> ken gilbert Wrote:
> mike, one thing to keep in mind is any exhaust gas pressure in the pipe
> will cause the o2 sensor to skew its reading.
> it's really an issue on turbo setups and not so much on NA rigs, but
> 2smokes generally run with higher EGBP than most NA setups due to
> purposefully slow bleedown.
Ken, I think the bigger issue for high-power 2-strokes is that the sensor doesn't read AFR directly, it literally measures oxygen content. Especially when you're not on the pipe, there is significant blow-through/short-circuiting of fresh mixture (read: oxygen) through the exhaust port, which will cause it to read super lean, even if you're running rich. And like any engine, 2- or 4-stroke, if you run so rich that you have some misfiring, perceptible or not (like when you're on the edge of 4-stroking), the gauge will read dead lean due to the unused oxygen.
So I'll mainly be using EGT to tune, as well as seat-of-the-pants/sound/experience, as well as acceleration data from the GoPro. O2 is the least helpful parameter due to its 2-stroke limitations, so it's mostly just for curiosity :)
The GoPro GPS data isn't terribly accurate, and the accelerometer data is noisy, but I'm working on a Kalman filter that uses both of them to get a nice clean signal. With some assumptions regarding aerodynamic drag (taken from empirical data from a few sources to get in the ballpark, which is good enough for comparing two jettings), and using the same almost-flat test ground as the upcoming video, I can get a reasonably accurate estimate of power to the wheel. I'll have more on that soon, once I get the Kalman filter sorted a little better. (edited)