Horsepower and Torque questions

"zeontestpilot" (zeontestpilot) 07/13/2015 at 07:32 • Filed to: Question

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So I have a few questions about horsepower and torque for you guys...

1. What’s considered the ‘norm’ for hp and torque? Does it matter on the car’s size (Compact, mid-size, etc), the decade it was made it, or is it just whatever the manufacturer feels like putting into the car?

2. My pt has 150 hp with 165 lbs of torque, my prix is 200 hp with 230 lbs of torque. My dad just leased a new Kia and it has 145 hp with 130 lbs of torque. Why would they make the car’s torque smaller than the horsepower? Is it because of fuel efficiency or some other reason?

Thanks for your responses!

Arch Duke Maxyenko, Shit Talk Extraordinaire > zeontestpilot 07/13/2015 at 07:37

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1. Do some statistics, brah

2. Because

Flavien Vidal > zeontestpilot 07/13/2015 at 07:38

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Pretty much only american cars have as much or more torque than HP. Everywhere else in the world, people prefer higher RPM and higher power rather than torque... Torque also depends a lot on how big the engine actually is, therefore, europe and japan tend to produce less torquy engine than the US.

Denver Is Stuck In The 90s > zeontestpilot 07/13/2015 at 07:43

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Wow, all your cars have incredibly flat torque curves. And to answer your question, from what Ive seen at least; your PT’s torque curve is pretty common for 4 pots. My moms CRV has 180hp and 185lb ft. Your Prix also has pretty common torque for a V6, our Odyssey has 210hp and 229 lb ft

zeontestpilot > Flavien Vidal 07/13/2015 at 07:44

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Really? Huh, that does make sense. I had a friend, who has a semi-newer Chevy Malibu with a i4 engine, and the torque is lower too. So it might be the engine selection, like you said.

I just know that everyone is pushing for better mpgs, so I thought maybe lower torque helped with that.

zeontestpilot > Arch Duke Maxyenko, Shit Talk Extraordinaire 07/13/2015 at 07:45

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Statistics, eh? Ok, what do you drive, and what's the hp and torque for it? :)

Denver Is Stuck In The 90s > Flavien Vidal 07/13/2015 at 07:45

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“Pretty much only american cars have much more torque than HP.”

Hehe, ya. My truck has 160hp and 225 lb ft of torque. I agree with this statement, still alot of fun though

zeontestpilot > Denver Is Stuck In The 90s 07/13/2015 at 07:49

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Huh, they are? Interesting. I have no knowledge outside the cars I have, so I need to ask to learn more.

So the odyssey gets 210 hp? That’s pretty decent. Though, I know the weight factors into the numbers as well for who’s faster. Now to figure out what each one of my cars weight...

Flavien Vidal > Denver Is Stuck In The 90s 07/13/2015 at 07:52

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I agree, I’m a big muscle car fan (Despite owning a Mini 1000 and also despite buying the absolute total opposite of a muscle car: An Rx7 :D ) and I enjoy torquy american engines a lot. Loved cruising around in the city in the Corvette in 5th gear at 30mph without ever needing to touch the gas pedal :)

It was my city cruise control: shift into 5th as early as you want and let it go. It would reach 30mph and stay there despite the hills and the occasionnal required braking... No problem AT ALL :)

AthomSfere > zeontestpilot 07/13/2015 at 07:54

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These aren’t just numbers, there is a relationship. Torque is a measure of force and HP is a unit of power.

T = HP * 5252 / RPM
HP = T * RPM / 5252

You have to know something about the RPM obviously too...

Flavien Vidal > zeontestpilot 07/13/2015 at 07:57

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Well more torque means less revving, therefore less gas consumption. On the other hand, it means bigger engine required therefore more gas consumption.

Less torque means more revving therefore more gas consumption. On the other hand it means smaller engine, therefore less gas consumption.

:)

It’s 2 different systems that overall reach the same results... Each manufacturer chooses what they want or what their customers tend to prefer: In the US, bigger engines with more torque, in Europe/Japan, smaller high revving engines

zeontestpilot > AthomSfere 07/13/2015 at 07:58

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I knew they were related, didn't know it was like that though. I'm...still learning about cars. I refuse to think of them as a appliance, so I learn what I can, :).

zeontestpilot > Flavien Vidal 07/13/2015 at 08:00

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Wow, thanks for that explanation! :D

79 horsepower monster > AthomSfere 07/13/2015 at 08:07

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Torque is force times distance, not just force.

Flavien Vidal > AthomSfere 07/13/2015 at 08:09

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That works for an electric engine, but gasoline engines don’t work the same...

