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Old 10-16-2011, 08:56 AM   #1
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Default High(er) Res Crank Trigger Wheel

Hi guys,

I have a 93 Miata that I will eventually be turboing. In the meantime, I am going to convert it over to run on a standalone system and get all the bugs out first. The standalone I will be using will be similar to a PROEFI

In any case, I am researching options for crank trigger wheels. I have done some searching, and have found the few people on MT that have made their own adapters. Looks like some have adapted EDIS wheels, while others have taken a mill to the stock 96 and up crank trigger wheel and cut their own teeth, and still others have used a DIYAUTOTUNE wheel with a custom machined adapter.

Here is my criteria:
- At least 12 teeth although more is desirable. 36-1 would be best. The ECU has a limited list of possible teeth patterns that will work.
- Able to fit on the crank nose somewhere - using some sort of adaptor maybe?
- Does not require machining - as I don't have a mill or lathe at my disposal.
- Can be Welded on, but I'm worried about lateral runout and my ability to minimize it.
-I will weld up some sort of custom bracket for the speed sensor (will probably be a hall effect sensor).

So far, based on my criteria, I have narrowed it down to:

The trackspeed engineering 12 tooth crank wheel.
Trackspeed

So, I have a few questions:
-Am I missing anything cheaper and/or easier than this? Also, would prefer more teeth.
-Does anyone sell an off the shelf adaptor to use a DIYAUTOTUNE wheel with a miata?
-Will the trackspeed wheel work with a stock 93 crank pulley? If not, and I have to use a 96 crank pulley, what do I do about the v belt versus multirib? I don't have power steering or AC, so just the water pump and alternator to worry about.

Any help / advice would be appreciated.
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Old 10-17-2011, 07:25 PM   #2
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I honestly don't think more than 12 teeth will buy you much.

Just get the TSE wheel.
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Old 10-17-2011, 07:32 PM   #3
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I've never seen an off-the-shelf solution to mount a 36-1 wheel on a Miata. When I did mine (using the DIY 4" wheel) I had to lathe my own adapter and weld up a custom sensor mount. Details on that here: https://www.miataturbo.net/megasquirt-18/wheel-timing-success-last-20241/



(Ignore the bolt in the middle- it just gave me a place to put a wrench to turn the crank by hand, and was removed during normal operation.)

Frankly, it was a pain in the ***. Had the TSE wheel been available at the time, I absolutely would have gotten that instead. You'll still have to do just a bit of fudging to get the crank sensor mounted up properly (I'm not sure if the 1.6 oil pumps even have the correct hole for use with the NB or '96-'97 OEM sensors) but it is definitely a much cleaner solution overall.

And I concur with Jason- compared to the massive improvement in going from the stock belt-driven CAS to any kind of crank sensor, the difference in resolution between a 12 tooth wheel and a 36 tooth wheel will be minuscule.
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High(er) Res Crank Trigger Wheel-finishedleftzj3.jpg  
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Old 10-17-2011, 07:51 PM   #4
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On my AEM there was a huge improvement going from factory NB 4-tooth crank trigger wheel, to the TSE 12-tooth. The test was blipping throttle in neutral from idle, with a timing light and the timing set to 10* on the AEM. It went from 6* of error, to zero.
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Old 10-17-2011, 08:11 PM   #5
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That's quite interesting, and something I didn't measure when I did mine.

I was using an MS1, so my 36-1 wheel was effectively being decoded as through it were a two-tooth wheel. My static timing accuracy (eg: holding throttle steady at 6,000 RPM) was quite good- only about 1 of error. I did not, however, test the dynamic accuracy. I would assume my error there would have been similar, and I also assume that the error would always tend to be towards more advance, which is exactly where you don't want it.

Fortunately, the rate at which the engine is capable of accelerating while under load (eg: with a car attached to it via the transmission) is somewhat lower than the rate at which it is capable of accelerating in neutral, though I admit the difference isn't all that much in first gear with a small turbo.
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Old 10-17-2011, 08:13 PM   #6
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Quote:
Originally Posted by JasonC SBB View Post
On my AEM there was a huge improvement going from factory NB 4-tooth crank trigger wheel, to the TSE 12-tooth. The test was blipping throttle in neutral from idle, with a timing light and the timing set to 10* on the AEM. It went from 6* of error, to zero.
I',m looking forward to this with my TSE wheel.
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Old 10-17-2011, 08:29 PM   #7
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Does anyone have an answer for whether the TE wheel will fit on a 93 crank pulley? And, if not, what to do about the v-belt versus multirib?
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Old 10-17-2011, 08:32 PM   #8
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Error was worst at low RPM - the effective sampling rate of crank position is lower. As revs climbed I could see error diminish.

Also the worst case at higher RPM would be a full power upshift without lifting. Sudden drop in RPM would cause timing to advance momentarily theoretically, with a low resolution trigger wheel.
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Old 10-17-2011, 11:01 PM   #9
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Quote:
Originally Posted by Frank_and_Beans View Post
Does anyone have an answer for whether the TE wheel will fit on a 93 crank pulley? And, if not, what to do about the v-belt versus multirib?
The Trackspeed Engineering 12 tooth crank trigger wheel will bolt right onto a 93 crank/pulley.
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