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User avatar
By DaveyB
Hi peeps.

Looking through the manual it says the Speedy can use an opto senor for crank timing, but looking through Tuner Studio it doesn't show it, unless I'm missing something.

The question is, can Speedy use an opto sensor for crank timing and if so how?

The reason for the sensor is that I am having issues due to the high rpm of my project engine, which has been fitted with a hall sensor. The engine is a 2 stroke v-twin running at 13,000rpm and redlining at 13,750rpm using Alpha-n. So I am hoping if I use a opto sensor with a 360 dot wheel, the timings will be more accurate. At the moment I am also running a separate programmable ignition unit to run the sparks but also to control the powervalves. It uses a pair of VR sensors for the timing.

Any advice would be greatly received.

User avatar
By DaveyB

I get that an opto sensor will give you a nice 0V to 5V square wave pulse. But how do you select it in Tuner Studio, especially if the disc is segmented for one dot per crank degree?

User avatar
By DaveyB
Cheers Guys.

My thoughts were to copy the Nissan 360 opto style of wheel. But instead of using four additional cylinder timing slots, was to use a single row 360-1 wheel. This would give a better pulse train that can be measured at high rpm speeds. The missing slot would be set at 89 degrees ATDC with the first slot set at 90 degrees ATDC. This would be part of the exhaust phase of the engine cycle. This is a two stroke engine so every slot in the timing wheel would equal one degree of crank rotation.

I'm current running a 36-1 wheel with a hall sensor, which doesn't seem to stay steady from 9500 rpm upwards (tried a number of hall sensors and scoped the output). This means that one tooth equals 10 degrees of crank rotation, which is too wide, especially for the fuel timing. I have read somewhere, the timing tooth count must be divisible by 360. But as Tuner studio won't read 360 teeth, if I used 180 slots to give a 2 degree crank resolution, would this not be doable? Would it be better to increase the number of missing slots, from say 1 to 2?
Don't think of the number of teeth as accuracy. Think if it as the sample rate.

The maximum suggested for speedy is 60-2. As I understand it, there is no real benefit past that resolution.

However, 60-2 is probably going to be a struggle at 13k rpm. It should be ok at about half that.
User avatar
By DaveyB
That's the issue though, as the speed goes through 9500rpm the resolution from the hall sensor starts to flatten out and is not as defined as it was at lower speeds. Hence the thoughts of using an optronic disc and sensor which will give a clearly defined pulse train hopefully up to the engines red line of 13,000rpm.

Do you know why the 60 tooth wheel has two teeth missing rather than just one? For the 60 tooth wheel, each tooth represents 6 degrees of crank rotation, therefore two teeth equals 12 degrees. However, on the 36 tooth wheel each tooth equals 10 degrees, so a single missing tooth equals 10 degrees of crank rotation. For general applications I suppose the resolution isn't so much of an issue, but for research, having the better resolution would be a major benefit.
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