OT: HP vs. Torque

[Colin]

After 10 years, I had to spend $340 on pulley assembly (last year) and new starter for my Mazda/Ford B2300/Ranger pick-up. With 130K on the dial, the handwriting is on the wall: in a few years, I might have to spend over $300 a month for repairs. When the monthly cost of repairs exceed the monthly cost of financing a new car, it is time to buy a different (used, of course) vehicle. So now is the time to start shopping for a new car. OK, truth be told, I am always shopping for new cars, stereo and aquarium stuff.

Short of test driving every possible model (just as many as speakers), comparing the weight, engine size, HP and torque for the price, comfort and passengers is difficult form the specs.

How do they derive HP and torque?

Lighter, tighter Japanese cars are quick and nimble with 150HP at 6300 RPM, while cushy Americans have 200HP at 5900RPM?

Who sets the standard/benchmark for HP and torque and how?

Thanks!

[sfogg]

"How do they derive HP and torque?"

By measuring it on an engine dynometer. They actually just measure the torque of the engine at all the RPM points and from that calculate HP.

HP = ((torque * RPM) / 5252)

Shawn

[picky]

I'm only going to attempt to explain the answer to Colin's question: "Who sets the standard/benchmark for HP and torque and how?" The following is fact and NOT my opinion.......

Colin: I've been mainly in the design/engineering-side of the auto industry for the last 25 years here in Detroit. I can tell you that among other features, HP is mainly driven by each car-marker's marketing department. The marketeers ask the potential customer what they want, and then they tell engineering to budget and deliver it. Right now, everyone, including the imports, are in the midst of a horsepower race. The average consumer has been duped into believing that in all cases, MORE is always better! That's why we see vacuum cleaners and other tools and appliances being marketed by how many AMPS or WATTS they draw (which is an absurd measure of an appliance's real ability). The same goes for automobiles. Just because the label says "Hemi" (for example) doesn't mean the package is any better, or as useful, as anyone else's.

So, why don't the engineers simply forsake marketing's demands, speak up and deliver more practical vehicles than they are being told to design? Because history shows us it doesn't work very well when engineering goes out on it's own to try and meet the customer's needs. Engineering does not really have a commodity that goes out canvassing the public for their opinion. Even so, when we do get public feedback, it must be filtered to a degree. Why? It's because the loudest suggestions we hear don't always represent the largest group of buyers. In this instance, I am speaking in terms of special interest groups that have an environmental agenda.

Not to ruffle any feathers here. I am simply giving you an example: I will refrain from using any brands names here. The auto industry made one particular attempt at producing an electric vehicle and putting out into the market on the West side of the country. We were told by the SIGs, "If you build will it. They will come!" Well, after several billions dollars worth of development in DC motors, drag co-efficiency and battery technology, we did, and they did not! No one wanted to drive these "earth-friendly" vehicles. Instead, full-size truck sales soared in that region! And, to think we tried to sell them in the very region that was screaming the loudest for them. We were forced, instead, to lease them instead of sell them and there were still very few takers. Despite the fact that these cars were quite fast, no one wanted them. They are now all off the market. We learned that until future battery technology improves greatly, electric cars are not currently practical.

Back to marketing: and now we have cross-over vehicles (a cross between a sedan and and SUV) and hybrids that run on gasoline and electricity for fuel efficiency. Yet, gas prices are into the mid $2 range and the customer is still telling us they want more horsepower! But, now they want it in smaller vehicles. Go figure! It's just like trying to hit a moving target!

For me: I understand that the SIGs would like us all to use less and downsize our vehicles. With that said, I suppose it's hard for me to understand just how a person can feel more socially and environmentally-conscience while giving up a large SUV and instead driving a overgrown "station wagon" that has over 400 horsepower?

Note: Due to my lifestyle, I drive a 4-door, mid-sized, 4x4 pickup truck, I don't drive far to work and I do not see me changing that any time soon. When it snows, I am usually the only one into the office on-time.

[formica]

Picky: Alternative fuel vehicles are the future, but the EV may have been just a little ahead of it's time. Gas is still too cheap and consumers not ready. Gas here was 3.80$gal last week... but we still get women wanting their SUVs (granted, less than in the US). It's a large change and it'll take some adaptation.

I kinda like small vehicles with high HP engines ... but then again I have no use for a large SUVs. I mean, how many buyers will fill em with 2x4s and take a ride through the bush?

