Lean burn secondary ignition waveform

Why is the secondary ignition waveform sharp when the air-fuel ratio is lean?

Fuel molecules are conductive. The lack of fuel results in a lack of conductivity/higher resistance within the spark plug gap. Higher resistance requires higher voltage to maintain spark. Likewise, the inverse is true. Excess fuel creates a less resistive/more conductive condition within the spark plug air gap, requiring less voltage to maintain spark.

In the case of lean burn, the ignition waveform is useful for judging, but I did not understand the reason. Thank you.

What scope do you use to see the ignition waveform? Which one is best?

I use Snap-on, Picoscope, ATS eScope, and AESwave's uScope. (But, I'm a bit of a nerd, with an addiction. )

Which one is best? That depends on your needs.


Snap-on scopes are very good. But, they lack the ability to zoom in after capturing a waveform. You must record/capture at the most zoomed in level that you need. Then, you can zoom OUT to see the "Big Picture". Snap-on has a voltage input ranged of up to 400V and requires no attenutation for capturing ignition coil primary voltage. The Sample Rate of Snap-on scopes is 6 Million Samples Per Second, divided by the number of channels in use. All channels share a common ground.

Picoscope is the "Top-shelf" labscope. The PicoScope 4000 Series can capture up to 400 million samples per second. Zooming capabilities of the Picoscope are phenomenal. With a maximum input voltage of 200V, an attenuator is needed to capture ignition coil primary voltage. Each channel uses its own reference to ground. Picoscope has finely tuned software (free to download and use) that offers the ability to create math channels, reference waveforms, decode CAN-bus, and more.

ATS eScope has phenomenal zooming capabilities, as well. However, a sample rate of 1 million samples per second, divided by the number of channels in use, can't compare to Picoscope. It is, still, plenty of sampling power for most automotive applications, though. With a maximum voltage input of 500V, it requires no attenuation to capture ignition coil primary voltage. Where the eScope lacks in sampling power, it makes up for it with ease of use. eScope has functions that automate some of things that can be done manually with the Picoscope. Such as, identifying misfires by plotting crank frequency and labeling cylinders, a signal generator output, a MOSFET pull-down output for activating solenoid/relays, and more. The eScope shares a common ground with all channels.

The uScope is a very good, very affordable, pocket-size, single-channel scope. It, also, has a sample rate of 1 million samples per second. It is sold at AESwave.com. Picoscope and ATS eScope can, also, be purchased at AESwave.com. www.aeswave.com/uScope-Basic-Kit-p9621.html

If you start out with a single channel scope, you will quickly want more channels. The same is true if you start out with a 2, or 4-channel scope.

Any scope is better than no scope.

I use the uscope, GTC505 ignition analyzer for the ignition waveform. There is also HANTEK 2D82. Thank you.

I am a beginner so I would like to study here. Thank you.

I understand in your article that car technicians will eventually reach the pico scope. How did you learn picoscope?