Rolling Road?!

[Boyo]

How do these work? Sorry for the dumbass question but ive never actually seen one in RL. Ive just watched a video of a clio172 on a RR and can't understand whats going on!
Does the guy actually 'drive' the car so to speak?
Again, sorry for the stupid question im just interested!

[Lowe]

The car is put on the rollers. It's driven up to about 40mph, then put in 4th gear. The computer is set to a trigger point.. usually about 50mph. The operator nails the throttle to the floor and takes the car to the red line - as it does so the computer is triggered which started to record data from the rollers. Once it's at the red line they ease off and the rollers can work out how powerful the engine is from the resistance through the wheels to the rollers.

Bit difficult to explain, I'm sure someone else will put it in english.

[Trash Man]

Made perfect sense to me

[Jiff Lemon]

You can also do clever stuff like put the engine under varying load - so you can hold the car at 3000rpm on light throttle, give it full throttle and not have it move from 3000rpm. Good for correcting weak/rich spots in your fuel map.

[Tumble]

That's on a Brake-Dynomometer isn't it?

Where the roller has a brake on it, and it's set at a specific force so the computer knows how much energy you have to put into it to get it going, and it can work out how much energy is being input from the speed of the roller or the heat from the brake. That's why horse-power is quoted as bhp - brake horsepower.

[sdp]

How do they get a figure at the flywheel?

[Zak33]

at the flywheel is now quite simple...ONCE the Car has peaked.....revved its arse off the driver puts his foot on the clutch so the engine is disconnected.....now the ROLLING ROAD puts its own power through the rollers and works out HOW MUCH HORSE POWER IT HAS TO USE, to make the gearbox and wheels turn at the same speed........it then works out the loss that the gearbox and drive created

[XTR]

clever stuff... ya learn summit new everyday.

[Barakka]

Originally posted by Zak33
at the flywheel is now quite simple...ONCE the Car has peaked.....revved its arse off the driver puts his foot on the clutch so the engine is disconnected.....now the ROLLING ROAD puts its own power through the rollers and works out HOW MUCH HORSE POWER IT HAS TO USE, to make the gearbox and wheels turn at the same speed........it then works out the loss that the gearbox and drive created

I was told it was just calculated based on the HP at the wheels, multiplied by some figure which was why you get varying figures for the flywheel depending where you go (they use different multipliers).

[wol]

Originally posted by Barakka
I was told it was just calculated based on the HP at the wheels, multiplied by some figure which was why you get varying figures for the flywheel depending where you go (they use different multipliers).

I suppose that would work but isnt as accurate.


Never knew that about working out the BHP at the engine. That man is a wealth of knowledge.


Zak how do you know so much about cars?


Wol

[XTR]

Originally posted by wol


Zak how do you know so much about cars?


Wol

He's not human!

[Zak33]

*blushes*.....it just goes in my head, and wont go away again.

Besides...I live and breath the damn things......start work at 9 finish at 6 ish.....no set breaks, some days its busy, other days its not, work all day Saturday too....used ot work Sundays at old garages, been a parts man, and valeter (good job), a salesman, a finance man, a Motability salesman, and now a Sales Manager.

same old thing for nearly 14 years.....you're bound to learn SOMETHING if you work in the motor trade for 14 years and go rallying a bit as well

But Hexus gives me a chance to share it with you all, without being biased.....

see my next thread about Vectra's to see what I mean