OEM 36-1 Wheel
02-03-2014, 11:50 PM
#43
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Ah you just reminded me, I've got an aftermarket pump for 1.6 laying around:
It looks like you are right about it being untapped. M6 is the correct size I'm guessing? I hope that hole is there on my OEM pump to make things easy.
It looks like you are right about it being untapped. M6 is the correct size I'm guessing? I hope that hole is there on my OEM pump to make things easy.
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09-24-2014, 02:16 AM
#46
I pulled this from an old email, maybe it will help.
CAS is a cam angle sensor that's mounted on the exhaust camshaft at the back of the head on 90-97 miatas. The exhaust camshaft has 2 notches on it where the CAS fits. Inside, are 2 trigger wheels, one with 2 teeth and one with 4. The 4 teeth is the crank signal and the 2 teeth is the cam signal (one tooth is bigger than the other).
By simply cutting off some teeth inside the CAS you can turn it into a "1 signal per cam revolution" that Megasquirt needs.
None of this is relevant to you. For NBs the crank and camshaft signals are already separated. The cam signal I believe is 2-1 pulse. That is, on the camshaft wheel there are 2 "nubs" on one side and 1 nub on the other. So it goes
_||_________|_________||_________|_________||_____ ____|_________||
If you grind off the 2 nubs you will also end up with the "1 signal per cam revolution", e.g.
____________|____________________|________________ ____|___________
Now for Megasquirt settings. First, I would recommend getting the car to run with JUST the trigger wheel and add the camshaft sensor later. You only need the camshaft sensor to run full sequential. So you will *have* to run wasted spark/batch fuel to begin with. If you already wired for sequential, megasquirt 3 can still handle it - just use "Wasted COP" mode.
For ignition settings
- choose "trigger wheel"
- "Single wheel with missing teeth"
- 36 teeth, 1 missing
- the missing tooth offset, I think, is 90*
Once its running confirm the timing with a timing light and confirm you have the rising edge/falling edge correct. If the timing is not right adjust your missing tooth offset a bit.
After its running in batch mode, to utilize the camshaft sensor, simply enable "Use CAM signal" option. Then you can switch to sequential.
good luck,
-JB
CAS is a cam angle sensor that's mounted on the exhaust camshaft at the back of the head on 90-97 miatas. The exhaust camshaft has 2 notches on it where the CAS fits. Inside, are 2 trigger wheels, one with 2 teeth and one with 4. The 4 teeth is the crank signal and the 2 teeth is the cam signal (one tooth is bigger than the other).
By simply cutting off some teeth inside the CAS you can turn it into a "1 signal per cam revolution" that Megasquirt needs.
None of this is relevant to you. For NBs the crank and camshaft signals are already separated. The cam signal I believe is 2-1 pulse. That is, on the camshaft wheel there are 2 "nubs" on one side and 1 nub on the other. So it goes
_||_________|_________||_________|_________||_____ ____|_________||
If you grind off the 2 nubs you will also end up with the "1 signal per cam revolution", e.g.
____________|____________________|________________ ____|___________
Now for Megasquirt settings. First, I would recommend getting the car to run with JUST the trigger wheel and add the camshaft sensor later. You only need the camshaft sensor to run full sequential. So you will *have* to run wasted spark/batch fuel to begin with. If you already wired for sequential, megasquirt 3 can still handle it - just use "Wasted COP" mode.
For ignition settings
- choose "trigger wheel"
- "Single wheel with missing teeth"
- 36 teeth, 1 missing
- the missing tooth offset, I think, is 90*
Once its running confirm the timing with a timing light and confirm you have the rising edge/falling edge correct. If the timing is not right adjust your missing tooth offset a bit.
After its running in batch mode, to utilize the camshaft sensor, simply enable "Use CAM signal" option. Then you can switch to sequential.
good luck,
-JB
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09-26-2014, 05:40 PM
#48
I talked to DIY a week or two back, they said that the 36-1 + VVT support had been pretty much abandoned due to a lack of perceived gains with doing so.
