We have been working on this project for about two years, it's an Aprilia RSV (motorcycle), a 990cc V-twin sport bike modified with a supercharger belt driven by a custom shaft extension on the balancer shaft penetrating the right side engine case. To contain detonation and for charge cooling, we are using water/methanol spray upstream of the supercharger and both throttle bodies as there's no room in this densely packed bike for an intercooler. Boost is a modest 12.5 psi. Many other engine changes were also done, including custom ground cams, different pistons, and exhaust in addition to the usual flow porting etc. The custom add on computers and other electronics are extensive, not to mention the intake/exhaust plumbing, rising rate fuel pressure regulation scheme, boost sensitive fuel mapping, etc.
The result on a Factory Pro (eddy current) dyno is 184 brake horsepower at the rear wheel, nearly double the stock output. The more common "inertial" dyno most people are familiar with (a Dynojet for example) reads 25-30 % higher, and is far less useful for serious engine development. The amazing number isn't the peak power, it's the fact that this engine produces 100 hp at 18% throttle! The bike weighs 400 pounds ready to ride.
What an animal to ride....with the stock aerodynamics the bike is still spinning the tire through the lights at 175 mph! Our data logging showed 207 mph wheel speeds at 176 trap speeds. We ran into the traction equals drag problem, more effective streamlining is next on the list.
Here's a couple of pics:
We spent three days in this dyno room. The sound pressure during 11000 rpm full bellow pulls rattles your bones.
This is the bike fully assembled just before we took off for Goliad, Tx, where the event is held. Goliad is 3.67 miles southwest of the middle of nowhere. Micah on the left, Marc, and myself.
Riding the beast. Note: this pic is taken at about the 1/4 mile mark, the bike is still clawing at the sky at 135 mph.
On the sixth pass Friday, the front cylinder went soft just before the lights (we suspect compression ring failure), the bike coasted though at 172 mph and we parked it when were only beginning to understand the changes we needed to make. Now what? Here we are at Goliad with the mega deluxe AF1 diesel RV and air conditioned trailer/workshop and the pit bikes etc, and we still have two days to ride. Fortunately Micah is the biggest Aprilia dealer in North America (Af1 Racing), so a phone call (or two...) and one of his guys was enroute with another bike for us to ride......an Aprilia RSV4, the latest and greatest sportbike on the planet. In this case the showroom demo ha ha. As soon as we got our hands on it, we applied the lessons we learned Friday
The first time I even sat on it I went 173 mph, what a superb bike.
RSV4 pics
The unlimited class bikes look more like this one. They feature 1260cc+ 4 cylinder turbo charged engines with nitrous, programmable boost controllers that ramp up the boost with road speed, and air shifters that shift in 3 milliseconds. 500~600 rear wheel horsepower is the norm. The fastest speed of the meet was a bike that went 261 mph!
There were about 200 cars entered, and about 100 bikes, the fast cars all make 1700~2000 horsepower using twin turbo setups at an astounding 65 pounds of boost. The fastest car was a Ford GT (there were about a dozen being run) that went 250.7, the second fastest was a Lamborgini, also with 1700 horsepower. All cars that go over 200 are required to have parachutes for stopping. One guy was running a Porsche based mongrel with a C2 body sporting a raked windshield, a home made 996 front end, and a 3.6 breathing 55 pounds of boost. The intercooler was as big as a Peterbuilt radiator. It went 226, then I think the engine scattered.
This kind of event is highly addictive, and of course it was really fun having a week long "man-cation" with my buddies centered around speed. We'll be back to Goliad, but first the Mohave Mile in September.
