View Single Post
      04-12-2019, 12:33 PM   #25
Private First Class

Drives: M2 Competition 6MT Black
Join Date: Feb 2007
Location: Raleigh, NC

iTrader: (0)

Originally Posted by motex View Post
Brake horsepower (bhp) is the measure of an engine's horsepower before the loss in power caused by the gearbox, alternator, differential, water pump, and other auxiliary components such as power steering pump, muffled exhaust system, etc
This basically describes SAE gross HP used long ago.

Today, auto manufacturers advertise SAE net HP...

“When achieving a net-horsepower number, the engine must be tested in as-installed condition, utilizing factory-specific ignition timing, fuel delivery, exhaust (including manifolds and mufflers), and other accessories like the alternator and water pump. In short, this delivers a closer approximation of how much power an engine produces as installed in the car.”

This SAE net HP figure becomes wheel HP after considering the transmission, driveline, differential efficiency losses.

“The net rating system was used until 2005, when the SAE issued standard J2723. This standard clarifies the existing methodology, but also requires an independent observer be present when the testing is done.”