Additional Wheel Decoder Features

sean-keys · Post by **sean-keys** » Sun Dec 02, 2007 2:56 pm

I have an engine with a two track cam wheel. The first track has 360 slots, the second track has 8 slots with varying length. How hard would it be to modify the the code to have an option for the second "wheel" to trigger when a specified number of teeth trigger from the first "wheel".
Example the second trigger rises and 8 teeth pass from the first wheel before the second trigger falls.

Sean

6040solder · Post by **6040solder** » Sun Dec 02, 2007 3:14 pm

I would imagine the answer is the same as it was for the RB series wheels, ie, too many interupts for the 360 teeth. afaik, the 60-2 is the most you can use before its too much for the processor.

this is a nissan vh41 or vh45 is it?

somewhere around is a thread on how nissan go about doing it. it involves some clever logic, and effectively an electronic dizzy. if you built the same circuit, you could use ms to fire the coil for each event, and the circuit to route it to the correct cylinder.

sean-keys · Post by **sean-keys** » Sun Dec 02, 2007 4:22 pm

Chevy LT1 5.7L V8. Do know what the max int/sec is?

Post by **muythaibxr** » Sun Dec 02, 2007 4:35 pm

We don't know what the maximum number of interrupts is, but 360 teeth is not something we're going to be able to handle.

sean-keys · Post by **sean-keys** » Sun Dec 02, 2007 6:55 pm

I suppose that's what BG are planing on using the Xgate version of the MCU in the future. At least that's what I read. Thanks for answering my question. I will use a crank wheel instead. Have you heard of people using waisted spark with a 60-2 on a V8. I suppose a 36-1 could be used, but I like the idea of resolution. Especially sine I read that the MSII extra "counts down" between teeth.

Post by **muythaibxr** » Sun Dec 02, 2007 10:29 pm

I don't think even the xgate would be fast enough to decode that wheel at higher revs.

36-1 or 60-2 will work fine. 60-2 will just be a bit more accurate.

Ken

Matt Cramer · Post by **Matt Cramer** » Mon Dec 03, 2007 10:27 am

Since that wheel type first appeared on a Nissan in 1982 (at least, that's the first documented case I've seen, the L28ET), I wonder how they controlled spark with the processors available back then. My guess is that they used a crude counting algorithm that didn't interpolate between slots.

Post by **muythaibxr** » Mon Dec 03, 2007 10:54 am

I don't think they used their main CPU to do it directly. I think they had separate dedicated hardware to do it. What would be the point of having all those teeth if you don't use them somehow.

Ken

6040solder · Post by **6040solder** » Mon Dec 03, 2007 11:11 am

muythaibxr wrote:I don't think they used their main CPU to do it directly. I think they had separate dedicated hardware to do it. What would be the point of having all those teeth if you don't use them somehow.

correct :-)

found it :

http://www.msextra.com/viewtopic.php?p=149427#149427

http://www.calaisturbo.com.au/printthre ... ge=2&pp=40

enjoy :-)

Post by **jsmcortina** » Mon Dec 03, 2007 5:24 pm

I ditched the opti-spark and used a 36-1 on an LT1 I'm helping with.

Low-res video: http://www.youtube.com/watch?v=_0KoF7qnRv0

James

6040solder · Post by **6040solder** » Mon Dec 03, 2007 5:29 pm

The thing with the RB engines at least is that they are native COP, and the coils are small and heat easily, so wasted spark is out, and even if ms2 did 6cyl cop, you would save 5 outputs by doing it that way with the little helper circuit. i wonder if an oem ecu could be tapped into for that purpose, or perhaps copied for that part only. for cop purposes, i think its a nice design they came up with.