Ignition Timing for Dummy Mechanics

typical ignition timing marks

Sadly enough, it's surprisingly common for our research staffers to run across freelance posts that seem to be well-polished, authoritative content... but once read are shown to be the work of someone who just harvested factoids from someone else and, often, reworded them. It's the rewording and re-ordering that gets these freelancers into trouble; trouble like returning DotD Lori Kilchermann generated for herself in the WiseGEEK.com post, "What is Ignition Timing?"

Right out of the box, Kilchermann showed her unfamiliarity with the concept of ignition timing, when she explained that,

"Ignition timing is the relation of spark to the position of an internal combustion engine's pistons. Measured in degrees of the piston's stroke within the cylinder wall..."

Say what? It is not "degrees of the piston's stroke," Lori, it is degrees of rotation of the crankshaft! Apparently they don't teach that in auto-shop classes at Kilchermann's J-school. Lori continued her daffynition by explaining that timing is, in her words,

"...it is relative to the before or advanced relation of the piston to the top dead center of its stroke, or the after or retarded position."

No, timing isn't "relative to" that "relation," it is defined as that relationship: timing advance is a set number of degrees (of crankshaft rotation) before TDC (top dead center); retarded is a set number of degrees after TDC. More Kilchermann sloppiness ensues in her description of how to use a timing light:

"With the engine running, timing is set by using a timing light and taking a reading from the engine's harmonic balancer. The balancer is attached to the crankshaft and is marked with lines and numbered in degrees both before and after top dead center of the piston in its stroke."

Really? marked with lines and numbered? We call bullshit, Lori: the numbered scale (if any) is typically on the crankcase, not the harmonic balancer. That's not to mention that the timing marks in many cars – especially older cars that normal people can actually work on themselves – are on the flywheel pulley, not the (often nonexistent) harmonic balancer. Of course, Kilchermann's greatest sin is that she doesn't explain how to advance or retard the timing while using the timing light. No, dear readers, the word "distributor" does not appear anywhere within her post. Perhaps she thinks one somehow adjusts the harmonic balancer! No wonder Lori is our Dumbass of the Day!

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