How relevant is BHP per tonne

cossey3 said:
1900Nm @1800 rpm is ~480bhp and that is ultimately why it has the effect.
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My bad....

Model
Scania R420

Engine
Scania DT12 11 Inline six charged cooled Euro-4 with HPI unit injectors and turbocompounding
Fuel type: Diesel
Cylinders: 6
Bore/Stroke: 127 x 154mm
Capacity: 11.7 litres
Compression Ratio: 17.0:1
Maximum net power: 414hp(309kW) at 1,900rpm
Maximum net torque: 2,100Nm(1,549lbft) at 1,100-1,350rpm
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BigglesPiP said:
He was guessing the RPM, he got pretty close.

The massive torque at the peak torque RPM is providing just short of 400bhp, that's why it shifts without a trailer.
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But the max power is delivered way past the engines peak torque output the torque has dropped off a cliff by that point.

Maximum net power: 414hp(309kW) at 1,900rpm
Maximum net torque: 2,100Nm(1,549lbft) at 1,100-1,350rpm
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550 Rpm past peak in the torque delivery of that engine is some cliff, all of the "lunge forward" which is the only way I could describe it, comes in the peak torque rev range if you follow? yes, it continues to pull, but as the engine gets near to its red line, it feels like you have backed off the throttle - the rapid acceleration is getting the shift right from say 7th @ 1350 - 1450 rpm into 10th and being able to ride the torque in the higher gear - the limiter then cuts in & spoils the fun... :( :o :D

I'm not picking argument, I'm describing , or trying to, the seat of the pants feel. its all witchcraft to me really :o I'm genuinely interested in how all this torque / bhp crap works! :)
 
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R420LA6X2/4MNA said:
But the max power is delivered way past the engines peak torque output the torque has dropped off a cliff by that point.
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That because power is torque multiplied by RPM.



550 Rpm past peak in the torque delivery of that engine is some cliff, all of the "lunge forward" which is the only way I could describe it, comes in the peak torque rev range if you follow? yes, it continues to pull, but as the engine gets near to its red line, it feels like you have backed off the throttle - the rapid acceleration is getting the shift right from say 7th @ 1350 - 1450 rpm into 10th and being able to ride the torque in the higher gear - the limiter then cuts in & spoils the fun... :( :o :D

I'm not picking argument, I'm describing , or trying to, the seat of the pants feel. its all witchcraft to me really :o I'm genuinely interested in how all this torque / bhp crap works! :)
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So what your saying is the power comes in at that start of the power band? If you could somehow reach 1900RPM before 1300RPM you'd get an even bigger lunge.

Just believe us, torque gets you nowhere, power as a result of torque doing work makes you fly.
 
Dandle said:
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.
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Evo have the 535d at 6.4 seconds, so slower than the 535i, just as you would expect. Unfortunately no figures for a 535i but the 335i (1610kg so a fair bit lighter) does it in 5.6s.
 
Smokey26 said:
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.
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I'm not saying the total drag is worse than a car, but the drag coefficient is very poor. A typical car might have a Cd of ~0.3, a bike could be from 0.5 to as high as 0.9. Obvioulsy the bike only has about 1/3 or less of the frontal area so total drag force would be similar or less.

Why do you think superbikes get such crappy fuel economy when they only have to pull ~180kg+rider around?
 
Alibaba99 said:
Evo have the 535d at 6.4 seconds, so slower than the 535i, just as you would expect. Unfortunately no figures for a 535i but the 335i (1610kg so a fair bit lighter) does it in 5.6s.
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Evo only have data for the E60. There was no E60 535i.

Car and Driver in the US have a stock 335i dragstrip tested at 4.9 seconds to 60.
 
Car and driver tends to use American seconds, they differ to the rest of the world and when used in comparison tests are always shorter for American cars.....unless longer is best then they tend to be longer.
 
Dogbreath said:
I'm not saying the total drag is worse than a car, but the drag coefficient is very poor. A typical car might have a Cd of ~0.3, a bike could be from 0.5 to as high as 0.9. Obvioulsy the bike only has about 1/3 or less of the frontal area so total drag force would be similar or less.

Why do you think superbikes get such crappy fuel economy when they only have to pull ~180kg+rider around?
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15,000 revs?
 
BigglesPiP said:
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.
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SAE car would for sure, better traction off the line....same engine

Typical bike power to weight, 1000cc machine, you have 210kg and 80kg rider, so with approx 190bhp you get 655bhp/ton. Problem is aero's of a brick and lack of grip.

Bikes stop surprisingly well though if you get it right as nearly all the bikes weight and momentum transfers to the tiny front tyre...it's abit of a urban myth

0-100-0 times

1. Bugatti Veyron - 9.90
2. Suzuki GSX-R1000 -10.70
3. Ariel Atom S'Charged - 11.00
4. Ariel Atom 450 - 11.05
5. Atom Private Owned - 11.05
6. Caterham CSR260 - 11.95
7. Brooke Double R - 12.50
8. Porsche 911 Turbo - 12.50
9. Ford Focus WRC - 13.57
10. Lamborghini Gallardo - 13.65
11. Ascari KZ1 - 13.80
12. Corvette Z06 - 13.80
13. Alpina B6 - 14.80
14. BMW M6 - 14.95
15. TVR Tuscan 2 - 15.00
16. BMW M5 - 15.20
17. Audi RS4 - 15.80
18. Aston V8 Vantage - 15.81
19. BMW Z4M Roadster - 15.95
20. Porsche Cayman S - 16.46
21. Lotus Exige S - 16.60
22. Nissan 350Z - 18.80
23. Vauxhall Astra Sprint - 18.85
24. Vauxhall Astra VXR - 19.05
25. Renault Megane F1 - 20.55
26. Mazda 6MPS - 21.00
27. Ford Focus ST - 21.35
28. Vauxhall Vectra VXR - 22.35
 
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