Ignition timing with Pertronix Ignitor and strobe light

[vette]

Back from from vacation and from Bosch! Here is what they found:

To recap:

1. First of all I found with a strobe light the ignition timing to be set at 45° at idle and 65° at about 4500 rpm.
2. I then replaced the old no resistance igniton wires with new no resistance wires and measured 30° at idle, but still not 15° (may be due to electrical interferences)
3. Next thing I did was to replace #1 sparkplug wire with a resistance wire --> but no difference!

Bosch measured 23.9° BTDC! They use a computer system which a strobe light with advance control is attached to.

View attachment 45482

So, my strobe light ist about 6° off!

But what about 23.9°? They confirmed, that the enginge is running very well with this timing.


Lutz, in your recap your point #3 says that you replaced the #1 spark plug wire with a resistance one. and it made no change. I believe there is alot of electrical interference going on there. the other no resistance, non-shielded wires are creating alot of magnetic interference. It seems surprising to me that 2 different timing lights (yours & your friends) as well as the Bosch system can't time your engine. If you change out all your wires to resistance onces, I wonder if the timing would then show to be in the traditional parameters. Dave.

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[Lutz Kramer]

Lutz, in your recap your point #3 says that you replaced the #1 spark plug wire with a resistance one. and it made no change. I believe there is alot of electrical interference going on there. the other no resistance, non-shielded wires are creating alot of magnetic interference. It seems surprising to me that 2 different timing lights (yours & your friends) as well as the Bosch system can't time your engine. If you change out all your wires to resistance onces, I wonder if the timing would then show to be in the traditional parameters. Dave.

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I'm not sure if this would solve the case. Electrical noise is only created when electric current flows through a wire and only at that time and as long as the current is flowing. So, no current no noise. When #1 sparkplug is firing the strobe can only be affected by the current running through this wire and the interfrences created thereby and not by the other wires since they are not current-carrying. Therefore in my opinion it should be sufficiant to replace only #1 sparkplug wire for testing purposes.

 

[Keoke]

Logic sounds good Lutz.

However;
The entire ignition system [plastic dizzy cap and unsurpressed plug wiring ] may be participating in the noise generation at this time.

Consider:
The generated EMF from the #! plug circuit could conduct / radiate to and energize the remaining wires causing them to add some to the overall field.???

 

[Michael Oritt]

Lutz--

What kind of spark plug wires are you using?

 

[Lutz Kramer]

Lutz--

What kind of spark plug wires are you using?

Hi Michael,
right now I'm using a common 7mm flexible silicon ignition lead with copper core with no resistance, but I just ordered a 7mm Premium High Performance HT Ignition Lead Cable - Low Resistance Red Silicol with 350 ohm per foot resistance from Green Spark Plug Co. Ltd. in Uk, Part no: GPLHRSR7



1. Synthetic string made of glass fiber and poliamid, sustains the ferrite core.

2. Ferromagnetic compound absorbing interferences all along the cable. Its anti-interference system 2+3 ensures greater ignition current and longer spark duration

3. Corrosion resistant electric conductor spirally Sound around the ferromagnetic core, ensures the conduction of high voltage ignition current and simultaneous absorption of magnetic energy by the ferrite core inside the cable.

 

[Michael Oritt]

Lutz--

Though much of this discussion is above my pay grade I asked because perhaps some interference allowed by solid core wires may be part of the explanation? if this makes no sense and/or has already been asked and answered please ignore.

 

[Lutz Kramer]

Final report:

Two days ago I bought an old Bosch strobe light from the 70ies, which is not connected inductively but in between the distributor cap and the plug wire, so there is only a little chance that interferences have any influences on the measurements of the ignition timing. The Bosch strobe showed the same results like the measurements documented by Bosch last week: 24° BTDC at idle, while the new inductively working strobe light still shows 30°.

Then I changed the no resitance sparg plug wires with High Performance HT Ignition Lead Cable - Low Resistance Red Silicol with 350 ohm per foot resistance.

The Bosch strobe was still at 24°, but the new inductive strobe changed from 30° to 24° BTDC. So the non resistance spark plugwires were responsible for the faulty indication of the inductive strobe light.

Anyway it is definitely true that my BJ8 with its 298° camshaft has to be set to 24° BTDC at idle to run the engine perfectly.

Lutz

 

[steveg]

Lutz,
Thank you for following up!