Old Car, Old Scope?

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hexibot43
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Old Car, Old Scope?

Post by hexibot43 » Sun Aug 04, 2019 3:28 am

I never thought that working on some of these old cars would be such a pain. As a mechanic I always get others telling me how easy I have it working on all these older cars. Here is one to prove them all wrong.

I just recently picked up a "New" to me Old Sun Scope - and this was the pattern I was given on an old 1950 Chrysler New Yorker. Why? It worked flawlessly on the the car I looked at before it, and the car I looked at after it. I tried syncing off different cylinders without any luck.
50ChryslerStraight8.mp4
From A Sun 1400 Scope
(6.79 MiB) Downloaded 30 times
No idea what to make of this? Has anyone else ever seen anything like this? I tried
1950ChryslerNewYorker.png
From my 4 channel PicoScope
This was the same car looked at with my PicoScope. I have a pattern, but I can't understand why it was telling my the pattern is exceeding the scale of -5kv....100kv. I'm no where near 100kv. I don't think the coil is capable of such levels. Hmm. It looks close to the -5kv

But what was causing the Sun scope to go so crazy? And these old cars are suppose to be so easy......

Steve Smith
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Re: Old Car, Old Scope?

Post by Steve Smith » Mon Aug 05, 2019 2:49 pm

Hello and thank you for the post.

Could you confirm if there is a running issue with this vehicle?

It would appear the event captured by the PicoScope has identified why the Sun Scope is responding like it is.

What we can be sure of is it is specific to this vehicle (1950 Chrysler New Yorker)

I agree on the coil reserve for this car should not reach 100 kV but it would be interesting to qualify just what it can deliver.

My gut feeling is we may have noise/shielding issue being detected and displayed by both scopes (The Sun Scope with abnormal behavior)

Would it be possible to shield the HT leads from one another with "separation or foil" (Oblivious be aware of leakage with the foil)

Could be reroute the HT Pickups as another possible?

Could you post the psdata file shown in your image as there may be additional detail in the 100 kV peak when we zoom in?

I hope this helps, take care.....Steve

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hexibot43
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Re: Old Car, Old Scope?

Post by hexibot43 » Mon Aug 05, 2019 4:56 pm

Yes to all of the above. I have set up a station for my PicoScope Now. Always set up. As soon as the new parts for the distributor arrive, and I've put it all back together I will scope it again (with foil) and see what happens. Looking forward to seeing it on the scope with my IMAC 27" screen. Yes I've gone Apple for a bit. We'll see how it goes.

Marcello

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hexibot43
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Re: Old Car, Old Scope?

Post by hexibot43 » Tue Aug 06, 2019 1:47 pm

Steve Smith wrote:
Mon Aug 05, 2019 2:49 pm
Hello and thank you for the post.

Could you confirm if there is a running issue with this vehicle?

It would appear the event captured by the PicoScope has identified why the Sun Scope is responding like it is.

What we can be sure of is it is specific to this vehicle (1950 Chrysler New Yorker)

I agree on the coil reserve for this car should not reach 100 kV but it would be interesting to qualify just what it can deliver.

My gut feeling is we may have noise/shielding issue being detected and displayed by both scopes (The Sun Scope with abnormal behavior)

Would it be possible to shield the HT leads from one another with "separation or foil" (Oblivious be aware of leakage with the foil)

Could be reroute the HT Pickups as another possible?

Could you post the psdata file shown in your image as there may be additional detail in the 100 kV peak when we zoom in?

I hope this helps, take care.....Steve
I am still currently waiting for a few more parts for this distributor. The mechanical advance was not returning to base timing correctly. It would stick. Pulled it a part and cleaned it up and re-lubricated it. That would not have effected the scope pattern though.

I brought a couple sheets of aluminum foil to work today in preparation. How does one do this though? Just wrap it around the king wire? And the scope pickup. My king wire is fairly short at about 8". Never done this before. The interference would be from the wires between cap and plugs?

Iver
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Re: Old Car, Old Scope?

Post by Iver » Wed Aug 07, 2019 8:27 am

The interference would be from the wires between cap and plugs?
Interference will be every where. All the HT leads. From coil to Distributor. The Spark in the Dizzy from rotor to lug, then leads to plugs.
Wrap the lot up !!!

However KV increase is always due to Compression and dry air in the cylinder. the things that make it harder for electricity to travel across the gap. Also high resistance in HT leads or a big gap at rotor (either side)

Should that spark be outside the cylinder in ambient conditions then the path of least resistance is where the spark will go. It wont take much kv for that and it will show.

Tie all the foils together and put a scope channel on them With an attenuation ready to take the mega kv if there is a leak.

Of course none of the above explains the annomoly in the 2 scopes giving different readings.
Bang them both on together, run it take a picture.

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