The Lotus Cars Community banner

1 - 10 of 10 Posts

·
Registered
Joined
·
2,709 Posts
Discussion Starter #1
Is it BHP per tonne or per ton? How do you calculate it for a car? How does the elise compare with other cars?

And is there a difference between HP and BHP?
 

·
Registered
Joined
·
1,086 Posts
yes it Ton

BHP is crank/flywheel HP, the number that is usually associated with the HP of the car.

if you see whp you know its wheel horsepower, a number you get by doing a dynamometer run.
 

·
Registered
Joined
·
181 Posts
BHP, or Brake Horsepower, is how much power is produced at the crank of the engine, before it runs through the transmission and to the wheels. It's called this due to how the power used to be measured, using a 'brake' dyno.

WHP, Wheel Horsepower, is how much power the car actually puts down to the ground. The transmission has frictional losses, so WHP is always less than BHP. AWD cars tend to have more losses than FWD or RWD cars, but a good rule of thumb is about 10-15% loss.

HP by itself could refer to either, but usually refers to BHP if there's no other context clues.

I suppose you use 'tonne' or 'ton' if you live in England or the USA. Here, it's BHP per ton (2000 lbs). You simply find it by dividing the horsepower of a car by how many tons it weighs. Usually, here in the US, you'll see pounds per horsepower, which is just the weight of the car divided by how much horsepower it has.

A Lotus Elise weighs 1980 lbs, and puts out 190 bhp. So, it has 191 hp/ton, or 10.42 hp/lb. F1 cars have ~1250 hp/ton, while a Prius has about 73 hp/ton.

Here's a site that has a pretty comprehensive listing of other cars:
Power to Weight Ratios of All Current Cars.
 

·
Registered
Joined
·
2,709 Posts
Discussion Starter #6
ahhhh ok, cool.

I'm assuming if a car for example weighed 1 ton and had 300 hp, it would have 300hp per ton and if another car weighed 2 tons w/ 500hp it would have 250hp per ton... right?


but there are short tons and long tons...
 

·
Registered
Joined
·
6,945 Posts
Actually, the correct and traditional definition is:

The Oxford Pocket Dictionary of Current English | Date: 2008
brake horse·pow·er

the available power of an engine, assessed by measuring the force needed to brake it:
 

·
Registered
Joined
·
36 Posts
either tonne or ton - up to you. tonne is the metric unit 1000kg or 2204 lbs. ton is the imperial unit 2240lbs. I think there is also an unofficial short ton of 2000lbs
 
1 - 10 of 10 Posts
Top