MoTeC Global Forum

Hi,
Despite I searched in the help files, documentation and forum, I found very poor informations about lambda control, and all its parameters. May be it is due to my bad english

Is there any documentation that explain better how it works ?
My questions are:
- Having a base fuel map, will the M800 continously update the main fuel table ?
- If yes, how are handled the new fuel maps ? Do I need to resend the map after having read them with the PC ?
- What are all the parameters ?
- ....

My apologize for these begginer questions.
Angelo

Hi Angelo, what actually are you trying to do? My guess is that you want to use closed loop lambda control yes? Firstly of course your ecu must have the Lambda function enabled, then it is fairly straight forward to do. The main variance between tuners is usually the numbers/setting in the Lambda Table ( which is the lambda settings your trying to tune to ie .90) I rarely use it on road cars, but always use it in race cars simply because the sensors deteriorate rather quickly, different fuels vary the time they last. What type of engine/car is it your working on?

Cheers

Hi Angelo.


1. No the M800 will not update the map.
It will just trim the fuel to get to the right lambda aim value that the user specified in the lambda table.
It will also just trim by the amount that you set it to and at the rate that you specified. You can also set the step sizes

2. If you want to fix the fuel map.
Set up the logging to look at what the lambda control is doing. Then from the logging see how much fuel it needs and where and change the fuel map accordingly.

Cheers
M

My goal is to finalize the fuel map on my bike. I have a base fuel table which need to be tuned on track.

Ok, I understand that the trim is a single value, trying to "instantly" compensate the fuel map. Correct?

I understand that it could correct for a globaly rich or lean fuel table?
But what append if I have rich and lean sites and the motor runs through them during acceleration? Is the lambda correction fast enough?

Thanks for any information.

Angelo

Hello Angelo,
The biggest delay with the Closed Loop Lambda function is the actual Lambda sensor reading itself. Remember that the ECU will react extremely quickly to sensors and RPM to change the fuel pulse width based on your fuel tuning BUT it takes a certain amount of time for that mixture to be burnt in the cylinder and then get passed through the exhaust valve and then make its way to the sensor. So if you try to run the Lambda Control "Rate" too fast the ECU is changing the fuel based on incorrect information.

The test you need to do is to work out the "delay" in the exhaust system. Start at low RPM with the engine warmed up and at a constant load (data logging is best for this), go to the Fuel Overall Trim and put in 20% and watch how long it takes for the Lambda reading to stabilize at the richer reading, at idle for example it could be up to 1.5 seconds. Raise the RPM and repeat the test and note how long it takes again. As the RPM goes up obviously the delay time comes down and will eventually be constant. This will be affected by just about everything, engine size, exhaust design, etc.

You will use this information in your Lambda Control "Rate" table. Remember if the new fuel mixture takes 0.8 seconds to get from the cylinder to the Lambda sensor you cannot try to correct faster than this. Lets say you set the Rate at 0.4 seconds and the Lambda reading is lean, the ECU will be making two fuel corrections before the first one has reached the Lambda sensor, this will lead to Lambda Control "hunting".

Also, if the engine runs through a rich then lean site in a shorter time than the Lambda delay then you are in a bit of trouble, I would suggest tuning the engine completely before using this function, it is not designed to help with poor tuning and can only react as fast as its feedback information.

I hope this helps.