While I'll be the first to admit that 36 teeth might be more than is needed.... has anyone looked at their jitter with the different wheels?
While I'll be the first to admit that 36 teeth might be more than is needed.... has anyone looked at their jitter with the different wheels?
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09-27-2014, 08:12 AM
#49
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The only real justification I've ever heard for 36t over 4t was from Jason C hypothesizing that a high tooth count wheel will exhibit slightly less predictive error during moments of extremely high transient ∆-RPM.
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09-27-2014, 02:48 PM
#50
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Interestingly the worst case for timing error when you have few tooth is at low RPM. You can think of it as because the sampling rate is low at low RPM. On my AEM FWIW which only effectively times off of 2 teeth with the factory trigger wheel, the error was on the order or 5* when blipping the throttle off idle. When I had 6 effective teeth, it was ~2*. With a 12+1, it was unreadable. Idle got noticeably smoother going from the factory to the 6 or 12 tooth wheel.
The worst case at high RPM I think is when you do a hard upshift and the clutch drops RPM very quickly. The rapid crank deceleration would cause the timing to be over advanced with few teeth.
I would think going from a 12+1 to a 36 tooth wheel would be very return-diminishy.
The worst case at high RPM I think is when you do a hard upshift and the clutch drops RPM very quickly. The rapid crank deceleration would cause the timing to be over advanced with few teeth.
I would think going from a 12+1 to a 36 tooth wheel would be very return-diminishy.
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09-27-2014, 03:02 PM
#52
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There is no difference between the stock 4T and the FM 36-2 with an MS2/MS3.
The spark angle is rock-solid (with a timing light) at idle and when bliping the throttle, up to 5K RPM.
The spark angle is rock-solid (with a timing light) at idle and when bliping the throttle, up to 5K RPM.
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09-27-2014, 03:07 PM
#53
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Did you try the test even at say, a fixed 15* advance? I've found that it's significantly worse when the requested spark event occurs just before a tooth (which is at 10* BTDC for the factory trigger wheel).
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09-30-2014, 02:51 PM
#55
Yeah - that's interesting. I've always had a gut feeling that 12 tooth is the way to go - more than that and you're spending all your time worrying about predictable things anyway. Mine's been reasonable at OEM 4 tooth, but I haven't really beat it up. The CAS was dismal which I blamed on the belt.
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09-30-2014, 09:12 PM
#56
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FM 36-2 with NB cam trigger is supported. 949 Racing 36-1 with NB cam trigger will be supported in the future (when Emilio sends me data captures).
I have a FM wheel on my car. I am unable to perceive a difference in spark timing as compared to the original 4t wheel, nor am I able to perceive improvement in dyno results. I do believe that there is gained resolution with the valve timing with the extra crank teeth however, as I noticed much error in VVT Target vs actual after the install, and had to retune the PID. The Miata's VVT cam trigger is pretty low resolution.
I have a FM wheel on my car. I am unable to perceive a difference in spark timing as compared to the original 4t wheel, nor am I able to perceive improvement in dyno results. I do believe that there is gained resolution with the valve timing with the extra crank teeth however, as I noticed much error in VVT Target vs actual after the install, and had to retune the PID. The Miata's VVT cam trigger is pretty low resolution.
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10-01-2014, 01:28 PM
#58
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There are only so many wheel patterns that it makes sense to support. We already support 2 other patterns with a 3rd coming. Why do we need 4 different Miata wheel decoders? My human eye can not detect a difference between stock and 36-2 crank triggers under any condition.
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10-01-2014, 02:34 PM
#59
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Only because TSE sell a 12+1. I was under the impression it was popular.
Was this blipping the throttle off idle? Was it with the timing set to 15* BTDC so that the requested spark even is *just before* a tooth arrives?
My human eye can not detect a difference between stock and 36-2 crank triggers under any condition.
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