Top Gear Dyno ?

[Fun_Bucket]

Watching Top Gear tonight, (repeat episode)

Hammond is testing a GT500, and he puts it on the Dyno and claims that it's 60 hp short of the manafactuers claimed output.

But don't manafactuer's measure their power output at the flywheel, not at the drive wheels?

If i am right i am wondering how they made such an error, and how Ford would have reacted about them making such claims about their car.......

[soop]

You can deduce RWHP from FWHP though.

Ford probably reacted the same way as every other car company that has been slagged off on that show! :P

[edals]

Only way would be is to take it to where it was very first tested then test it again to be sure. But every car maker is different.

[carra909]

different dynos give different readings,
atmospheric differences in air density and temp,
and being a demo car, it would have a fir bit of spirited driving and engine ware on it.
yadda yadda yadda

[Grennan]

Soop is right, you can calculate the other power figures if you have another one.

It also depends on the dyno. Pretty much every dyno will give a different reading and you can bullshit readings depending on how tightly you strap it down etc.

[f1tzy]

As always only mph over the 1/4 tells the truth

[delcowizzid]

if i remember that episode they say on it that the dyno worked out the drag of the running gear on the overun .after the powerun you goto neutral and let the dyno wind its self down and it works out the drag of the driveline and can then calculate a pretty accurate FWHP

[woteva]

It also depends on the dyno. Pretty much every dyno will give a different reading and you can bullshit readings depending on how tightly you strap it down etc.

So true. Even different operators can get different readings on the same dyno. Have also heard that changing rim size can give better readings as well.

[soop]

60hp is close enough to what the Manufacture stipulated.
Beats the crap out of Nissan and the GTR anway. "By this car, we've no bloody idea how it'll compare to the next one, But I'm sure its good!"

[Darren_L]

I noticed the exact same thing last night. And there was no mention about some special sort of dyno that estimates flywheel hp.
Once again, the Top Gear hosts clearly have no technical knowledge of cars
Hammond was questioning Ford's 500hp claim (every manufacturer quotes flywheel hp). Yet expected the rwhp to match the fwhp........ it would be great if we had zero % driveline losses.
fairly basic knowledge for a car enthusiast......

[soop]

You can expect it to match. So long as you don't expect the numbers to be the same

[Maxxiz]

different dynos give different readings,
atmospheric differences in air density and temp,

Seriously? :/ you think "atmospheric differences" would create a huge difference? Maybe like 1-2 hp MAX...

[Decicrate]

Seriously? :/ you think "atmospheric differences" would create a huge difference? Maybe like 1-2 hp MAX...

It can make a MASSIVE difference depending on how the dyno software interprets the conditions, eg air temps, humidity and then you have barometer readings.

You don't need much of a change in hectopascals to see a big difference in the power read out.

[MasterOfReality]

Don't manufacturers use engine dynos to calculate a true fwhp without ancillaries, and thats whats stated in the specs?

I remember reading about this in an old Street Machine magazine years ago.

[VKCOMMO]

That's what I thought, so they could also get the highest figure to help it sell

[CSP]

Yes. Manufacturers specify fwkw. The Top Gear figures were DERIVED fwkw figures. I.e. derived from the rwkw figure based on drivetrain loss and therefore what the likely current fwkw output is.

It's not rocket science.

[soop]

^^
Exactly, They could have derived it fairly accurately as well.

[immortality]

Don't manufacturers use engine dynos to calculate a true fwhp without ancillaries, and thats whats stated in the specs?

I remember reading about this in an old Street Machine magazine years ago.

that is what manufacturers use to do many moons ago. these days advertised power should be what the engine produces with basic ancillaries like waterpump, alternator, power steering pump etc

[soop]

I think they should quote RWHP to be honest. Makes more real world sense.

[Darren_L]

Yes. Manufacturers specify fwkw. The Top Gear figures were DERIVED fwkw figures. I.e. derived from the rwkw figure based on drivetrain loss and therefore what the likely current fwkw output is.

It's not rocket science.

it's not correct either

the driveline loss calculation method isn't even close to giving an accurate fwhp figure... You can't calculate driveline loss, there is no set formula. An educated guess at best.
besides, I don't recall there being any mention of it being 'derived'

the figure they came up with sounds more consistant with being straight rwhp, not derived fwhp

[soop]

Matter of opinion, and until they say otherwise this whole thread is a guess so....?