![]() Click here for more companies that support Dragbike.com! |
Fun with spark plugs |
Post Reply
|
Page <1 567 |
| Author | ||
geek
Senior Member
Joined: 08 January 2004 Location: United States Online Status: Offline Posts: 1856 |
Quote Reply
Posted: Yesterday at 8:36am |
|
|
Yes, that is pretty crazy. I figured by the time I returned the wire would have been a dead short. If I put a boot on it I could take the pressure up higher or I could put it on a DC power supply and see where it falls apart.
For all three tests, the current is pretty much the same. Current decay seems to be in the 400uS range. The transformers 3dB points are at 120Hz to 20MHz. This is a ferromagnetic unit. The transformer is not good for the range you want to see. Also, I found this little gem of a post from Nology talking about spark durations:
The patents are on-line for the MC-4 and they do provide details for it's output circuit. The Google patent search works well. If you can't find it, I saved a copy and can send them to you or see if I can find the link again.
Dang, looks like too little sleep (had to edit) Edited by geek - Yesterday at 11:34am |
||
|
As I proof my post, my finger on the send key, I pause, read it once more, then press. Mark
|
||
![]() |
||
geek
Senior Member
Joined: 08 January 2004 Location: United States Online Status: Offline Posts: 1856 |
Quote Reply
Posted: Yesterday at 11:56am |
|
|
I came across this article that also talks a little about the duration.
If you really want to know what the spark duration is, I think I have some high speed fibre optics that we could watch the light coming off the gap. This would give us a direct way to know if there are photons present or not. Let me search my junk pile.
|
||
|
As I proof my post, my finger on the send key, I pause, read it once more, then press. Mark
|
||
![]() |
||
geek
Senior Member
Joined: 08 January 2004 Location: United States Online Status: Offline Posts: 1856 |
Quote Reply
Posted: Yesterday at 10:17pm |
|
|
So you want to see some faster speeds....
For this next test I made up a little capacitive probe to clamp onto the wire. Jist is similar to the cap wire. The clamp goes to another cap to setup a divider network and this is fed to the scope. I tried to test the probes flatness with little luck. There is no DC or low frequency response and it is not flat anywhere. Just an overall bad setup. You can buy a probe like this for $50 or so and maybe get some better results. This first plot shows the standard wire with no braid. We can see the Arc time is about 20nS. Next we can see the effects of the braid on the wire. You can see that it is not real stable. This old scope can run in RIS mode and has an analog BW of 4GHz. For the time, it was bleeding edge. When running this mode you have to limit the inputs (normal for a high speed DSO) and the trigger would have to be very stable. In this case it's not so the phase noise is bad. Anyway, here is the rise time of the standard wire. Now, my guess is this is not really what it looks like. I mean, getting back to my home made clamp on probe. We would be kidding ourselves. It does appear that my home made capacitor wire has little effect. |
||
|
As I proof my post, my finger on the send key, I pause, read it once more, then press. Mark
|
||
![]() |
||
geek
Senior Member
Joined: 08 January 2004 Location: United States Online Status: Offline Posts: 1856 |
Quote Reply
Posted: Yesterday at 10:31pm |
|
|
One you could buy
http://www.picoauto.com/secondary-ignition-pickup.html They have some interesting screen shots of the ignition waveforms including the secondary. However, notice that what they show where I am looking in these last plots is nothing more than a line on the screen. http://www.picoauto.com/waveforms/Ignition/ |
||
|
As I proof my post, my finger on the send key, I pause, read it once more, then press. Mark
|
||
![]() |
||
shmot
Groupie
Joined: 04 September 2007 Location: Finland Online Status: Offline Posts: 83 |
Quote Reply
Posted: Today at 1:03am |
|
Shape of the line is like discharged capacitor. Maximum current was the same in both cases(?) Can you tell what is maximum value of current? This was in open air? Capacitor effect should increase when breakdown voltage increases because energy stored to capacitor increses (E=C U^2). What was the wire resistance? In nology wires that was 460 ohm. Longer wire and incrased resistance should increase discharge time (and reduce current). Capasitor will decrease voltage rise time. That will have to have some effect to boot breakdown. Maybe boot breakdown will only happen with CDI-ignitions. I suppose that with magnetos and coil ignitions voltage rise time is longer. |
||
![]() |
||
geek
Senior Member
Joined: 08 January 2004 Location: United States Online Status: Offline Posts: 1856 |
Quote Reply
Posted: Today at 7:05pm |
|
Assuming your asking about peak currents, If you look at the first two plots the voltage is about the same. We covered the limitations of the current transformer. Again, I am not even sure if the voltage means anything. The probe is no good at this frequency so I can't use this to give any indicator of current. Then this old scope is just not going to cut it. I would not even trust the time scale as I am afraid that this whole thing acts like a filter at the frequencies we are interested in. So no absolute numbers, only relative. Best we can conclude from this is that the braid makes a small difference, broadening the arc and slowing the rise time. No surprise. Wire was the same as before: 16" of 8.5mm dia. Accel 300, 9" of braid providing 42pF @ 1KHz. Plug was the same, D9EA 0.022 gap
Not sure I follow what your getting at. Yes stored energy will increase with voltage but it sound's like your thinking there is something more to a capacitor. I think the two graphs of the arc show the capacitor effect pretty well. |
||
|
As I proof my post, my finger on the send key, I pause, read it once more, then press. Mark
|
||
![]() |
||
Post Reply
|
Page <1 567 |
| Forum Jump | Forum Permissions ![]() You cannot post new topics in this forum You cannot reply to topics in this forum You cannot delete your posts in this forum You cannot edit your posts in this forum You cannot create polls in this forum You cannot vote in polls in this forum |