Torque is effort, BHP is workrate, it's the latter that gets you down the road! Otherwise a routemaster bus would be tear us up off the lights. You can have as much torque as you like, unless it's made far enough up the rev band it won't equal decent horsepower.
Some diesel cars are faster than petrol cars with more horsepower because the generally turbocharged diesel will be making near it's peak power over a 2.5-3K rev band, the equivalently sized normally aspirated petrol car may have more peak power but the area of power under the curve is much less, it's making much less than peak power each side of the peak of the curve - as I said it's horsepower that gets you down the road.
In your case however, we are comparing apples with oranges, the Smart only has 69% of the power of the Fiesta - that's pretty significant!
Edited by SteveLee on 28/01/2010 at 16:40
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What a load of rubbish has been talked!! Torque at the engine is only part of the equation-the only torque that will give you performance is the torque at the wheels-to work this out,you need the gearbox ratios,final drive ratio and the rolling radii.
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The makers and journalists have to find out what the ultimate performance is, but the 0-60 time is pretty meaningless, unless you find it vitally necessary to shred your clutch gearbox and tyres:) More real world indicators are the rolling acceleration times, if given. This may reduce the ultimate power advantage of the Fiesta.
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As nortones2 syas 0-60 time is pretty meaningless. At low speeds any car with any pretense of performance is going to be turning the tyres into expensive smoke an possibly the cluth into an expensive burning smell. Far better measure would be 40-100. Power is still the thing that matters or rather useable power. As other posters have pointed out total power under the curve is what really matters.
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What a load of rubbish has been talked!! Torque at the engine is only part of the equation-the only torque that will give you performance is the torque at the wheels-to work this out you need the gearbox ratios final drive ratio and the rolling radii.
This is the age of computerised design, the gear and final drive ratios will be appropriate ones to maximise the use of power (and spread of) as well as allow comfortable cruising and decent mpg. This isn't the 1960s where a guy with an HB pencil behind his ear will sometimes get the gearing hopelessly wrong or a financially stretched company tries to use the same gearbox ratios and final drive across the range, so given that, horsepower figures against the weight of the vehicle will give you a reasonably accurate sense of the vehicle's performance.
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As gross approximation it is engine power vs vehicle+driver weight that accounts for acceleration figures. (nb. note SteveLee's comment on forced induction - same peak power should be a bit quicker than a NA engine as the area under the rpm/torque curve will be greater = more work done through the rev-range)
There are so many confounding factors that no simple formula will work for all cars.
Even different ambient temperatures can significantly affect power output (and to an extent wind resistance).
And also: take manufacturer's figures with a pinch of salt, and in real world driving you'll find automatics not as much slower than manuals as the figures would have you believe.
Edited by Lygonos on 28/01/2010 at 17:59
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>>What a load of rubbish has been talked!!
No, not really - see Steve's answer.
NC hits the nail on the head - 44% more power, 32% better 0-60, so mostly about power. The Fiesta will presumably be heavier which will account for some of the gap between the percentages.
At maximum torque, if at similar revs, the engines having similar torque will have similar power - the Smart if lighter will probably pull ahead. However it looks as if the Fiesta has higher torque and/or higher revs at maximum power which gives it the all important power advantage when flat out.
Plus which a Smart is just rubbish ;-)
Edited by Manatee on 28/01/2010 at 17:58
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Have a read of this:
www.carkeys.co.uk/features/technical/636.asp
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Have a read of this: www.carkeys.co.uk/features/technical/636.asp
Ugh!, nasty!
One example of the nastiness;
" Physicists define power as "work done" "
No, they do not! Power is defined as work done **per unit time**.
The mathematics of road load prediction and gear ratio matching have been known and practiced for a long time before computers were involved.
One interesting aside is that the 3 cylinder diesel will have a large flywheel to smooth out the torque fluctuations - which will mean the effective mass of the vehicle when in low gears will be much higher than a trip to the weighbridge might suggest. This won't help its 0 - 60 times.
Edited by Number_Cruncher on 28/01/2010 at 19:00
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Is the smart an auto?
From our experience of the original cars the smart time is probably more accurate than the Fiesta as the ECU has more control. The smart had rev limit protection to protect the clutch, so you couldn't floor it and get an instant take off. The ECU limited the power.
Change points are also critical. The smart had a 6 speed box, the Fiesta 5. Fiesta will do 60 in third, the smart 4th and gearchanges weren't quick.
So whilst power and torque affect it, it wont be as much as the raw figures suggest due to mechanical differences.
Compare 30-50 and 50-70 times and see how close the cars are.
We used to get better take off in the smart by putting it into first, then tapping the throttle until revs were up to about 5,000 - doing this quickly means the clutch doesn't engage. At 5,000 floor it and it would do a much better start.
We also found better times could be had if you floored the gas pedal before changing up the gearbox as it increased the engine revs ready for the next gear.
I doubt the testers did any of this.
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I'll bet they did! Its not exactly arcane. And worse.... If I recall, makers expect the transmission to take a number of road-tester type starts, before demise of the kit. Six, I think it was.
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What year Fiesta?
AFAIAA a 1.4 Fiesta is 96bhp.
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0-60 time is pretty meaningless in the real world. What matters is 30-50 or 50-70, torque helps there.
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Bromptonaut,
"0-60 time is pretty meaningless in the real world. What matters is 30-50 or 50-70, torque helps there"
Hmmm...
Not so sure about that one...
When my Diesel FR was standard (150ps) before the remap (180-200 ps) I used to drive to & fro from work across large roundabouts during rush-hour.
