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BMW diesels for Cadillac?
BMW BMW General Discussions (alt.autos.bmw)
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#71
 
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Re: BMW diesels for Cadillac? -
12-08-2004
, 12:01 PM
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In article <ecDtd.4$752.719 (AT) news (DOT) uswest.net>, Ramone Cila <dontw (AT) nt (DOT) spam> wrote: Since I doubt few will tow heavy with a 3 series and figure most are looking for sporty response, the increased torque levels are irrelevant given the already better response of the 3.0 petrol. In most give and take driving in traffic, the diesel can feel more lively due to the much higher torque at low revs. |
experience. Compared to the petrol 530i, it didn't spin as freely or
generate an equal amount of liveliness in stop and go.
The 535D is supposed to be a different animal, but once again with the price
increase one could consider the 545, rather than the 530, as an alternative
and have far more response, speed, liveliness and *fun*.
If the BMW diesels cost the same as the gas cars (like Mercedes do) then
they would have a better chance here, but given the average of 18% cost
increase for the diesel people aren't going to agree that fuel efficiency
will make up the difference and still be satisfied with the performance.
#72
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not wanting to start the inevitable hp vs. torque discussion, but torque is still the force which accelerates the car  Sure, but if it does that slower than the less expensive petrol engine and then runs out of breath at high speeds/rpms, where horespower kicks in, who cares what its' torque levels are...unless towing is a concern. It could have ten times the torque levels of the petrol car, but if it wasn't capable of greater acceleration the American market will probably react indifferently to it. |
of torque and revs. So doesn't exist independently. Torque will usually
peak someway beneath the maximum power, but if it fell off rapidly enough,
the two could *conceivably* occur at the same rpm. The difference between
diesels and petrol engines is that the torque peak on a diesel occurs at
lower rpm, and the rev range where useful torque is produced may well be
lower. Hence commonly higher gearing. However, in these heady days of
variable valve timing, forced induction and maybe even variable
compression ratios, nothing is set in stone.
--
*Fax is stronger than fiction *
Dave Plowman dave (AT) davenoise (DOT) co.uk London SW
To e-mail, change noise into sound.
#73
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In most give and take driving in traffic, the diesel can feel more lively due to the much higher torque at low revs. I haven't driven the 535D, but I have the 530D, and that was not my experience. Compared to the petrol 530i, it didn't spin as freely or generate an equal amount of liveliness in stop and go. |
traffic. In such traffic in the UK, my BMW (petrol) never gets a chance to
spin anyway. ;-)
I was reasonably impressed with my test drive of a 530D auto - it felt
slightly more lively at town speeds than my current 528.
--
*I was once a millionaire but my mom gave away my baseball cards
Dave Plowman dave (AT) davenoise (DOT) co.uk London SW
To e-mail, change noise into sound.
#74
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not wanting to start the inevitable hp vs. torque discussion, but torque is still the force which accelerates the car in a modernturbodiesel, the max. torque is obtained from 1500 rpm. this means that the car accelerates instantly when pedal is pressed, without the need to downshift or rev the engine. the max. torque of 330i is 300Nm/3500 rpm, and for 330d the numbers are 410Nm/1500 rpm. |
reply. It is easy to show from Newton's second law that POWER (hp) produces the
acceleration - NOT torque. The reason you think it is torque is because that for
any given rpm, the engine with more torque (i.e. the diesel) ALSO produces more
hp at that rpm - hence greater acceleration.
Different people have different driving styles. Since a normally aspirated
gasoline engine doesn't develop either torque or horsepower until relatively high
rpms, you have "that delay" off-the-line until you get the rpms up (or pop the
clutch at high rpm). Lots of people either don't like revving to higher rpm
(dunno why) or don't like the necessary delay compared to a diesel.
Result is people that like shifting a low rpms tend to prefer diesels, or large
V8's. People that like to rev to high rpm will extract all the horsepower (and
required acceleration) from a smaller 6. Neither is right or wrong - just
different.
Frank
#75
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I was reasonably impressed with my test drive of a 530D auto - it felt slightly more lively at town speeds than my current 528. |
engine really changed the car.
#76
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In article <imGtd.18$752.1393 (AT) news (DOT) uswest.net>, Think you're a bit confused about torque and BHP. |
I am pointing out that unless that great torque can be used to develop high
end horsepower.....who cares. 10 times the low end torque is essentially
meaningless if high end horsepower is unachievable, and as good as the new
diesels are, they still haven't bridged that gap in a way that compares to
petrol response.
#77
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Since a normally aspirated gasoline engine doesn't develop either torque or horsepower until relatively high rpms |
and bhp. At any rpm. If it developed neither, it wouldn't turn. It only
needs to develop just slightly more than its losses through friction, etc,
of course.
Torque is simply a measurement of weight and distance without time being a
factor. Add time to the equation and you get BHP.
To get BHP from torque use this formulae.
2 x pi (22/7 or approx 3.142) x torque (ft.lbs) x rpm (revs per minute)
--------------------------------------------------------------------------
33,000
Do this and you'll find out the BHP your engine is developing at maximum
torque. Which is always less in practice than the peak bhp. As is the
torque, generally, at maximum bhp. The torque you can also work out at
peak BHP by using this formulae.
--
*Always borrow money from pessimists - they don't expect it back *
Dave Plowman dave (AT) davenoise (DOT) co.uk London SW
To e-mail, change noise into sound.
#78
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Raybender <raybender (AT) sbcglobal (DOT) net> wrote: Since a normally aspirated gasoline engine doesn't develop either torque or horsepower until relatively high rpms Please. Any motor of any type which works and turns develops both torque and bhp. At any rpm. If it developed neither, it wouldn't turn. It only needs to develop just slightly more than its losses through friction, etc, of course. |
than that under the diesel's 3.0L HP curve. As Ray says, it's HP that
gives acceleration, because you have to measure the *WORK* done
to get to a specific speed. Torque != work. That's all that Ray was
trying to say (and Ramone, also, I believe.)
Floyd
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