Buying a car based on HP or torque ratings is like buy a set of speakers based on their efficiency or FR curve. It's part of the equation, but there is so much more to it.

Rob

[Tom Adams]

"Who sets the standard/benchmark for HP and torque and how?"

I'm not really sure what you mean by benchmark. Are you looking for power-to-weight ratio?

Shawn covered the how portion but remember, not all manufacturers use the same rating system for Hp. For comparison purposes, the SAE figures can be used. A better method is to look at the data from Car & Driver or others that use a chassis dyno to obtain Hp and torque - i.e. power at the rear wheels (or front wheels depending on the drive).

Your choice of flavor would depend on the intended use of the vehicle. If you plan on towing or hauling stuff, you want an engine that will develop it's peak torque rather early in the rpm range and hold that torque almost to redline. Small, revvy engines might make good Hp, but have a very peaky torque curve. Now, if you just plan on a run-a-round type car, then torque isn't such a big deal.

BTW, if you're thinking about replacing that B2300 with another small truck, I've got a recommendation. While my Nissan pickemup has been in the shop, my dealer has given me an '05 Frontier extended cab pickup to drive and it is one damn fine truck. Ride quality is very good, it's quiet & smooth, gas mileage is around 22 or so (not bad for a 4.0 liter V6), and it just recieved the Insurance Institute for Highway Safety's very good marks for offset frontal collision. If I didn't need the extra towing capacity of my Titan, I would definitely buy one.

Tom

[hwatkins]

My two cents - if you want the real skinny SFogg is one of the best (and maybe the best on an audio board) regarding automobile specs and how changes can be made. We first met on a BMW board and the guy is pretty much dead on regarding tweaks and modifications to engines. So here goes my comments---

Torque curves give you the best sense of what the car 'feels' like. If the torque rises rapidly at the lower RPMs you will feel a bit of slam off the line. Most American and rear wheel drive performance vehicles are known for a sharply rising torque as you increase RPMs to a fairly early plateau (not always true - a generalization). Many of the Pacific rim engines have a more gradual torque curve and a much higher redline.

HP is a measure of energy that is most informative if measured at the driving wheel(s) since this will not have any of the losses that occur when transferring the energy from the engine to the road. Unfortunately no maunfacturer will provide that measurement. A seat of the pants review would be HP per pound if you are interested in HP to help you make a decision.

Higher torque at lower RPM = either vehicle used for towing loads or a 'butt squatter' off the line performance car.

Higher torque at higher RPM = either a casual highway performer or an Indy race car.

There is no good or bad here, just different feel when driving or different purposes. Two distinctly different torque curve cars - BMW Z3 and Honda S2000 are both equally fun to drive. Off the line in the Z3 you pop the clutch at 1500 - 2000 rpm, with the S2000 you may do so above 2500 rpm.

I recommend you let your butt tell you which you like best.

[picky]

hwatkins: In this realm, I completely agree with you! Case in point: I drive the truck I mentioned before, but my wife wanted a performance-oriented vehicle. In short; she wanted a "driver's car". She got one, too!

Mrs. Picky drives a 1996 SVT Cobra Mustang that has only 21,000 miles on it. It's a solid rear axle car and it has the higher torgue band of which you speak. The second row of intake valves in the 32-valve engine begin to open around 3,600 RPM and from there the torque comes on very quickly. The redline is somewhere around 6,500 RPM if memory serves me correctly. At 305 HP it is very easy to drive around town, but it's best at home on the highway. It passes better than any car I've driven! The only thing that bites is that the car burns only 93 octane and that's about $2.65/gallon! Yet, the car gets surprisingly great mileage if driven at normal speeds.

[Champagne taste beer budget]

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On 4/11/2005 10:09:45 AM Colin wrote:

How do they derive HP and torque?

Lighter, tighter Japanese cars are quick and nimble with 150HP at 6300 RPM, while cushy Americans have 200HP at 5900RPM?

Who sets the standard/benchmark for HP and torque and how?

Thanks!

----------------

Colin, I looked around the SAE site, but it's not very user friendly. I did find this that expains how they derive the numbers. Hope it helps.

One horsepower is an estimate of the power a standard workhorse can exert:

550 ft.lbs/sec. Before applying any formula, we must first identify the

units of torque on you engine. Torque may be listed as foot-pounds or as

Newton-meters. As you made no specification, I will assume you automobile

secifications use foot-pounds.