Flavien Vidal > zeontestpilot 07/13/2015 at 08:09

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No, these calculations only work for an electrical motor, not for a car engine.

Gonemad > zeontestpilot 07/13/2015 at 08:10

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Well, really old semi-trucks have 360HP... but they can output it from 1000 rpm. 36 liter engines, with humongous torque. Exactly designed to haul ass, but they can’t run.

Meanwhile, really shitty cars with 1-liter engines have 90HP... screaming at 4600 rpm. Most bikes have 1-liter engines and 300HP, which means... screaming revving engines.

It all depends on how low revving you want before the fun begins. And how long you want the engine to last. Therefore, there is no right or wrong, each one is built for a purpose.

Cé hé sin > Flavien Vidal 07/13/2015 at 08:35

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I live in one of those places full of diesels and they all have much higher torque than hp figures

Jayhawk Jake > zeontestpilot 07/13/2015 at 08:40

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Dat Sanic Tho

Flavien Vidal > Cé hé sin 07/13/2015 at 08:45

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Yeah but I thought we were talking about cars not trucks :D

Joking aside, of course diesel cars are different...

crowmolly > Flavien Vidal 07/13/2015 at 09:02

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Huh? How so?

Cé hé sin > Flavien Vidal 07/13/2015 at 09:02

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Turbo petrols too...

Flavien Vidal > Cé hé sin 07/13/2015 at 09:07

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Because both side try to compensate what they lack... Ooh course tons of add-ons can be added to modify the torque curve... But basically gas NA vs NA, this is how both size of the ocean work when it comes to building engines.

MultiplaOrgasms > zeontestpilot 07/13/2015 at 09:08

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Is there even such a thing as a norm for hp/torque? Obviously this depends on the era when the engine was made, and you could say that hp/torque are about the same, however that would exclude high displacement engines with low output (pre-war luxury engines, some american V8s etc). It’d also exclude pretty much all turbo engines (those can sometimes have twice as much torque as hp or more).

Flavien Vidal > crowmolly 07/13/2015 at 09:13

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Because a gas engine does not have a linearlineartorque curve and torque is easily modified depending on how the engine is set up and everything....

For example my car is 190hp at 9000rpm.... And no it doesn’t make 110lb/ft.

You can also change to peek torque rpm with simple ECU modifications. Without changing the HP figures out RPM numbers. This is why this calculation only works with electric engines.

Milky > zeontestpilot 07/13/2015 at 09:22

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As for the “norm”, the last year with a number I could find is 2008. The average car sold had 222hp. Thats certainly only gone up too.

BloodlessWeevil > zeontestpilot 07/13/2015 at 09:35

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1. There really is no norm as such. Asia and Europe vehicle can get away with less power because they generally have lower speed limits and less intense acceleration requirements than the US.

2. Peak power is directly related to rpm. For a given engine, you can increase peak power by making the red line higher. Some methods for doing this will lower peak torque, but usually not by a significant amount. Many countries tax by engine displacement (or so I’ve heard,) making small high reving engines more desirable even if it brings a penalty in efficiency (I am an engineer, so I mean thermodynamic efficiency when talking about engines.)

Generally torque (across the power band) is directly related to displacement. Peak power is also directly related to torque at the red line. This means that a large, low reving engine might generate the same peak power as a small, high reving engine.

zeontestpilot > Jayhawk Jake 07/13/2015 at 09:46

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I saw Transformers 4 for the first time yesterday, the Sonic was the highlight I thought, in a otherwise poor movie. I was REALLY hoping it was a transformer itself, but it wasn’t, :(. Preferably with a cool name like “Exhaust Note” or “Backburner”

zeontestpilot > MultiplaOrgasms 07/13/2015 at 09:48

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See, this is why I asked. There doesn't seem to be a norm, which is informative in itself. :)

zeontestpilot > Milky 07/13/2015 at 09:50

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That's higher than what I anticipated, but still pretty neat, :).

uofime-2 > Flavien Vidal 07/13/2015 at 09:59

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Those equations are always true. Where did you hear they only work for electric motors?

crowmolly > Flavien Vidal 07/13/2015 at 10:08

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Here’s an LS3 cam comparison chart.

If you take any TQ point, multiply it by RPM, and divide by 5252 you get the corresponding HP number. Makes sense since that’s how dynos get HP from testing.

Every dyno sheet has hp and tq cross at 5252 because of the formula.

Or do I just need more coffee since I’m reading you wrong?

