senseiturtle

"Horsepower sells cars, torque wins races"

A wonderful old addage that turns out to be absolutley false. Before I start summarizing why HP matters and TQ really doesn't, let's do some background reading...

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Quote: "Horsepower IS the factor that determines whether you win."
http://www.heumann.com/m5/hp_torque.html

Quote: "There are no exceptions; a car running at its (net) power peak can accelerate no harder at that same vehicle speed. There is no better gear to choose, even if another gear would place the engine closer to its torque peak. You'll find that a car running at peak power at a given vehicle speed is delivering the maximum possible torque to the tires (although the engine may not be spinning at its torque peak). This derives immediately from first principles in physics."
http://www.allpar.com/eek/hp-vs-torque.html


And my favorite... the best so far... and a recommended read for all--

Quote: "It is better to make torque at high rpm than at low rpm, because you can take advantage of *gearing*."
http://vettenet.org/torquehp.html

Google "Horsepower vs. torque" if you want hundreds of other articles.
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After you've poked through all that, you should have a good grasp of what I'll be saying below. If not, then the below info can serve as a good cliff's notes.


Let me bring up a tC (160/163, 2900+lbs) vs. RSX-S (210/142, 2800+lbs) example to explain why HP matters. Similar vehicle weights. tC has more torque. tC has shorter gearing. So why does the RSX win? High revs, which translate to higher Horsepower. The RSXS is better able to utilize its gearing by being able to pull "longer" in each gear, per-se, through its higher revs. Therefore, its horsepower is what makes it win.

And let's compare the tC ( 160/163, 2900+lbs) vs. the EP3 Si (160/130, 2750lbs). You might be thinking "the tC has more torque to offset its weight." Well, while the tC does have more torque, and technically builds HP faster, the reason it keeps up with the EP3 in spite of its heavier weight is due to the fact that it DOES put more HP down to the wheels, stock for stock. Average dynojet dynos place the tC at the low 140s, and the EP3 at high 130's. EP3'ers might not like to hear this, but given the above articles and facts, how else would you explain it?

---- Conversely, if acceleration was based on TORQUE, not power, in addition to gearing/weight... then a tC would DEMOLISH an EP3 si, RSX-S, CelicaGTS, and several other Variable-Valve 4-bangers stock for stock.... and we'd all be getting our asses handed to us by TDI golfs (which dish out monsterous levels of torque, but little HP). Thankfully this isn't the case.



So why would anyone want a torquey motor?
Torque has an effect on launches, but not as much as one would think. The only reason torque is "nice" is that it helps to prevent bogging at high-power launches. Each time you launch, the sudden jump in engine load will cause a reduction of RPM before the motor can "push back" and accelerate the car.

Think of how your houselights dim when you turn on a big vaccuum cleaner, then come back to full brightness gradually. Your motor's torque (and therefore, power) does the same thing.

In addition, since torque is the force you feel, higher torque cars feel faster. This makes for more fun, but not necessarily more speed. Drive around the block in an Altima SE-R, and you think that your S2000 feels slow in comparison... but when that little honda goes flying by, you'll understand that the butt dyno is deceiving.

Please let me know if you should have any questions, complaints, corrections, or concerns... I'm completely willing to help out, and make any corrections if need be.

-Thanks,
Ryan T.

ERIC-TC

I test drove an A/T civic 06 which is supposed to have like 140HP and when I punched the throttle when merging into the highway -Nothing happened! Tha car was a total dog. I'm not sure if the engine was not fully warmed up or if the engine forces you to get the 40MPG they claim.

When I test drove the A/T TC and I punched it (in the same spot), The butt-dyno was off the meter . Note: My previous ride was way underpowered so It seemed like a lot to me...

