Take a blank sheet of paper, and design the quickest turbo bike you can imagine.
Back in the 1990s, Barry was running his turbo CBX Honda funnybike with Hilborn-style mechanical fuel injection. Mike had sold some of his unfinished compound turbo GPz750 project to Lorcan who ran it as a single turbo with a DTA electronic ECU. Impressed with the control and information gathering ability of the DTA, Mike and Barry fitted the same DTA ECU to the CBX. With the new ECU, they quickly found the limits of the old Honda engine, and a new project was born…
The new project would boast the basis of a Top Fuel engine, a strong chassis designed to allow easy access to the motor and gearbox, a compound turbo system and cutting edge electronic control. Methanol was chosen as the fuel for its low cost and ability to resist detonation at very high cylinder pressures.
Why compound?
The heart of the bike is the compound turbo system. Nitromethane Top Fuel bikes can make 1500hp+ from 1700cc, but conventional single turbo alcohol or petrol funnybikes can’t make enough boost efficiently to match the explosive power of supercharged nitromethane. Our solution to this problem is to compound two turbos together – a large one to flow lots of air, and a smaller one to multiply the pressure the large one makes. Tractor pullers have been using this technique for years, but this is the first time this technique has been applied to a dragbike, or any motorcycle. Here’s how it works:
On Storm the low pressure turbo outputs boosted air to a chargecooler, this then feeds into the inlet of the high pressure turbo. This turbo doesn’t “know” it is receiving air that has already been pressurised. Both turbos can make 3:1 pressure ratio efficiently, so with 1 bar of atmospheric pressure going into the large turbo the theoretical boost available is:
1 x 3 x 3 =9 bar. Take off the 1 atmosphere you started with = 8 bar (120psi approx) of “boost”.
Or, to put it another way, the big turbo takes a large amount of air and compresses it into a third of the volume. The small turbo then compresses it again by the same ratio. You then have intake air compressed to 9 times it’s original density.
On the exhaust side, both turbos receive exhaust gas from the engine. A controlled butterfly valve “vents” the small turbo into the large one to control its speed. The large turbo has a conventional pop-off wastegate that controls overall boost and vents to atmosphere. Effectively, the inlet operates in series and the exhaust operates in parallel. This arrangement gives high inlet pressure with (relatively) low exhaust pressure, aiding the supercharging effect.
Engine
Storm uses a Top Fuel style engine with a Puma crank and a custom made 16 valve cylinder head. The head is made from a special alloy stronger than valve seat material, so needs no seat inserts or skulls.
The gearbox is essentially 2 x Bentec two-speed planetary transmissions mated into a single case to make a 3 speed. Top gear (third) is direct drive, first and second gears are underdrives, with different ratios.
The clutch is a design unique to Storm and is powered by CO2, with the pressure applied and controlled by an electronic boost controller using two programmable “ramps”; one based on engine rpm and one based on time (from when the anti-lag button is released by the rider). It has 27 square inches of piston area, so every 1psi of CO2 pressure equals 27lbs of clutch plate clamping force. We can run up to 150psi pressure, so 4000lbs of force. There are no centrifugal arms, weights or springs, so any amount of pressure can be applied (or released) at any point during the run, unlike a mechanical system.
Primary drive is by gear, preventing the drive belt breakages conventional fuel bikes suffer from, and also making the engine narrower than some conventional top fuel designs.
Chassis
The 103″ wheelbase chassis is designed to transfer as much weight as possible to the rear wheel, while keeping the front on the ground at speed. Storm runs a full fairing, land-speed style front mudguard, flat undertray and an extended tail to maximise the aerodynamic effect for high terminal speeds.
Boost control
Power, they say, is nothing without control. Storm uses a Motec ECU, M&W CDI ignition and NLR boost control, similar to the engine management technology Superstreet and ProStreet bikes have used to make giant strides in the last 20 years.