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Last page update was 27 Mar 2011

Fisher Fury R1 Performance

So how much of the stuff you hear about bike-engined cars is true? There seems to be a lot of pub talk and hype. Some people say that there is no way a 150bhp BEC will do 0-100mph in less than 10 seconds. And I guess this is what I'm hoping to prove or disprove one way or another but, I don't think it is that simple. There are a large number of factors that affect performance as this web page hopefully shows. One thing I'm sure of though, is that no two bike-engined cars are alike, so sweeping generalisations are best left in the pub. I'm going to focus on the facts, the design issues and my own measurements, taken using calibrated and accurate equipment. A few things to note:

The Engine

When you decide to build a bike-engined car, this is the hardest decison to make, bar the actual make and model of the car itself. Obviously the power and torque characteristics vary depending on the engine chosen and the year. To give you an example, I'm using a 2003 R1 engine which is fuel injected. Earlier engines (pre-2000) used carbs and later engines (2004 onwards) are a totally different design. The later engines were known to have more peak power but less power and torque lower down the rev range. A bike engine in a (road legal) bike is to some extent a compromise, having to meet noise, emissions and packaging constraints. When you extract it and place it in a car, a lot of those constraints are removed, even within the limitations of the SVA test. After the SVA test bike-engined cars often get modified further for track days and racing, the main constraint left being noise regulations.

Many engines use piggy-back or intercept controllers to modify ignition timing and fuel injection, to optimise the engine for the modification made on installation in a car. A good rolling road session can liberate the full potential of the engine to better use the bigger air filters possible, the custom tuned manifolds, the removal of air-injection systems and addition of free-flow exhausts. Track day cars often do not feature a power sapping catalyst either. This means that a bike engine in a car can (but will not always) generate more power than the stock bike from which it was extracted. Bike-engined cars do not go fast enough to utilise the ram-air effect associated with some large sports motorbikes.

Power And Weight

With an open air filter arrangement and a custom 4-2-1 manifold the power is estimated to be around 160bhp but, this has yet to be confirmed on a rolling road. But even rolling roads figures are based upon some assumptions and the measurements have error margins and are not absolute. I'm not sure that I can ever publish a power figure here that everyone would agree on. From the rolling road results I've seen so far, it was definately worth spending the money on a tuned 4-2-1 manifold as it provides real improvements in power and torque.

So far, my calibrated AP22 estimated peak power at 175bhp. This sounds high to me. It is based upon the total vehicle weight I'd entered, which was 530Kg (includes car and driver). When all dressed up I weighed myself at 102Kg. This means the engine is more powerful than expected or the car weighs less than I expected. Either of which is good news. I've now weighed the car to be exactly 450Kg with half a tank of fuel. I will get it properly weighed and corner weighted fairly soon, to confirm these numbers. This puts the power-to-weight ratio at around 400bhp/ton.

How you weigh the car is going to make a difference to some of the other numbers. Most manufacturers quote dry weights (no oil, water, etc.) but this is a meaningless figure in my view. The weight that really counts as far as I'm concerned, is the one measured just before you get in the car and drive off. With a light-weight bike-engined car the amount of fuel in the tank is also going to be a significant contributing factor and the standard approach seems to be to measure weight with a half full tank. This is the measurement that I'm planning to make and use on this web site. Petrol weighs 0.737Kg per litre.

We also can't forget the driver, a significant part of the overall mass to be moved in a bike-engined car.

Aerodynamics

Most seven-style cars are notorious for their brick like aerodynamics at speed. This is one reason why I went for a Fury over a Striker and my Fury will reach 130mph significantly quicker than a comparable Striker. All other things being equal, it will also have a higher top speed. The aerodynamics are going to play a small part in the 0-100mph time but will pretty much insignificant in the 0-60mph time.

Transmission

The transmission design and implementation is going to have a huge impact on the performance of a bike-engined car:

Wheels And Tyres

Wheels are important in two ways. Firstly, they are unsprung mass as well as total mass and power is used to make them accelerate along with the rest of the car. Secondly, they have rotational mass which is even worse. It's essential to use as light a wheel as you can and one with minimal rotational mass (i.e. as much of the material is as close to the wheel centre as possible). The limiting factors here are strength and reliability. The size of the wheel also dictates the size of the tyre and since this goes on the outside, it's rotational inertia is also higher on a larger wheel, even if the overall diameter remains the same.

