NA Bolt in trigger wheel upgrade
#1
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Bolt in upgrade trigger wheel for the NA. We originally designed these for KA24 and SR20 Nissans, but wouldn't you know that the Nissan CAS and Miata CAS use the same size shutter wheel.
This won't magically remove timing error caused by belt stretch or cam twist under load, but it will provide for better resolution than the factory wheel can. Compatible with MegaSquirt or any other programmable ECU. It's definitely not going to work with your stock ECU. The CKP ring can be set up as a 12-1 wheel at crank speed, and will allow for batch fuel and wasted spark ignition. This eliminates the need for a 2nd tach input if you plan to run batch. The CMP wheel has 1 tooth to enable sequential fuel and/or ignition as desired.
http://www.diyautotune.com/catalog/n...4de-p-472.html
Note that the CKP ring is the *inner* ring on this wheel, and the CMP wheel is on the outer ring. Please wire your harness accordingly.
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As a speculative observation, the combination of this wheel plus the stock '96-'97 crankwheel and sensor (with the removal of two of the wheel teeth) would seem to allow full sequential operation on any 1.8 NA, plus the added benefit of decreased timing error from the elimination of belt stretch.
Very cool stuff, Ben.
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Thanks Joe.
Interesting point, but I'm not sure if a 2 tooth crank wheel would actually be more precise than a 12 tooth cam wheel. Could make for an interesting experiment.
Interesting point, but I'm not sure if a 2 tooth crank wheel would actually be more precise than a 12 tooth cam wheel. Could make for an interesting experiment.
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It drops into your current CAS. I'm pretty sure the stock Miata CAS has CKP on the outside and CMP on the inside, so you'll need to switch those 2 wires on your adapter board. Then change your tach input in software from 4G63 to toothed wheel. Your trigger wheel settings are dual wheel, 12 tooth main wheel at crank speed with 1 missing tooth.
If you're not running sequential, you can set the trigger wheel for single wheel with missing tooth instead of dual wheel. The CMP ring is only needed for sequential.
If you're not running sequential, you can set the trigger wheel for single wheel with missing tooth instead of dual wheel. The CMP ring is only needed for sequential.
#7
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I may be missing something, but that doesn't look like it will bolt into this:
http://forum.miata.net/vb/showthread...=387335&page=2
I know their are actually 2 different NA CAS's, one magnetic and one optical, but I think they both use the style of 'wheels'.
http://forum.miata.net/vb/showthread...=387335&page=2
I know their are actually 2 different NA CAS's, one magnetic and one optical, but I think they both use the style of 'wheels'.
#8
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It drops into your current CAS. I'm pretty sure the stock Miata CAS has CKP on the outside and CMP on the inside, so you'll need to switch those 2 wires on your adapter board. Then change your tach input in software from 4G63 to toothed wheel. Your trigger wheel settings are dual wheel, 12 tooth main wheel at crank speed with 1 missing tooth.
If you're not running sequential, you can set the trigger wheel for single wheel with missing tooth instead of dual wheel. The CMP ring is only needed for sequential.
If you're not running sequential, you can set the trigger wheel for single wheel with missing tooth instead of dual wheel. The CMP ring is only needed for sequential.
I know their are actually 2 different NA CAS's, one magnetic and one optical, but I think they both use the style of 'wheels'.
I assume that setting base timing is still the same: lock at 10 degrees and rotate CAS until on target?
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EDIT:
from a thread on m.net:
"the earlier CAS is an optical unit that reads holes punched in a disk while the later unit is magnetic based."
I've got one of each, if yall want to ship me a disk I'll certainly check if it fits in a 1.6 cas
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Edit2:
from DSM thread ( http://forums.turbobricks.com/showthread.php?t=224740 )
I bet the sensors are the 'same deal', and since I have 2, I can tell you that the 1.6 looks like the optical type from this page (from the outside anyway)... and the 1.8 looks like the 'hall effect' version from that page (based on the back covers, 1.8 has the convex bump on it) I can also tell you 100% that they swap back and forth (I've run my 1.8 car with the 1.6 CAS in it)
So, does this make 1.6 CAS's more valuable to us?
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Last edited by ianferrell; 05-13-2011 at 02:04 PM.
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This plate would not be compatible with a hall-effect style CAS.
I only have a single datapoint here, but I do know that the CAS which was installed in my '92 when I bought it was of the hall-effect style. I don't know with certainty whether it was the original unit, however the vehicle had less than 50,000 miles on it when I purchased it and there was little evidence of any maintenance having ever been performed on it, so I suspect that it was the original unit.
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Odd, maybe they interchanged them ***** nilly? Is it possible there was a TSB at some point and mazda replaced optical ones with hall units? The hall units are thought to be more reliable as they don't have LEDs that can go bad. (rare we all know, but it can happen)
My brothers 93 had the optical CAS in it (the spare '1.6 cas' that I have)
My brothers 93 had the optical CAS in it (the spare '1.6 cas' that I have)
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Of course, God only knows what the service history is on that vehicle. The engine is a shortnose, but I've absolutely no idea whether it's original.
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This is what the inside of the optical CAS looks like with stock shutter wheel.
![](http://fixjunk.com/solomiata/solomiata2/Miata16CAS.jpg)
This is the later hall effect CAS. It has a domed back. Our shutter wheel is not compatible.
![](http://fixjunk.com/solomiata/solomiata2/Miata18CAS2.jpg)