Join Date: Sep 2006
Location: Southern Minnesota
Autotune is definitely helpful. I wouldn't say it's perfect, but it will steer you in the right direction. I have a dyno, and I tune these, and I can explain a couple of the challenges of these.
So with 1 cylinder, pulling from 1 throttle, it's important to understand that the flow through the intake is not smooth, it's in very dramatic pulses. There are pressure waves traveling through the intake, kind of like when you slap your hand over the end of a pipe. You hear a tone, and you can feel it with your hand. That energy is happening in the intake, but at a far greater energy.
The length of the intake, cam timing, and even the exhaust system, all manipulate those pressure waves.
A carburetor "feels" these waves, and somewhat adjusts accordingly, but they throw it off also, because the carb doesn't care which way the air is going through it, it gets fuel mixed either way. This is why carbs are not real accurate, and if you look at a dyno sheet, you see the A/F ratio bouncing all over the place. Ideally, it stays within a certain range and is called good enough.
With this efi system, you get the opportunity to account for this, but it makes tuning them kind of tricky. That 3 button controller you have will not account for that effect. It will get as close as a carb, but no closer. A power commander 5 has a map. The ECM has a map, much like it that is operates off of. At each throttle position, and each RPM, it knows to inject X amount of fuel. The map in the ECM can't be changed, but it will always do the same thing, and will account for temp and barometric pressure differences.
The values in the PC5 map, are a reflection of the percentage of fuel that it will add or take away from what the ECM is injecting. So it's important to keep in mind that the numbers on the PC5 map do not show how much fuel is given, but how much it's manipulating things.
The autotune will record while you ride, and it will come up with recommendations for changes to make. If I remember right, it won't kick in until a certain rpm, because reversion, and over scavenging can affect it's readings. So you're on your own for the range that it doesn't reach. However, after accepting it's changes a few times, it should have things pretty spot on. You should see much smaller differences being made.
One thing to watch for is known as "yoyoing". If you get into a part of the map where there are big swings in what is going on, the autotune can be tricked, and it may overreact rich lean rich lean, until it gets back in line. So if you see huge swings in your map, you may want to smooth them.
All of that said, you can double check all of this with a wide band, which is handy anyway for the range that the auto tune doesn't reach. In the end, you will have a far better tune than a carb or 3 button tuner could ever hope for. As an added bonus, you can tune for any future mods that you decide to do.