Follow up test with a CDI ignition

-
N

Newbomb Turk

Well-Known Member
Joined
Sep 1, 2023
Messages
4,430
Reaction score
4,900
Location
In The Clouds
I made this video to show the difference between a CDI ignition and an inductive ignition. Again, it’s not a one is better than another test, but to show the differences in spark energy and timing retard.

 
A single point at 10,500 with very little retard. Amazing. Thanks tor the test.
 
Last edited:
toolmanmike said:
A dual point at 10,500 with very little retard. Amazing. Thanks tor the test.
Click to expand...


That’s a single point distributor I grabbed out of a pile a couple of years ago for testing. I didn’t even check dwell or anything.

Maybe when it gets dark tonight I’ll grab a Mallory dual point distributor and test it as a stand alone ignition.

It won’t retard.
 
Newbomb Turk said:
That’s a single point distributor I grabbed out of a pile a couple of years ago for testing. I didn’t even check dwell or anything.

Maybe when it gets dark tonight I’ll grab a Mallory dual point distributor and test it as a stand alone ignition.

It won’t retard.
Click to expand...
Have you ever tested a chrysler electronic distributor running HEI (4 pin) conversion? That is the set up I have in my Grey Van, which I will be tuning (per my latest video)
 
With the right points. CH-14 4500 IN lb 15-17, CH15n in lb 22 is 6500 accel or mallory 28 in lb 10K Spring pressure so it does not float is the key here.
 
Turk,
Not trying to be argumenative, but offering a possible reason for the retardation. Timing lights typically use a Xenon lamp, not sure of the light source in your m/c. Either type, a certain amount of time is reqd for the lamps to come on [ illuminate ]. The crank does twice as many rotations at 6k compared to 3k. But the time period for the light to illuminate does not change with rpm. At 6k, the crank has rotated further before the timing light comes on...& shows up as retarded ign. So is the 'retard' [ or some of it ] the light playing 'catch up' because of increasing rpm?
 
Bewy said:
Turk,
Not trying to be argumenative, but offering a possible reason for the retardation. Timing lights typically use a Xenon lamp, not sure of the light source in your m/c. Either type, a certain amount of time is reqd for the lamps to come on [ illuminate ]. The crank does twice as many rotations at 6k compared to 3k. But the time period for the light to illuminate does not change with rpm. At 6k, the crank has rotated further before the timing light comes on...& shows up as retarded ign. So is the 'retard' [ or some of it ] the light playing 'catch up' because of increasing rpm?
Click to expand...


I’m not saying that’s not possible but how do you explain a points distributor showing no retard or very little retard?

I don’t know the answer to that.

And that of course goes back to using one timing light.

Using the dyno timing light, then going home and using your timing light (not you in particular but you as in anyone) and then going to the track, forgetting your timing light and borrowing a light at the track.

I’ve seen that before. You now have the potential for inducing error by 200%.

I need to buy a scope but I haven’t had time to look around and see what’s out there. I need to and eventually I’ll get one.
 
I am not doubting that there is some amount of retard in any ign system. Could it be due to coil differences? It is well known that there is retard with magnetic trigger ign due to distortion in the p/up signal as rpm increases.
 
I like that you used a point distributor this time. Very cool. It's also a diferent type of trigger signal. I think similar to a square wave pattern of a digital signal. I'm not saying you conclusion is wrong that this Mallory box has less retard than the hirev 7500 box. But you have introduced another varible by using the points distributor in place of the Chrysler electronic distributor. Just for the sake of arguement what if you triggered the Mallory box with the Chrysler electronic distributor and it retarded like it did with the hirev 7500 box? Is this a test you can do?
 
Bewy said:
I am not doubting that there is some amount of retard in any ign system. Could it be due to coil differences? It is well known that there is retard with magnetic trigger ign due to distortion in the p/up signal as rpm increases.
Click to expand...

That I’ve checked, just not with any of the Mallory 7 boxes. They only take one Mallory coil and two MSD coils but I don’t have theMSD coils.

I have tested with different coils and I never say any difference. I heave never tried an E coil but I have one here now I can use.
 
92b said:
I like that you used a point distributor this time. Very cool. It's also a diferent type of trigger signal. I think similar to a square wave pattern of a digital signal. I'm not saying you conclusion is wrong that this Mallory box has less retard than the hirev 7500 box. But you have introduced another varible by using the points distributor in place of the Chrysler electronic distributor. Just for the sake of arguement what if you triggered the Mallory box with the Chrysler electronic distributor and it retarded like it did with the hirev 7500 box? Is this a test you can do?
Click to expand...


That I can do. When I get done with two engines on the dyno I’ll get back to that test.

And the stand alone test with the Chrysler and HiRev boxes.
 
The MSD boxes can also be triggered by points or magnetic pickup.
The extra challenge with the autotronics stuff is the MSD boxes fire multiple times in the low rpm range.

Timing lights can all have a delay due to their workings but the dial backs are for obvious reasons going to show the most slew.

That thread on moparts started because of a timing light

Mallory Unilite timing issue

Playing with a big block, chasing an off idle stumble. While checking the distributor, I noticed that the timing would retard as much as 8 degrees when I snapped the throttle. Made sure that the vacuum advance was disconnected to prevent false readings. Still the same result. Timing isn't ...
board.moparts.org board.moparts.org

For how switching time relates to degrees Tuner posted:
"For some perspective do the math:
6000RPM / 60 seconds = 100 revolutions per second
100 revolutions per second X 360 degrees = 36,000 degrees per second.
Each degree is 1/36,000th of a second or .00002778 sec."
from Spark Lead (may have to join speedtalk to see this thread)

Multi-sparks and (some) timing lights
 
Last edited:
I'm also interested in seeing how the timing retard compares if you run the same CDI with an electronic distributor. These videos are very informative; thanks for posting them!
 
You must log in or register to reply here.
-

Back
Top