horsepower
01-18-2004, 09:21 PM
#1
Intermediate
Thread Starter
Join Date: Jan 2004
Location: Maine
Posts: 43
Likes: 0
Received 0 Likes
on
0 Posts
horsepower
can someone explain what horsepower means in terms of Bhp and SAE hporsepower? How do they measeure the "work" that an engine does? Any info would be great just to clarify it in my head? Thanks
Also, I have an 85 with 288 hp. Is that Brake HP or is it SAE HP and what would it mean if it was vice-versa? Thanks again.
Also, I have an 85 with 288 hp. Is that Brake HP or is it SAE HP and what would it mean if it was vice-versa? Thanks again.
01-19-2004, 12:28 AM
#2
Addict
Rennlist Member
Rennlist Member
look here http://howstuffworks.lycoszone.com/horsepower.htm
SAE HP is based upon very specific ways of testing as defined by this standards group.
My understanding (could be wrong) is that Brake HP is usually associated with engines tested out of the car on a test bed. Some sort of clalibrated "brake" device is used to measure the power, vs. a high mass drum based device where the rate of acceleration is used to calculate power (as most chassis dynos are).
SAE HP is based upon very specific ways of testing as defined by this standards group.
My understanding (could be wrong) is that Brake HP is usually associated with engines tested out of the car on a test bed. Some sort of clalibrated "brake" device is used to measure the power, vs. a high mass drum based device where the rate of acceleration is used to calculate power (as most chassis dynos are).
01-19-2004, 01:04 AM
#3
Burning Brakes
Join Date: Aug 2001
Posts: 1,117
Likes: 0
Received 0 Likes
on
0 Posts
jsals2k,
I think what you might actually be looking for is the difference between SAE "gross" and SAE "net" HP.
Most, if not all, HP figures in the USA are published according to the SAE ''net''definitions. Other countries have different "sactioning bodies" if you will, like most of Europe uses DIN figures (lately, usually published in Kw) and Japan has the JIC HP standard, a smidge different than our own, there are others, but I digress a bit. There are conversion factors that are available out there if you are interested.
Basically (yes, this is a bit oversimplified) SAE HP comes in 2 different flavors: "gross" and "net''.
''Gross'' HP would be what you get on an engine dyno, using none of the installed accessories (eg, a/c, alt, p/s pump, air pump, etc) operating. IIRC, you could use open headers, and tune it to pour gas down the carb, to get that good old fashioned, unrealistically high late 60s HP number.
''Net'' HP is on the same dyno, but this time all accessories are installed and operating. As well as the emissions package, i.e. the cats and exhaust, just like the car is actually delivered (more or less) to the end user.
Back during the last round of the "HP Wars" of the late 50s through late 60s, everybody quoted 'gross' HP. Why? Simple. It was a bigger, sometimes way bigger, number. The insurance companies kinda killed that off, as well as the whole emissions thing. And there was SO much room for "playing" with the numbers, they were pretty much a joke as far as consistency goes.
There are several ways of measuring HP at the flywheel with an engine dyno, the all use some measure of ability to do work in the face of some external resistance. As Rich stated,some folks use mechanical resistance (the classic 'brake' for which it is named), or you can use an electrically based system (eddy current), or a hydraulically based system to figure out how much work (HP) the engine can do. These systems all (IIRC)determine ''brake'' HP. They get the same measurement using different tools.
Rear wheel HP (RWHP) is what most enthusiasts speak of these days, since its relatively cheap and easy to get to a chassis dyno, and get a reading at the rear wheels. 'Tis a much bigger pain in the butt to get to an engine dyno room, and a far bit more expensive.
HTH,
Greg
I think what you might actually be looking for is the difference between SAE "gross" and SAE "net" HP.
Most, if not all, HP figures in the USA are published according to the SAE ''net''definitions. Other countries have different "sactioning bodies" if you will, like most of Europe uses DIN figures (lately, usually published in Kw) and Japan has the JIC HP standard, a smidge different than our own, there are others, but I digress a bit. There are conversion factors that are available out there if you are interested.
Basically (yes, this is a bit oversimplified) SAE HP comes in 2 different flavors: "gross" and "net''.
''Gross'' HP would be what you get on an engine dyno, using none of the installed accessories (eg, a/c, alt, p/s pump, air pump, etc) operating. IIRC, you could use open headers, and tune it to pour gas down the carb, to get that good old fashioned, unrealistically high late 60s HP number.
''Net'' HP is on the same dyno, but this time all accessories are installed and operating. As well as the emissions package, i.e. the cats and exhaust, just like the car is actually delivered (more or less) to the end user.
Back during the last round of the "HP Wars" of the late 50s through late 60s, everybody quoted 'gross' HP. Why? Simple. It was a bigger, sometimes way bigger, number. The insurance companies kinda killed that off, as well as the whole emissions thing. And there was SO much room for "playing" with the numbers, they were pretty much a joke as far as consistency goes.
There are several ways of measuring HP at the flywheel with an engine dyno, the all use some measure of ability to do work in the face of some external resistance. As Rich stated,some folks use mechanical resistance (the classic 'brake' for which it is named), or you can use an electrically based system (eddy current), or a hydraulically based system to figure out how much work (HP) the engine can do. These systems all (IIRC)determine ''brake'' HP. They get the same measurement using different tools.
Rear wheel HP (RWHP) is what most enthusiasts speak of these days, since its relatively cheap and easy to get to a chassis dyno, and get a reading at the rear wheels. 'Tis a much bigger pain in the butt to get to an engine dyno room, and a far bit more expensive.
HTH,
Greg
