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500 HP, too many horses? - Page 4

post #46 of 53
1/4/11 at 12:08am
IMHO, 500 HP is too much for the average driver to handle. I've seen a lot people drive like complete asshats in beat-up Oldsmobiles, I'd hate to imagine them behind the wheel of a 500 + hp exotic. Just because you can afford it, doesn't mean you should get it. Kinda strange though, besides those videos Andre posted, every high-performance exotic I've seen (R8s, Porsches, Lamborghinis, Ferraris......you name it) were driving completely normal and were just going with traffic. It's the jackasses in the full size pickups who try to drive them like race-cars that stick out and cause accidents. Well, in these parts anyway.
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post #47 of 53
1/4/11 at 4:36pm
Quote:
Originally Posted by A Y View Post
OK boys, let's have a reality check here. Since the horsepower curve of a car rises roughly in proportion to its RPMs, you will be generating max horsepower only near redline. So what kinds of speeds are you going near redline?

Let's look at a 2010 Ford Mustang GT with the following specs: 5 gears with ratios of 3.38, 2.00, 1.32, 1.00, 0.62, a final drive ratio of 3.55, 235/50-18 drive tire size (http://www.autoguide.com/new-cars/20...um/specs.html), and a 6000 RPM redline. You can quibble here and there about different gear boxes and drive ratios, and max redline, but roughly speaking, this gets you these top speeds at each gear (http://www.catherineandken.co.uk/sti/tyres.html to calculate):

Gear:MPH
1: 40
2: 68
3: 103
4: 137
5: 220

Since you only see the effects of horsepower in overcoming wind resistance (primarily) and rolling resistance (very distant 2nd), both of which are maximized at high speeds, there is no way you will ever use or need 500 HP unless you are wringing the car out near redline in 5th. At lower speeds that are legal or near-legal (ie. up to maybe 3rd gear in the chart above), you simply are not horsepower-limited.

And even if for some reason you need 500 HP to go 40 MPH, how many of you drive all the way to redline for each gear? Because that's the only engine speed where you're going to make your max horsepower.

So tell me again, when exactly do you need 500 HP on the street?

--Andre

Looks pretty constant for nearly 2,000 RPMs to me:

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post #48 of 53
1/4/11 at 4:58pm
Quote:
Originally Posted by acecow View Post
Looks pretty constant for nearly 2,000 RPMs to me:
What's constant? The torque? I didn't say otherwise, and that's not abnormal. Look up the dyno of a Nissan 350Z --- that V6 also has a flat torque curve, and consequently a rising HP curve. --Andre
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post #49 of 53
1/4/11 at 5:08pm
Quote:
Originally Posted by A Y View Post
What's constant? The torque? I didn't say otherwise, and that's not abnormal. Look up the dyno of a Nissan 350Z --- that V6 also has a flat torque curve, and consequently a rising HP curve.

--Andre

I meant the HP curve. What I'm saying is that while most cars don't have a flat curve, some do. Maybe that's the case with the Porsche as well.
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post #50 of 53
1/4/11 at 5:25pm
Quote:
Originally Posted by acecow View Post
I meant the HP curve. What I'm saying is that while most cars don't have a flat curve, some do. Maybe that's the case with the Porsche as well.

That HP curve is not flat --- it rises with RPMs, peaks at 6K, and then starts falling. By constant, I mean constant with respect to RPMs, not constant slope.

--Andre
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post #51 of 53
1/4/11 at 7:41pm
OK, we're really failing to understand each other here. I drive a 335xi (in Southern California, nonetheless. if you ever see a 335xi with stick shift, you know it's me) and I posted its dyno chart above. The HP curve is "kind of" constant from around 5 to around 6.75 thousand RPM. I can feel it in the engine response. My point is, with a nicely tuned car, the speeds at which you get the most out of the engine are broader than you posted. Do understand, that I generally agree with you here, but I think you are over-exaggerating a little. EDIT: Not my car's power chart. Just a reference for a turbo 3-series.
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post #52 of 53
1/4/11 at 10:59pm
Quote:
Originally Posted by acecow View Post
OK, we're really failing to understand each other here. I drive a 335xi (in Southern California, nonetheless. if you ever see a 335xi with stick shift, you know it's me) and I posted its dyno chart above. The HP curve is "kind of" constant from around 5 to around 6.75 thousand RPM. I can feel it in the engine response. My point is, with a nicely tuned car, the speeds at which you get the most out of the engine are broader than you posted. Do understand, that I generally agree with you here, but I think you are over-exaggerating a little.

EDIT: Not my car's power chart. Just a reference for a turbo 3-series.

^^acecow, I think what you are feeling is torque, not hp. unless you routinely track your car on an oval you are not driving with hp, you are driving with torque. virtually every car will have a peak hp near the redline, unless you are running a restrictor plate or something else that will flatten the curve at revs above a certain level. a torque curve that peaks early and stays flat through the range is ideal and that shape will produce a steep, upward sloping hp curve. when the torque begins to drop, the hp continues to rise but less steeply. A car with a flat hp curve would generally imply that torque peaks very early and declines steadily and significantly with revs (think basic calculus and note how the inflection points are the same for both curves on just about every dyno chart you see). although used synonymously torque and hp are not the same, they are related.

but lets back up a second...this thread is like comparing wines on the basis of varietal or stereos on the basis of watts per channel . it ignores fundamental drivers of a car's handling...weight, distribution, size and compound of tires, suspension, traction control (bane of my existence), and drivetrain (e.g. rwd/awd/fwd/4wd).

500hp in an s600 is still boring, in a porsche turbo it is fun, yet 450hp in an f40 is scary as hell (and really, really fun )
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post #53 of 53
1/5/11 at 3:12pm
Torque*RPMs/5252 = Horsepower. Torque is in foot-lbs, and horsepower is in ... well ... horsepower.

From there you can see how horsepower curves follow torque curves (or vice versa). Torque is slightly tricky to interpret because of gearing, tire diameter, and RPMs. When car reviewers quote torque numbers, it's almost always meaningless because they don't include those pieces of information. Note how torque and HP curves intersect at 5252, as you can see in acecow's graph.

With a flat torque curve, you can also see why HP will peak at redline. And you can also see why race cars always try to push RPMs as high as possible: you can get a lot of horsepower, and the torque at high RPM can be usefully geared down to do a lot of work because of the high RPMs. Think of a Dremel or a dentist's drill.

That's not great on the streets because hardly anyone (except squids) drive at redline, and our street gears are too far apart to take advantage of it even if we were squidy. That's why lots of torque at low RPMs in a wide range is useful for street driving: you can get going faster, and you don't need to keep the engine in a narrow band of RPMs.

--Andre
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