The IC inside the CDI

[Louis]

Still waiting for the tools, so sadly not much progress is done

Although preparing all the wires from the cdi with connectors so it will be easier to disconnect one cable at the time to measure witch pin changes.

Also also preparing a steady 12V adapter to measure thinks in side the house (well its getting colder out there )
Hopefully all this all will be ready tomorrow.

Next thing is a thought/idea off me.

If I use a frequentiegenerator and put a signal on the pickup wire of 35 hertz
(1200rpm : 60 = 35 hertz) and use a two channel oscilloscope
Connect channel 1 on the pickup signal (measuring the 35 hertz) put channel 2 on the rpm/coil signal measuring the outcomming ignition signal.

If I trigger those values equal to each other would I not measure the 19 degrees (base setting)
(The 19 degrees is the only value we know (19 degrees at 1200rpm))

If I divide the measured outcome signal from channel 2 with 19 Then I will have a vulva for one degree.
So when rise the input signal from 35hertz to lets say 50hertz (3000rpm) the outcome signal will change too.
Measuring that result you mutiply that with the 1 degree value given you the degrees at 3000rpm.

If some one can follow my idea
would this work??


If this is possible you could read the ignition curves very exact

Cheers

[Fotis]

Hello Louis,
If you read my post you will notice that i did exactly the same but instead of using a tone generator i used my soundcard and instead of an oscilloscope i used my soundcard again!
And yes, it works....you will see a difference in the curves and you will also notice the limiter function after some rpm. You will also notice the power valve moving when ypu reach 5500rpm.

[tzr-v4]

Hello Louis,
If you read my post you will notice that i did exactly the same but instead of using a tone generator i used my soundcard and instead of an oscilloscope i used my soundcard again!
And yes, it works....you will see a difference in the curves and you will also notice the limiter function after some rpm. You will also notice the power valve moving when ypu reach 5500rpm.

Did you use the output sound card to simulate the pickup signal ?
Louise is looking to test the CDI in "real" life situation if we could said...

I'll pickup at the lab tomorrow the board, sockets, resistor... to make a IC emulator this weekend (if other family members are ok  )
 

[Louis]

Fotis,

Yes I have read your post, and the idea is based on it.

What I'm trying to say is can I measure the outcome signal like that?
Without the income off the HT coils?? will it give a rpm signal?
And
Can the value at 35 hertz be divide with 19 degrees so you will know what 1 degrees is?

If we know what value 1 degree is, we can calculate all other hetz.
This will give very accurate ignition curve values

[Louis]

Olivier,

I'll pickup at the lab tomorrow the board, sockets, resistor... to make a IC emulator this weekend (if other family members are ok   )

Great work we are all on the move

Have opened a (broken) ignitech to see what for kind off Ic they are using.
But they have glue/waxed the whole circuitboard. Have removed the outside but you will keep a black box.

Can I remove that glue by throwing it in petrol?? (don't worry it was already broken)

[Fotis]

Did you use the output sound card to simulate the pickup signal ?

Yes I used the line out for generating the signal and the line in to read the out put as an oscilloscope. The only thing you have to do is make sure you use the right voltage dividers to protect your soundcard. Obviously you will take the out put signal before the amplification (just follow the trace from the big capacitor)

Can the value at 35 hertz be divide with 19 degrees so you will know what 1 degrees is?

If we know what value 1 degree is, we can calculate all other hetz.
This will give very accurate ignition curve values

hmm I dont understand what you want to achieve by doing this...The only thing that CDI does is delaying the signal. So if you put the input and output signals on your oscilloscope you will be able to pick up the advance curve by comparing the difference of the signals. Depending on your oscilloscope settings you will be able to calculate the exact time difference of the curves

Have opened a (broken) ignitech to see what for kind off Ic they are using.
But they have glue/waxed the whole circuitboard. Have removed the outside but you will keep a black box.

Can I remove that glue by throwing it in petrol?? (don't worry it was already broken)

I am very curious about their design...You can soak it in a solvent for a day that will soften the rubber a bit. But I am afraid you have to scrap it with a screwdriver very carefully. Just dont push hard as you might damage the parts.
You say its broken but once you open it you might find an easy fix!

[tzr-v4]

Louis,

look for potting removing on google you'll find the type of chemical to use.

We are use to talk about degree to speak about ignition but the IC is only counting time.

The pickup is "fired" by the rotor at a given crank angle due to the mechanical setup.
This angle is the maximum advance the CDI can make if the spark is produced with not retard.
That value is at least 28° on the 3MA because CDI curve has 28° advance at 3000rpm so mechanical angle should be greater.

The IC will compute for a given rpm value the time to wait (retard) before firing the spark to get a the end the right advance value in degree.

With your oscilloscope, you'll be able to measure the time between the pickup signal and spark (or the driving spark signal on the IC).
The pickup signal frequency will gives you the rpm after some small maths (correct me if I'm wrong it is late...).
3MA has a waisted spark ignition so :

F_real = F_pickup / 2 = Rotation Per Second  /*RPS*/
RPM = 60 * F_real

F_pickup = 200Hz -> F_real = 100Hz -> RPM = 6000

For an Angle_advance of 22° at 6000 RPM T_retard is computed as follow
RSpeed = 360 * F_pickup / 2 in ° per s

Angle_mechanical = 28°
Angle_retard = Angle_mechanical -  Angle_advance = 6°
T_retard = Angle_retard / RSpeed = Angle_retard * 2 / (360 * F_pickup)

T_{retard at 6000rpm} = 6 * 2 / (360 * 200) = 16.6666 10^-3 s = 16.6666 ms

So at 6000rpm the IC has to wait 16ms after the pickup signal before firing the spark and it uses a timer to count this delay (we should add the counting frequency to compute how many counting cycle the timer should do).

