From last November:
Heading to Byron Dragway, our favorite test track, we saw shades of Bonneville with an early morning rain that kept us in the trailer until early afternoon. Once the track was dry and clear it was time for fun.
loading the bike…
Deciding what fuel percentage to run was another question that needed to be answered. The system as originally set up was to run 60%. Now 60% is a ratio of 60% nitromethane to 40% Methanol. Nitromethane has its own set of rules and characteristics when it is used as a motor fuel. Originally developed as a solvent for cleaning printing presses in the early 20th century it was, I believe, first used as a motor fuel byGermany near the end of WWII. Having lost their petroleum sources, synthetics were the next thing to turn to for powering their military vehicles. The Komet was an aircraft using this as a fuel.
With the CHNO3 formulation, it can be seen to have a hydrocarbon element to its makeup. It is the tail end of the formula that makes the difference. See those three oxygen molecules? It is the oxygen-carrying ability that makes the power. It doesn’t need the outside air to mix and combust in the same ratio as gasoline or alcohol. It brings its own to the party. I am not a scientist, but have, since first running nitro in 1982, realized that many amazing things can happen when nitro is properly run. Some not so great, but equally entertaining things when it is not.
Early on many different compounds were mixed with nitromethane to “improve” its power delivery. Such things as Benzene, Toluene, and most commonly Propylene Oxide (P.O.) were added in varying percentages themselves. The most common effect was to sensitize the nitro. This makes nitromethane, which chemically is a cousin of nitroglycerine. There is a dye in modern nitromethane used for fuel that turn blue if it happened that you add an alkaline element to the mix, thus sensitizing it. We inadvertently did this with the very first batch we used in 1982 by using a methanol that had an alkaline trace in it. The mixture turned very blue. (read: Aaaaaah!) It was at that time I just very carefully and slowly walked out to the back and gently poured it out on the gravel. There are many stories of mishaps with sensitized nitro, but I digress… Incidents like this prompted a ban on any additives to nitromethane (besides methanol).
Using the recommended 70% nitro/methanol ratio seemed a bit sporty, looking at the weather station and the amount of burnable air that day. In the interest of keeping a cushion, we opted for 60%. Ten percent lower seemed to be a good place to start.
Fueling up the bike, we had no idea what the fuel consumption would be and after running the blown fuelers years ago and using 2 to 2 1/2 gallons a run, we put in three gallons.
Out to the staging lanes and then it was time. Doing a somewhat tentative burnout, the first run was a 10.979 seconds at 132.84 mph. Not bad for a 750cc motor and much more rewarding than the gunshot manifold explosion the first time we came there with a new combination earlier in the year.
Back we went to the pits and topped up the fuel and then realized the fuel consumption was about a half a gallon a run. I guess three gallons was a bit of overkill.
Turning up the springs on the clutch and adding 5 degrees more ignition timing, we went back out and got in line.
Less than an hour later, the next pass was a 10.078 @134.75 mph. The increased engagement rpm and power from the timing change helped the 60 foot time, lowering it .331 seconds that translated into a .091 second drop in the e.t. A good result from tuning changes.
Next we decided to raise the fuel percentage. Going from 60 to 70% and turning in the clutch springs again got us a 9.819 @ 137.89 mph with a 1.561 60 foot time. It appears we are finding the tuning-responsive areas of the platform. It appear to like timing and fuel percentage. The clutch didn’t seem to engage any higher, so we opted to look at what else to fiddle with.
Well, not wanting to deliberately damage the engine, turning in the clutch another ½ turn was about it at this point. The result of a bit more aggressive riding yielded a 9.767 @ 137.68mph with a 1.606 60 foot time. This showed us the platform showed promise and we needed to find something more in the clutch and/or gearing as the 60 foot times had quit improving after the third run.
(this is a testing pass so a jumped light doesn’t matter)
All in all it was a very good day. I had more fun with a motorcycle than I have had in many years. It was an initial proof of concept that worked, showing that a person could take a well-prepared bike out and make four passes in three and a half hours on a nitro bike and not blow it up, make changes, see the effects and have some fun. You didn’t have to be some sort of wizard to do it, either. Now back to the shop and look at things to see if there were any issues cropping up. The folktales about nitro were proven to be just that. It sounded good, smelled good and ran good. What more could you want? A lower e.t. of course!