how the LM1815 works). So putting extra resistance on one signal and not the other will skew the zero-crossing reading, which is bad. The shunt resistor between the two wires keeps both signals 'even' but still drops the peak voltage generated at higher RPM speeds.
Also the MAX9926 chip is really the best of the bunch; so if you set it up correctly with the shunt resistor, it WILL work for everybody with that setup, and it will take out the touchiness of individual sensors, air gaps, etc. It's a really robust circuit; not that you want to bother, but with the shunt resistor I'll bet you it would also work perfectly with your OLD sensor too!

EDIT: And Malcolm was really on the right track at first by bridging the SB2 on the board to use its built-in shunt resistor, but I suspect that 5k resistor is intended for 'other' trigger wheels and the 60-2 wheel needs the 10k resistor as indicated in the Microsquirt manual. Re-reading Malcolms last post, I think he has done things correctly by putting in a 10k shunt resistor in place of the 5k, but hopefully he'll confirm this for us!

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