Horsepower...what is it? - DPChallenge Forums

Canon EF 24-70mm f/2.8L USM

06/02/2005 03:52:03 AM · #33

FOR SALE

horsepower to weight ratio plus gear ratio is also important. RWHP is in the end what you really need to know.

p2jvr

Canon EOS-40D

Canon EF-S 17-55mm f/2.8 IS USM

06/02/2005 04:51:45 AM · #34

I don't know if 400 horsepower actually is equivalent to the power of 400 horses as in the animal. I don;t know how accurate that is. [/quote]

Thought you might like to know that Jamesw Watt invented the term horsepower. He sold his steam engines to pit owners. A six horsepower engine would replace six horses - simple and effective. 1 horsepower = 746 Watts

nova

Canon EOS-6D

Canon EF 35mm f/1.4L USM

06/02/2005 07:06:27 AM · #35

Originally posted by SDW65:

Explanation of 5252

First, 1 horsepower is defined as 550 foot-pounds per second. The units of torque are pound-feet. So to get from torque to horsepower, you need the "per second" term. You get that by multiplying the torque by the engine speed.

But engine speed is normally referred to in revolutions per minute (RPM). Since we want a "per second," we need to convert RPMs to "something per second." The seconds are easy -- we just divide by 60 to get from minutes to seconds. Now what we need is a dimensionless unit for revolutions: a radian. A radian is actually a ratio of the length of an arc divided by the length of a radius, so the units of length cancel out and you're left with a dimensionless measure.

You can think of a revolution as a measurement of an angle. One revolution is 360 degrees of a circle. Since the circumference of a circle is (2 x pi x radius), there are 2-pi radians in a revolution. To convert revolutions per minute to radians per second, you multiply RPM by (2-pi/60), which equals 0.10472 radians per second. This gives us the "per second" we need to calculate horsepower.

Let's put this all together. We need to get to horsepower, which is 550 foot-pounds per second, using torque (pound-feet) and engine speed (RPM). If we divide the 550 foot-pounds by the 0.10472 radians per second (engine speed), we get 550/0.10472, which equals 5,252.

So if you multiply torque (in pound-feet) by engine speed (in RPM) and divide the product by 5,252, RPM is converted to "radians per second" and you can get from torque to horsepower -- from "pound-feet" to "foot-pounds per second."

Oh baby!!! Did you write this -without even an edit- or did you copy it? I knew there was a reason I've faved you :)
(Actually it's because I like your work, but that post is a thing of beauty too).

lonewolf

Canon EOS-50D

06/02/2005 07:21:20 AM · #36

I have a Colorado and I love it!!!!!!!

nova

Canon EOS-6D

Canon EF 35mm f/1.4L USM

06/02/2005 07:36:52 AM · #37

Originally posted by lonewolf:

I have a Colorado and I love it!!!!!!!

I bought mine in August, and I totally agree with you. Nice little truck, I think the new 5-cylinder is going to prove to be a winner in the long term too.

lonewolf

Canon EOS-50D

06/02/2005 07:58:18 AM · #38

I have had mine for a year. Couldn't ask for a better truck. Hauls my dirtbikes and gear just fine. The 5-cylinder is great, power and gas milage.

Canon EF 70-200mm f/2.8L IS USM

06/02/2005 10:53:56 AM · #39

True, when comparing HP numbers you need to consider the RPM that the advertised HP was achieved, but HP is still a very relevant number and a good indication of the engineâ��s power. You just need to consider at what RPM that HP was achieved. An engine with max HP at a low RPM (my Jeep with 150hp @ 3000rpm) is going to feel much different then a vehicle with the same max HP at a higher RPM. Note that I'm guessing they measured the HP at the RPM redline on both engines??? If that's the case and the Colorado has a higher redline it probably would feel a little more powerful and considering engine alone would do better in a race.
However, if you are looking at HP and trying to figure out which vehicle is going to be faster, you canâ��t. For that you need to factor in gear ratio, tire size, vehicle weight, drag coefficientâ�¦

Make it easy and get the Tacoma, 245hp @ 5200 RPM, 282 lb-ft at 3800rpm. You get pretty good low-end torque and plenty of top end power, plus it gets 20mpg! I love mine. (and if it matters, I believe it's just as much American made as the GM and Ford)

theSaj

Canon EOS-20D

06/02/2005 11:40:11 AM · #40

A Welsh engineering company has made a motor to be used on electric cars that will make them as fast as a Ferrari. There are no gears - the motor provides enough torque at one revolution per minute to put a vehicle into motion - and it spins at up to 2,500rpm. "Size for size, we can provide 400% more torque than any type of motor currently available," says managing director John Bryant."

//slashdot.org/article.pl?sid=05/06/01/2259253&tid=126&tid=99

(Okay, can I get this with a fuel cell, 7-8 passenger SUV?)

Prof_Fate

06/02/2005 11:52:49 AM · #41

Theoretically, elecrtic motors have infinite torque.

As to HP and RPM and such. No, red line has nothing to do with HP or max HP. It is a mechanical limit, usually defined by when the valves 'float'., or cannot be kept closed by the valve springs. THere is also a maximum speed that pistons can move in a cylinder, and beyond that they come apart and or the strength needed to hold things toghether begins to exceed what can be spun that fast (law of diminishing returns)

Manuy things go into determining the HP/torque curve, and much of that is just marketing.