This butt-dyno test was performed the same night in the same place (The dealer had Honda on one side of the lot and Toyota/Scion/Dodge on the other)

Anyone else experience the lack of throttle reponse on the new Honda Civic?

jsa3mm

Thank you for the info.

cmndrjamesbond

Sensei is absolutely correct in his analysis. Considering the fact that torque is scaled by gearing through the drivetrain while power is constant (don't jump down my throat here, I'm referring to power at a discrete rpm with all other conditions equal) . The best way to compare the power output of two cars is to look at the whp output through an entire gear. A Honda S2000 may have a redline of 9000 rpm and only make 140 some ft-lbs of torque, but when you consider that its gearing is about 2/3 as tall as the typical car, that toque is magnified by a factor of 1.5 on its way to the wheels when compared to our 163 ft lbs with a 6200 rpm redline.

boomshakadae

i feel the tcs gears are off. maybe just my impressions, but i think it should be improved

Fushyuguru

Good resources for those new to the debate. Keep in the back of your mind the lack of a significant stroke length, internal rotational+orbital inertia, 3 face actuation, high rev (however a rotary at 9000rpm, it's rotors move at 3000 rpm - much slower than comparable piston engine) and wide powerband of a rotary and some may start to understand why torque never mattered much to us rotor-heads. The physics for pistons go to hell.

wubaru

how effective is torque vs hp in drag races vs circuit races. is hp still the winner?

senseiturtle

HP is still the winner, no matter what type of race.

A car is accelerating at its highest rate possible when it is maximizing its average horsepower, which can only happen around the horsepower peak.

In circuit races or autoX courses, it is important to balance the highest revs possible with the time lost in the downshift. All this to maximize the average HP over a period of time.

Charade_Detomasso

Both in abundance is whats best, but in a street car good torque delivery is necessary. Torque is what helps the 400lb HEAVIER and 30 hp LESS tC get to 0-60 almost as fast as a celica GT-S (7.8 seconds tc, 7.1 seconds Celica).

Try and twist physics all you want, but HP is porportionally related to torque, and if you have no torque, you will have to spin your engine to x000 rpm to get power. Gearing will only go so far to help you before it bites you in the @$$.

This argument of torque vs hp is overdone. Both have their advantages and disadvantages, and any real tuner would know how to optimise the relationship between both, and which works for what scenario. Most important overall is the power delivery, cause if you have a car developing 400ft-lbs of torque at 2000 rpm and cant rev past 5000, it aint worth it. Likewise if you have to rev to 10,000 rpm before you start to make 400hp.
The best compromise should be to have an engine that reaches close to its peak torque by 3500rpm and continues with it up to 7000 rpm or so. Best of both worlds. A.k.a a broad and HEALTHY powerband, which is developed from torque

cmndrjamesbond

Since when are 7.1 and 7.8 close? Also, how do you figure 180-160=30? The only 2ZZ that puts out 190 is the one in the elise and exige.

engifineer

You really cant compare the two as seperate entities.. peope tend to forget that in a system, you cant just take one peice ata time. HP is directly related to the torque and rpm, so you cant have one without the other. Having a bunch of torque and low rpm (like many deisels) produces a lot of horsepower. Having lower torque and higher rpm also produces hp. The higher rpm application is great for taking advantage of gearing.

But it all lies in the application. But you still cant "compare" the two per se, they are part of the same end result. That is basic physics. It is where the torque lies in the powerband and how wide that powerband is that makes all the difference. In other words.. treat it as what it is.. a system, not a bunch of sequential parts.

senseiturtle

And thanks to Charade's semi-attack on the legitimacy of this thread, we can further define what horsepower truly means.

Right now you're probably thinking... " Wow, RPM is the most important thing, then!" ... Well, yes, it is important, but no, its not everything.

He's absolutley right. Torque is a vital part of racing. With 0 torque, no motor could ever move ANY car. In addition, if we've got a theoretical motor that makes 1-ftlb of torque but holds it to infinite RPM, while it will eventually out-accelerate any traditional motor, it'll take forever to get going since it does not BUILD horsepower quickly at all.... by the time it's making decent power (say, 300hp at 1,575,600 rpm), the race is probably over!

Therefore, let's look at torque's influence on the all-important horsepower.

1- Horsepower is defined as HP= [TQ*RPM] / 5252. Therefore, given equal engine speeds, the motor with more torque is always making more horsepower at any given point. A real-world example (numbers fabricated for illustration)....

A mustang GT V8 makes 310ft-lbs of torque at 3000 RPM. A scion tC makes half that, 155 ft-lbs at 3000 RPM.... so if you do the math, the tC is putting down 88 horsepower at that point, while the mustang is putting down around double that, 176. The mustang is picking up speed far more quickly than the tC already, and is moving through its powerband towards max HP quicker as well.

