psycho sport
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Registered: 27th Mar 03
Location: Guildford Surrey Drives: Vauxhall Monaro
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some people on here rave about how torque is a better judge or performance than bhp.
can some one explain this to me then :-
the fiat punto 1.9 jtd has 100 bhp and 190 Ib/ft torque
the renault clio 172 has 172 bhp and 148 Ib/ft torque
yet the clio is quicker.
the punto 1.8 16v hgt has 130 bhp and 121 Ib/ft torque
and thats quicker than the 1.9 jtd!
some one care to help me push my understanding further?
would the mid-range power on the 1.9 jtd whop the clio??
discuss
[Edited on 02-04-2004 by psycho sport]
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Marc
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Registered: 11th Aug 02
Location: York
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dont think it works like that.
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broster
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Registered: 6th Dec 02
Location: Drives: E39
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torque comes into play on motorway speeds bhp is alleceration, like high revs etc. thats a very simple way to explain it
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DangerousDave16v
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Registered: 20th Feb 03
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as i understand, torque is more useful for acceleration, whereas power determines top end speed, although they are a function of each other so its unusual to have one and not the other.
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psycho sport
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Registered: 27th Mar 03
Location: Guildford Surrey Drives: Vauxhall Monaro
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what do you mean motor way speeds??
midrange? higher gears?
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vibrio
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quote:
Originally posted by psycho sport
some people on here rave about how torque is a better judge or performance than bhp.
can some one explain this to me then :-
the fiat punto 1.9 jtd has 100 bhp and 190 Ib/ft torque
the renault clio 172 has 172 bhp and 148 Ib/ft torque
yet the clio is quicker.
the punto 1.8 16v has 130 bhp and 121 Ib/ft torque
and thats quicker than the 1.9 jtd!
some one care to help me push my understanding further?
would the mid-range power on the 1.9 jtd whop the clio??
discuss
spread of torque and gearing. TDi are geared to take into account their very small power band. put your car in a gear and if you have 140lbft of torque from 2000-5000rpm then you'll accelerate at the same rate from 2000-5000rpm.
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psycho sport
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Registered: 27th Mar 03
Location: Guildford Surrey Drives: Vauxhall Monaro
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DangerousDave16v - this is not the case as i have just shown. torque and acceleration that is!
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DangerousDave16v
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Registered: 20th Feb 03
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i dont think you can compaire just a few cars.
diesels have a characteristic narrow power band and flat torque curve.
altho those punto jtd things arent that slow!
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blackula
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Registered: 26th Apr 03
Location: Cheshire
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I found this on a site, but changed it a bit, to make it make more sense.
Torque is often referred to as 'Twisting force' and the rate of twisting force is what determines how fast the car is along with gearing. The rate is determined by, yeah you guessed it POWER, and in cars this is commonly referred to as BHP, brake horse power..
E.g. and I hope this smacks the ‘all you need is torque’ diesel drivers round the back of the head...
Stand on the pedals of your grifter or chopper with full body weight. If the pedal is 12"
from bottom bracket and you weigh 200 lbs., you are
generating 200 lb. pound feet of torque. As much as the JTD punto nearly. But unless the cranks of your bike are turning, you have no work at all. No power (bhp comes under the heading, POWER) hasbeen generated. Horsepower = (torque in lb. ft. x rpm) / 5250. So, if rpm is
zero, there is no horsepower.
This makes more sense if you go back to the bicycle. You might
be able to pedal the bicycle with all your weight cranking the pedals at
maybe 30 rpm. Using the formula above, this is 1.14 horsepower. 30 rpm
and 200 lb. ft. or torque at the pedals would flatten most hills, depending on how the bike was geared. But, suppose you as a human were twice as
powerful in terms of horsepower, pedaling twice as fast? Look at the formula. If you could deliver 200 lb. ft. or torque at twice the rpm, you could
flatten the same hill at twice the speed. Imagine if you could deliver 200 lb.ft. of torque at 2000 rpm! Obviously a human can not.
What turns the wheels more powerfully depends on two things. The torque of
the engine as you mentioned, but also gearing. The more multiplication in
gearing, the more torque to the rear wheel. But, the higher the
multiplication, the lower the speed. So, how does one get high
multiplication AND higher speed? More engine rpm. Acceleration is
strongest in 1st gear, but one can not drop down to 1st gear for passing
on
the highway. Why? Because the engine can not spin that fast. Just like
you legs can not spin 2000 rpm in the example above.
To maintain high torque at the rear wheels, multiply the torque you have
with lower gearing and/or add more rpm. The Honda S2000 sports car is a
good example. It revs to 9000 revs, but has little torque. But, because
of
that rpm, it can multiply what little torque it has by quite a bit,
delivering strong driving force at the wheels. The current 2004 Yamaha R1
motorcycle does over 100 mph in first gear (6 speed), in part because of a
13,750 rpm redline. A diesel can also be geared low, but its low rpm
assures two things. One, if geared low, it will run out of breath
quickly,
with each gear having little range. And/or, when it does get up to speed,
it will be geared tall enough to negate what torque advantage it may have
had.
