ideal cam and crank wheel for single cyl

[sn95.ohh]

Ok so the plan is to run a microsquirt ecu on our KTM 560 single cylinder. Im still trying to figure out the whole cam and crank sensor deal.

As of right now ive figured that I can run a single triggering point on the cam side of things for synching. Now my question is about the crank. What ive seen is that the more teeth you run the greater resolution you can achieve because of the increase in pulses per revolution. But on a single cylinder cant I get away with running a single tooth on the crank?? The reason I ask this is because our current flywheel only has one tooth on it that the VR sensor uses to run our cdi.

If I could I would like to just continue to use this setup and take the sacrifice in lose of resolution as our current custom made ecu runs our fuel injection just fine with this one pickup.

So will the microsquirt be able to run with this one tooth pickup on the flywheel or should I machine teeth into the flywheel??

[Matt Cramer]

It is possible to run with one tooth on the flywheel, but not ideal. If you can redo the crank wheel, 12 teeth is a pretty good compromise between resolution and too many interrupts at high RPM.

[sn95.ohh]

Ok thats what I was thinking of running. The thing is is that we are running a trail tech flywheel now and the flywheel doesnt really leave room for a crank wheel to be put on the crank any where. But there is extra material on the flywheel to were I can cut the 12 teeth into it which was my original plan. Im just worried of messing up on the design and possible creating vibrations or balancing issues. I just wanted to run the single tooth to take the easy way out and keep it simple.

But I guess the ECU would only be updating twice per cycle with a single tooth?? which isnt very good but with a 12 tooth it would be refreshing and going through calculations 24 times per cycle?? And I guess thats what really matters right??

[myk777]

I run a 36-1 on the crank and a single tooth on the cam with my YFZ450 which operates to 11,000 this setup has been flawless with the extra code. I machined up a custom toothed ring that presses onto the stock flywheel which is read by an Allegro gear tooth hall sensor.

Mike

[sn95.ohh]

I run a 36-1 on the crank and a single tooth on the cam with my YFZ450 which operates to 11,000 this setup has been flawless with the extra code. I machined up a custom toothed ring that presses onto the stock flywheel which is read by an Allegro gear tooth hall sensor.

Mike

Do you have any pics of this setup?

[mfro]

I have a small 18-1 crank wheel (wasted spark) setup which works well (ignition only for now) until past 12000 RPM on a single.

[myk777]

I run a 36-1 on the crank and a single tooth on the cam with my YFZ450 which operates to 11,000 this setup has been flawless with the extra code. I machined up a custom toothed ring that presses onto the stock flywheel which is read by an Allegro gear tooth hall sensor.

Mike

Do you have any pics of this setup?

See the second page of this thread for some pics of my setup

http://www.microsquirt.com/viewtopic.php?f=38&t=23570

Mike

[sn95.ohh]

Awesome thanks. Ok so I have a few more questions.

Right now the motor runs a single long tooth with a vr sensor. I was planning to reuse the same sensor for my next setup. But the megamanual says that the sensor should be the same width as the tooth. Here is a pic of the sensor.



The two little pieces in the middle are the magnets so would I have to make the teeth the width of those magnets? They are only .100 in wide. That is tiny and would make for some pretty small teeth. So would I be able to make the teeth wider or should I just go with a bigger sensor??

Here is a pic of the current setup


Another thing im concerned with is the cam sensor. The way the cam is setup I wont be able to add a wheel to it. So I was thinking of drilling a hole into the cam gear and pressing a magnet into the cam gear and running a hall sensor to pick up the magnet. Would this be possible at all?? Here is what I was thinking. Putting a magnet where the black dot on the left is.

[mfro]

Don't think it really matters if the sensor is smaller than the tooth (as long as there is a clear signal). I think the manual advice rather meant you'll run into problems if the sensor is wider than the tooth since the MS will most likely see more than one tooth at a time with a multi-teeth wheel leading to problems.

KTM engine?

[dontz125]

A long tooth causes significant issues for the standard uS and MS VR hardware, as they are looking for the zero-crossing between the tooth edges. When the edges and the sensor are the same width, the zero-crossing happens pretty much at the same point every time. When the edges are a significant distance apart, the "zero-crossing" signal can happen at pretty much any time between those edges; when the tooth is 30 degrees wide, this is an intolerable error.

For a single long-tooth set-up like yours, I have to wonder if running your VR sensor to the OPTO input might not be the ticket - it will give you a single trigger pulse on the leading edge of the tooth (or trailing edge, if you hook it up backwards - not sure that it would particularly matter in this case).

Some people say that a single tooth isn't accurate enough - the OEM seemed to think so ...