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477 Posts
Try this comparison

> for street use low end torque is always much
> more useful. high end horsepower is great
> for the freeway or the racetrack. it's just
> more difficult to make low end out of a
> small displacement motor like the l28. the
> 3.1 liter engine build is a good way to
> build low end, as well as raising the
> compression ratio and installing a better
> cam.

That information is true, to a point. Try doing a comparison between the Acura Integra GS and GS-R. Both of these cars use a 1.8L DOHC, but the GS has 140hp, while the GS-R has 170. Also, the torque from a GS is about 125ft/lbs and the GS-R is about 110ft/lbs. The main difference between these two engines are the cams and intake manifold.

So, why is the GS-R faster??? The reason is because it has more hp, and produces it at a higher rpm. This means that the engine can remain in any given gear for a longer time, and produce more mph (work/time aka hp). While it may lack low-end launching capability, it makes up for it once it reaches high rpm. It is better to make torque at a higher rpm to take advantage of this, so that when you shift, you land right back into the 'fat' part of the torque curve, which keeps you moving. So, a torque curve that peaks higher is better than one that peaks lower, once you're moving.
But, a low-end torque is better to GET moving initially. This is why semi's produce only [email protected], but produce over 500ft/[email protected] of torque. But, this is why they have 13speeds!! Having more hp, would make them faster and reduce the need for so many gears, but then they would have more trouble to get moving. Make sense??

Basically, you want enough low-end torque, to get you moving, but don't want all of it in the low-end. You want the torque curve to keep extending, so that when you shift you are still climbing in torque, rather than having already peaked. This means you need hp, to get the rpms up and enable you to shift at a good rpm.

477 Posts
Exactly my point!

> here's another comparo. the new honda s2000
> vs. the bmw m roadster. i chose these two
> cars because they make the same amount of
> horsepower, but in two different ways. they
> also weigh close to the same. let's start
> with the honda- now depending on what you
> read, this car makes 240 hp @ 8500 rpm and
> 159 lb-ft torque @ 7500. the car has a curb
> weight of somewhere between 2500 and 2800
> lbs. the 0-60 time is between 5.5 and 6
> seconds. i haven't read about a quarter mile
> time yet. the bmw on the other hand makes
> 240 hp @ 6000 rpm and 236 lb-ft torque @
> 3800 rpm. the 0-60 time is between 5.1 and
> 5.3 seconds. the 1/4 mile time is 13.7sec/
> 101 mph. also bear in mind this car weighs
> almost 3100 lbs, at least 300 lbs more than
> the honda. looking at the numbers, the bmw
> should win anywhere on the street and in a
> drag race, but the honda should pull higher
> top speed numbers.

OK, the Honda: [email protected], 159ft/[email protected] Look at where peak torque is. When you shift, you are going to fall WAY below the peak torque. You'll probably fall around 5500-6000 when you shift. This is not very good, and hurts acceleration. But the Honda still has 0-60 of 5.5-6.0 why?? This is due to the HP. Because once it is in a gear, it can stay in that gear for a long time, this makes up for the utter lack of torque. I would bet You can probably hit 40mph in 1st gear. Probably hit 60mph @6500-7000rpm in 2nd. This proves the importance of gearing.

Now the BMW: [email protected], 236ft/[email protected] So if you shift @6000, you drop to @4000, which is right smack in the 'sweet spot' of the torque curve. So the BMW is making peak torque at a very useable rpm. The BMW will require shifting sooner than the Honda, but will pull harder in each gear compared to the Honda.

So, the moral of the story is:
The BMW needs to shift to stay moving, while the Honda can stay in a gear for a long time, but suffers when you shift. Great example of hp vs. torque.
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