AdamSM33

Quick question, is there a way to wire the cam sensor from the 1999 to adapt to the 95 camshaft sensor on the back of the motor? I'd like to keep the clean look of the exposed cam gears.

Joe Perez

iTrader: (8)

If you are running the stock '99 ECU, then you must run the '99 cam sensor.













































































































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Well, technically I suppose that if you have access to a waterjet table or a laser cutting machine you could fabricate a custom plate for the '95 CAS to emulate the rather unusual pattern of the camgear on the '99 motor.

But apart from that, no.

AdamSM33

Hmm...that was another issue I was having. Will the '99 cas even pick up the '95 adjustable cam gears?

Joe Perez

iTrader: (8)

Adjustable cam gears were not stock on the '95 engine.

Assuming you mean aftermarket cam gears, then the answer is yes if they specifically incorporate NB-style timing bumps, and no if they do not.

blindboxx2334

iTrader: (1)

I also have a question pertaining to this:

Ive got a very slow 1.8 build goin on right now and i plan on putting it on my 00 once its done. I plan on using the 1.8 na one. To also have sweet sweet exposed cam gears. Is there anything differnet that has to be done to the diyms to make it play nice with the cam sensor? The nb one is 3 wires and the na one is 4 wires.

Joe Perez

iTrader: (8)

The NA ('90-'97) CAS is actually two sensors in one, which is the reason it has four wires: Power, Ground, Signal 1 (CMP) and Signal 2 (CKP). There are two basic styles (one uses a flat plate with holes in it and optical sensors that shine through them, the other uses two rotors and magnetic sensors) but the fundamental idea is the same.

One of the signals (CKP) gives four evenly-spaced pulses per cam revolution, corresponding to two pulses per crank revolution, or one pulse per ignition event. This signal is functionally analogous, therefore, to a crank sensor. The other signal gives two unevenly-spaced pulses per cam revolution, and is thus the "cam signal" as it is used to determine the phase of the engine by the position of the camshaft, but is not used to derive precise timing information.

At left, you can see the inside of the optical-style sensor, to visualize how the two sets of slots are arranged. The outer set is the CKP set, you can see three of the four slots, The inner ring is the two uneven CMP slots.




Now, on the NB, you have two separate sensors- one on the cam, one on the crank. Each has three wires (power, ground, signal). Together, these two sensors give essentially the same information to the ECU as the NA's one CAS, although the patterns are different and they are thus non-interchangeable.

Any MS built with the MS1 CPU can use only the NA-style CAS, as it lacks the computational muscle to decode the NB's pattern, which is more complex. Any MS built on the MS2 or MS3 CPUs can use either the NA-style CAS or the NB-style crank and cam sensors.

It is preferable to use the NB-style sensors when possible. In particular, the fact that the crank sensor reads a plate rigidly coupled to the crank itself, rather than a spinning disc on the end of a cam which has a somewhat stretchy belt in between it and the crankshaft, means that timing is more stable with the NB crank sensor.

blindboxx2334

iTrader: (1)

thank you for that explanation. i know the NB sensors are better. but what about using the TSE 12t trigger wheel with a modified CAS? will that help make the timing more accurate?

https://www.miataturbo.net/trackspeed-engineering-miata-accessories-85/trackspeed-engineering-12-tooth-crank-trigger-wheel-49814/

im still going through that thread. but from what i understand:
-buy the 12t trigger
-you need a 96-05 crank pulley, not the 94 & 95 ones.
-NA guys can find the connector "from a driver side power door lock from a NB"
-modify your na cas. (still not sure how to do)


also that leaves me one more question. which would be better to use? 90-93 CAs or the 94-97 CAS?


edit:****, i guess now i can use a differnt type of sensor (hall sensor?) so i dont even need the CAS. this ***** too confusing for me. i know nothing about electrical. i guess i need to read more. and ill worry about it more when the time comes i guess. i just dont wanna be buying the wrong ****. since i do plan to buy a CAS soon.... or since i cant go another route (hall sensor), i guess not??

Joe Perez

iTrader: (8)

If you cut one tooth off of a 12t wheel, (making it a 12-1 wheel) then you can run with no cam sensor at all in batch-fire mode. This is how I set up my '92. The only thing adding a cam sensor gets you is the ability to run full sequential spark and fuel (and only on the MS2 / MS3) which IMO is fairly trivial compared to the enhanced accuracy of a crank-triggered system.

soviet

iTrader: (10)

For the second option (full sequential spark & fuel), you need to modify your CAS, correct?
Also I believe the crank sensor came on OBD2 cars, not just NBs. Because my 96 definitely had one along with a timing disk & thinner pulley boss.

Finally, the crank position sensor bolts right up to any 1.8 block because the mounting hole is there. Just might be covered in layers and layers of dirt.

blindboxx2334

iTrader: (1)

Ah, i see. Sounds cool. Maybe ill have to go that route instead. One less thing to fail on my build.... Right?

So you just use an oem miata crank sensor with the trigger wheel? It sounds nice and simple. I like.


And soviet, iirc from what i was reading earlier in some of the threads, the na blocks have the hole, you just have to tap it.

Joe Perez

iTrader: (8)

You need some kind of cam signal to run full-sequential, yes.

If using a "generic" wheel (eg: 36t, 12t, etc) then to the best of my knowledge, the cam signal must be one pulse per revolution. Those settings which allow other styles of cam signal (eg: 4G63, 99+ Miata, etc) are all hard-coded in the software for those specific applications.

It's entirely possible that this has changed with the MS3- I honestly know very little about the software on it.

But going back to where blindboxx2334 came in, he has a couple of obvious options:

1: Use an unmodified NA CAS. (bleh.)

2: Use a 12t wheel with one tooth removed and run in batch mode.

3: Use a 12t wheel with all teeth intact, and add a cam signal by either modifying the plate inside an NA CAS or physically grinding two of the three raised bumps off of the intake cam pulley (this assumes he us using a stock or stock-like pulley and not cutting away the part of the valve cover which holds the sensor.)


The '96-'97 cars did come with a crank sensor, however both the sensor itself and the toothed plate which it reads are different from those found in NBs.

The NB sensor gives an open-collector squarewave output just like the NA CAS. You know this already, I assume.

The crank sensor used in the '96-'97 models, by comparison, was a raw VR sensor (two wires) which output a differential AC waveform. It was also physically somewhat different, and I believe that it mounted to the engine in a different location (I won't swear to that last bit, as I have only ever worked on one '96 engine)

The two are in no way compatible or interchangeable, although with the removal of two teeth (and the addition of a one-pulse-per-rev cam signal), the stock '96-'97 crankplate and sensor could be used with a Megasquirt, and I assume that the 12t wheel would also work with the '96-'97 sensor, albeit with the aforementioned qualifications.




I haven't personally run the 12t wheel that's recently become available- on my own build, I used an EDIS-style 36-1 wheel and fabricated a mount for it and the sensor.

But yes, it's my understanding that the 12t wheel is intended to be used with an OEM-style NB crank sensor.