I firmly believe that knowledge is the most important tool in anybodys tool box. I would like to share some of the things that I have learned over the years. Today we start with Victory fuel injection. I hope when I am done that you may have learned something. To some this may be review, but it never hurts to have a refresher course.
Unlike your car a Victory motorcycle has very few sensors. They are as follows:
1] Barometric sensor[baro] – this is to allow the ECU to change maps depending on elevation. Think of it as having infinitely variable jets.
2] Oil temp sensor[temp] – this tells the ECU actual engine temperature. The main purpose for this sensor is cold start enrichment.
3]Air temperature sensor[AT] – since air density is effected by temperature. The Air temperature sensor, like the Barometric sensor, allows the ECU to adjust mixture for varying conditions.
4] Speed sensor[SS] – not only tells the speedo how fast you are going. It tells the ECU speed , and rate of change. It also works as a load sensor.
5]Crankshaft position sensor[CPS] – tells the ECU the crank angle so it knows when to fire the injectors,and the plugs.
6] Throttle position sensor[TPS] – on the Vic this is the big daddy. It not only gives throttle angle, and rate of change, It is also how the ECU sets base mixture.
7]ECU[Electronic Control Unit] Is the brains behind the whole thing.
Now that we know what the parts are here is how it works[simplified]. We are all familiar with the term “map” as it is referred to in EFI, but actually there is a large collection of maps. This is where the AT, and Baro sensors come in. By cross referencing the two sensors the ECU can select a map area based on air conditions. Once that is done the ECU looks at the Temp sensor to allow enrichment for cold or warm start/run.
Now we begin to fine tune things. After the map area is selected. The ECU looks at the TPS. The base voltage signal from it narrows the process to one map[This is the reason that TPS setting is so critical]. Within this map[think of a series of thousands of boxes set up in tight rows] Lets say we are in the bottom left box at idle, and that if you slowly twist the throttle we will move in a diagonal line up the chart. Each box adds a little bit more fuel. If we jab the throttlle quickly we shift from the bottom left to a few boxes right,and continue the diaginal line up. If we are moving[under load] We start off up a few boxes, and as we accelerate we move up the old diagonal line. At cruise we stay in one box,and on decel we go diagonally down towards our idle position[bottom left]
So basically any change in throttle angle moves us diagonally to the right. Rapid change moves our start point directly to the right, and load[as determined by speed] moves our starting point up. this is a simple explanation for a simple system. The real kicker here is that since an injector fires in milli seconds. All this is happening in nano seconds. The faster the ECU works the better the mixture control.
Contributing author to Cycle Solutions
with victory technical input from Kevin Cross of Kingpin Cruisers.
http://www.kingpincruisers.net
