Quoted power outputs: are they consistent / accurate?
Discussion
Something of a pub discussion that I would love to know more about!
Manufacturers habitually state - and journalists regurgitate - and punters (blindly..?) quote the standard power outputs of cars, sometimes to the exact digit.
Take the Ferrari 296 as a completely random example; it's figures sit at 889bhp and 546 lbs/ft.
Or my slightly more down-to-earth mk1 TT Quattro; 225bhp and 207 lbs/ft.
Is this factually consistent - or even accurate?
One assumes these are crank figures, and largely close or identical across a given sample of the same engine. Is there any data, such as an independent test of the outputs, to confirm these are not wild fantasy?
Of course this might not apply to smaller or bespoke manufacturers, or those who claim 'handmade' engines, but in general - how accurate are these power figures?!
Manufacturers habitually state - and journalists regurgitate - and punters (blindly..?) quote the standard power outputs of cars, sometimes to the exact digit.
Take the Ferrari 296 as a completely random example; it's figures sit at 889bhp and 546 lbs/ft.
Or my slightly more down-to-earth mk1 TT Quattro; 225bhp and 207 lbs/ft.
Is this factually consistent - or even accurate?
One assumes these are crank figures, and largely close or identical across a given sample of the same engine. Is there any data, such as an independent test of the outputs, to confirm these are not wild fantasy?
Of course this might not apply to smaller or bespoke manufacturers, or those who claim 'handmade' engines, but in general - how accurate are these power figures?!
Read UN ECE R85.
https://op.europa.eu/en/publication-detail/-/publi...
It's how it's regulated.
Also, lbs/ft? In 2023?
https://op.europa.eu/en/publication-detail/-/publi...
It's how it's regulated.
Also, lbs/ft? In 2023?
GroundEffect said:
Funnily enough I found that shortly before making this thread - the cynic in me can't be convinced that a set of regulations doesn't necessarily facilitate a standardised engine-specific approach when concerned with a sample of X identical blocks; hence my looking for (and currently failing at finding) an independent test. 'Rules are made to be broken' etc etc 
*removes tin-foil trilby*kambites said:
GroundEffect said:
Also, lbs/ft? In 2023?
lbs/ft has never been a unit in any year. 
Resolutionary said:
GroundEffect said:
Funnily enough I found that shortly before making this thread - the cynic in me can't be convinced that a set of regulations doesn't necessarily facilitate a standardised engine-specific approach when concerned with a sample of X identical blocks; hence my looking for (and currently failing at finding) an independent test. 'Rules are made to be broken' etc etc *removes tin-foil trilby*kambites said:
GroundEffect said:
Also, lbs/ft? In 2023?
lbs/ft has never been a unit in any year. And my point on the lbs/ft is that lbs/ft isn't a unit. It's lbft. Very different thing.
GroundEffect said:
But these ARE the independent tests? They are witness tested and tested for conformity of production as well.
And my point on the lbs/ft is that lbs/ft isn't a unit. It's lbft. Very different thing.
I had a pretty good flick through that regulation and apart from it stating how to conduct a given test to their standards, there wasn't any empirical data or even a suggestion (that I found) as to how many of the same power train should be tested in order to corroborate a specified power figure worth publicising. And my point on the lbs/ft is that lbs/ft isn't a unit. It's lbft. Very different thing.
That's what I'm most curious about I guess - at what point does a manufacturer / a regulatory body deem these numbers consistent and accurate (replicable?), and what is the fluctuation in real terms, for consumers? I get the feeling that if we were to dyno 100 brand new Ferrari 296'es, we might not get exactly 889bhp each time.
And I agree with the lbft vs lbs/ft correction, I just copied and pasted it from the listings on here. Seems an oversight for such an organisation..
200 bhp - or 800 bhp imho doesn't really tell you too much (without the accompanying torque graph) and enable one to read at what rpm the quoted maximum torque and bhp figures are achieved at. The 'unknown' factor, irrespective of what figures the manufacturers are quoted (and whether that are rear wheel or crankshaft) has to be - how much power will the car's electronic 'nanny' system actuallyallow through to the accelerator pedal? - even if 'nanny' is turned-off......is it really completely 'off' without some residual traction/yaw control. In short your freshly purchased 800 bhp monster may only be 'allowing' you to use (depending on traction etc) a similar degree of power to the 200 bhp car.......
Resolutionary said:
Is this factually consistent - or even accurate?
One assumes these are crank figures, and largely close or identical across a given sample of the same engine.
My limited understanding is that "bhp" figures are at the crank with ancillaries such as alternator and water pump connected. I doubt they include A/C compressor engaged and I'm not sure about the power steering pump (where applicable).One assumes these are crank figures, and largely close or identical across a given sample of the same engine.
