detecting misfires

[Yves]

Based on what can you detect a cylinder misfire in a log ?

[billr]

RPMdot, maybe? At one time I expected that was done by the knock sensor, looking for some "noise" from each combustion event, and not too much in a certain frequency. I'm beginning to understand that the knock sensor filtering is too fussy to be used for both purposes like that.

[dontz125]

A quick lean spike on the WBO2 is usually a good indicator. Since the O2 sensor detects, well, O2, a sudden surge in unconsumed oxygen suggests the event that consumes the O2 didn't happen.

[elutionsdesign]

Lean spikes.

[billr]

With a V-8 do you get much in a lean spike if you only have one WB for a bank? My BBC (1-8-4-3-6-5-7-2) has two cylinders firing close on each bank; and even ignoring that, at WOT and high rpm (where misfire is most likely and annoying!) there is so much exhaust going by the WB that I wonder if it can react fast enough to show random 1-cycle misfires. I'm not saying you guys are wrong, just asking...