28i vs E89 3.0 coupe bhp/torque didn't make sense?

sars said:
... and how both cars are clearly geared for good 0 to 60 times
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With a 7k red line good 0-60 gears fall out of the woodwork for cars in the 250-350Nm range & 6 speed boxes. Lower the red line/limiter 500rpm and the gearing puts them a little bit bellow 60mph/100km/h.

TT, that still looks fairly rubbish torque wise. Was that a JB4?
 
techathy said:
sars said:
... and how both cars are clearly geared for good 0 to 60 times
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With a 7k red line good 0-60 gears fall out of the woodwork for cars in the 250-350Nm range & 6 speed boxes. Lower the red line/limiter 500rpm and the gearing puts them a little bit bellow 60mph/100km/h.
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That's a bit of a naive statement, if you had a slightly lower max rpm, engineers would alter the final drive to compensate. Designers work with what they have, low 0 to 60 times is marketing desirable and so they develop accordingly. For example you can see this philosophy between the 3.0si e85 and the 3.0 e89 in the 0 to 62 times, the e89 is heavier but the time taken for the 62 dash is identical for the manual with the same engine, the 28i manual has also identical 0 - 62 acceleration @ 5.7 seconds
 
It's observational analysis. Plenty of cars out there which miss out on 60 & 62mph by less than 5mph, & also have a marginally higher all important lower CO2 rating, where a simple final drive tweak could fix. But, as I found out with my 120dx there's a drivability cliff face - lower, even by a fair margin, isn’t a problem but cross the too tall line & you just fall off the urban drivability cliff. Those extra 500-800 rpm mean BMW's gearing tends to drop nicely into the 'just over' category while still being in the drivability range. This only applies to manual cars for the most part.
 
and you just hit the nail on the head, why diesel cars in manual form do not make quick 0 to 60 times as a similar powered petrol car, which was one of the OP's later questions, which I explained some time ago and hence I return to my previous statement that it was more complex than you originally stated. 8)
 
The reason diesels have low 0-60 times is because they typically average a lower kN/ton per mph. The 125i has 1.5-2% higher kN/ton per mph than the 125d between 5 & 60mph in auto guises but about 3.5% less than the 125i manual

125d (6.3s 0-60)
1st - 9-26mph (32mph)
2nd - 13-40mph (47mph)
3rd - 20-59mph (70mph)

125i auto (6.2s 0-60)
1st - 6-34mph (36mph)
2nd - 9-50mph (53mph)
3rd - 14-75mph (81mph)

125i man (6.4s 0-60)
1st - 6-34mph (36mph)
2nd - 11-62mph (67mph)
 
techathy, ignoring your mixed units, the kN/ton/mph basically equals time, so not sure dividing by velocity is appropriate or correct in that argument, though as I previously agreed the specific force is.
 
Since I am a simpleton, and this decision of power and force - i am thinking this is an star wars forum :rofl:

sars said:
techathy, ignoring your mixed units, the kN/ton/mph basically equals time, so not sure dividing by velocity is appropriate or correct in that argument, though as I previously agreed the specific force is.
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There is only one solution to this question, in top gear style "DRAG RACE" :driving: :rofl:
 
Yikes I just spend 20mins reading this thread and now I know nothing at all about engines :lol: :thumbsup: .

What I do know is my old Fiat Coupe had a Turbo and was made from plastic and tin. It could embarrass an M3 Evo, in it's day. But in terms of fine control & finesse, through the drive chain, it was such a blunt instrument, compared to a half decent NA engine. I know the twin turbos, are far more subtle. But remember It's not just about grunt, it's about :driving:
 
sars said:
techathy, ignoring your mixed units, the kN/ton/mph basically equals time, so not sure dividing by velocity is appropriate or correct in that argument, though as I previously agreed the specific force is.
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You're calculating an area so it's kN/ton multiplied by mph not kN/ton over mph. I use all the time for analysing my TT rides, but it's awkward metric to use, albite useful due to natural power normalising, as you're necessarily substituting time for velocity .
 
techathy said:
sars said:
techathy, ignoring your mixed units, the kN/ton/mph basically equals time, so not sure dividing by velocity is appropriate or correct in that argument, though as I previously agreed the specific force is.
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You're calculating an area so it's kN/ton multiplied by mph not kN/ton over mph. I use all the time for analysing my TT rides, but it's awkward metric to use, albite useful due to natural power normalising, as you're necessarily substituting time for velocity .
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but that's not what you said per means divide by as in metres PER second or m/s

techathy said:
kN/ton per mph.
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second. by multiplication you don't just get an area. it is area per cubic time or m^2/s^3 which if you multiply by the mass we're back to power and back to the beginning of this discussion, I'm still not convinced it's as meaningful as N/kg in each gear, but we can agree to disagree

edit, thinking more m^2/s^3 is specific power or more commonly known as power to weight ratio :D
 
I'm blaming my coach because he's the one who introduced me to that metric... :lol:

Where does the 3rd dimension come from? We are effectively multiplying a force by time. Are you making mass the 3rd dimension?
 
Using SI units

Force = mass x accel = kg x m/s^2

thus specific force = N/kg = kg.m/s^2/kg = m/s^2 = acceleration

from your theory N/kg x m/s is basically acceleration x velocity = m/s^2 x m/s = m^2/s^3 = specific power

Power = Watt = kg.m^2/s^3.

hope his helps
 
sars said:
Using SI units

Force = mass x accel = kg x m/s^2

thus specific force = N/kg = kg.m/s^2/kg = m/s^2 = acceleration

from your theory N/kg x m/s is basically acceleration x velocity = m/s^2 x m/s = m^2/s^3 = specific power

Power = Watt = kg.m^2/s^3.

hope his helps
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Which means you're looking at things way too deeply & thus missing the point completely ;)
 
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