Particularly if I was in the left-lane taking the 2nd exit, I noticed that a lot of 1.4 Fiesta size cars & 1.6 Astra sized cars with 100Bhp or less could quite easily overtake my car - beating me to the 2nd exit, cutting-in from the right-hand lane even when I was still accelerating quite swiftly with 3/4 of the PSI from the turbo.
They can ram the car in 2nd gear upto 60 & this gives them a huge advantage for overtaking quickly.
If I really wanted to drop a cog & accelerate alongside them to block them from doing it my FR could have done that without too much grief - but doing this will cause a pit-manouvre type collision so its best to let them cut in.
Having a TDi, I have noticed that a lot of 80-100Bhp cars are obviously no match for a 150 when the pedals to the metal but they can definately hold their own ground against a TDi when they want. Especially if I have left it in a higher-gear or the PSI is around 3/4 of the way. People say they are slow but I think if they can hold their ground against a 150, they are still quite fast & offer enough adequate speed to be potentially dangerous driven in the wrong hands.
Obviously on a race-track its different, but everyday 1.4's & 1.6's on a normal road might look like harmless overtakable cars but they can be little wolves hiding in sheeps skin. Thats the magic of Petrol Twin-cam engines with fuel injection & 16-valves I suppose.
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Thats the magic of being in the right gear.<<
There, fixed it for you.
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Lygonos,
Diesel Turbo lag + being in a high gear is not a good mix.
Easily done though, I've often thought - hey that nice chick in the 1.4 Fabia MPI is shifting rather fast for a 1.4. Shes getting away from me!
Oops, hang on, I'm thrashing it in 4th gear under 2,000 RPM, no wonder why!
- Shift it back to 2nd or 3rd gear in the torque range then floor it! - She won't be able to run or hide! ha ha
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Just out of interest where do all these drivers come from that are trying to race you, PeP?
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b308
In rush-hour traffic its just typical behaviour for people to deliberatly use the incorrect lanes just to queue-jump or get ahead of everyone else, People just want to get home ASAP rather than safely.
I was in the left-lane of a roundabout, intending to use the 2nd exit (straight ahead) an irate woman in an 09 Fiesta Zetec overtook me in the right-hand lane also intending to use the same exit. I let her go as I just could not be bothered. I didn't realise there was also an additional Vauxhall Corsa overtaking me from the right aswell - doing exactly the same thing as what the Fiesta did. Both cars used the right hand lane on the roundabout approach to overtake me in a fit of "Must get home" syndrome. As I was approaching my exit & signalling off - the other manic woman in the Corsa almost pit-manouvred me from behind getting to the exit.
After the Fiesta did it I thought: Enough is Enough now, you are not going to bully me when I'm in the correct lane for the appropriate exit - I'm putting my foot down on this one - quite literally.
Got flashed by the female in the Corsa but it was her own fault!?
Edited by Peterexhaustpiper on 29/01/2010 at 16:18
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I was refering to your other tales really... just you seem to get more than your fair share of people who drive aggressively towards you... ah well, I suppose it keeps them away from me! ;)
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b308
I have a personalised reg which probably answers the question of encountering more idiots then most people -> I've been trying to sell it for 6months now because it is purely a magnet for idiots, if you knew my plate you will understand why I get so much greif from other motorists. Its not rude in any way, It relates to the cars make/model/secification <- I'm not saying exactly what it is in a public forum but I'm sure you have some idea of what it might spell. Same numberplates as MG** ZRS for an MG ZR or C0R54 for a Vauxhall Corsa.
I get it all the time when I'm out, One time a guy was harassing me over my plate calling me this & that - who do I think I am, when I did nothing to him. He was saying I'm an idiot because he didn't like what my plate says <- what can I do? it came with the car - its not my fault its on there!
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Is it one of these?
www.barryboys.co.uk/phpBB2/viewtopic.php?t=23500
Made non-clickable as mucho bad language.
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No mines more relating to the car itself.
that ones Sha**y on an MGF
Mines the same as having MG** ZST on an MGZS
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I noticed a lot of 1.4 Fiesta size cars & 1.6 Astra sized cars with 100bhp or less could quite easily overtake my car Thats the magic of Petrol Twin-cam engines with fuel injection & 16-valves I suppose.
They'll have a better throttle response with no turbo to have to wait for to boost up, but more importantly, they're lighter. A diesel Leon is quite a heavy beast from a standing start. Put a 100 bhp petrol engine in a Westfield and that's a formidable weapon.
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"They'll have a better throttle response with no turbo to have to wait for to boost up, but more importantly, they're lighter"
Not if you drop to the lowest possible gear over 2,000RPM & gave it full boot then the 1.4/1.6 Fiesta/Astra sized cars trying to overtake are going to be toast. If you have an FR Mk1 or have driven an FR with the 150 Diesel then you will know that despite the heavy weight & understeer, they can still out-handle the steel wheeled cars. FR's understeer but have lots of grip from the wide-wheels. If you had say, an Astra 1.6 at 98Bhp then tried to keep up with an FR around a corner, you would probably slide over & crash whereas an FR will grip the corner.
They are heavy from a standing start but they will still beat a 100 horsepower car
0-60 FR TDI: 8.5
0-60 1.4/1.6 100Bhp average car: 10.5
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Hmmm, a Smart is rubbish then, is that officially or just in your opinion ??
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It was a joke explanation, albeit a feeble one, for the performance difference as the ;-) gave away.
I have never driven one, so it is not my opinion. It may be official though ;-)
Edited by Manatee on 29/01/2010 at 07:21
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