Engine performance identical across a range? Highly unlikely. You can find wide variances across a range of apparently identical mass produced engines. It's an inevitable consequence of mass production where an assortment of parts, each of which has a "tolerance", are brought together at random to build the engine. Most engines will probably be "typical" examples but the inevitable bell-curve will result in some engines being particularly good and some engines being particularly poor. This can be readily seen in the many threads asking what is acceptable oil consumption. The average engines probably just remain average engines; the tight engines probably just wear more quickly until they become average engines and settle down; the loose engines might drink oil from day one and never lose the habit. Probably all of them will be absolutely fine for the life of the car.
roscobbc said:
200 bhp - or 800 bhp imho doesn't really tell you too much (without the accompanying torque graph) and enable one to read at what rpm the quoted maximum torque and bhp figures are achieved at. The 'unknown' factor, irrespective of what figures the manufacturers are quoted (and whether that are rear wheel or crankshaft) has to be - how much power will the car's electronic 'nanny' system actuallyallow through to the accelerator pedal? - even if 'nanny' is turned-off......is it really completely 'off' without some residual traction/yaw control. In short your freshly purchased 800 bhp monster may only be 'allowing' you to use (depending on traction etc) a similar degree of power to the 200 bhp car.......
Yep, it's a very complicated subject boiled down to one figure.If you want to know how fast a car is on the road, look at its acceleration figures at road speed, 0-60, 0-100 and 30-130 mph are much more useful.
and then consider if that 0-60 is actually
0-60, no 1ft rollout
0-62, no 1ft rollout
0-60 with a 1ft rollout
0-62 with a 1ft rollout
0-58 with bad recording equipment
then consider what tyres they were on, were the tyres warmed up, what the surface was, and what the ambient temperature was. oh and the altitude the test was conducted at...
0-60, no 1ft rollout
0-62, no 1ft rollout
0-60 with a 1ft rollout
0-62 with a 1ft rollout
0-58 with bad recording equipment
then consider what tyres they were on, were the tyres warmed up, what the surface was, and what the ambient temperature was. oh and the altitude the test was conducted at...
Nomme de Plum said:
Power kW
Torque Nm
ICE output degrades significantly over time.
No it doesn't, not sure why people say that as if its gospel, it can degrade but its not a given.Torque Nm
ICE output degrades significantly over time.
So many factors, of course if its never been serviced it may do but there is no reason why a twenty year old engine cant make book figures.
If it was it would mean that say a thirty year old car would be making like half its headline figure or less.
Seen plenty of engines make good power despite being old with high mileage, you cant predict that it degrades year on year in a uniform way.
A lot of cars in the past were over quoted which may be part of it, nowadays with more turbo models some manufacturers seem to under quote, stuff like the new Supra is mean to be 340 bhp but people are seeing quite a lot more.
brillomaster said:
and then consider if that 0-60 is actually
0-60, no 1ft rollout
0-62, no 1ft rollout
0-60 with a 1ft rollout
0-62 with a 1ft rollout
0-58 with bad recording equipment
then consider what tyres they were on, were the tyres warmed up, what the surface was, and what the ambient temperature was. oh and the altitude the test was conducted at...
All irrelevant. 0-60, no 1ft rollout
0-62, no 1ft rollout
0-60 with a 1ft rollout
0-62 with a 1ft rollout
0-58 with bad recording equipment
then consider what tyres they were on, were the tyres warmed up, what the surface was, and what the ambient temperature was. oh and the altitude the test was conducted at...
0-60 is stand still to 60 mph, nothing more, nothing less.
Tyre are whatever the car is sold with, inflated to recommended psi at ambient temperature.
Altitude is pretty irrelevant unless you're talking about doing it up a mountain, and if so, more fool you.
brillomaster said:
and then consider if that 0-60 is actually
0-60, no 1ft rollout
0-62, no 1ft rollout
0-60 with a 1ft rollout
0-62 with a 1ft rollout
0-58 with bad recording equipment
then consider what tyres they were on, were the tyres warmed up, what the surface was, and what the ambient temperature was. oh and the altitude the test was conducted at...
And you can add to that 1 or 2 people (of what weight) on board and how much fuel was in the tank, not to mention optional aids like LSDs and launch control.0-60, no 1ft rollout
0-62, no 1ft rollout
0-60 with a 1ft rollout
0-62 with a 1ft rollout
0-58 with bad recording equipment
then consider what tyres they were on, were the tyres warmed up, what the surface was, and what the ambient temperature was. oh and the altitude the test was conducted at...
J4CKO said:
A lot of cars in the past were over quoted which may be part of it, nowadays with more turbo models some manufacturers seem to under quote, stuff like the new Supra is mean to be 340 bhp but people are seeing quite a lot more.
Is that measured at the crank or on a rolling road?Chris
liner33 said:
Its quoted from the crank but often (In the case of the Supra ) makes more than that at the wheels with a "calculated" figure approaching 400hp at the crank
Yeah I've been on lots of rolling road days for various marques where you always see that (and the tuner swears their rolling road is the most accurate in the country 
). Until someone puts it on a bench dyno for a like-for-like comparison, I remain skeptical.Chris
bcr5784 said:
brillomaster said:
and then consider if that 0-60 is actually
0-60, no 1ft rollout
0-62, no 1ft rollout
0-60 with a 1ft rollout
0-62 with a 1ft rollout
0-58 with bad recording equipment
then consider what tyres they were on, were the tyres warmed up, what the surface was, and what the ambient temperature was. oh and the altitude the test was conducted at...
And you can add to that 1 or 2 people (of what weight) on board and how much fuel was in the tank, not to mention optional aids like LSDs and launch control.0-60, no 1ft rollout
0-62, no 1ft rollout
0-60 with a 1ft rollout
0-62 with a 1ft rollout
0-58 with bad recording equipment
then consider what tyres they were on, were the tyres warmed up, what the surface was, and what the ambient temperature was. oh and the altitude the test was conducted at...
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