Skythe

Horsepower is a popular topic of discussion. It's a feature that drives car sales and it's used extensively in the marketing of performance add-ons. Is it really just makerting tool used by companies or is "Horsepower" an good unit to measure how much "power" a car can produce. Before you shy away from this post, consider the following...

(Torque x Engine speed) / 5,252 = Horsepower

Since horsepower is a product of the amount of torque that is produced at any given RPM, isn't torque really the "power"? From this formula I see that horsepower is a reflection of how much "work" an engine is doing, but this formula tells me that torque is power and horsepower is just a relative correlation.

When asked about the difference between horsepower and torque, people often say 'torque is what pushes you into your seat" or "torque is what moves you." If that is true, then why all the hype and fuss about how much horsepower a certain mod will give you, especially when all that person is measuring is "max horsepower" Shouldn't we be more interested in how much torque can be gained with mods and also, where in the rpm band that added power is achieved?

So, if torque is what dyno's measure and is the real thing moving you and not the horses, why all the fuss? Perhaps we are just products of conditioning from mass marketing and misinformation?

Brothers of the 8, share your thoughts. Give comments and feedback. If there are any errors in my reasoning, I'm sure someone will kindly fill in the gaps or make suggestions.

playdoh43

the industry use peak horsepower as the standard, which is the max hp at a single rpm, a single point on the powercurve. so its neglecting a lot of information about an engine. it is however not any less accurate than peak torque for the same reason.

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If you want a more precise measurement of how fast a car is relative to other cars, I propose you compare (hp + torque)/weight. this is still not taking into account a lot of factors, but this should be more accurate with real world 0-60 and 1/4 mile times.

kw1k

Yes.

mike1324a

Yes it is very important! We NEED as much as we can get over a strong powerband in a car with as little weight as possible.

mikeb

I must agree

Crazy Rx-8 Driver

look at semi trucks.. a lot of torque... but not alot of horsepower. torque is how much weight you can move, aka "work"

so if the car is very light.."lotus elise for example... do we need a lot of torque? what if the vehicle is extremely heavy.. say 3500-4000lbs... i would say torque would matter.



i think horsepower to weight ratio is more important then anything, since torque and hp are correlated with one another.

Krankor

Perfectly said, bravo.

Everyone likes it when you can reduce a complicated thing to a simple number. It's great for marketing, but it generally doesn't convey that much information. I worked in software performance engineering, and the company's major marketing focus was getting the product to perform well on this one particular industry benchmark. They'd jump through amazing hoops to get good numbers out of this benchmark, whether or not this had anything to do with the way a real customer would use the product. In fact, the benchmark was in lots of ways a poor measure of ultimate user performance (producing a perfect benchmark is pretty much impossible). I think its pretty much the same thing with horsepower, it's just one point arbitrarily pulled out of a curve, and is a VASTLY overrated measure of anything. If I'm looking at performance, I'm more interested in 1/4 mile times. I'm new to car performance, but with motorcycles I have found that 1/4 mile time gives me an excellent predictor of how the motorcycle will feel to me when I ride it.

allmotorRX8

id second that

yiksing

Yes, horsepower is just as important as torque, bottomline we all want massive flat like torque over a long rpm range in our car.

Deslock

https://www.rx8club.com/showpost.php...1&postcount=24
https://www.rx8club.com/showpost.php...&postcount=254

Gohan

Yes, horsepower does matter

RX8-TX

Power is relative to work done over time, or over a working range in this case (engine work range = rpm band). In my humble opinion, gearing, weight, suspension & contact patch are also important. Why gearing? Well, it'll determine the amount of work / energy the driven wheels will receive from the engine. In other words, its converting stored energy into motion.

Why weight? It'll take a lesser amount of work to move a mass of (M-10), than it will to move (M-5).

Suspension & contact patch? You got it figured out by now.

Paying attention at "peak" numbers is also futile. Or at least when it comes to using something everyday. If you have to stay at a 100% utilization in order to extract usable power from something, you better turn around and find something else. That applies not only to engines but, processors, tools, xmas lights putting 100% load on your home's power grid, etc...

