My requirements for the engine are:
- Light in weight. The 2003 Yamaha engine and gear box weighed in at 60.5Kg dry weight.
- More power. ~250bhp at the crank would be nice.
- >100lb-ft torque output.
- Rev limit around 12,000rpm, ideally closer to 14,000rpm.
- Reasonable MPG figures. My Fury has averaged 28mpg over the last five years, which is pretty good considering the way it gets driven!
This car isn't about large amounts of horse power, headline numbers or lap times. There are many family hatchbacks with over 200bhp. In a 400Kg car, you don't need large power outputs to give it 'supercar' acceleration. I'd rather sacrifice power for weight. The numbers that count to me are on-the-road weight and bhp/ton.
My 'worst case scenario' is that I use a current Yamaha R1 engine and end up with ~180bhp in a 400Kg car. This engine requires fairly minimal modifications to work well in a bike-engined car and a tuned 4-2-1 exhaust manifold, uprated clutch, sump baffle and slight oil over-fill is all that is required. This is what I currently have installed in my 450Kg Fisher Fury R1 and this is already a faster car than I really need on UK roads.
180bhp in a 400Kg car equates to 450bhp/ton. To put this in context here are a few weights and bhp/ton figures of cars I'd be happy to own (figures from EVO Magazine):
- Bugatti Veyron Super Sport = 1838Kg and 654bhp/ton
- Ford GT = 1583Kg and 353bhp/ton
- Lotus Elise S2 SC = 870Kg and 254bhp/ton
- McLaren MP4-12C = 1434Kg and 419bhp/ton
- McLaren F1 = 1137Kg and 560bhp/ton
And yes, I know the weight of the driver becomes more significant as the weight of the car becomes lower but, trust me on this, it doesn't make that much difference. The other thing to bear in mind, is that this car is geared for acceleration and a much lower top speed. My Fisher Fury R1 doesn't do a bad job of keeping up with a Yamaha R1 motorbike up to 100mph because it has gearing (and traction) on its side.
Andy Bates from AB Performance is using 2008 Honda Fireblade engines in his race cars and is getting very good power outputs in excess of 180bhp.
Suzuki GSX1300R / Hayabusa
The engine I currently have in mind for this car at the moment is a normally aspirated but modified 2011 Suzuki Hayabusa 1340cc, in-line, DOHC liquid-cooled engine. Typically this engine requires a dry-sump installation when used in a bike-engined car.
Maximum power is 146 KW 195.7 hp @ 9800 rpm and maximum torque is 154 Nm @ 10200 rpm
Whilst designing this car, I will always have the installation of a car engine in mind as well. It doesn't appeal to me but I'm curious to know how easy the same car could handle a more conventional car engine.
The plan is to mount the engine in the front of the car close to the rear bulkhead and low down in the car.
The radiator will also be mounted in front of the engine, as per the motorbike installation. This results in minimal pipework and low volumes of coolant.
This installation configuration is also ideal in many other respects. It keeps the bike electrics and wiring loom standard and simple to install. It also makes it possible to use the bike exhaust manifold.