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Old 03-05-2016, 04:40 PM   #1
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Default Getting rid of the cas and coil pack

in my adventure of turbo'ing my Miata I've come to realize the stock coil pack isn't helping me much. to get rid of it, the simple solution would be coil on plugs, correct?

as for the cas, would a crank trigger setup, say like for the NB, replace it? or am I missing something?
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Old 03-08-2016, 02:20 PM   #2
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Nothing like this has been done before. You'll be breaking new ground, and I'm sure a lot of us would be interested in your results. Record your progress and take lots of pics for us.
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Old 03-08-2016, 02:32 PM   #3
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For some reason, I'm feeling generous...


Quote:
Originally Posted by itsMikey View Post
in my adventure of turbo'ing my Miata I've come to realize the stock coil pack isn't helping me much. to get rid of it, the simple solution would be coil on plugs, correct?
Yes. This has been done many times. Some use Toyota COPs, some use GM CNPs, some use kits sold by various vendors with various coils.



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Originally Posted by itsMikey View Post
as for the cas, would a crank trigger setup, say like for the NB, replace it? or am I missing something?
Which ECU are you using?

The NB crankwheel won't help you at all unless you are also running an NB head, since the NB cam sensor needs to accompany the NB crank sensor in order for any ECU to be able to decode the signal.

If you're using a stock ECU, forget it. Unless you want to design, build and program a custom microcontroller so simulate the output of an NA CAS based on some other pattern, it ain't gonna happen. No off-the-shelf solutions here.

If you're using an aftermarket ECU, then there are a bunch of options. Several companies make crankwheels that fit the Miata, and Mazda even used a 36-1 wheel on certain engines (there's a thread about it in the ECU section here) which can be used.
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Old 03-08-2016, 02:40 PM   #4
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Quote:
Originally Posted by Joe Perez View Post
The NB crankwheel won't help you at all unless you are also running an NB head, since the NB cam sensor needs to accompany the NB crank sensor in order for any ECU to be able to decode the signal.

If you're using a stock ECU, forget it. Unless you want to design, build and program a custom microcontroller so simulate the output of an NA CAS based on some other pattern, it ain't gonna happen. No off-the-shelf solutions here.

If you're using an aftermarket ECU, then there are a bunch of options. Several companies make crankwheels that fit the Miata, and Mazda even used a 36-1 wheel on certain engines (there's a thread about it in the ECU section here) which can be used.
Can B series engines run off just a crank trigger? Batch fuel and spark? Or sequential.
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Old 03-08-2016, 02:44 PM   #5
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Quote:
Originally Posted by aidandj View Post
Can B series engines run off just a crank trigger? Batch fuel and spark? Or sequential.
B engines can run off of crank alone in batch mode, but not on a stock NB crankwheel. They need a wheel with a distinctive once-per-rotation feature (typically a missing tooth), whereas the NB crankwheel has four teeth, spaced out in two equal groups.

Last edited by Joe Perez; 03-08-2016 at 03:23 PM. Reason: "but," not "nut."
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Old 03-08-2016, 02:46 PM   #6
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Interesting.
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Old 03-08-2016, 02:46 PM   #7
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Quote:
Originally Posted by itsMikey View Post
in my adventure of turbo'ing my Miata I've come to realize the stock coil pack isn't helping me much.
it's actually helping you quite a great deal, without it, the car wouldn't run.

Quote:
as for the cas, would a crank trigger setup, say like for the NB, replace it? or am I missing something?
why bother?
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Old 03-08-2016, 03:14 PM   #8
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Quote:
Originally Posted by aidandj View Post
Interesting.
Why is it interesting? This is a universal truth for all even-fire, spark-ignition piston engines.

In order to run on only one trigger input (eg: a crankwheel) the ECU has to be able to determine the absolute position of the crankshaft. It needs to be able to tell when #1 is at TDC, and when it's at BDC.

A crankwheel with all evenly-spaced teeth gives you an ambiguous indication in this regard. Taking the stock NB wheel as an example, it'll tell you that some piston is at TDC, but not which one. In most present-day applications, a cam sensor is used to give a pulse which tells the ECU "the next time you see an indication from the crankwheel that a piston is at TDC, that'll be the #1 piston, and it'll be at TDC on the beginning of the intake cycle," or something like that.

You can get away with not using a cam sensor if you're willing to run wasted spark and batch-injection. You do this with a missing-tooth wheel. When the ECU sees the missing tooth pass by it knows "#1 is approaching TDC." It doesn't have enough information to know whether that's #1TDC on the exhaust/intake transition, or #1 TDC on the compression/ignition transition, but this doesn't matter for batch-injection and wasted-spark, since it's going to do the same thing (fire the plug and open the injectors) either way.
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Old 03-08-2016, 03:15 PM   #9
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Just interesting to me. Learn something every day. I figured it would have to be a missing tooth wheel.
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Old 03-08-2016, 03:45 PM   #10
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Maybe we can dredge more info out of this thread.
You know, in order to help the OP hah.

How far can the na6 ignition system go?
On a stock piston vvt motor (with crank and cam sensors), I'm at 150kpa with a base pressure of 85kpa and have seen as low as 11.0:1 afr's during tuning at full tilt in 3rd/4th.
No issues....
Dwell is at whatever the ancient diyautotune recommendation was for the na6.
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Old 03-08-2016, 04:18 PM   #11
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Quote:
Originally Posted by leboeuf View Post
How far can the na6 ignition system go?
Typically they can go at least .030", sometimes more.
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Old 03-09-2016, 11:32 AM   #12
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Quote:
Originally Posted by leboeuf View Post
How far can the na6 ignition system go?
It varies how well stock coils will work for you. Most people don't have any issues with stock coils ever as long as they are on a stock motor. On my 94 I started getting spark blow out on the dyno around 10psi. I have seen other people run 300whp with stock coils and zero issues.
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Old 03-09-2016, 01:32 PM   #13
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On my '99, when I had the leaky waste-gate actuator, I got to 12psi at 7K RPM, with no trouble on the stock coils and .036" (IIRC) gaps. I want to go to COP's simply to get the coil packs out of the way of the coolant re-route, and so that I don't have to replace the expensive buggers at an in-opportune time (in other words, for reliability). Sequential spark should be a plus as well, but I'm not sure on how much.
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