Info Please on Hi-Res (360 + 4, 6, or 8) Optical Cas Wheels

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Subaru_EA82_4EAT_AWD
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Info Please on Hi-Res (360 + 4, 6, or 8) Optical Cas Wheels

Post by Subaru_EA82_4EAT_AWD »

Hi, I am wondering if a few people can chime in here please and help me understand a few things about these optical wheels,

I have A Subaru EA82Turbo engine which I'm looking into Megasquirting, it has a 360 + 4 Optical Cas Wheel.

My questions are these:
  • How does the OE system (1987) use these CAS wheels?
  • How Would Microsquirt use these CAS wheels?
  • How Would MS2 use these CAS wheels?
  • How Would MS3 use these CAS wheels?
This is the particular wheel in question, numbers referring to inner slots are approx. straightline lengths in mm, red line is where pickup is on #1 dtc:
ImageThanks
Want a neat way to Check & Set Ignition timing AND CRANK the motor at the same time BY YOURSELF?
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seishuku
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Re: Info Please on Hi-Res (360 + 4, 6, or 8) Optical Cas Whe

Post by seishuku »

Typically the OEM ECU will catch the leading edge of the inner slots, the count the outer slots until it sees the falling edge of the inner slot... The outer slot count determines phasing, in this case the longer slot = TDC.
In cases where there are coil-on-plug is used, each slot is different, so the computer can tell where it's at with out a full rotation sync.

And of course, the number of inner slots is based on the number of cylinders the engine has.

Nearly all Nissans use this system as well.
Healey3000
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Re: Info Please on Hi-Res (360 + 4, 6, or 8) Optical Cas Whe

Post by Healey3000 »

Hi,

I've done a lot of poking around on these Nissan wheels and the many variants. I have a document that may shed some light (attached)
Nissan Triggers.pdf
jsmcortina
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Re: Info Please on Hi-Res (360 + 4, 6, or 8) Optical Cas Whe

Post by jsmcortina »

I'll have another look at this later in the week.

James
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Subaru_EA82_4EAT_AWD
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Re: Info Please on Hi-Res (360 + 4, 6, or 8) Optical Cas Whe

Post by Subaru_EA82_4EAT_AWD »

Sweet, thanks James.
Want a neat way to Check & Set Ignition timing AND CRANK the motor at the same time BY YOURSELF?
A little thing I made up... https://youtu.be/PajlPNF5mmQ
Subaru_EA82_4EAT_AWD
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Re: Info Please on Hi-Res (360 + 4, 6, or 8) Optical Cas Whe

Post by Subaru_EA82_4EAT_AWD »

I took a better photo of it
Image
Want a neat way to Check & Set Ignition timing AND CRANK the motor at the same time BY YOURSELF?
A little thing I made up... https://youtu.be/PajlPNF5mmQ
Subaru_EA82_4EAT_AWD
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Re: Info Please on Hi-Res (360 + 4, 6, or 8) Optical Cas Whe

Post by Subaru_EA82_4EAT_AWD »

Bump,
What I am trying to find out is how MS(3) handles the 360 + 4 slot wheel, I have heard it only uses the 360 at cranking but I haven't been blessed with a proper explanation yet. If anyone can help with that I would be very greatful...
Want a neat way to Check & Set Ignition timing AND CRANK the motor at the same time BY YOURSELF?
A little thing I made up... https://youtu.be/PajlPNF5mmQ
jsmcortina
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Re: Info Please on Hi-Res (360 + 4, 6, or 8) Optical Cas Whe

Post by jsmcortina »

What kind of explanation do you want?

James
I can repair or upgrade Megasquirts in UK. http://www.jamesmurrayengineering.co.uk

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Subaru_EA82_4EAT_AWD
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Re: Info Please on Hi-Res (360 + 4, 6, or 8) Optical Cas Whe

Post by Subaru_EA82_4EAT_AWD »

Well I'm interested to know go MS uses the hi res wheel?

