Ilmor develop 5-stroke motor. What?
They may not have had the best track record with bikes, but Ilmor's new 3-cylinder motor could be the future
ILMOR had dropped off the radar after their MotoGP effort went sour, but they're back with a bang, and an unconventional one at that.
The UK-based engineering company, who supply engines and technology to F1, NASCAR and MotoGP, have developed a 5-stroke motor.
The Ilmor 5-stroke prototype uses a 700cc turbocharged engine, with a fairly average peak power of 130bhp at 7000rpm, but a monster 120ft/lb of torque at 5000rpm.
The engine uses two overhead camshafts, one is high pressure, the other low pressure. The high pressure camshaft turns at half the crank speed while the low pressure crankshaft rotates at the same speed as the crank.
The highpressure cam works with the outer two cylinders, in the same way a standard 4-stroke engine would, but the low pressure camshaft works with the central larger cylinder gathering exhaust flow from the outer cylinders. The engine is designed to be far more fuel efficient than a traditional four-stroke four-cylinder counterpart.
The advantages of the Ilmor 5-stroke are as follows:
* A secondary cylinder provides an additional expansion process enabling extra work to be extracted, hence increasing thermodynamic efficiency.
* The engine runs an overall expansion ratio approaching that of a diesel engine – in the region of 14.5:1
* Minimised pumping work due to the downsizing effect from highly rated firing cylinders.
* The compression ratio can be reduced to delay knock onset without a reduction in performance.
* Because the firing cylinders can be very highly rated, the engine is relatively compact.
* The fuel consumption does not rise as rapidly with increasing BMEP, as retarding rejects more energy into the expansion cylinder.
* The engine uses 100% conventional technology and so requires no new manufacturing techniques.
With fuel efficiency being such a hot topic in MotoGP, this more fuel efficient motor could give any team running it an advantage, the only trouble is, current MotoGP rules don't allow turbos. But all that could change..
