[SROC3]

A buddy of mine is insistent that manufacturers (at the dealership and in their brochures) advertise Rear Wheel Horsepower and NOT Engine Horsepower. We got into this discussion as we were talking about him getting his Porsche Turbo ordered and he was saying Porsche advertises RWHP, so naturally BMW does as well. My simple explanation to him was that all over LA you see on the Billboards too "300 Horses....etc" and also in the manuals and car magazines. We all know that another good explanation is that when we dyno our cars the HP ratings are of RWHP and when you factor in the drive train loss, then you come up with the manufacturers advertised numbers. They obviously do this for marketing purposes and because most of the general public does not know any better. Now, am I missing something here? or am I spot on and my friend is just living in his own world of misconceived perfection?

[chbrules]

I know Ford claims 500HP on the GT500, but that's just at the engine. Top Gear dyno'ed it and got 450HP at the wheels. Then you have BMW who claims 300HP, where it's actually 306HP, at the wheels, then the engine is like 350HP or something. BMW's figures are all jacked up on the 335i, though.

Like most anything, people like bigger numbers. They don't care where you get them from so long as their number is bigger than someone else's.

[zenmaster]

Originally Posted by chbrules

BMW's figures are all jacked up on the 335i, though.

No.

[radgator1]

Your buddy is correct, the numbers BMW advertises are rear wheel numbers, though admittedly sandbagged a bit.

[SROC3]

Originally Posted by radgator1

Your buddy is correct, the numbers BMW advertises are rear wheel numbers, though admittedly sandbagged a bit.

That can't be. Then why do dyno graphs of 335is mostly show in the range of 270HP and 285TQ?

[radgator1]

Originally Posted by SROC3

That can't be. Then why do dyno graphs of 335is mostly show in the range of 270HP and 285TQ?

Sorry I was tired when I wrote that, you are correct, the numbers are at the flywheel not rear wheel but reported low.

[-Ryan-]

I don't think any company advertises it's rear wheel numbers.

[serge]

Originally Posted by SROC3

A buddy of mine is insistent that manufacturers (at the dealership and in their brochures) advertise Rear Wheel Horsepower and NOT Engine Horsepower. We got into this discussion as we were talking about him getting his Porsche Turbo ordered and he was saying Porsche advertises RWHP, so naturally BMW does as well. My simple explanation to him was that all over LA you see on the Billboards too "300 Horses....etc" and also in the manuals and car magazines. We all know that another good explanation is that when we dyno our cars the HP ratings are of RWHP and when you factor in the drive train loss, then you come up with the manufacturers advertised numbers. They obviously do this for marketing purposes and because most of the general public does not know any better. Now, am I missing something here? or am I spot on and my friend is just living in his own world of misconceived perfection?

Your friend is wrong You are right

[SteveMD]

Nobody advertises WHP.

That manufacturer would be at a disadvantage because Joe Average car purchaser is not aware of crank vs WHP and therefore may prefer a car stating crank HP over a competitor stating WHP.

BTW, that floored me when Clarkson whined about the GT500 only having 450 RWHP. Duh!

[SROC3]

ahhh yes......now I can rest easy. i just won $100 thanks guys!!!

[zenmaster]

Originally Posted by SROC3

ahhh yes......now I can rest easy. i just won $100 thanks guys!!!

Share the wealth!

[SGP335i]

Always flywheel

[merritt]

Using an engine dyno to determine the crank horsepower of an engine is the best way to be consistent. OEM manufactures develop their motors on an engine dyno. They run them constantly for hours in very controlled environments. The same conditions can be recreated for multiple engines. It makes sense to use those power numbers as the most illustrative figure of how an engine performs.

Once drive train components and the dyno rollers of a chassis dyno come in to play numbers become much less consistent. Calibrating a chassis dyno is a difficult and sometimes rather dangerous task.

The main thing though is that there is an SAE standard for certifying the power output of an engine. The testing procedure dictates where the power of the engine is measured:
http://www.sae.org/certifiedpower/details.htm

[Coldintake]

Originally Posted by SteveMD

Nobody advertises WHP.

That manufacturer would be at a disadvantage because Joe Average car purchaser is not aware of crank vs WHP and therefore may prefer a car stating crank HP over a competitor stating WHP.

BTW, that floored me when Clarkson whined about the GT500 only having 450 RWHP. Duh!

Thank you..

Honestly, it feels like 5 year olds are having this debate.

Porsche doesn't Advertise RWHP, Neither does Ferrari, Nor does BMW.

I wish there was a retarded smilee on this forum, although I can see why they don't have one.... it would get used excessively.