Project X

[madforitkev]

So todays learning curve was Variable Reluctance Sensors.

My CDI has three of these little gems.

Apparently some smart bloke called Faraday worked out that magnets and coils of wire when used the right way can generate voltage....and the VR sensor was born!! (eventually).

Anyway, they generate a voltage that feeds the CDI at each precise timing point then voila! we have a spark, or at least we should.

Prior to dynoing (December), I have had a few runs out and while it has been OK, the results have been strangely intermittent and she has been running rich occasionally. This lead me to look at spark.

Anyway the VR thingy has to pass over a metal thingy on the rotor and looking at mine, they were a bit 'off'.

Apparently they need to be a bit more central to the rotor pickup. Chatting to the nice man at HPI and given I have the only one of these on the Planet as far as I know, he quite fairly said 'add spacers' . I had already worked that out......

Summary. Its better and I will try different spacers as this and the combination of air gap is what does the trick. Most are set between 0.3 to 0.5mm which seems dammed tight but I have noticed if I increase the gap to even 0.5 the spark is crap.

Anyway this is all going in the bin with the new EFI development but it needed figuring out.

I think the petrol smell in the workshop is improving my mental agility.....

[teazer]

Yep, That needs to move our a fair bit to get a decent signal pulse.

[Alan H]

I understand what you're saying, but changing the power of the generated spark by altering the magnetic field & pulse by adding spacers is summat I need to actually see to appreciate.
I get the movement of the trigger at the same time of maximum generated (induced) emf, and understand your pain getting them to happen together and at the right time.
More power (sic) to your gap. I'll stick to points.

[madforitkev]

Alan

My understanding is that basically the CDI uses a FET (field effect transistor) to switch and the input needs a big enough drive signal to fully drive the output (low or high).

So if the input voltage is half ass'd then the output is half ass'd (speaking technically), then the spark is half ass'd.

So better positioned sensor over the pickup means max voltage generated etc. etc.

Again and being fair I was sold a prototype (lighting and ignition in a RH assembly) so I was expecting to fiddle.

Temporary washer spacers have improved it. Proper spacers in manufacture. Then chuck it all in the bin and start again post dyno......

[Alan H]

I get the basics, but we never did electronics down to component level other than knowing what they did and a bit on 'tweaking'. All that was about 40odd years ago, so mostly forgotten, thankfully. I had enough on with motor theory and control etc. when I was doing HNC and started my degree (but not finished due to falling out with the course co-ordinator at Barnsley College, you'll not be suprised to know!)
The Coal Board courses were on big heavy stuff mainly, but the plc and pc programming came in handy in later life when I was commissioning 'stuff'.

[teazer]

Think of it like a weak magnet passing by a chunk of steel. If it's close, there's a significant force and if the gap is large or it's not centered, the effect is smaller. The disturbance in the force has to be strong enough to be detected - or in this case has to be strong enough to switch the circuit and fire a plug. If the sensor gap is too large, the signal pulse is weak or insufficient to reliably trigger the circuit.

And if the pick up is off to one side, the pulse is weak. As long as the center of the pickup is over the main part of the reluctor, it should be fine.

If someone has a 'scope maybe they could post pictures of the signals.

[madforitkev]

Yep, I've got a scope. That's what gave me the first clue.

And its obviously non linear so a small difference makes a big change.

Thankfully I did/do some electronics so it kinda makes sense and if it doesn't I hit it and that always fixes it anyway!!

[madforitkev]

Just for fun I thought I would post a few renderings and get a bit of an opinion poll going.

I just cant decide on the main colours (other than I want to stick with the gold wheels and highlights).

Here are my favourite options with links to the actual candy colours.

The frame sidebar will be high polish (or matt black!!)

Suggestions on a post card??? I think I have finally gone project blind......

https://www.houseofkolor.com/kolors/det ... ref=kolors

https://www.houseofkolor.com/kolors/det ... ref=kolors

https://www.houseofkolor.com/kolors/det ... ref=kolors

[Alan H]

Blue looks nice. Good contrast in colours with the ally and wheels.

[madforitkev]

Got my 36 tooth timing wheel water jet cut today.

Using Grandad's old wrench and a drill, I do believe I have an ignition system .......sort of....

That should bolt nicely on the starter clutch and away we go !!