Hey guys!

When I log AFR, how many ms does the value lag behind the timing and fuel values?

i.e. While the fuel is being injected, obviously the wideband sensor can't tell you that afr yet since the fuel hasn't been burned yet and traveled down the exhaust past the sensor... The sensor hasn't taken the value yet and sent the value to the controller to be processed into a number and sent via the serial cable to the laptop where it's finally being logged.

So how many ms average is the offset? I'm mainly concerned with higher load conditions? (Which I assume has less lag since the gas moves quicker with high boost and rpm).

Via Evoscan I'm logging at about 5 samples a second, so 200ms intervals... If I want a more accurate picture when graphing the data, would it for example be better if I move all the AFR values up by a frame?

 

I'm no expert but wouldn't that have a non-linear relationship with rpm?

 

If you are only getting 5 samples per second, you should probably reduce the number of channels you are logging. Logging 8-10 channels I usually see closer to 12-15 Hz.

The time lag between the wideband and the ECU will be exhaust velocity dependent. At low loads and engine speeds, it is pretty substantial. At WOT, it is negligible.

At low speeds, you can simply look at IPW and the wideband to get an idea. You will see IPW cycle around a bit and to the the wideband will lag that cycle by a phase shift. That phase shift is essentially the time delay.