Is hp the same as bhp?
Discussion
It's been nagging me 
for a while but now it's come to a head...is hp the same as bhp? Reading two articles for the new Suzuki hybrid (please don't judge), one quotes its electric engine at 15hp the other at 25bhp. Who's right, or are they both? Anyone who can answer this is doing better than my rudimentary scan with google. Thanks.
for a while but now it's come to a head...is hp the same as bhp? Reading two articles for the new Suzuki hybrid (please don't judge), one quotes its electric engine at 15hp the other at 25bhp. Who's right, or are they both? Anyone who can answer this is doing better than my rudimentary scan with google. Thanks.I'm a motorsport engineering student at university, so I have an idea of the subject but am willing to defer to those with greater knowledge/experience. My understanding of the subject:
Horsepower is simply a unit of measurement of power. It's only really any good for advertising these days, and the actual maths is done with watts which is an SI power unit.
The reason you hear "brake" horsepower or "wheel" horsepower or "flywheel" horsepower is this - when you're measuring power produced on an existing car (as opposed to for example doing the maths on theoretical figures for a brand new engine design), the problem is that you have to actually take the measurement somewhere! So sometimes it's on a rolling road, sometimes it's on an engine dyno, etc. But, apples and oranges, you can only really compare like for like - because of all the drivetrain losses in the system, if you've measured on a rolling road then the only true value you can get is the wheel power; most places will use a formula estimating the drivetrain losses from which they can estimate your actual engine power.
It could be argued it's all semantics anyway as torque is what's really used not power
I;m getting a bit rambly now so if anyone can correct me feel free, this is half research half hearsay half guesswork.
edit: The man above makes a good point too, applied loads are important.
Horsepower is simply a unit of measurement of power. It's only really any good for advertising these days, and the actual maths is done with watts which is an SI power unit.
The reason you hear "brake" horsepower or "wheel" horsepower or "flywheel" horsepower is this - when you're measuring power produced on an existing car (as opposed to for example doing the maths on theoretical figures for a brand new engine design), the problem is that you have to actually take the measurement somewhere! So sometimes it's on a rolling road, sometimes it's on an engine dyno, etc. But, apples and oranges, you can only really compare like for like - because of all the drivetrain losses in the system, if you've measured on a rolling road then the only true value you can get is the wheel power; most places will use a formula estimating the drivetrain losses from which they can estimate your actual engine power.
It could be argued it's all semantics anyway as torque is what's really used not power
I;m getting a bit rambly now so if anyone can correct me feel free, this is half research half hearsay half guesswork.
edit: The man above makes a good point too, applied loads are important.
No, I may be wrong, I remeber at uni testing a single cylinder Peaugot test enigne that not been started since 1954 and measuring fuel consumption and applying a water brake and using a lever to increase the speed loads to determinie it's HP.
So that makes the BHP the rating without any loads applied to it? Right?
Edited to say that this was in 1990! By far the best project I ever did.
So that makes the BHP the rating without any loads applied to it? Right?
Edited to say that this was in 1990! By far the best project I ever did.
Edited by Harji on Wednesday 20th April 20:37
OwenK said:
I'm a motorsport engineering student at university, so I have an idea of the subject but am willing to defer to those with greater knowledge/experience. My understanding of the subject:
Horsepower is simply a unit of measurement of power. It's only really any good for advertising these days, and the actual maths is done with watts which is an SI power unit.
The reason you hear "brake" horsepower or "wheel" horsepower or "flywheel" horsepower is this - when you're measuring power produced on an existing car (as opposed to for example doing the maths on theoretical figures for a brand new engine design), the problem is that you have to actually take the measurement somewhere! So sometimes it's on a rolling road, sometimes it's on an engine dyno, etc. But, apples and oranges, you can only really compare like for like - because of all the drivetrain losses in the system, if you've measured on a rolling road then the only true value you can get is the wheel power; most places will use a formula estimating the drivetrain losses from which they can estimate your actual engine power.
It could be argued it's all semantics anyway as torque is what's really used not power
I;m getting a bit rambly now so if anyone can correct me feel free, this is half research half hearsay half guesswork.
edit: The man above makes a good point too, applied loads are important.
Hi Owen, thanks for the reply very insightful, although most of it skimmed the top of my head... I was aware that the B (in bhp) referred to brake, but that was about it... I actually made a typo, the quotes were 15hp and 20bhp. Given that it came from a reliable source, do you think 20bhp could be 15hp? Or should I just bite the bullet and go with the press release's 15hp?Horsepower is simply a unit of measurement of power. It's only really any good for advertising these days, and the actual maths is done with watts which is an SI power unit.