What I mean is, what does it do differently when it has a decoder to suit the specific wheel and it's 360 outer and 4 inner slots, rather than just using the trailing edge of the 4 inner slots when it doesn't have a proper decoder?

I.E. What is gained from a proper decoder? The OE ECU must have used a hi-res wheel for a reason...

This is a genuine inquiry as I am very keen to properly understand this.
Thanks.
Want a neat way to Check & Set Ignition timing AND CRANK the motor at the same time BY YOURSELF?
A little thing I made up... https://youtu.be/PajlPNF5mmQ
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Re: Info Please on Hi-Res (360 + 4, 6, or 8) Optical Cas Whe

Post by jsmcortina »

Subaru_EA82_4EAT_AWD wrote:Well I'm interested to know go MS uses the hi res wheel?

What I mean is, what does it do differently when it has a decoder to suit the specific wheel and it's 360 outer and 4 inner slots, rather than just using the trailing edge of the 4 inner slots when it doesn't have a proper decoder?

I.E. What is gained from a proper decoder? The OE ECU must have used a hi-res wheel for a reason...
By detecting the width of the low-res slots, the decoder can run sequential fuel and spark because it knows which cylinder is which. Without that information you can only run batch fuel and distributor spark.

James
I can repair or upgrade Megasquirts in UK. http://www.jamesmurrayengineering.co.uk

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Subaru_EA82_4EAT_AWD
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Re: Info Please on Hi-Res (360 + 4, 6, or 8) Optical Cas Whe

Post by Subaru_EA82_4EAT_AWD »

Is that the only difference?
No advantage to timing control?
The OE setup is bank fire injection
Want a neat way to Check & Set Ignition timing AND CRANK the motor at the same time BY YOURSELF?
A little thing I made up... https://youtu.be/PajlPNF5mmQ
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Re: Info Please on Hi-Res (360 + 4, 6, or 8) Optical Cas Whe

Post by jsmcortina »

No other benefits that I can think of.

James
I can repair or upgrade Megasquirts in UK. http://www.jamesmurrayengineering.co.uk

My Success story: http://www.msextra.com/forums/viewtopic ... 04&t=34277
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Subaru_EA82_4EAT_AWD
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Re: Info Please on Hi-Res (360 + 4, 6, or 8) Optical Cas Whe

Post by Subaru_EA82_4EAT_AWD »

I read somewhere on here that there is an advantage when starting, is that untrue?
I've also read that the more cas resolution you have the more stable your ignition timing control will be, is that also untrue?
Want a neat way to Check & Set Ignition timing AND CRANK the motor at the same time BY YOURSELF?
A little thing I made up... https://youtu.be/PajlPNF5mmQ
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Re: Info Please on Hi-Res (360 + 4, 6, or 8) Optical Cas Whe

Post by jsmcortina »

The main advantage to the "Nissan CAS" decoder is that you can keep your stock trigger wheel for the patterns that are supported.

James
I can repair or upgrade Megasquirts in UK. http://www.jamesmurrayengineering.co.uk

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Subaru_EA82_4EAT_AWD
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Re: Info Please on Hi-Res (360 + 4, 6, or 8) Optical Cas Whe

Post by Subaru_EA82_4EAT_AWD »

So for batch injection and ignition there's no advantage over using the 4 inner slots? Even with the DIY wheel?
Want a neat way to Check & Set Ignition timing AND CRANK the motor at the same time BY YOURSELF?
A little thing I made up... https://youtu.be/PajlPNF5mmQ
Matt Cramer
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Re: Info Please on Hi-Res (360 + 4, 6, or 8) Optical Cas Whe

Post by Matt Cramer »

The DIY wheel can get you a bit more spark timing accuracy over the inner 4 slits, although this is mostly useful if you run into issues with the engine kicking back while cranking.
Matt Cramer -1966 Dodge Dart slant six running on MS3X
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