BMW_Dude

A Swedish company that makes specialist engine test equipment has come up with an answer to the perennial bar-room argument about how much power a car engine really produces.

Stockholm-based Rototest, whose chassis dynamometer bolts directly onto the wheel hub, has been testing cars since 1995. It has collated the figures from more than 500 tests and concluded that in the average car only around 90 per cent of the quoted peak engine power is available at the wheels.

“We see this measurement as an interesting way to define customer value,” says company boss Christian Engstrom. “It is what you as a customer get as available performance compared to the claimed performance that you paid for.”

Manufacturers providing more power than their official claims include Mazda, VW, Skoda and Mini. Three of the top five models had forced induction engines.

“It’s very difficult to tell exactly why they do well, but maybe the car we tested is better built or that the manufacturer under-quotes the power for marketing reasons. They are also press cars and there is a chance they are in, let us say, peak condition,” explains Engstrom.

During homologation — the legal hurdle that all cars have to jump before production can start — each model must take an EU power test, which measures the engine alone, with no gearbox attached and in lab conditions, producing a figure for flywheel power. Once in production they are allowed a five per cent variation against the quoted figure, says Rototest.

Its all-time worst performer was a 1996 Nissan Primera 2.0, whose CVT gearbox absorbed a shocking 23 per cent of the engine’s quoted output.

That result is comparable to the more recent 2005 Range Rover Sport Supercharged, whose 385bhp engine produced only 78 per cent of that figure at the wheels.

Audi has three models in the worst five — a 2005 A6 Avant 4.2 quattro automatic, a 2007 S6 Avant auto and a 2006 RS4 — which were unable to produce nearly 20 per cent of their quoted power output at the wheels.

Much of these losses are due to the car’s four-wheel drive systems, as a comparison between the V10-powered S6 and the similarly engined, rear-wheel-drive BMW M5 shows. The BMW loses just seven per cent of its claimed 500bhp.

The complete set of figures is available at - ONLY REGISTERED AND ACTIVATED USERS CAN SEE ALL LINKS - CLICK HERE TO REGISTER.

Source = Autocar

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The Emperor

Interesting to say the least...

Mirage77

I guess AWD have more friction, mechanicals, etc that draws away all that power.

Just_me

Thats what I've saying so long, thats why the Rs6 need more power than M5 and E63

PC Valkyrie

Oh my.....what an awesome site. Many thanks for the post. It is very interesting to see a single source testing all of these cars in the same way so you can actually compare measured output between cars and see how much power loss there is to the wheels compared to the stated manufacturer's claims of HP at the crank.

Mirage77

- ONLY REGISTERED AND ACTIVATED USERS CAN SEE ALL LINKS - CLICK HERE TO REGISTER

The GTI did extremely well.

Splenditenes

Thats interesting news.. maby Audi needs to cut the AWD system in the RS6.

YoUhimhER

does s3 only come with quattro grim? cuz if it does, quattro is truly impressive, it transfers 100% of stated horspower and 103% of stated torque to the wheel.

PC Valkyrie

I don't think that is the proper interpretation of the data for the S3.

HP and torque numbers that manufacturers claim are those produced at the CRANK of the engine (before connecting to the transmission and the drive wheels).

When cars are tested on a dyno, what is measured is HP and torque produced at the DRIVE WHEELS. What is commonly known is that you can never transfer 100% of the HP/torque from the crank onto the drive wheels. There always is unavoidable power loss through the various components of the drivetrain (like the transmission, differentials, etc).

Historically, automatic transmissions with torque converter have always had more power loss through the drivetrain than manual transmissions. That is why an automatic transmission car historically has always been slower than the manual version of the same car. Same thing with AWD cars.....with more components, there is more opportunity to have less than 100% transfer of power from the crank to the drive wheels.

In other words, it is impossible to generate MORE HP/torque at the drive wheels than at the crank of the engine. The only explanation of the results of the S3 is that the engine of that particular S3 had much more HP at the crank than Audi has claimed.

Another example of this is the popular BMW 335i. It is rated at 300HP and 300lb-ft torque (in N. American spec). Yet many people have dynoed the 335i and found that the power figures at the wheels are fairly close to the numbers BMW claims at the crank. What most people conclude is that the actual power output at the crank is much higher than what BMW claims, rather than concluding that the BMW drivetrain is extrememly efficient.

Mirage77

Yes, S3 comes only in Quattro.

PC is exactly right.

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