Soldato
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citation needed.
Edit: actually by F1 you mean mclaren don't you? That makes more sense now.
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How relevant is BHP per tonne
- Thread starter Born_2_Kill_83
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citation needed.
Edit: actually by F1 you mean mclaren don't you? That makes more sense now.
It tends to mean most below 100mph than above. For big speeds in short spaces (VMax for example) you need big horses to get to say 180mph then big horses and good aero to get past it. For big acceleration in short times both light weight and lots of horses help, or a good power to weight, but then you also need good traction. R500 Caterham will spank most cars to 80mph, over that many supercars will start to hall it in and from 100 to 150mph many cars that are heavier will spank it because they have horses and better aero. Now throw some bends in and it all gets more complex with more parameters. It can be said that a solid BHP per Tonne is good, but if you need 10,000bhp because you car weighs 10 tonnes it propably means around a track you still won't be that quick.
It's why statistics are one element and tell very little about real world performance on their own.
It's why statistics are one element and tell very little about real world performance on their own.
Just one point I wanted to post up quickly before I go out.
no one has commented on Motorcycle BHP/Ton ratios so far (Unless I missed it)
Surely they are good in that respect as well as aerodynamics?
Please dont flame me for putting my penny in
That's because we hate motorbikes and there is a seperate subsection for the organ donors of this forum to use
Ok doke, Just wondered if it helped/hindered anyones arguements either for or against.That's because we hate motorbikes and there is a seperate subsection for the organ donors of this forum to use
Soldato
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Bikes have epic power to weight and drag, but they have sod all grip, the SAE car would beat the CBR600RR off the line even with its restrictor in the inlet. Bikes are also slower in the bends and very weak on the brakes.
Torque is relevant to speed, I know this forum likes to write off torque figures as rubbish though.
Take the new 535d which is 1795kg(auto) and 299bhp is will accelerate 0-60 in 5.7s. With a power to weight ratio of 167bhp per tonne.
The 535i (with the same auto box) is 1775kg with 306bhp so 20kg light with 7 odd more bhp. That does the 0-60 sprint in 6.1s and has a power to weight ratio of 172bhp per tonne.
0.4 of a second to 60 is a lot more power required at those times and with less bhp. The d has up to 600nm of torque which will be spread fairly evenly across its shorter rev range and the i has 400nm but more than 2000rpm more to play with.
I not saying that all diesel engines are fast by any means but at the same time you cant just write torque off as rubbish.
Take the new 535d which is 1795kg(auto) and 299bhp is will accelerate 0-60 in 5.7s. With a power to weight ratio of 167bhp per tonne.
The 535i (with the same auto box) is 1775kg with 306bhp so 20kg light with 7 odd more bhp. That does the 0-60 sprint in 6.1s and has a power to weight ratio of 172bhp per tonne.
0.4 of a second to 60 is a lot more power required at those times and with less bhp. The d has up to 600nm of torque which will be spread fairly evenly across its shorter rev range and the i has 400nm but more than 2000rpm more to play with.
I not saying that all diesel engines are fast by any means but at the same time you cant just write torque off as rubbish.
Bikes have terrible aerodynamics, much worse than a car.
Yes but would the cross sectional area being a lot smaller make up for that.
Nah, cheesewire does for bikes.
Soldato
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Torque has nothing to do with that, it is solely down to the power curve's bandwidth and the gearing.
In this case you have been confused by the published maximum bhp.
But is that not what everyone uses for power to weight ratio? Thats like saying the bhp published has nothing to do with it. In which case power to weight ratio is worthless.
Deleted member 66701
Deleted member 66701
Correct - my car has 180bhp thus 300bhp/ton. It does 0-60mph in 4.2s but tops out around 125mph (geared for 140mph).
1900Nm @1800 rpm is ~480bhp and that is ultimately why it has the effect.
you would get the same effect with 950Nm @3600rpm or even 190Nm @1800rpm.
the reasons HD engines go for low revs big torque is that of longevity and fuel economy.
the number that relevant is the power at the rpm the engine is operating at not the peak power figure or any torque number
you would get the same effect with 950Nm @3600rpm or even 190Nm @1800rpm.
the reasons HD engines go for low revs big torque is that of longevity and fuel economy.
the number that relevant is the power at the rpm the engine is operating at not the peak power figure or any torque number
On paper (Power to weight) wise my GTI was quicker than my Soarer, but it feels that the Soarer is the faster car between the two (Probably due to the Soarer having 100BHP+ up on the GTI), so I don't think that it is the be all and end all.
That being said, I do think that it is one of the most accurate ways of gauging a car's performance based purely on readily available facts and figures.
My next "track" car will be bought and modified with the golden 300BHP/Tonne target squarely in mind.
That being said, I do think that it is one of the most accurate ways of gauging a car's performance based purely on readily available facts and figures.
My next "track" car will be bought and modified with the golden 300BHP/Tonne target squarely in mind
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How do you work that out? it's 3 feet wide. A decent superbike with 150+ BHP will easily do 160mph+. A car needs a hell of a lot more power than that, and BHP/tonne has little to do with top speed.
Soldato
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Thank you.
Yes, the best statistic would be average bhp acrosss the rev range used through gears when accelerating per ton. But lacking that the peak bhp/ton is the best figure we've got.
Ether way, it's the power that's making you move, not the torque.