The amount of work done over a usable range is what matters to me. Now, many of you will say "Why the heck are you driving an RX-8!!!!???"; well, it has plenty of what I use everyday, throughout a very decent band. I don't drive @ 8,500 rpms in every gear, every second, every day. Although I do make use of what I consider that "extra" lil' bit of juice that comes high-up on the rpm band.

After all my babble, the more power, the more fun it gets -well, most the times!

TODreamer

yes...yes it does

Sephiroth

http://www.mazda6tech.com/index.php?...id=9&Itemid=49

Check that article. It talks about HP as well as torque, gearing, weight, drag, etc.

RX8-79

Because in this country they shove the bigger-is-better mentality down our throats. So, to some, the bigger the hp number, the better. Never mind if car x has "298" hp and is slower than car y with 268.

yiksing

Horsepower is simply how long u can put that amount torque to the wheels (rpm wise)

KYLiquid

if you gave most people (esp. americans) the choice of 2 sports cars, both looked identical (since a lot of people dont care about looking into weight, gearing, ect) and 1 had 300hp, the on ther had 260hp. Most would chose the more powerful car, if the costs were the same or close to the same. People just want that braggin factor. Even if they were later told that their car was just as fast as the lower power one. I think most wouldnt care.

We drive TQ, when you put your foot down, you are using TQ.

Part of the reason people will say things all the time like "i want a car with 325hp" or "the rx8 is slow, if it only had 300hp" in reality there are so many factors to a cars performance, even if you are only focused on straight line speed that having a 'snap shot' of a cars power doesnt mean anything. Even more so when you remeber that the power number was on THAT car that they tested, on that day, under those conditions. So the real world value of how much power that new car you just bought on the lot is going to be diffrent from what the article in the paper or whatever said.

gonnahanvan8

It only matters if you have a small *****.

Skythe

HEY HEY, when you park that thing in the garage....does it say....is it in yet?

gonnahanvan8

ummm, maybe the garage is too big.

yiksing

Very good point, explains why some wanna go straight fast coz they don't dare to corner fast.

Skythe

This is pretty much what i was implying. People care too damn much about horsepower ratings, which are a solid implication of how much "work" or "stress" an engine or parts can handle or how much "work" is actually being done, but really doesn't say much about how much power is getting to the wheels and how hard is it gonna pull or push you.

like...the dreaded B16 engine from honda, produces something like 210Hp but that rating is somewhere in the higher RPM's cuz of its high compression but with all things considered and you go some backwards math you can figure that it ain't really producing all that much torque which is really what's driving the car. but since the car is small and light, it's a much needed improvement. But when you look at the actual numbers the B16 seems like a lot of hype.

take for instance, the new Mitsu Raider, a freakin V8 but OHNOZ, 230Hp and the V6 model has a rating of 210hp....hmm..WTF??? but looky here 290ft/lbs of Tourqe.

Transam kid 01

iTrader: (1)

yup...and torque too!

BaronVonBigmeat

A) The equation you gave has torque and RPM. I'm not sure why you would conclude that "torque is the power"

B) Horsepower is a reflection of work...per unit time. Note that torque has no measurement of time. ( the generic power formula is (force x distance)/time )

C) You can increase engine output by increasing torque. Or, you can increase the RPM's. Either will do.

D) Yes, average power is a better number to look at than peak HP, especially for a street-driven car.

E) People always say that "dynos measure torque", which puzzles me. A quick glance at a dyno chart clearly tells us that they measure torque and RPM's.

If torque is everything, would it be smart to put cummins diesels in performance cars? If I replaced my renesis with a chevy 305, would it be faster? It has more torque! But it can't do more work per unit time. It can do less work in the same time, or the same work in more time. Racing is all about getting the work done (1/4 mile or 500 laps or whatever) in the shortest amount of time. Therefore, torque is an incomplete assessment of what an engine can do. It has no measurement of time.

Obligatory modular depot article:

http://www.modulardepot.com/?show=articlesdet&aid=44

280RX-8

Some women prefer the small bananas.