engine size and travel distance

tomstickland

thescouselander wrote: »

I just don't believe it - what you're saying is impossible with such a low amount of power. Perhaps your idea of satisfactory performance is just different to mine.

It's not impossible at all.
90BHP is enough for a top speed of around 110mph indicated in a medium sized car.
Weight doesn't come into top speed.

thescouselander

cyclonebri1 wrote: »

You know mate, there's a term widely used in motor sport circles, and it applies equally on the road;

"Power wins pub arguments, torque wins races" ????????????????????

The motorway network is not a performance track, adequate acceleration is all that is needed.


Oh, my last track car weighed in at 635Kg, had approaching 250bhp from a NA |Vx engine. Nothing under 60K could even shadow it on the road or track.
I understand "satisfactory performance", and I understand where it's needed and where it's not.

Can I ask, have you ever owned, (rather than just "dont believe it", shades of Victor here), a small engined modern diesel? You may say yes, but I honestly wouldn't believe you either.

I have never owned a small modern diesel but I have driven quite a lot and I have never liked them.

As for your motor sport term I don't think its right (entirely). Its power that makes the car move, not torque. To get a car to a certain speed to need to impart a certain amount of energy to get it there. The faster you get the power out of the engine that faster you speed up its as simple as that.

Just look at the engines they use in F1 - lots of power but relatively little torque.

Flearoy

thescouselander wrote: »

I just don't believe it - what you're saying is impossible with such a low amount of power. Perhaps your idea of satisfactory performance is just different to mine.

Don't compare a 100 hp diesel with a 100 hp petrol. The former will have a shed load more torque, available at lower revs, than the latter. I had a 1.5 DCi 80 Clio, which as the name suggests had only 80 HP. It did however have only 5% less torque than the Clio 2.0 Sport of the time (which incidentally had about 175hp), but in my diesel, the peak torque as at 2k rpm, not 5k rpm. As such, my little diesel, driven properly, was a very rapid car, and laughed at hills, and would do WAY over the limit easily on even the steep bits of the M62.

Who wants to rag their car to the redline everywhere?

thescouselander

Flearoy wrote: »

Don't compare a 100 hp diesel with a 100 hp petrol. The former will have a shed load more torque, available at lower revs, than the latter. I had a 1.5 DCi 80 Clio, which as the name suggests had only 80 HP. It did however have only 5% less torque than the Clio 2.0 Sport of the time (which incidentally had about 175hp), but in my diesel, the peak torque as at 2k rpm, not 5k rpm. As such, my little diesel, driven properly, was a very rapid car, and laughed at hills, and would do WAY over the limit easily on even the steep bits of the M62.

Who wants to rag their car to the redline everywhere?

I dont think its a matter of petrol or diesel - 100hp in a fully loaded Passat isn't going to be a good driving experience (in my opinion) no matter what the fuel. Others may disagree, that's fine, but I still wont be buying one.

Cool_Username

Well I'm surprised they're putting such small engines in big cars these days - I found it hard to believe that an Astra estate I saw a year ago had a 1.3 CDTI engine - seemed so small for a relatively big estate car.

Now I'm finding out they're putting 1.2 engines into big Skoda Octavias etc!

the182guy

I do a lot of motorway miles in my Clio 1.2 petrol. It's nippy enough to get up to speed on the slip road and any overtaking. Feels fine to drive on the motorway and on my last run I got 59mpg.

cyclonebri1

thescouselander wrote: »

I have never owned a small modern diesel but I have driven quite a lot and I have never liked them.

As for your motor sport term I don't think its right (entirely). Its power that makes the car move, not torque. To get a car to a certain speed to need to impart a certain amount of energy to get it there. The faster you get the power out of the engine that faster you speed up its as simple as that.

Just look at the engines they use in F1 - lots of power but relatively little torque.

Fraid not, torgue gets it moving, bhp keeps it up there, not much use when working up and down the gears.

Didn't thing you would have had a modern diesel, no desrespect but they are far better than you portray.;)

motorguy

thescouselander wrote: »

I dont think its a matter of petrol or diesel - 100hp in a fully loaded Passat isn't going to be a good driving experience (in my opinion) no matter what the fuel. Others may disagree, that's fine, but I still wont be buying one.

If you often drive 'fully loaded', then no, i wouldnt either.

Mine (110BHP) is used for a 50 mile return commute daily with just me in it. At the weekends its usually either my wife or my son in it. Sometimes it gets to tow a trailer to the dump.


I find it perfect for me. AND over the 200 or so miles i've done this week, its done 73mpg

thescouselander

cyclonebri1 wrote: »

Fraid not, torgue gets it moving, bhp keeps it up there, not much use when working up and down the gears.

No, thats not how the physics works, it is power that moves the car. Torque is merely a force, no work has been done until there is some movement (or rotation of the engine in this case) and once you start mixing torque with revolutions you are measuring power.

