Tuning with MyECU

This page last modified 23 November 2008

This page outlines some concepts and strategies relevant to tuning your bike with MyECU. Before continuing you should have read the MyECU owners manual or the Optimiser owners manual.

The Map

The map is a two dimensional array of timing values. The horizontal axis is the engine speed and the vertical axis is the throttle position. Each element of the array gives the position of the spark, the position of injector pulse and the duration of the injector pulse. On MyECU there are 15 points along the throttle axis and 16 points along the RPM axis giving 240 data points.

The Map Array

As you ride your bike, the varying throttle and engine speed moves you around the array. Most of the time the engine will not be positioned over the intersections of  lines on the array but will be somewhere between the 4 corners as shown in the diagram below. MyECU uses interpolation to work the timing at the points between the lines. Another way to think of it is a weighted average of the 4 nearest points.

Engine between breakpoints

To adjust a point on the map it is necessary to position the engine close to an intersection so that the weighted average is basically the same as that point. This is relatively easy to do with a dyno as the engine speed and throttle position can be held accurately at any position. It can be done to a degree while riding for the most common areas of the array but it is much more challenging and dangerous if your attention is taken off the road.

On the road, most transitions across the map are usually vertical. This is because the engine speed is relatively stable and  the throttle position constantly changing to suit road conditions. This is especially the case when in a tall gear. We can use this to our advantage when tuning the bike on the road.

The Dyno

This is the simplest and quickest method to tune the bike. You should have done a few adjustments to your map to get your bike in a ridable state first and be familiar with making adjustments either with a text editor or the ECUController. A constant speed dyno is not required but one that can produce an air/fuel ratio versus RPM graph is. This is best done with MyECU in open loop mode.

The simplest technique is to hold the RPM at say 2000RPM and set the throttle to the required level. Now allow the bike to accelerate to maximim RPM. Using the A/F graph produced, make adjustments to the relevant map line and then download the map to the ECU. This should be done a number of times for each throttle setting. You should do this for 1/4, 1/2, 3/4 and full throttle at a minimum. Other throttle values can be done at home by doing your own interpolations.

If you are running with an exhaust gas sensor and running MyECU closed loop with the Optimiser , the process is even simpler. Using the same dyno strategy of holding low RPM, setting the throttle and then letting the RPM increase, the Optimiser can automatically update the map. The acceleration must be slow enough to allow the update process to occur. MyECU can only store a limited number of map changes, so after 2 map lines, you should upload the map and then download the map with the ECUController.

On the road

In closed loop mode it is possible, with the Optimser, to tune portions of the map as you ride. These portions are the parts that are encountered under normal riding where the engine position in the map can be kept reasonably constant. The way I do this is to select a speed and gear to put the engine' s RPM on a line and a throttle setting to maintain constant speed. You can usually do small throttle adjustments so that three or four rows can be covered for short periods of time. After doing a few rows at that RPM you again adjust speed/gear to move the engine RPM to the next column.

Over time this method can cover a good deal of the map that you normally use. Given that your initial map is reasonably close to ideal, this may be all you require to get the bike performing to your satisfaction.