Going back to the formula, it should be evident that I can apply more
torque
to a wrench than the R1 motorcycle mentioned, but I can not apply that
force
while spinning the wrench at something like 10,000 rpm. Fact is, a model
airplane engine generates miniscule torque, but because of its sky high
rpm,
the amount of work it does is more than a human can do with 200 lbs. of
force on bicycle pedals at 30 rpm.
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corsa120
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Registered: 4th May 02
Location: Northamptonshire
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torque is the pull of the vehicle
if u take a standard 1.6 16v corsa with one person
then take same car but with 5 people in and run them up the quater mile the one with a single person would win because the car would lose torque because of the extra weight
torque also comes with capacity of engines, imagine if u had 2 olympic sprinters make them both have a race but one has to carry a back pack full of rocks he would lose because his torque (stamina) would get the better of him
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MattyB
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Registered: 13th Nov 01
Location: 118.5bhp :D
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i still dont under stand really. But i know this:
2 cars. Each with 100bhp. However, one diesel with 170lb/torque. One n/a petrol with 80lb/trq.
Run both up the strip with just driver. It will be pretty close, but only due to TDs shabby g'box.
However, load both up with 5 people, and the diesel will take the clear victory, as the torque 'supports' the power. The petrol has no torque, and so struggles to accelerate at the same pace.
I see it as 'Torque' is the turning force of the engine. Meaning, even with 5 people, the diesel can still deliver coz it still has the torque to turn the wheels, even with the extra weight. The petrol cant.
Matt
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MattyB
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Registered: 13th Nov 01
Location: 118.5bhp :D
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Another nice example is:
Tuned 1.6 16v = 150bhp and 100lb/trq
Standard 2.0 16v = 150bhp and 144lb/torque
Might be close on acceleration to bout 50 coz of having lighter block, but then XE will piss all over it 
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vibrio
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quote:
Originally posted by MattyB
i still dont under stand really. But i know this:
2 cars. Each with 100bhp. However, one diesel with 170lb/torque. One n/a petrol with 80lb/trq.
Run both up the strip with just driver. It will be pretty close, but only due to TDs shabby g'box.
However, load both up with 5 people, and the diesel will take the clear victory, as the torque 'supports' the power. The petrol has no torque, and so struggles to accelerate at the same pace.
I see it as 'Torque' is the turning force of the engine. Meaning, even with 5 people, the diesel can still deliver coz it still has the torque to turn the wheels, even with the extra weight. The petrol cant.
Matt
look at the fiat multipla. both 105hp but the JTD is slightly quicker than the 1.6(lighter)
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Andy
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Registered: 28th Dec 99
Location: Cumbria, UK
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torque is the turning force that an engine can produce. bhp is the rate of work that can be done by adding together all those turns or pushes. Since acceleration = force dvided by mass, you might assume that the more torque (turning force) an engine makes, the faster it will accelerate. However, if you have an engine that only makes half the torque, but can make that torque at 4 times the revs, you can use the law of levers and gearing to multiply up that torque at the wheels - in this case, the force at the wheels would be twice as bigger - ie twice as much acceleration. So when you look at torque figures, you need to see at what revs that torque is produced in order to get a feel for how it's going to affect the car's performance. A peak torque figure of 240lb/ft at 2000rpm sounds impressive, but it produces no more power at the wheels than a peak torque figure of 60lb/ft at 8000rpm with the right gearing. However, the spread of torque across the revs is very important. If a car makes it's peak torque across a wide rpm range, the driver can keep his foot planted for longer without having to change gear to get back in the torque (or power) band. If two cars have the same bhp figures, the one with the biggest spread of peak torque will be the quickest in real driving conditions
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Russ
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Registered: 14th Mar 04
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only 1 in 20 clio 172's actually have 172 break. more like 168/169
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vibrio
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quote:
Originally posted by Andy
torque is the turning force that an engine can produce. bhp is the rate of work that can be done by adding together all those turns or pushes. Since acceleration = force dvided by mass, you might assume that the more torque (turning force) an engine makes, the faster it will accelerate. However, if you have an engine that only makes half the torque, but can make that torque at 4 times the revs, you can use the law of levers and gearing to multiply up that torque at the wheels - in this case, the force at the wheels would be twice as bigger - ie twice as much acceleration. So when you look at torque figures, you need to see at what revs that torque is produced in order to get a feel for how it's going to affect the car's performance. A peak torque figure of 240lb/ft at 2000rpm sounds impressive, but it produces no more power at the wheels than a peak torque figure of 60lb/ft at 8000rpm with the right gearing. However, the spread of torque across the revs is very important. If a car makes it's peak torque across a wide rpm range, the driver can keep his foot planted for longer without having to change gear to get back in the torque (or power) band. If two cars have the same bhp figures, the one with the biggest spread of peak torque will be the quickest in real driving conditions.
also the AA man with the biggest cock gets my ass
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Kris TD
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Registered: 25th Mar 02
Location: Ware, Hertfordshire
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heavier it gets the more torque is needed, look at a motorbike, they have bugger all torque, but they dont need it cos they hardly weigh anything. yet they still can run 170 bhp
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