Ok, so if you increase the torque output from the engine, the car will accelerate faster but ultimately the torque increase has caused an increase in power output.

cyclonebri1

thescouselander wrote: »

No, thats not how the physics works, it is power that moves the car. Torque is merely a force, no work has been done until there is some movement (or rotation of the engine in this case) and once you start mixing torque with revolutions you are measuring power.

Ok, so if you increase the torque output from the engine, the car will accelerate faster but ultimately the torque increase has caused an increase in power output.

Look try this for size to see how it actually works in cars, forget the physics, you don't feel them. I have radically reduced it.

[FONT=Arial,Helvetica,Geneva,Swiss,SunSans-Regular]Torque and Horsepower - A Primer[/FONT]

[FONT=Arial,Helvetica,Geneva,Swiss,SunSans-Regular]From Bruce Augenstein, [EMAIL="rba@augenstein.ultranet.com"]rba@augenstein.ultranet.com[/EMAIL][/FONT]

[FONT=Arial,Helvetica,Geneva,Swiss,SunSans-Regular]There's been a certain amount of discussion, in this and other files, about the concepts of horsepower and torque, how they relate to each other, and how they apply in terms of automobile performance. I have observed that, although nearly everyone participating has a passion for automobiles, there is a huge variance in knowledge. It's clear that a bunch of folks have strong opinions (about this topic, and other things), but that has generally led to more heat than light, if you get my drift :-). I've posted a subset of this note in another string, but felt it deserved to be dealt with as a separate topic. This is meant to be a primer on the subject, which may lead to serious discussion that fleshes out this and other subtopics that will inevitably need to be addressed.[/FONT]

[FONT=Arial,Helvetica,Geneva,Swiss,SunSans-Regular]OK. Here's the deal, in moderately plain english.[/FONT]

[FONT=Arial,Helvetica,Geneva,Swiss,SunSans-Regular]Force, Work and Time[/FONT]
[FONT=Arial,Helvetica,Geneva,Swiss,SunSans-Regular]If you have a one pound weight bolted to the floor, and try to lift it with one pound of force (or 10, or 50 pounds), you will have applied force and exerted energy, but no work will have been done. If you unbolt the weight, and apply a force sufficient to lift the weight one foot, then one foot pound of work will have been done. If that event takes a minute to accomplish, then you will be doing work at the rate of one foot pound per minute. If it takes one second to accomplish the task, then work will be done at the rate of 60 foot pounds per minute, and so on.[/FONT]

[FONT=Arial,Helvetica,Geneva,Swiss,SunSans-Regular]In order to apply these measurements to automobiles and their performance (whether you're speaking of torque, horsepower, newton meters, watts, or any other terms), you need to address the three variables of force, work and time.[/FONT]

[FONT=Arial,Helvetica,Geneva,Swiss,SunSans-Regular]Awhile back, a gentleman by the name of Watt (the same gent who did all that neat stuff with steam engines) made some observations, and concluded that the average horse of the time could lift a 550 pound weight one foot in one second, thereby performing work at the rate of 550 foot pounds per second, or 33,000 foot pounds per minute, for an eight hour shift, more or less. He then published those observations, and stated that 33,000 foot pounds per minute of work was equivalent to the power of one horse, or, one horsepower.[/FONT]

[FONT=Arial,Helvetica,Geneva,Swiss,SunSans-Regular]Everybody else said OK. :-)[/FONT]

[FONT=Arial,Helvetica,Geneva,Swiss,SunSans-Regular]For purposes of this discussion, we need to measure units of force from rotating objects such as crankshafts, so we'll use terms which define a *twisting* force, such as foot pounds of torque. A foot pound of torque is the twisting force necessary to support a one pound weight on a weightless horizontal bar, one foot from the fulcrum.[/FONT]

[FONT=Arial,Helvetica,Geneva,Swiss,SunSans-Regular]Now, it's important to understand that nobody on the planet ever actually measures horsepower from a running engine. What we actually measure (on a dynomometer) is torque, expressed in foot pounds (in the U.S.), and then we *calculate* actual horsepower by converting the twisting force of torque into the work units of horsepower.[/FONT]

[FONT=Arial,Helvetica,Geneva,Swiss,SunSans-Regular]Visualize that one pound weight we mentioned, one foot from the fulcrum on its weightless bar. If we rotate that weight for one full revolution against a one pound resistance, we have moved it a total of 6.2832 feet (Pi * a two foot circle), and, incidently, we have done 6.2832 foot pounds of work.[/FONT]

[FONT=Arial,Helvetica,Geneva,Swiss,SunSans-Regular]OK. Remember Watt? He said that 33,000 foot pounds of work per minute was equivalent to one horsepower. If we divide the 6.2832 foot pounds of work we've done per revolution of that weight into 33,000 foot pounds, we come up with the fact that one foot pound of torque at 5252 rpm is equal to 33,000 foot pounds per minute of work, and is the equivalent of one horsepower. If we only move that weight at the rate of 2626 rpm, it's the equivalent of 1/2 horsepower (16,500 foot pounds per minute), and so on. Therefore, the following formula applies for calculating horsepower from a torque measurement:[/FONT]

