Pardon my ignorance - Camaro5 Chevy Camaro Forum / Camaro ZL1, SS and V6 Forums

jabbar · 04-26-2010, 10:32 AM

But what's the difference between the HP numbers from the factory, 426HP for LS3, and the RWHP I'm seeing on the forums, around 350-370? How much is a cars HP based on it's RWHP?

Seems like everyone just refers to the horse power at the rear wheels but how is that translated to what the engine makes total?

Matster · 04-26-2010, 10:37 AM

Quote:

Originally Posted by jabbar

But what's the difference between the HP numbers from the factory, 426HP for LS3, and the RWHP I'm seeing on the forums, around 350-370? How much is a cars HP based on it's RWHP?

Seems like everyone just refers to the horse power at the rear wheels but how is that translated to what the engine makes total?

Jabbar, rule of thumb for the LS3 is between 12 -15% drive train lose. So you can work the numbers in the other direction as well.

SlingShot · 04-26-2010, 10:39 AM

The factory measures HP at the flywheel/crank on an engine dyno. Those are the numbers you see advertised. The numbers that count are the rear wheel HP that is done on a chassis dyno. There is a power loss through the transmission and the rest of the drivetrain. Factory numbers are used for marketing. The rears wheel power is used by tuners to measure the power gains after doing mods to the car. They will do a base dyno test to get a starting point, then again after their work is done to see the difference...

Russell James · 04-26-2010, 10:42 AM

There is roughly 15% loss through the drivetrain.

So a 426 hp rated at the flywheel would wind up roughly 85% @ 362 ish RWHP.

Or you could reverse do the math if all you knew was the RWHP. 362 x 100 / 85 = 426.

jabbar · 04-26-2010, 10:54 AM

Ahh ok I get it. So if I had 400 rwhp then I have about 470 at the crank hp aka bragging rights of 470Hp?

ron10 · 04-26-2010, 11:02 AM

there you go.so to know your true HP produced out the rear,you need to have a dyno done on your car.

04-26-2010, 10:32 AM	#1
jabbar Drives: 300C Join Date: Mar 2010 Location: SE Michigan Posts: 153	Pardon my ignorance But what's the difference between the HP numbers from the factory, 426HP for LS3, and the RWHP I'm seeing on the forums, around 350-370? How much is a cars HP based on it's RWHP? Seems like everyone just refers to the horse power at the rear wheels but how is that translated to what the engine makes total?

04-26-2010, 10:39 AM	#3
SlingShot Drives: 2012 ZL1 - #670 Join Date: Jun 2009 Location: Seminole, Fl. Posts: 8,009	The factory measures HP at the flywheel/crank on an engine dyno. Those are the numbers you see advertised. The numbers that count are the rear wheel HP that is done on a chassis dyno. There is a power loss through the transmission and the rest of the drivetrain. Factory numbers are used for marketing. The rears wheel power is used by tuners to measure the power gains after doing mods to the car. They will do a base dyno test to get a starting point, then again after their work is done to see the difference... __________________

04-26-2010, 10:42 AM	#4
Russell James Drives: '15 SS 1LE, '69 Z28 drag car Join Date: Dec 2009 Location: Mich Posts: 4,482	There is roughly 15% loss through the drivetrain. So a 426 hp rated at the flywheel would wind up roughly 85% @ 362 ish RWHP. Or you could reverse do the math if all you knew was the RWHP. 362 x 100 / 85 = 426.

04-26-2010, 10:54 AM	#5
jabbar Drives: 300C Join Date: Mar 2010 Location: SE Michigan Posts: 153	Ahh ok I get it. So if I had 400 rwhp then I have about 470 at the crank hp aka bragging rights of 470Hp?

04-26-2010, 11:02 AM	#6
ron10 Drives: 2010 2SS IOM L99 Join Date: Jan 2010 Location: LOUISVILLE,KY.. Posts: 7,545	there you go.so to know your true HP produced out the rear,you need to have a dyno done on your car.