Flavien Vidal > uofime-2 07/13/2015 at 10:19

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How are they true??? Take any engine numbers and check it out for yourself.... It never applies

For example: a NA 12a rotary produces 127hp at 7000rpm and 103lbft of torque at 4000 rpm. These are not calculations but facts.

This is why you don’t “calculate” the torque of an engine but why you put the engine on an engine bench and test itit. This method only works for electrical motors.

Flavien Vidal > crowmolly 07/13/2015 at 10:28

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Then how would you explain so many engines having torque figures so far off ??

Mazda 12a engine: 127hp at 7000 rpm and 103lb/ft at 4000rpm

But this applies for many other engines of course.

Of course powerful American engines with a much more linear torque curve comparable somehow to electrical motors have much closer results to those from this equation. Enhance your LS3 example.

uofime-2 > Flavien Vidal 07/13/2015 at 10:29

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I don’t think you understand the equations, they merely say that if you know the torque (at an rpm) you can calculate the horsepower and vise versa.

This is important because torque is easy to measure, so on a dynamometer you can measure the torque and rpm points and use that data to calculate the power.

Where people get confused and I suspect this is where you got lost is that at an rpm an engine can produce a range of torques and corresponding horsepowers.

Flavien Vidal > uofime-2 07/13/2015 at 10:33

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Ooh OK I see what you mean... But then for a gas engine this is useless since peak power does not mean peak torque?? No? Therefore you cannot calculate the peak power by knowing the peak torque like you would with an electrical engineer, sort of rendering this equation useless?? No?

crowmolly > Flavien Vidal 07/13/2015 at 10:34

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You are comparing figures at different RPM points. Of course those are different, that’s part of the engine’s design with tuning, cam profiles, etc. This is not an equation to determine peak hp from peak torque.

I’ll bet that 12a engine makes 78.4 hp @ 4000.

TheOnelectronic > zeontestpilot 07/13/2015 at 10:35

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Most things have been covered already, but;

the main difference is high torque motors “feel” faster, because they make more of their power at cruising RPMS. Something like an S2000 or an RX-8 that has very little torque but revs to 9k can move, but you have to be fairly high in the rev range to get that power. That means that if you’re cruising down the highway and want to speed up, you’ll need to downshift a few times to really get much acceleration. Something with an 8 liter V-10, though, will offer very immediate pull very low in the rev range.

Flavien Vidal > crowmolly 07/13/2015 at 10:38

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Yes, I understand it a bit more through another post now... But as I answered, this equation is a bit useless for gas engine since peak torque doesn’t equate peak power... Knowing the peak power will never tell you how much torque an engine can make and vice versa. Unlike it would with an electrical motor... No?

crowmolly > Flavien Vidal 07/13/2015 at 10:47

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Well, not exactly. The formula defines how HP and TQ are related in any situation. It just so happens that the behavior of an electric motor gives a peak for both at the same time.

But the equation was not meant to associate peaks and valleys. Just how to get HP from TQ at a given RPM.

This equation is probably programmed into every engine and chassis dyno ever built.

Flavien Vidal > crowmolly 07/13/2015 at 10:49

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OK OK I understand a bit better now thanks... Until now I never understood how this could be working with a gas engine but I get the whole point of it now :)

Thanks!

crowmolly > Flavien Vidal 07/13/2015 at 10:59

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:)

One other *little* thing to note is regarding dyno sheets (like from chassis pulls). Sometimes if you read one it looks like the curve doesn’t cross at 5252 like it should. The software occasionally scales the curves funky. The sheet will always cross unless something is broken.

Jayhawk Jake > zeontestpilot 07/13/2015 at 11:02

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There’s a toy of it that transforms, and its name is Rollbar

uofime-2 > Flavien Vidal 07/13/2015 at 11:08

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You are correct, you cannot know the peak power only by knowing the peak torque on a IC engine. The torque usually decreases at higher rpm, although not quickly enough to cause the torque and horsepower peaks to be at the same rpm.

the equations doesn’t become useless but it does have limitations since you cannot assume the same things you can with an electric motor.

Denver Is Stuck In The 90s > zeontestpilot 07/13/2015 at 16:23

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The Odyssey weighs 4200lbs so its kinda meh, but if you mash on it the power is there. Out CRV on the other hand... Weighs 3800lbs. It's frightening on the highway

Denver Is Stuck In The 90s > Flavien Vidal 07/13/2015 at 18:44

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I should try doing that in 5th. I wonder if my truck would do that

AthomSfere > uofime-2 07/13/2015 at 20:54

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I’d like to know that too? Didn’t realize electric was old to have its own set of weird myths already!