Jaguar 6 Liter v12 factory crank signals

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jhkm12345
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Jaguar 6 Liter v12 factory crank signals

Post by jhkm12345 »

I have a 1995 xjs v12 engine with Marelli ignition that I'm installing a ms3 Gold box from efisource.com

I'm looking at original factory sensors and I have a question that seems has differing opinions.

The engine has two, two wire VR sensors reading the crank speed. One of which reads engine position via 1 tooth on the front crank pulley, the other reading the teeth on the flywheel ring gear.

so I have 1 tooth per revolution to read from on the front and 160 to read on the flywheel side.

I understand this will not work with full sequential and I'm not interested in running full sequential. I intend on running the motor as if it has 2 distributors (dual dizzy) with 2 coil output wasted spark and fuel in batch, to 4 groups of 3 cylinders as the OEM harness was originally wired.

I do see in the hardware manual that it is supported in 'dual wheel' settings that you can run a non-missing toothed wheel along with a single tooth wheel, both on the crank.

http://www.msextra.com/doc/pdf/html/MS3 ... 1.3115.png

http://www.msextra.com/doc/pdf/html/MS3 ... e-1.3.html


My question is this. I keep reading posts about how flywheel teeth is not supported in the code as it's too high. but all these posts are old and not from an era where ms3 has been worked out. Does anyone have any thoughts on whether this will work or not? I hate to go through the effort of building a bracket, to hang a sensor, on a wheel I have to make, on a motor that already has two perfectly good sensor mounting spots, with two perfectly good sensors installed.
jsmcortina
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Re: Jaguar 6 Liter v12 factory crank signals

Post by jsmcortina »

That isn't supported as-is. A few flywheel options exist experimentally but additional hardware is required.

Using a 36-1 or 60-2 wheel on the crank is your best option.

James
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jhkm12345
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Re: Jaguar 6 Liter v12 factory crank signals

Post by jhkm12345 »

well that's unfortunate... I figured it would be too easy!
dontz125
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Re: Jaguar 6 Liter v12 factory crank signals

Post by dontz125 »

Don't despair - it's ALMOST that easy. 8)

A quick check of Google shows that a single D-type flip-flop can function as a divide-by-2 frequency divider. Wire that in between your flywheel VR circuit and the MS3 card, and the 160-0 wheel becomes an 80-0 wheel. Note that you'll need a second VR circuit for your single-tooth crank input.

While this won't give you full sequential, it WILL permit 6-channel semi-sequential, as well as 6-channel wasted spark.
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jsmcortina
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Re: Jaguar 6 Liter v12 factory crank signals

Post by jsmcortina »

Fitting a regular missing tooth crank wheel is a more common path to take and doesn't require R&D of custom electronics.

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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dontz125
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Re: Jaguar 6 Liter v12 factory crank signals

Post by dontz125 »

*scratching head* A single D-flop in an established configuration isn't really what I'd call custom electronics. I agree that installing a proper missing tooth wheel is the better solution, but I have no idea how hard installing that wheel will be, or if the OP is interested in such a thing. I'm pointing out a means of carrying out his original plan.
QuadraMAP Sensor Module -- PWM-to-Stepper Controller -- Dual Coil Driver
Coming soon: OctoMAP Sensor Module
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jhkm12345
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Re: Jaguar 6 Liter v12 factory crank signals

Post by jhkm12345 »

fair enough. I've drawn out a 36-1 wheel and will have it cut out on a waterjet this week.

I'm sure the single d flop would work with some tweaking, but I'm more concerned with getting it functional quickly than creating potential hickups.

in theory though, could a signal divider be used to simulate a cam signal for full sequential down the road? taking a one tooth sensor off the crank to half speed?
Marek
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Re: Jaguar 6 Liter v12 factory crank signals

Post by Marek »

Can you get a cam sensor out of this?

No, because the point of a cam sensor is knowing whether you are on the compression stroke or not and so anything derived from the crank signal (which doesn't give you this information to start with) doesn't bring this new data in from anywhere.

kind regards
Marek
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