The power exerted by a rotating object is the torque it exerts multiplied by

the speed at which it rotates. In standard English units, this would be

foot-pounds multiplied by radians/second. It is a special property of

radians that allows this product to be foot-pounds/second: a radian is a

distance around an arc divided by the length of the radius (feet per foot).

We start with 1 horsepower. We want to get to (foot-pounds)x(rpm).

1 hp = 550 ft-lbs/sec = 550 (ft-lbs)x(rad/sec)

1 rad/sec = 60 rad/min

= 33,000 (ft-lbs)x(rad/min)

1 revolution=2(pi)radians

1 rpm = 2(pi) rad/min

1 hp = 5252 (ft-lbs)(rpm)

As for source of rpms, that varies from moment to moment. The number of

rpms will probably be greatest in the lowest gears. When rpms get too

great, a vehicle is usually shifted to a higher gear and a lower rpm for the

motor. The torque tends to be greater in lower gears, when the car is

trying to speed up. Once at cruising speed, all the engine needs to do is

keep the car moving.

Look at the greatest rpm listed on the scale of your tachometer. Use this

as a reasonable maximum. Multiply this by your engine's greatest torque.

This is an estimate of your vehicle's maximum horsepower. Actual value can

vary with speed, with how well oiled the car is, even with humidity.

In rereading it, it's not as specific as I'd hoped. Do some poking around at the SAE site and I'm sure you'll find the actual information you're looking for. How the numbers feflect in a particular vehicles driving characteristics is a whole nother can of worms based on gear ratios in the driveline, allowable slippage if an automatic transmission, final drive ratio, tire size, etc.

[IAmtnbikr]

If you really want power...put on a "belt-driven hoodscoop", lol!

If you're at all interested...go to my site:

http://www.oldanimotorsports.20megsfree.com

The single most fun car I drove is the one on the home page, needless to say!

[rplace]

Not wanting to hijack your thread, but I read about the Z3/S200 comparison and totally agree - different but fun in their own way. Like speakers needing to be listened to cars need to be driven to figure out what works for you.

Until 3 weeks ago today I was not too concerned with safety in a car. Much more concerned with HP and Torque then gas mileage or safety. I bought a 2001 BMW Z3 for the fun of it and have always had a love affair with rag tops since my 1979 Triumph. Check out these crash pictures. http://www.terrik.com/BMWcrash/ Through no fault of my own (other driver lost control) I was almost in a head on collision with a SUV. The SUV rolled. One passenger was killed the other thrown about 20 feet from the car. The driver was more or less OK. I was literally unscathed. Not a scratch. I am so thankful for my survival and feel so bad for the others. Makes me wonder why me.

Forget your pickupget a BMW X3 or an X5. I know not nearly the same utility there. For at least the time being I am an avid supporter of BMWs safety commitment.

Picky, what part of Detroit? I grew up in Plymouth, owned my first house in Redford and Graduated from U of M. My dad worked for GM for 35 years. I know a fair amount about the auto industry. So you dont think I am a total tradermy other vehicle is a Yukon XL. Now there is a gas pig. However all of my HT construction needs (8 feet drywall sheets, 2X4s, Klipschorns, you name it) have fit in the back with the gate closed and not a drop of rain on any material/equipment traveling in that thing.

Wear your seatbelts!

Rich

[sfogg]

Rich,

Sorry to hear about your Z3.

Glad to hear the car did its job to protect you though.

I have seen *lots* of pictures of various Z3 crashes and they are *tough* little cars. From people hitting Moose on the highway to falling asleep at the wheel at 75mph and rolling it multiple times and walking away.

http://www.waycoolinc.com/z3/essentials/accidents/accidents.html

Last fall in my wifes 323i sedan a monster Dodge extended Van with a wheelchair lift (HEAVY) ran the light at the end of my road and t-boned us at about 45mph. My 10 month old daughter was in the back and the van hit basically the rear wheel/door area on the drivers side. Spun us around 180 degrees. My daughter and wife were fine, I bruised a rib with my own elbow as I was still holding onto the wheel tight. No glass broke in the car and the rear door still opened and closed OK.

Up until that time my in-laws didn't think my wifes car was a safe vehicle... they can from the old school that a safe vehicle is a BIG vehicle. That changed their mind.

Shawn

[picky]

rplace: I'm in Allen Park. My son has a place in Redford. I went to U of M too for Mechanical Engineering.