The reason you hear "brake" horsepower or "wheel" horsepower or "flywheel" horsepower is this - when you're measuring power produced on an existing car (as opposed to for example doing the maths on theoretical figures for a brand new engine design), the problem is that you have to actually take the measurement somewhere! So sometimes it's on a rolling road, sometimes it's on an engine dyno, etc. But, apples and oranges, you can only really compare like for like - because of all the drivetrain losses in the system, if you've measured on a rolling road then the only true value you can get is the wheel power; most places will use a formula estimating the drivetrain losses from which they can estimate your actual engine power.
It could be argued it's all semantics anyway as torque is what's really used not power
I;m getting a bit rambly now so if anyone can correct me feel free, this is half research half hearsay half guesswork.
edit: The man above makes a good point too, applied loads are important.
Thanks for the help all. Very useful. Mostly
Think it's the same.
It's a measurement of energy production. I think about 750 Watts. It was originally used to measure steam engine power.
Before we had dynomometers they used some brake device to stop the engine spinning and measure the power it was producing. Became known as Brake horse power.
Ex77
It's a measurement of energy production. I think about 750 Watts. It was originally used to measure steam engine power.
Before we had dynomometers they used some brake device to stop the engine spinning and measure the power it was producing. Became known as Brake horse power.
Ex77
ks.
Horse power is referring to the comparable output between an engine and a horse. James watt devised it to help explain to people how good his motors were.
Brake horse power refers to how you measure horse power: the power it takes to brake an engine. This is where a dyno comes into it: what torque does the dyno have to produce at what speed to hold the engine at a steady speed? Hence braking the engine.
I think going back to the OP you have simply read conflicting reports. Essentially, brake horse power and horse power are the same thing. Note how I said essentially.
I am however open to correction.
Brake horse power refers to how you measure horse power: the power it takes to brake an engine. This is where a dyno comes into it: what torque does the dyno have to produce at what speed to hold the engine at a steady speed? Hence braking the engine.
I think going back to the OP you have simply read conflicting reports. Essentially, brake horse power and horse power are the same thing. Note how I said essentially.
I am however open to correction.
OwenK said:
I'm a motorsport engineering student at university, so I have an idea of the subject but am willing to defer to those with greater knowledge/experience. My understanding of the subject:
Horsepower is simply a unit of measurement of power. It's only really any good for advertising these days, and the actual maths is done with watts which is an SI power unit.
The reason you hear "brake" horsepower or "wheel" horsepower or "flywheel" horsepower is this - when you're measuring power produced on an existing car (as opposed to for example doing the maths on theoretical figures for a brand new engine design), the problem is that you have to actually take the measurement somewhere! So sometimes it's on a rolling road, sometimes it's on an engine dyno, etc. But, apples and oranges, you can only really compare like for like - because of all the drivetrain losses in the system, if you've measured on a rolling road then the only true value you can get is the wheel power; most places will use a formula estimating the drivetrain losses from which they can estimate your actual engine power.
It could be argued it's all semantics anyway as torque is what's really used not power
I;m getting a bit rambly now so if anyone can correct me feel free, this is half research half hearsay half guesswork.
edit: The man above makes a good point too, applied loads are important.
Sorry mate but very little of that is true Horsepower is simply a unit of measurement of power. It's only really any good for advertising these days, and the actual maths is done with watts which is an SI power unit.
The reason you hear "brake" horsepower or "wheel" horsepower or "flywheel" horsepower is this - when you're measuring power produced on an existing car (as opposed to for example doing the maths on theoretical figures for a brand new engine design), the problem is that you have to actually take the measurement somewhere! So sometimes it's on a rolling road, sometimes it's on an engine dyno, etc. But, apples and oranges, you can only really compare like for like - because of all the drivetrain losses in the system, if you've measured on a rolling road then the only true value you can get is the wheel power; most places will use a formula estimating the drivetrain losses from which they can estimate your actual engine power.
It could be argued it's all semantics anyway as torque is what's really used not power
I;m getting a bit rambly now so if anyone can correct me feel free, this is half research half hearsay half guesswork.
edit: The man above makes a good point too, applied loads are important.
Well atleast it wasn't when I did my motorsport engineering degree.
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