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At this point, I'm hoping that you realize that RPM is important because it serves as a "multiplication factor" for horsepower.

300 ftlbs @ 5252 RPM = 300 hp.
300 ftlbs @ 10,504 RPM = 600hp.
300 ftlbs @ 15,756 RPM = 900 hp... and so forth... In fact, most F1 engines make a "pathetic" 270 ft-lbs or so, but hang onto it until upwards of 18,000 rpm... and the end result being some of the most responsive, fastest-accelerating motors in the world at around the 1,000 horsepower mark.
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So now, if we're going to make torque somewhere in the powerband, where do we want to make it? The ideal answer is everywhere! The perfect motor makes good torque, and as much torque at 1000 rpm as it does at redline. But, real-world motors are not perfect. Due to displacement, camshaft timing, airflow characteristics, and other factors... we are forced to make a choice of where peak torque occurs, and must deal with a steady decline in torque thereafter.

If we choose to make more torque up high than down low (like what happens with big cams), we'll get huge increases in power up-top... but we'll have to deal with making no power down low. Additionally, if we choose smaller cams and make our torque down low, then we lose a lot of the multiplication factor for HP, and our top-end will suffer.

I hope this has helped to clairify. Torque isn't useless, but realize this same celica GTS is only making 111 ft-lbs and clearly out accelerating us. Weight plays a big role, but the celica does make more HP.

engifineer

and the RSX has the advantage even with lower torque because it revs higher yes... hp = ( tq * rpm/5250). So it is using its torque at a higher rpm to produce more hp... again you CANT have one without the other. You have three variables just in that portion alone that are all working together.

savior

listen to sensei and engi

unsungfate

GREAT THREAD!!

engifineer

I thought I would clarify one point that confuses some at first glance before it gets brought up. If you analyze the equation for HP you will notice quickly that on any dyno graph the HP and TQ lines will intersect at 5252 rpm. But, if you look at a lot of graphs posted you will not always see this. If you think about it, most of the graphs posted online are plotting WHP against engine rpm as well as using a not so accurate tool as far as exact numbers are concerned, which will skew things some. On a BHP graph the two will intersect. So at 5252 rpm your BHP and torque will be equal. Just thought I would throw that in since I am sure a few people are looking at that wondering.

cmndrjamesbond

Horsepower and torque are always equal at 5252 rpms. No exceptions. This is whether it is at the wheels, or at the engine. I've never seen any dyno where the two do not intersect at 5252. A dyno does not actually measure torque or horsepower. It measures the acceleration and velocity. Given these two factors, as well as the known weight of the drums, the power and torque can be easily calculated.
If you were to see a discrepancy in the torque and horsepower, than whatever software they are using to perform the computations and plot it is f-ed. Or, it is highly likely that the customer decided to misrepresent his car in some way, perhaps altering the plots without this knowledge.

IpOdWhYtEtC

Correct me if im wrong in saying...

Because the TC isnt a high rev car like a RSXS, Torque would be a better gain than HP because we need the Biggest number possible (Torque) to multiply by our low RPMs to compensate for the "lower" rev and quick gears.

Typhoon

^^ thats how I understand it as well. However now I am curious with some engine upgrades and some kind of managment that removes the rev limiter on our cars and have it rev at 7500 what would be the result of doing that or would one not get any positive results due to a diff engine?

senseiturtle

Well, adding torque will never hurt... but we ALWAYS want to add HP, so to speak.

Camshaft upgrades will play a key role in the future. If we could shift the torque peak upwards in the range (and preventing torque from dying off above 5500), we'd make significantly more HP.

If you have the choice to "tune for torque," or "tune for HP." Always tune for HP.

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Now, as a side note, the maximum amount of torque a motor can make is limited. It too is based on a formula, which I won't be getting into. Bolt-ons increase torque by increasing the MEP on the piston's surface, and the other factor is displacement. You can only raise the MEP's so far using boltons, and at that point, it's either increase the displacement or increase the compression ratio.... both of those has their troubles in accomplishing...

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HP is not limited to displacement, so eventually, you'll get to a point where your mods will make much more HP than they do torque, simply by manipulating the existing torque and making it more beneficial for racing.