[davettf2]

Peeps, I'm considering replacing the old Weber system on my Cagiva Elefant with a Seeduino set up. The existing system is 30 years old and the fuel pump relay voltage is only just acceptable. Plus the corrosion of the steel cover screws in the housing indicates that repair will be difficult! Thus we come to the possible Speeduino set up. My first issue is that I will need to install a suitable trigger wheel. The current intention is to attach a trigger wheel to the existing cam wheel that is driven direct from the crankshaft. This has the advantage that I can replace the existing sensor which looks on the the face of the cam wheel. This gives me an effective outer diameter of 98mm. Using a 15mm radial width tooth a 36 tooth wheel would give a spacing of 8.5mm at the outer edge. Is this sufficient to trigger a sensor or should I be looking at a 24 tooth wheel. Thoughts and comments would be appreciated. There's a significant amount of machining required and I would like to do only once.
Cheers
Dave

[LAV1000]

Does it have an OEM trigger wheel ?
I know on the ST2 944 cc engines they use a 48-2 trigger wheel at cam speed.

[davettf2]

Yes, it does have a trigger set up off the cam, but it’s different to the later Ducati’s such as the ST2, in that there is only a single trigger ‘tooth’ on the cam wheel. To be honest was unaware of how the later Ducati’s achieved timing. The early Weber systems as on my Elefant uses a crankshaft sensor for RPM measurement and a cam wheel sensor for crankshaft / piston position.
Looking at your photo I assume that the ST2 timing wheel is driven from the end of the end of the cam shaft with a quill in the slot.
Attached is a photo of my original camshaft gear, I have acquired a cam wheel similar to what is on the ST2 to which I will add a supplementary toothed wheel which will locate in the slot.

[LAV1000]

Why don't you use the ST2 wheel as is ?

[davettf2]

The ST2 Wheel I have only has the single 'chop' in the teeth, which will only give a single pulse. I was under the impression that the Speeduino needed a multiple tooth wheel. Also, the position of the existing cam sensor is set inboard from the gear teeth, again so it only gives one pulse for 720 degrees of crank rotation.

Cheers
Dave

[LAV1000]

Dave,
If your ST2 trigger wheel looks the same as the picture I posted before.
Then it wil work on speedduino.
ST2 sensor is reading sideways so it sees the 48-2 pattern.
You need to shim the sensor to get it close enough to the wheel.
Speeduino works on the 48-2 trigger wheel, have a setup running on the bench.

Mine ST2 engine runs in 900IE Elefant

[davettf2]

Hi, Hopefully below is a picture of the wheel acquired, which I believe is the same as in your picture, however the sensor on the original 900ie engine is centred on the single blade in my previous picture. Thus not sure if it will pick up the 48 - 2 teeth. One I think I need to try before getting to far along the machining route. Many thanks for the heads up as this may well save me faffing about.

Cheers
Dave

[davettf2]

A belated update, one issue I have with the Elefant version of the Ducati engine is that the cam sensor is mounted slightly nearer the rotational axis than the ST2 sensor. Thus it is unable to read the 48-2 teeth sufficiently to get a decent waveform. I spent several weeks looking at alternatives, considering both machining the flywheel (I have both cam and crank sensors) and / or using a modified later cover. In the end neither option looked sensible given costs and the amount of machining / fabrication required. Thus we went for making a set a teeth that I could fix to the ST2 cam gear. It has taken a couple of attempts (perhaps should have gone with the original thoughts!) but we have succeeded. The attached picture shows the gear set up on the ST2 gear and mounted within a test fixture. Also attached are the waveforms before and after the VR conditioning circuit. Will be looking to possibly clean the waveform up a little before taking the step to go NO2C.



Cheers
Dave

[LAV1000]

Looks nice !
Are you not worried about the extra rotating mass ?
How did you hookup sensor and scope, I am seeing weird signals.
Keep in mind that the ground wires from both scope input cables are connected to each other...

[davettf2]

Hi, Not to worried about the additional mass as I have still to machine some more off, which will involve putting several holes in the flange. Also the disc is only 1.6 mm thick.

I will retry the setup again as I probably need to be more careful with the grounding of the sensor. I should be able to get back to playing shortly!

Cheers
Dave