[FONT=Arial,Helvetica,Geneva,Swiss,SunSans-Regular]Torque * RPM[/FONT]

[FONT=Arial,Helvetica,Geneva,Swiss,SunSans-Regular]Horsepower =

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[FONT=Arial,Helvetica,Geneva,Swiss,SunSans-Regular]5252[/FONT]

[FONT=Arial,Helvetica,Geneva,Swiss,SunSans-Regular]This is not a debatable item. It's the way it's done. Period.[/FONT]

[FONT=Arial,Helvetica,Geneva,Swiss,SunSans-Regular]The Case For Torque[/FONT]

[FONT=Arial,Helvetica,Geneva,Swiss,SunSans-Regular]Now, what does all this mean in carland?[/FONT]

[FONT=Arial,Helvetica,Geneva,Swiss,SunSans-Regular]First of all, from a driver's perspective, torque, to use the vernacular, RULES :-). Any given car, in any given gear, will accelerate at a rate that *exactly* matches its torque curve (allowing for increased air and rolling resistance as speeds climb). Another way of saying this is that a car will accelerate hardest at its torque peak in any given gear, and will not accelerate as hard below that peak, or above it. Torque is the only thing that a driver feels, and horsepower is just sort of an esoteric measurement in that context. 300 foot pounds of torque will accelerate you just as hard at 2000 rpm as it would if you were making that torque at 4000 rpm in the same gear, yet, per the formula, the horsepower would be *double* at 4000 rpm. Therefore, horsepower isn't particularly meaningful from a driver's perspective, and the two numbers only get friendly at 5252 rpm, where horsepower and torque always come out the same.[/FONT]

[FONT=Arial,Helvetica,Geneva,Swiss,SunSans-Regular]In contrast to a torque curve (and the matching pushback into your seat), horsepower rises rapidly with rpm, especially when torque values are also climbing. Horsepower will continue to climb, however, until well past the torque peak, and will continue to rise as engine speed climbs, until the torque curve really begins to plummet, faster than engine rpm is rising. However, as I said,horsepower has nothing to do with what a driver *feels*.[/FONT]

[FONT=Arial,Helvetica,Geneva,Swiss,SunSans-Regular]You don't believe all this?[/FONT]

[FONT=Arial,Helvetica,Geneva,Swiss,SunSans-Regular]Fine. Take your non turbo car (turbo lag muddles the results) to its torque peak in first gear, and punch it. Notice the belt in the back? Now take it to the power peak, and punch it. Notice that the belt in the back is a bit weaker? Fine. Can we go on, now? :-)[/FONT]

[FONT=Arial,Helvetica,Geneva,Swiss,SunSans-Regular]The Case For Horsepower[/FONT]

[FONT=Arial,Helvetica,Geneva,Swiss,SunSans-Regular]OK. If torque is so all-fired important, why do we care about horsepower?[/FONT]

[FONT=Arial,Helvetica,Geneva,Swiss,SunSans-Regular]Because (to quote a friend), "It is better to make torque at high rpm than at low rpm, because you can take advantage of *gearing*.[/FONT]

[FONT=Arial,Helvetica,Geneva,Swiss,SunSans-Regular]For an extreme example of this, I'll leave carland for a moment, and describe a waterwheel I got to watch awhile ago. This was a pretty massive wheel (built a couple of hundred years ago), rotating lazily on a shaft which was connected to the works inside a flour mill. Working some things out from what the people in the mill said, I was able to determine that the wheel typically generated about 2600(!) foot pounds of torque. I had clocked its speed, and determined that it was rotating at about 12 rpm. If we hooked that wheel to, say, the drivewheels of a car, that car would go from zero to twelve rpm in a flash, and the waterwheel would hardly notice :-).[/FONT]

[FONT=Arial,Helvetica,Geneva,Swiss,SunSans-Regular]On the other hand, twelve rpm of the drivewheels is around one mph for the average car, and, in order to go faster, we'd need to gear it up. To get to 60 mph would require gearing the wheel up enough so that it would be effectively making a little over 43 foot pounds of torque at the output, which is not only a relatively small amount, it's less than what the average car would need in order to actually get to 60. Applying the conversion formula gives us the facts on this. Twelve times twenty six hundred, over five thousand two hundred fifty two gives us:[/FONT]

[FONT=Arial,Helvetica,Geneva,Swiss,SunSans-Regular]6 HP.[/FONT]

[FONT=Arial,Helvetica,Geneva,Swiss,SunSans-Regular]Oops. Now we see the rest of the story. While it's clearly true that the water wheel can exert a *bunch* of force, its *power* (ability to do work over time) is severely limited.[/FONT]

[FONT=Arial,Helvetica,Geneva,Swiss,SunSans-Regular]

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[FONT=Arial,Helvetica,Geneva,Swiss,SunSans-Regular]This article was originally published on the Corvette Forum[/FONT]

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