I'm familar with RWHP as most of us have been to one of these dynos that measure from the rear wheels. But what's the difference between BHP and CHP?

 

BHP Brake Horsepower
CHP Crank Horsepower

Crank horsepower is probably a term that people have just made up to estimate engine horsepower based off of rear wheel numbers. BHP is what is actually measured on an engine dyno.

 

Brake horsepower is WHAT is measured...it's an old-school term that isn't used much anymore, being tossed in favor of the plain term "horsepower". The "brake" part coming from HOW it was measured: by device called an engine brake.
Crank horsepower is WHERE that measurement is being taken from, as is RWHP.
Crank horsepower is sometimes called CrankShaft HorsePower (CSHP) or even FWHP or FlyWheel HorsePower.
It can get rather confusing, sometimes.

Larry
code5coupe

 

Then there's SADHP: Standardized A$$ Dynomometer Horse Power.

 

Just remember Tom, no matter HOW you measure it, MORE is BETTER!

 

Then there is GHP, Gorilla horsepower. That is usually measured by several guys after a few beers while staring at the engine.

 

I've also seen FWHP used to abbreviate "Forward Wheel HP" - 'member...not all cars are RWD!

 

Through 1970 HP was reported as gross HP due to the competition between manufacturers. In 1971 the Society of Automobile Engineers, SAE stepped in and changed the rating to NET HP to better reflect the installed conditions.

Manufacturers would run the engines out of the cars with nothing to hold them back. They experimented with engine temperature and ambient temperature to obtain maximum HP.

 

??????????.....

Yes "horsepower" is WHAT is measured......
but,
"brake" is one type of HOW it is measured...this is usually obained directly on an "engine dyno" using a electric dynometer....which could simply be described as an electric motor trying to run in the opposite direction as the internal combustion motor...by measuring the electric power it takes to maintain constant speed you can determine the motor horsepower

"gross" refers to measuring the engines horsepower (on an engine dyno) when all of its own needs are furnished externally.....water circulation, fan cooling, alternator, no air cleaner, no exhaust.....every trick in the book to to get a big horsepower number

"net" refers to measuring the engines horsepower (on an engine dyno) with all the normal power using accessories attached to the engine..

"crank" refers to WHERE the horsepower is we are talking about....usually data obtained from an engine dyno..."gross" or "net"...often now we estimate what would be at the crank based on data obtained at the rear wheels...

"rear wheel" refers to horsepower at the rear wheels and is obtained using a chassis dynometer.......horsepower is calculated based on the acceleration rate of the large drum that the wheels drive..

"rear wheel" is a more true measure of "net" horsepower because now you have subtracted the drive train losses along with the losses associated with engine things, like alternator....

"corrected" usually refers to adjusting horsepower measurements to "standard" atmospheric conditions

Now what I don't know.....how is horsepower obtain on an "inertia" dynomoter related to "brake" horsepower..........example: changng to a lightweight flywheel would not change brake hp since friction would not change....but the extra inertia of weight would effect the "inertia" dyno reading..

 

[QUOTE=LT4BUD a electric dynometer....which could simply be described as an electric motor trying to run in the opposite direction as the internal combustion motor...by measuring the electric power it takes to maintain constant speed you can determine the motor horsepower[/QUOTE]

I've never heard of a dynamometer that used that particular method, but I suppose it's possible. Would take a HECK of a big electric motor to equal 400-500hp......

Larry
code5coupe

 

[QUOTE=rocco16I've never heard of a dynamometer that used that particular method, but I suppose it's possible. Would take a HECK of a big electric motor to equal 400-500hp......

Larry
code5coupe[/QUOTE]

Used in some local motor factories......

Several kinds tho..

http://www.taylordyno.com/eng/maineng.html

http://www.mustangdyne.com/

Actually in some industrial worlds a 500hp motor isn't all that big.....10,000hp is big!!!

 

[QUOTE=rocco16]I would suspect that the electric motor does not need an HP rating equal to, or even near, the HP of the internal combustion motor it is measuring. The electric motor would be considered the "load" on the engine, and the HP is most likely calculated by the "Rate of change" over a specified time which the engine turns the opposing electric motor. I could be so full of it scares me, but being an enginner, this is how I would design one...

 

I think its "Front Wheel horsepower"... Not sure though.

-Joe