Oscillations in lambda values above 2000 RPM

[srivsaga]

Hi,

I am trying to run the Royal Enfield Classic 500 cc single cylinder two - wheeler engine using an M150 ECU. Currently, I am tuning the VE Table from scratch using lambda values from a wide band LSU 4.9. I have done some calibrations of the VE Table up to 2000 RPM and have faced no major issues as such. But above 2000 RPM, there are severe oscillations (from .8 to about 1.2) in the Lambda Values and I am unable to figure out the reason. I have turned the closed loop fuel off. I know that there is something wrong with the fuel system, some incorrect timing or fuel film is not right, but I don't know the exact reason.

A snip of the telemetry display of fluctuations is attached in the following link:
https://drive.google.com/file/d/1X-DAR3eJv4Mmr7SCLQm-k3dc7uao0fgp/view?usp=sharing

Has anybody ever experienced a similar issue? Any suggestion would be much appreciated.

Thanks & regards,
Sagar

[David Ferguson]

Have you tried putting your hand over the exhaust to increase the back pressure and reduce the tendency of non-combustion air influencing the reading. How far is your 4.9 sensor from the tip of the exhaust.

For closed loop it's critical to get Fuel Closed Loop Period table correct. Turn on Close Loop, and determine the values for the table by reaching a steady state condition, note the Exhaust Mass Flow, then change the Fuel Mixture Aim by 10% and see how long it takes for the Exhaust Lambda to reach the new Fuel Mixture Aim. Do this for several RPMs and you can get the shape of the table and fill in some values for the trends.