Tyre Diameter

Don't under estimate the effect that tyre radius will have on performance (assuming non slip conditions for now to keep it simple)! As an example, I'm using Yokohama A048R tyres in 185/60R13 size on the front and back of my car, which have a diameter of 550mm. If I was to change these to a larger width 205/60R13 tyre of the same make, the diameter increases to 573mm, an increase of 4.2%. This means that a theoretical 0-60mph time of 4.00 seconds would increase to 4.17 seconds and a theoretical 0-100mph time of 10.00 seconds would increase to 10.42 seconds, which is significant.

Tyres also wear and the cars ability to accelerate will improve as the tyre wears, up to a point. Well before you get to the tread wear indicator the grip from the tyre will degrade, reducing your ability to quickly accelerate from a standing start. Assuming my current tyres lose 4mm in tread depth (diameter reduces by 2.5%), the theoretical 0-60mph time falls to 3.94 seconds and the theoretical 0-100mph time falls to 9.85 seconds.

What could happen if you went for larger wheels such as 14" or even 15" and chose your tyres badly? If I was to put a the same Yokohama A048R tyre in a 205/60R15 size on my car, a theoretical 0-100mph time would increase from 10.00 seconds to 11.36 seconds! And this is simply down to the variations in tyre diameter, which is not totally unconnected to the tyre width.

One other factor to consider is that tyres with a large diameter also have a larger contact patch and thus provide more grip, hence the reference to non-slip conditions at the start of this section. If standing starts are your thing, then your tyres are probably operating under slip conditions for longer periods of time. This may shift the balance back in favour of larger tyres and if I was trying to optimise my car purely for recording 0-60mph or even 0-100mph times, I would test out larger and wider tyres on the rear of the car.

Tyre Width

Wider tyres can improve traction up to a point.

Results So Far

0-60mph

This is a fairly variable measure of a cars performance and it depends on many factors on the day. It is also brutal on the transmission and not that repeatable. It is often hard to reach the manufacturers claimed figures for 0-60mph times. I'm really stuggling to find a way to get the power down without spinning up the rear tyres.

For some perspective, the best times I measured some of my other cars are:

So far I've only managed a few tests with the AP22. The biggest factor has been the cold weather and relatively cold tyres. They spin far too much when cold. Analysing the best times between the 10mph segments (from multiple runs) shows a 0-60mph time of 4.50s is the theoretical best I would be able to manage so far. As well as the cold tyres, the road surface has been far from ideal. I'd like to think I could record a time below 4 seconds but it is going to need better conditions and a bit more practice with the starts.

0-100mph

This is better real-world measure of a cars performance. It is less dependent on getting a good start and more indicative of the real ability to pass things on the road and track. Tests so far indicate a 0-100mph time below 11 seconds is achievable. I've only managed to time this once so far though and did a rather pitiful 14.71s but, it was a bad start and I took 7.00s to reach 60mph .

Acceleration Results

Lowest times recorded between speeds so far are: Useful on country lanes: Useful overtaking: Fast overtakes:

Peak acceleration recorded so far is 1.05g at 21.9mph. This sounds a bit high to me though. I think this higher figure is a blip caused whilst changing gear. Whilst doing acceleration tests the figures are more typically around 0.45 - 0.65g and the highest I've seen is whilst not changing gear is 0.71g.

Fuel Consumption

I have few worries over this particular 'performance' figure but, I've included it here for completeness. My driving style in the Fury is rather different than that in my other cars, so I'm not sure what you can infer from these numbers. Initial measurements show that I'm averaging about 27mpg. I'm sure I could get this figure over 30mpg if I drove normally but, that would be missing the point of the car. I'm equally sure I could get it down to around 12mpg on a track day.

Microsoft Excel spreadsheet of MPG

AP22

The AP22 Performance Meter  allows you to get accurate performance data from your car, without expensive and permanent timing gear.

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