Thursday 8 May 2014

Faulty Lambda Sensor/Controller

After my last post I have got to further tuning the idle on the engine.

The last video was using 2 injection events per engine cycle in an alternating pattern. Basically, cylinders are grouped in pairs and controllable independently. Cylinders #1 & #4 are grouped as INJ1 and cylinders #2 & #3 are grouped as INJ2. 2 squirts alternating means all the required fuel for an engine cycle is injected in one go with the 2 banks alternating by 360 degrees and injector firing is untimed.

I then tried 4 squirts alternating which splits the required fuel into 2 injection events per cycle per cylinder with the two banks alternating by 180 degrees and firing is still untimed. My engine responded much better to 4 squirts alternating and was able to idle much smoother and also the off-idle response seemed sharper so I had found my base injector setting.

Once I had established that, I moved to trying timed, semi-sequential injection. At cranking I have timed the injection event to happen while the intake valve is open so that the fuel is being sprayed directly into the cylinder. At idle, the injection event is timed to end just as the intake valve opens and then this is advanced a little as the revs rise up until c.8,000RPM. This is going by recommendations in the megasquirt documentation and may be subject to adjustment as things progress.

The disappointing thing about it is that my Innovate LC-1 lambda sensor is showing faulty and so I haven't had the chance to test ride the bike yet. The sensor will read ok, if a little touchy, for about the first ten minutes of running and then it will display a full lean condition even though the idle is set to slightly rich. I have calibrated the heater and also carried out free air calibration on the sensor several times but with no results.

About 2 years ago before I started this project, I used the same sensor & controller in the same position in the exhaust to successfully monitor and tune my AFRs with the stock carb setup so I can only conclude that either the sensor or controller is faulty. After researching a little, it appears that many people have had the same problem with the LC-1 and in most cases changing the controller seems to have solved the issues.
In light of this, and rather than spend time troubleshooting either one or the other, I have bought a new PLX SM-AFR controller and sensor and so hopefully that will solve my sensor issues.

Now I just need to get back in the same country as the bike so I can continue testing with the new sensor.