Lambda, AFR, TPS.... WHAT?

Lambda, AFR, TPS.... WHAT?

Setting up the fueling on a racebike insures maximum performance, maximum drivability and also effects the durability of an engine. Using a dyno for this is a great way to get a base setting but when you are at different tracks in different conditions it's really nice to be able to fine tune this fueling to work perfectly in those conditions.
Recently a lot of people have been asking me how I go about doing this with race bikes I work on or have worked on in the past so I thought I could share some details here on the different possibilities.

Lambda CAN

Reading Lambda Values


  1. AIS System - Make sure the Air injection system is blocked or dissconnected or you will get strange readings
  2. Exhaust leaks - It's very important you don't have any exhaust leaks or again you will get strange readings

Autotune Devices

Several manufacturers make additional fueling systems for bikes for example dynojet (Power Commander) & Bazzaz. These have been around for a long time but only in recent years have they started to accept that fueling can be adapted in other places than just a dyno. Both manufactures can supply "AutoTune" packages that use a lambda sensor on a bike to read the air fuel mixture reading from the exhaust and adjust the fueling of the bike accordingly.
Below is an example of how the bazzaz system works which is really nice. When you set up the original map for the bike on the dyno you can create a Target AFR table which tells the bazzaz system at what rpm and tps you expect the AFR to be. If the bazzaz see's that the bike is not achieving this then it will make a suggestion on how much to change the fueling to get to this value. It's then possible to either select just some of these changes and apply them to the fueling map or accept all changes and apply them straight away.


AFR Loggers

There are a range of loggers you can buy for reading your Air Fuel Ratio when using the bike. Some of these have a really poor sample rate which gives poor results and others are much better. Here I am going to talk about the LCU-ONE sensor which can be bought from AIM and plugged into a range of their loggers including the Solo DL & Evo4.
As with all AIM products you can use the Race Studio software to analyse your results but this is where it can start to get confusing. There are so many different ways in which you can view this data depending on what you want to achieve so here are some of the options I show people when I'm helping them use AFR loggers.


A Histogram is a tool you can use to show you the percentage of time a value spends in a certain range. Using the histogram gives me a very quick overview of how good a bikes fueling is "in general". In the example below you can see that clearly the bike spends most of the time in the correct range over a lap.


XY Plot RPM vs AFR
Here I create an XY plot with the RPM on the x axis and the AFR values showing on the graph. In this example I can see in the 7500 - 10000 range the range is a bit too spread out so I have some work to do here. The erratic values you see along the top can be caused by things like traction control cutting or just by heavy engine braking.


XY Plot TPS vs AFR
This can be a useful graph to help smooth out certain throttle opening etc but be careful you will see around the 0% area a lot of high readings and this is because of engine braking.


Measures Graph over Distance
This graph can look a bit messy especially when you see it zoomed out like below. However you can follow the AFR readings over a lap while comparing to things like what gear you are in, rpm & tps. If the rider complains about the bike being harsh on the throttle at any point you can look here and see at that point on the track what the bike is doing and adjust the fuelling accordingly.

Messure AFR

Lastly, if I'm still not happy with the results I will export the RPM,AFR & TPS values to excel and build a table like you see in the bazzaz image at the top to show average AFR values with RPM on the x axis and TPS ranges on the Y axis.

Excel Example

All AIM products can be bought from us and we support all riders with help getting to understand how to use their data