With only the tuning of Natasha left I decided to enlist the help of a professional for this final step. My main reason for doing this was my lack of available time: the impending construction of my dream home was racing up ahead of me, and also a distinct lack of suitable workshop space meant I needed some assistance. After trolling through Yelp and making a couple of calls I found a shop that could help. Well, between them moving locations and the five weeks I waited for an appointment, something got lost in translation and they couldn't actually help me. So I took Natasha home and thought what to do next.
Because I changed the carbs, put pods on, and a different exhaust on Natasha from all the stock components, I knew that tuning would be a challenging final project. In some senses I was glad to had off this to someone with greater experience than myself. In my mind carb tuning is like black magic; something that is more art than science. But I started to think about how the pro's do it, and stumbled upon websites selling gas analyzers.
For several thousand dollars I could get a machine that would give me an accurate breakdown of the exhaust gases, and therefore allow me to figure out what is going on exactly inside the combustion chambers of Natasha. As much as I would love all that information my main consideration in tuning the carbs is just to get the engine running at an optimum level throughout the rpm range. In scientific terms this is called stoichiometric combustion: when all the fuel is burned completely. For gasoline engines this is a ratio of air to fuel of 14.7 to 1. If the air content is higher than the stoichiometric ratio then the combustion mixture is said to be lean; if the air content is lower than the stoichiometric ratio then the combustion mixture is said to be rich.
So all I really needed was an Air to Fuel Ratio meter, or AFR meter. Since this effectively measures the oxygen content it can also be called an O2 meter.
After much researching I found a product made by Innovate Motorsports that would measure the AFR of Natasha and not break the bank in doing so. As I looked at this product I saw the potential for really creating something tailor-made to my needs, and be a whole lot of fun building it at the same time. Their data loggers not only measure the AFR, but also had inputs for an RPM induction sensor, and four analog channels where other sensors could be attached. It wasn't long before I had a system built in my mind that would do more than just record the AFR. I could really gather some hard data, not only while the bike was stationary, but also make the system portable enough to take on the road, and gather engine information throughout the RPM range/different load conditions.
Of course this level of customization meant that I had to build my own box of electronics to make it all work. It wasn't going to be an off-the-shelf project. :)
Throttle Position sensor, and the associated 5V power supply. This is a rotational sensor that measure 110 degrees of movement and outputs a 0-5V signal. I haven't quite figured out the exact mounting for this yet, but I think I will modify a bar-end such that a short D axle can be attached and that be the stationary point on the bars so that the whole sensor pivot with the twist of the throttle.
Exhaust Gas Temperature sensor, which is very similar to the ECT, but as a simple probe.
Air Temperature sensor, which is a simple GM type air sensor, that again runs on 5Vs. In order to output a usable voltage it needs a 2.2k Ohm pull-up resistor. This sensor I will put in front of the pods to measure relative air temperature. (I actually bought two: one in a protective brass casing which would be useful for measure coolant temperatures, and a more exposed air temperature sensor. At the time of building the system I only had the pigtail for the coolant temperature sensor so that's the one you see featured.)
Because I wanted this to be mobile and specifically for motorcycles I modified a lot of the wiring to shorten it for use on a bike. It's all mounted on a 1/4" piece of black ABS plastic with 1" webbing for securing to the tank. To eliminate potential damaging vibrations and protect the tank I used a piece of 1" closed cell foam under the ABS base. (This was actually one of those sports cushions for when you go to see the Seahawks and don't want your butt to go dead sitting on the hard stadium seating for hours.) Power is supplied by the bike's battery and I swapped the cigarette lighter style plug for a standard tickle charger style. Natasha already has this plug fitted to her loom. To finish it all off I had an old GPS that I mounted on top to give an accurate speedometer reading. This isn't stored anywhere, and is just for potential speed testing later on.
So all this data gets written to a standard SD card on the LM-2, but it's also possible to hook up a USB cable and write everything directly into the application program that comes with the LM-2. Of course it's written for a PC and after looking at purchasing Parallels to run Windows on my Mac it was so much easier to just buy a laptop. One Facebook post later and $50, and I have an awesome little Dell that runs Windows XP and works perfectly.
But does it work? Well, after hooking everything up (except the throttle position sensor which I am still working on.) I fired Natasha up and watched the AFR readings, and started to see the various temperature readings climb. I didn't want to run her too long, just enough to get an initial reading so I knew where to go first with changing the carbs. Somewhat surprisingly it said that Natasha had a stoichiometric ratio of 35, which is incredibly lean. But when I removed the sensor from the exhaust pipe it was covered in sooty particles which would indicate a very rich combustion going on. So I'm off to a slightly rocky start, but at least I have data now that I can interpret, and it's definitely going to be a scientific journey tuning Natasha.