Personally, I don't believe that someone in the US who buys an imported car is a "traitor". The American company for which I work makes parts for the big three and for a large number of imports including Nissan and Hyundai. I drive a Ford Sport Trac that was assembled in Kentucky: The engine is from Germany and the transmission is from France. Does that make ME a traitor? I don't think so. Heck, the Ford 500 and the Freestyle are both built on Volvo chassis platforms. The Chevy Equinox is built in Canada, the engine is from China and the rest comes from Mexico and the Phillipines! It was only engineered in the US. To each his own as far as cars go. I love some of the imports!

[rplace]

Shawn, sounds like you dodged a bullet with that big rig. Glad you and your family ended up safe and sound. Ill check out the link. I forgot to mention that 10 days after the accident I was so impressed with the safety of the Z3 that I took delivery of a 2005 z4. Made the step up from 2.5i to 3.0i. The z3 and z4 could not be more different cars. At first I was not all that keen on the new one preferring the retro-throw-back style of a British roadster that the z3 seemed to embody. After only a few hundred miles in the z4 I cant believe how nice and refined it is. Truly a joy to driveand ya cant beat the drop top action! Added bonus the 3.0 comes with an upgraded sound system that includes Carver amps. I love my Sunfire/Carver home equipment.

Picky, you are wise beyond your years. I have had that same conversation with many, many people. My Z3 was assembled in South Carolina by US workers. It is a global economy we live in. Cars are literally made around the world. My traitor remark, while misspelled, was meant more of a joke for the Motor City types. So many of them are old school and if it did not come from the big three then you might as well be dissecting their children while still alive. I gave up even trying to breach the subject. Listen to the equipment YOU like and drive the car YOU want to drive and you cant go wrong. BTW I started off as a Mechanical Engineer at UofM, then switched my major to Computer Science after taking Thermo Dynamics 3 timesnot thermo I & IIbut Thermo I three times. I hated that class ;-) Maybe when I get up to see my parents (still live in Plymouth) I can bum an invite to the Picky HT, rumor is it sounds pretty darn good. I love the picks and the Red Wing jersey! We will invite ColterPhoto1 along too for good measure.

[Olorin]

Bummer about your Z3, Rich, though you came out okay and that's what matters. My wife and I just bought a Z3 for her to use as her daily driver and our getaway car. It's a 98 with the 2.8, 5 speed, and the hard top for times when the softie won't be coming down for a while. It is a FUN little car.

Me, I love the torque of the straight six. That thing has power on demand at any RPM from 1600 to the red line.

[hwatkins]

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On 4/11/2005 3:52:07 PM Olorin wrote:

Bummer about your Z3, Rich, though you came out okay and that's what matters. My wife and I just bought a Z3 for her to use as her daily driver and our getaway car. It's a 98 with the 2.8, 5 speed, and the hard top for times when the softie won't be coming down for a while. It is a FUN little car.

Me, I love the torque of the straight six. That thing has power on demand at any RPM from 1600 to the red line.

----------------

Yo Olorin - I sold my 97 2.8 Z3 in January after 7+ years. It was my escape car.

Shawn Fogg can help you with an air intake if you want a bit more kick and a throatier sound. I put a new cold air intake, freer flowing exhaust and had the chip reprogrammed to up the redline, match higher octane gas and remoce the top speed limiter. Added several suspension helpers, bigger wheels and put a bit more rubber on the ground. It was a very nice car to drive in the twisties at reasonably insane speed.

My advice - Whenever possible drive it above 3500 rpm....Have SFogg show you his hopped up, turboed baby.

Replaced with a 330 CI converatble with a hardtop for my lovely wife's daily driver. It will be missed.

[sfogg]

Henry,

Sorry to hear you sold the Z3, glad you had a lot of fun with it though. How many miles did you have on it when you sold it?

How do you like the 330? My father has one but not a convertible. Very nice car but the electronic throttle on it drove me nuts from the lag right at takeoff. A Shark Injector helped that. We also put a 3.38 rear end in it (stock 2.93) which made a big difference in performance. It pulled away from other 330s really easily after the diff.. he loved that mod. The E46s are nice cars all around IMO.

"Have SFogg show you his hopped up, turboed baby."

Nahh... no turbo... supercharged.

Shawn

P.S. With all this Z3 talk I'm getting confused on which board I'm on.