T_{retard at 3000rpm} = 0 * 2 / (360 * 100) = 0 ms

So at 3000rpm, the IC fires the spark immediately after the pickup signal is detected.
This is not easy to make so Angle_mechanical should be greater than 28° maybe 30°...

A modified woodruff key will change this Angle_mechanical so slide all the CDI curve.

[Louis]

Its getting difficult to explain what I want because English is not my languages

I'll try again.

I understand and its logical that the outcomming signal will change when you change the incomming signal. (the IC is following his program)

But by comparing/measuring those values they only tell you the time/voltage but no degrees.
The 3ma manual says that you have 19 degrees at 1200rpm

That 1200rpm wil be (1200/60=35Hertz)

If I set my incoming signal at 70Hertz (thanks Olivier two lobs at the flywheel) The value what you measure at the outcoming signal will be ....Ms With ....Mv
That outcoming measured signal value will be the 19 degrees.

Ones know that ....ms By ...mv Is 19 degrees. It will be easy to calculate what 1 degree is.
Knowing what 1 degree is you can calculate every outcome signal to degrees.

This I need to know when  drawing the curve on paper



Will come back on this, need some sleep now

Thanks guys for the input really appreciate it

Cheers

[tzr-v4]

Attention some basic error Louis (go to bed !!!)

The 3ma manual says that you have 19 degrees at 1200rpm

That 1200rpm wil be (1200/60=20Hertz)

If I set my incoming signal at 40Hertz (thanks Olivier two lobs at the flywheel) The value what you measure at the outcoming

If your pickup signal is at 40Hz (for 1200rpm) then the time T_mesured between the pickup signal and firing signal is the T_retard for F_real = 20Hz.

RSpeed = 360 * F_real = 360 * 20 =  7200 °/s

T_retard = Angle_retard / RSpeed

Angle_retard  = T_retard * RSpeed

Angle_{retard at 1200rpm} = T_mesured * 7200

Angle_mechanical = 19° + Angle_{retard at 1200rpm} 

Then you could use the computed value of Angle_mechanical for other pickup frequency (rpm)

Angle_{advance at XXXrpm} = Angle_mechanical - Angle_{retard at XXXrpm} 
Angle_{advance at XXXrpm} = Angle_mechanical - T_{measured at XXXrpm} * 360 * F_{pickup for XXXrpm} / 2

Going to bed now !!!

[Louis]

I'm a little bid embarrassed , don't know how I came at 35hertz.

Yes of course Olivier you are completely right, its 20 hertz for 1200rpm (40 hertz for the two lobe flywheel)

Olivier
I know you are trying to teaching me something.

But I don't get it. (what you mean)
The plan inside my mind does not calculate with Tmesured Tretard for Freal etc.

I'm on my work now, so don't have time to explain better
Will try again when I'm home

Cheers

[yanw]

The Xbox-modders I know use a heat gun/paint stripper to remove the goo on the Xbox motherboard. They have to be VERY careful.

[Louis]

Second attempt

(The ms are just example value's, don't know them for now)

Ok.

If I put a 40Hz (1200rpm) signal on the pickup wire it will go to the IC the IC will calculate the value for the outcome signal (ignition)
That outcome signal at 40Hz is measured at (example) 30ms

I know that the engine sparks at 19degrees at 1200rpm (19 degrees is 40Hz)

So 19 degrees divided by 30ms = 0,6333ms
1 degree = 0,63333ms

Now put a 100Hz on the pickup wire and the IC calculates a ignition signal, I measure the outcome signal at 17ms

So 0,63333 x 17ms = 27degrees

Etc etc.

(If it will be like this, it will be easy to draw the ignition curve)

That was my question, Could the outcome signal (ignition) be calculated like this???

[Louis]

Hello Yan,

The Xbox-modders I know use a heat gun/paint stripper to remove the goo on the Xbox motherboard. They have to be VERY careful.

I could give it a go like that, you mean it could meld off the circuit board with heat.
Through time have two destroyed ignitech boxes, So will give it a try

Cheers

[tzr-v4]

So 19 degrees divided by 30ms = 0,6333ms
1 degree = 0,63333ms

the 19° on the CDI curve is the angle between spark and TDC and the result of this computation :

Angle_advance = Angle_mechanical - Angle_retard

At 1200rpm,  1 degree is equivalent to XXX ms but at 2400rpm 1 degree is equivalent to  XXX/2 ms...

But you can not use 19° because your 30ms are linked to this number of degree :
Angle_retard =  Angle_mechanical - Angle_advance
I'll try to make an xls file...

[Louis]

Feels like I'm back in school

the 19° on the CDI curve is the angle between spark and TDC and the result of this computation :

I can follow you on this part
.


Slowly my thoughts are getting destroyed with this one

At 1200rpm,  1 degree is equivalent to XXX ms but at 2400rpm 1 degree is equivalent to  XXX/2 ms...

Think I see it now, the increasing HZ will shorten the outcome signal by xxxms, but also the IC is calculating his ignition signal compared to the HZ it is getting
Two variables.

Was never a quick student, but did like to know what I did wrong