The 05 Mustang V8

> Are you sure? I read a magazine dyno
> test recently and it stated the horses
> were around 240 which equates to 300
> gross power. The V6 could only muster
> 175 horses under the same dyno.
> Both numbers are no where near stated horses
> if they are indeed net and not gross rated numbers.

Car manufacturers do not advertise gross horsepower. They do not
advertise rearwheel horsepower. When you see an advertised horsepower
figure for a production car, it is stated in terms of SAE net flywheel
horsepower. This is not news. It has been this way since 1971.

Magazines and the general public never test SAE net flywheel
horsepower. When you dyno an engine with no accessories -- e.g., water
pump, alternator, power steering pump, AC compressor -- you are pretty
much testing according to the pre-'71 gross flywheel horsepower
standard. When you dyno a car on a chassis dyno (Dyno Jet, etc.), you
are testing rearwheel horsepower. It makes no sense to speak of gross
or net rearwheel horsepower; the terms gross and net just do not apply
to chassis dyno tests.

As far as the '05 GT's advertised figure of 300 net flywheel
horsepower, Car & Driver tested a 5-spd GT convertible in its June
issue. Its quarter mile trap speed was 103 mph. (The ET was 13.7
sec.) The car weighed 3673. Plugging those numbers into the trap
speed horsepower formula (hp = (trap speed/234)^3 * weight), a 103 mph
trap speed would require 313 rear wheel hp. From the formula you can
see that the hp number would go up if the stated weight of 3673 lb
weight was too low; it would go down if the weight was too high.
Applying a 20% drivetrain loss to 313 rwhp puts flywheel hp at 391.
Applying a 15% loss gives you 368 flywheel hp.

Who cares? A 13.7 @ 103 is a fantastic set of numbers for a $25,000
car.

180 Out

> Are you sure? I read a magazine dyno
> test recently and it stated the horses
> were around 240 which equates to 300
> gross power. The V6 could only muster
> 175 horses under the same dyno.
> Both numbers are no where near stated horses
> if they are indeed net and not gross rated numbers.

Car manufacturers do not advertise gross horsepower. They do not
advertise rearwheel horsepower. When you see an advertised horsepower
figure for a production car, it is stated in terms of SAE net flywheel
horsepower. This is not news. It has been this way since 1971.

Magazines and the general public never test SAE net flywheel
horsepower. When you dyno an engine with no accessories -- e.g., water
pump, alternator, power steering pump, AC compressor -- you are pretty
much testing according to the pre-'71 gross flywheel horsepower
standard. When you dyno a car on a chassis dyno (Dyno Jet, etc.), you
are testing rearwheel horsepower. It makes no sense to speak of gross
or net rearwheel horsepower; the terms gross and net just do not apply
to chassis dyno tests.

As far as the '05 GT's advertised figure of 300 net flywheel
horsepower, Car & Driver tested a 5-spd GT convertible in its June
issue. Its quarter mile trap speed was 103 mph. (The ET was 13.7
sec.) The car weighed 3673. Plugging those numbers into the trap
speed horsepower formula (hp = (trap speed/234)^3 * weight), a 103 mph
trap speed would require 313 rear wheel hp. From the formula you can
see that the hp number would go up if the stated weight of 3673 lb
weight was too low; it would go down if the weight was too high.
Applying a 20% drivetrain loss to 313 rwhp puts flywheel hp at 391.
Applying a 15% loss gives you 368 flywheel hp.

Who cares? A 13.7 @ 103 is a fantastic set of numbers for a $25,000
car.

180 Out