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Manufacturers BHP Figures...
scootz - 27/10/09 at 09:36 PM

Where do manufacturers generally take their BHP figures from? Flywheel or Wheels?

jeffw - 27/10/09 at 09:36 PM

Always the flywheel.

skodaman - 27/10/09 at 09:44 PM

Honda at least with their bikes used to measure bhp at the gearbox sprocket = flywheel and then add however much power it took to turn the engine when not firing. So their bhp figures were much higher than they would otherwise have been. To compare like for like they should all measure it at the rear wheel unless front wheel drive of course.

Mark Allanson - 27/10/09 at 09:45 PM

Computer generated figures without allowing for any frictional losses, or truthfulness!

scootz - 27/10/09 at 10:01 PM

Ta guys... often wondered!

Jeff - You mentioned in a previous thread that the B7 RS4 only makes 375bhp - I'm guessing this was at the wheels (can't be many owners who've gone for an engine-only dyno test)???

smart51 - 27/10/09 at 10:12 PM

quote:
Originally posted by jeffw
Always the flywheel.


Except the Suzuki Cappuccino. Kei cars are limited to 63 BHP by Japanese law. Suzuki re-read the rules and saw that it didn't say where the measurement should be taken so decided it would be at the rear wheels. Flywheel power is about 75 BHP.

Generally though manufacturers want the figures to look good so will measure where they are highest - the flywheel.

I saw something on TV that said Nissan (I think) take 10 engines off the production line and test them on the dyno, the published figure is the worst of those 10 engines. I guess they would say that so potential buyers think "mine will be better, won't it!"

matt_claydon - 27/10/09 at 11:26 PM

It's a strict procedure laid down in EC Directive 80/1269/EEC , witnessed by an engineer from a European Type Approval Authority.

There is no 'computer generation' involved, although technically the published figure is declared by the manufacturer and the official test determines that the test engine has an output within a small tolerance of this figure. It is therefore not necessarily exactly the test result that is published.

smart51 - 28/10/09 at 08:09 AM

quote:
Originally posted by matt_claydon
It's a strict procedure laid down in EC Directive 80/1269/EEC , witnessed by an engineer from a European Type Approval Authority.


Link to it here

britishtrident - 28/10/09 at 05:31 PM

quote:
Originally posted by skodaman
Honda at least with their bikes used to measure bhp at the gearbox sprocket = flywheel and then add however much power it took to turn the engine when not firing. So their bhp figures were much higher than they would otherwise have been. To compare like for like they should all measure it at the rear wheel unless front wheel drive of course.


Honda car hp figures tend to be wide of the mark also the 2.3ltre 158 bhp Honda engine Rover used in the 620 did have as much go as Rover's own 140bhp 2 litre engine in the 820.