The Jeep 4.0 engine that came out in 87 or 88 - it originally had more torque and less HP then the competing chevy vortec V6 of that era. Max HP was at 1700 rpm or some very low number like that. Great in a truck, great in a 4WD vehicle. A few years later, after Chrysler got a hold of Jeep, the 4.0 becam the 4.0 HO. Same engine. Some tweaks..now max HP was up, but it was listed at 4500 RPM or some other useless RPM for off roading.

Unless you floor it, 99% of your driving is done under 3500 RPM.

blindjustice

Canon EOS-7D

Canon EF 70-200mm f/2.8L IS USM

06/02/2005 11:54:57 AM · #42

my 98 golf has 115hp but oodles of torque. Thats the balls off the line that the jackass in the Honda civic next to me with the cherry bomb muffler doesn't have even with 40- more horsepower.

but really, hp is a sales ploy. we only need about 30 to push a big car at reasonable speeds, but god knows you need that car to have 300+ hp and a top speed of 165mph just in case you get a call from Nascar, I guess.

Case in point. the tractor I just boughgt, CC 1046 with 23 hp kohler..., about $1700. Why are the Cub cadet and john deere $8000 only sporting 17hp, 20 hp etc? because they put the money in the frame, etc and the extra horsepower in unnecessary!

They should change horsepower to "pdr's"
(penile deficiency replacement units"

rex

Canon PowerShot SD780

06/02/2005 12:04:35 PM · #43

My ride gets me from point A to point B and back to point A and has a radio attached for my entertainment that is all I care about.

Message edited by author 2005-06-02 12:05:03.

theSaj

Canon EOS-20D

06/02/2005 12:07:11 PM · #44

Hey...that's great...

We can use PDRs to rate lenses....

I am sure my 70-200mm f/2.8 IS would rate pretty high in PDRs and my kit lens rather low.

142 PDRs = 70-200mm f/2.8 IS
10 PDRs = 18-55mm Kit Lens
35 = Canon EF 50mm f/1.4 USM
300 PDRs = Canon EF 600mm f/4.0L IS USM

Formula for calculating PDR for rating lenses

PDR = (max zoom / f-stop) * M

Where M = Multiplier:
IS = 2.0
USM = 1.0
non-URM = 0.8

notonline

Canon EF 24-70mm f/2.8L USM

06/02/2005 12:18:45 PM · #45

Originally posted by blindjustice:

I have a 400+ hp car and still not enough. I love the power and the torque and use it for racing, so I believe that there is reason to have a lot of ponies. My winter beater is a little shit box 2000 hyundai something or other, my weekend is a 97' dodge pickup and my summer car is a 70 Plym. Duster which is the one that has over 400hp and yes it is very much needed.

Injection's fine but I'd rather be blown. :D

06/02/2005 12:58:57 PM · #46

Originally posted by Prof_Fate:

As to HP and RPM and such. No, red line has nothing to do with HP or max HP. It is a mechanical limit, usually defined by when the valves 'float'., or cannot be kept closed by the valve springs. THere is also a maximum speed that pistons can move in a cylinder, and beyond that they come apart and or the strength needed to hold things toghether begins to exceed what can be spun that fast (law of diminishing returns)

Correct, redline has nothing to do with HP, however redline point does have a big difference on how an engine will feel and perform when you drive it once it's in the car. Also, most engines will hit peak HP at the redline point.
With a higher redline you can shift later and thus start the next gear at a higher RPM. This lets you start the next gear higher in the powerband which makes a huge difference since there is less acceleration lower in the power band. Anyone that's ridden a street bike that redlines at 1200-1400rpm can attest to that. It doesn't affect HP but it does let you take more advantage of the avaialable HP.

pitsaman

Canon EOS-30D

Canon EF 50mm f/1.8 II

06/02/2005 02:26:49 PM · #47

Automakers should consider making special cars for female drivers.

Something like "Horsepower Lite "

They are enough crazy with 150 HP,300 or more would be very dangerous.
Something with lot of mirrors,storage space with deep holes under gas/brake pedals for high-hills,handy make-up and brush holders etc...

Message edited by author 2005-06-02 14:47:32.

Tamron AF 28-300mm f/3.5-6.3 XR Di LD Aspherical IF for Canon

06/02/2005 02:58:26 PM · #48

Originally posted by pitsaman:

Add a sensor that won't let the car start when it's raining/snowing and another that shuts the car off if they haven't changed the oil in the last 5,00 miles and I think you're on to something :)

Riponlady

Panasonic Lumix DMC-FZ35

06/02/2005 03:11:37 PM · #49

Originally posted by louddog:

Originally posted by pitsaman:
Automakers should consider making special cars for female drivers.

Something like "Horsepower Lite "

They are enough crazy with 150 HP,300 or more would be very dangerous.
Something with lot of mirrors,storage space with deep holes under gas/brake pedals for high-hills,handy make-up and brush holders etc...

Add a sensor that won't let the car start when it's raining/snowing and another that shuts the car off if they haven't changed the oil in the last 5,00 miles and I think you're on to something :)

What a sexist comment! What if I accused all male drivers of being inconsiderate, foul mouthed, reckless drivers who can't bear to be overtaken by a female, just because I have met some of these when driving? I really get p***** off when some stereotyped view like this is put forward even partially seriously.

I love driving, have a relatively fast car which I enjoy pushing to the limit and have driven in all weathers here in the UK and abroad. And I am not alone in this - my daughter has a Lotus Exige and drives brilliantly.
Sorry to rant but it's been a long day!!!!!!!

Pauline