I would love a logger that just did rpm. Really see what the clutch is doing. Would make tuning really easy. The mps unit is way too rich for my blood.
My first goal of this was to make something that people could use as a real tool and change it to fit their needs. Not like all the $1000 - $10000
systems I was looking at, most with 10Hz sample rates and 8 bits of resolution. My second goal was to make it so most people could afford it.
Sort of like the whole MegaSquirt EFI project. The nice thing is that the logger is VERY VERY simple compared to an EFI. I think the program that runs it is maybe 50 lines of C code right now. Because I used all open sourced tools to develop the unit, anyone can download them and make changes.
There was not much interest in it. So for now I am spending time making my prototype better.
Could you set up your data logger to do rpm using the tach output from the schnitz box. You can set the output to either 1 or 2 output signals per revolution.
It seems that if the ignition guys did one thing right, it was the tach signal. The Dyna SP 4000, MC-2 and my MC-4 all work the same. Because they need to work with other equipment like RPM switches, tachometers, shift lights and such they all seem to follow a standard. So, yes it will work.
To give you an idea of what you could see using a simple two channel logger, this first graph is the clutch slippage in percent. The logger knows the crank speed from the tach and measures the output shaft speed using a sensor. You enter all of your data about your engine and the program then knows what the ratio of the two should be. If the engine is spining at 1000 RPM and the output shaft is not moving, it's a good indication that the clutch is not engaged, or zero percent.
Two very interesting things about this graph. From the time I released the button to the time the clutch starts to engage is 0.6 seconds. Then it takes another 0.5 seconds to fully engage. But even more strange is the funny shape. It's not smooth like you would expect. And you thought my one video clip was soft!! LOL This was me playing with a restrictor on the output of the air cylinder to slow the release to try and keep the nose up. It would be like you letting your clutch lever out slow. The air ram chatters when I do this causing the oscillations. Even though I could tune for the delay, it was not consistant at all and caused the steel plates to get hot spots.
So I dropped this idea and started experimenting with lower static pressures. So, same bike, engine, tire, etc. No restrictor and very low spring force with a lot of arm mass.
Notice now that when I release the button, the clutch starts to engage after 0.05 seconds and is fully engaged after 0.22 seconds. More important is the shape.
The clutch gets to about 30% (slope A) and stays there for about 0.07 seconds doing a nice slip until the massive weights start to kick in (slope B). This keeps the shock down, tire from spinning and I would suspect allow the bike to run at Norwalk, or in my driveway with about the same results. This is the data from the last driveway video clip BTW. This seems to also solve the hot spot problem.
The next step would be to start pushing slope B back to slope A to get the bike to react faster. The only problem is if you push things too far you get something like this.
This is a graph of the output shaft in MPH. Now my engine tuning is not good enough to ever win me an award, but it sure is not so bad that it's causing this. So softer is slower, but it sure beats a 10" 4.5PSI bouncing ball. But then again, a little better driveway prep would go a long way to help this out. I need to buy some VHT for home use.
Ok, one last thing before closing the book on this subject. So, I can plot two shaft speeds in MPH, RPM, frequency, or take a ratio of the two there is one other interesting thing. This last graph shows how the bike accelerates. This graph is showing the change in output shaft RPM every 0.01 seconds. Anything greater than zero and the bike is speeding up, anything negative and the bike is slowing down.
You can see how it starts out nice and smooth then things start to get a little funny. At 5.2 seconds into the run the bike actually starts to slow down. Notice the bottom graph is showing boost pressure in PSIG. Notice that every time the bike shifts, the boost pressure rolls off. My bike uses a stock transmission so I kill on every shift for 0.05 seconds. Notice that the negative spike in the first graph happens after the bike shifts. The tire spun. We could see that the tire was not holding the track very well anyway prior to it giving way. Of course, higher pressures and we are making a tad bit more power.
Ok, the question should be how do I know the tire slipped and not the clutch. Well this is the whole point of the logger. I can plot the clutch slippage as before and see. If the clutch is not slipping, then it must be the tire.
Well, hope it at least gives you an idea of what you could do with two speed sensors and a logger if you did not know already. I get a lot of laughs with all of the electronics on my old bike.
