Cylinder Balance Test using 12V Battery Data

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I started playing with my new Picoscope 4425A and found a “cylinder balance test” in the included software program. This is a guided function that involves connecting leads to the 12V battery, cranking the engine and allowing it to idle, followed by selecting the number of cylinders and allowing the software to perform its analysis. Here is more info on the test:

https://www.picoauto.com/library/picoscope/cylinder-balance-misfire-detect

I am curious how battery/system voltage alone will allow a software program to determine cylinder balance. The software must be using differences in voltage drop to signify differences in compression between cylinders? I wonder if the test is as accurate as a relative compression test.
 
I assume it is measuring the delta in voltage, but I feel like a voltage regulator would mask at least a portion of what the test is looking for.

Would it not be helpful to have an input for the firing order and which cylinder is firing at any given time? From the link, it looks like it just assigns cylinders a bar graph value.

I would also wonder how much exhaust gas scavenging would factor in and how per-cylinder AFR's and EGT's affect the test.

Seems like a novel feature and I suppose this test is more intended to yield a Yes/No answer for the question of "Do I have a hurt cylinder?" I can also see how this could be helpful to diagnose a transverse V6 or V8 where one bank is not as accessible.
 
I started playing with my new Picoscope 4425A and found a “cylinder balance test” in the included software program. This is a guided function that involves connecting leads to the 12V battery, cranking the engine and allowing it to idle, followed by selecting the number of cylinders and allowing the software to perform its analysis. Here is more info on the test:

https://www.picoauto.com/library/picoscope/cylinder-balance-misfire-detect

I am curious how battery/system voltage alone will allow a software program to determine cylinder balance. The software must be using differences in voltage drop to signify differences in compression between cylinders? I wonder if the test is as accurate as a relative compression test.

It's part of the Hyundai GDS aswell for a few engines. Works consistently.
 
I assume it is measuring the delta in voltage, but I feel like a voltage regulator would mask at least a portion of what the test is looking for.
curious. It might not be voltage - it could be filtering for frequency - alts are fairly noisy.?
 
I started playing with my new Picoscope 4425A and found a “cylinder balance test” in the included software program. This is a guided function that involves connecting leads to the 12V battery, cranking the engine and allowing it to idle, followed by selecting the number of cylinders and allowing the software to perform its analysis. Here is more info on the test:

https://www.picoauto.com/library/picoscope/cylinder-balance-misfire-detect

I am curious how battery/system voltage alone will allow a software program to determine cylinder balance. The software must be using differences in voltage drop to signify differences in compression between cylinders? I wonder if the test is as accurate as a relative compression test.
I have seen this kind of test but they use a clamp-on DC ammeter.
 
I could see disconnecting the fuse for the injection, and then analyzing periodic ampere draw as ea cyl comes up to TDC on compression stroke...???
That would be a relative compression test.

The test being described in something else. Seems like it is a very general go/no-go.
 
I have the 4425 too - I don't generally use their diagnostic software, just the scope itself. I'll have to give it a look see though

I've always just used their Amp clamp for the relative compression. Always an easy and fast way to start when you have a misfire
 
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