[Champagne taste beer budget]

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On 4/11/2005 6:54:47 PM sfogg wrote:

Nahh... no turbo... supercharged.

http://ackthud.com/shawnfogg/pics/shawn_fogg.jpg">

Shawn

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Very Nice. Lag? What Lag? We don't need no stinkin' turbo lag!! We got's yer pressure right here, right now!!

[Indyjeep]

Speaking of safety in cars, one car I can say has some of the best safety Ive seen is a Jeep Wrangler. My Jeep has had the worst luck out, its been flipped and been hit by other cars twice. And it still runs like a great. Its been driven almost 40k miles in 2 years. It was flipped when I drove up a telephone pole guide wire that was too close to the road at a 4 way stop. Went up it at about 10-15mph, landed on my side, skidded bout 7 feet and my hood slammed into the telephone pole and flipped me around. The great thing was that when we got it on all four wheels, we put back in park(still stuck in drive) and started it right up. Drove like a champ, even if the alignment was a little off. All I ended up with is a bruised elbow from where I hit the door with it when I landed. Im lucky to be alive, about a foot back and that telephone pole would have crushed the hard top and my head along with it. Thats my story, but ya my jeep has major low end torque. So touchy off the line.

[hwatkins]

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On 4/11/2005 6:54:47 PM sfogg wrote:

Henry,

Sorry to hear you sold the Z3, glad you had a lot of fun with it though. How many miles did you have on it when you sold it?

How do you like the 330? My father has one but not a convertible. Very nice car but the electronic throttle on it drove me nuts from the lag right at takeoff. A Shark Injector helped that. We also put a 3.38 rear end in it (stock 2.93) which made a big difference in performance. It pulled away from other 330s really easily after the diff.. he loved that mod. The E46s are nice cars all around IMO.

"Have SFogg show you his hopped up, turboed baby."

Nahh... no turbo... supercharged.

Shawn

P.S. With all this Z3 talk I'm getting confused on which board I'm on.

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Turbo/supercharged - What's the diff?

The Z3 had 55,000 miles. It was still darned pretty and reasonably peppy (actually I made the guy wait a day so I could run it hard one last time). It went to the first looker on the only 65 degree day in January for my asking price.

On the 330 I too get a bit irritated with the lag. Being for my wife's daily it is automatic and it doesn't seem to be as noticable when I take it to manual. I will try the Shark injectors. The rear end will stay as is for now - that is a bit far for me to go. It is black and with the hardtop it is uniquely pretty. We have a hardtop hoist and the hardtop is now winched to the ceiling of the garage. With the top down it is definitely not as noisy as the Z3 and it is a bit more rigid as you would expect. It is still a bit sloppy when you compare it to the coupe, but that was expected. All in all we are pleased and we now have a couple of cars that can commute rather easily.

OK - back to audio stuff for a bit. This was kind of like old times.

BTW - you had the link to Rachel's site - is she still around with her Z3? Esmirelda was my car's twin...

[Olorin]

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On 4/11/2005 6:43:17 PM hwatkins wrote:

Yo Olorin - I sold my 97 2.8 Z3 in January after 7+ years. It was my escape car.

Shawn Fogg can help you with an air intake if you want a bit more kick and a throatier sound. I put a new cold air intake, freer flowing exhaust and had the chip reprogrammed to up the redline, match higher octane gas and remoce the top speed limiter. Added several suspension helpers, bigger wheels and put a bit more rubber on the ground. It was a very nice car to drive in the twisties at reasonably insane speed.

My advice - Whenever possible drive it above 3500 rpm....Have SFogg show you his hopped up, turboed baby.

Replaced with a 330 CI converatble with a hardtop for my lovely wife's daily driver. It will be missed.

----------------

(Warning, thread drift and off topic)

Hey Henry, it sounds like you had some real fun with your Z. The previous owners put 17" wheels (factory) and 245/45s all the way around. It's pretty grippy, and since I enjoy the turning-without-slowing-down-first aspects a lot more than the zippy-dooh-dah drag racing aspects of driving the car, that's a good thing. I don't think I need the top speed to be any higher -- that's just MORE trouble for me to get into. <:bigsmil:> We've only had it a couple weeks, so we're not really thinking of any mods at this point, though the air intake would be the first.

Have any mods to get it to make a little less power and burn LESS gas? Mrs. O's having some trouble with the "speed limit" and "cost of gas" portions of the equation.

I'll try the 3500+ idea. The thing is so torquey I really try to keep it low (except when I'm romping), again in the interest of economy. Any particular reason you liked to run it high?

O