Doubts about torque
 

I was watching a top gear vid about the new mazda rx8. It has 230 bhp but low torque. What does that mean?

basically it means for the car to pull hard it has to be in a high rpm range.

basically it means for the car to pull hard it has to be in a high rpm range.

edit- sorry delete this, my computer had some serious lag.

but what is most important? Lots of bhp or torque?

when they say 'low torque' did they mean it had a small amount of torque? Or it kicked in low down??

As it is an RX8, I think it is the latter. Torque, very generally is a good indication of in gear acceleration. Whicle raw BHP is a good indication of top speed. If you have a small amount of torque, when you put your foot down, it takes ages to pick up speed, but if you have a lot of torque you pick up speed quickly.

There is a certain rev-range in earch car, where torque is at an optimum. So when they say 'low torque', they may mean the torque is strong at low revs, which means you can be lazy with your gears.

If, lets say, your torque kicks in at 5,000 rpm, then while you are accelerating, you will feel the car accelerate quicker when you hit 5k, but if it kicks in at 1500rpm, then the car will in general accelerate quickly.

but what is most important? Lots of bhp or torque?

A balance. BHP is nothing without torque, and torque is nothing without BHP.

A lot of torque is what causes the wheels to spin while accelerating...so if you have too much it may be a bad thing. As I said before, the more BHP you have, in general the higher top speed.

I get it. thanks a lot. :wink:

No problem, there are people on here who know a LOT more than I do on the subject, but I think I am right in what I say lol

If a car doesn't have torque, it wouldn't go anywhere. Smaller cars with a descent amount of horsepower can get away with having a lower amount of torque (i.e. honda s2000 240bhp and 161lb*ft of torque). This car also weighs only 2850lbs.

The Mazda RX-8 has 238bhp and 164lb*ft of torque (which weighs 2950lbs).

Muscle cars have traditionally about the same or a higher amount of torque than horsepower. It all depends on what kind of feel you want when you step on the pedal.

So dragsters have lots of both, right?

dragsters have bitchloads of both yes. Torque is all about turning those wheels (torque=force*distance) so if your car has the power to turn the engine it can create alot of torque and that's why most larger engines have a longer stroke and that's the advantage of a long block over a short block.

Thnks. And I love your "little" collection. I have one myself, but all the cars have 20, 25 centimeters. lol

I have quite an extensive model collection too if that's what your getting at. I have 3500 Hot Wheels/Matchbox cars and about 30 other size models both made and bought complete.

Very true...except isn't Work=Force*Distance and Torque=Force*Lever Arm(in m or ft)?

I love miniature cars. But they are a bit expensive. I have about 50 bburagos, but it cost me lots of money. Just a question about the evo. Did you also try the Subaru? Just to know, because here in Portugal nobody has an Evo. Not even the cops! They have Imprezas. No idea why, cuz I love the Evo from day one!

yes torque is force*distance(that's what the Lever Arm is) that's why ALL Torque Wrenches are exactly 1 foot long hence Torque is in Lbs per feet, foot pounds of torque get it?

Yes I test drove the STi and the EVO and I prefered the EVO way more especially because it isn't as flashy and I have driven normal WRX's and actually liked some of the custom ones I've driven more than the STi.

firstly the longe stroke does not produce more torque solely because torque = force times distance(which is actaulyl incorrect). in fact the the propper equation for torque is torque = force times perpendicular distance, and therefore since the cylinder travels perpendicular to the motion of the cam shaft, the length of the stroke has no effect on torque in that respect. more torque is generated by engines with longer strokes b/c it have a higher compression ratio, which is the same principal as a turbo/supercharger, ie more air/fuel in a smaller area = more boom.

and no not all torque wrenchs are exactly 1 foot.. if you dont believe me look here. think about it, if u need to torque a bolt to 250 ft lbs , how are you going to do that with a 1 foot wrnch?! apply 250 ftlbs? damn hard if u ask me................

next time do your homework, or know what the fuck u're talking about before you post! :roll: and to think that your dad has all those muscle cars and u don't know what a torque wrench looks like?! do u have any pix of your so called dad's cars? or are you just another Donny? :twisted:

OK dick shit the Camshaft has nothing to do with the stroke of an engine that is the Crankshaft and Actually the equation is just Force*Distance so on those 2 matters you can kneel down and open wide and when I said all torque wrenches are 1 foot long I meant standard torque wrenches yes you can get longer ones but they will be really expensive and not too many things on a car go over about 160. actually more torque is created because of the longer Crankshaft that's why diesel's (the kings of torque) use long blocks not short blocks so once again kneel down bitch. And I went and looked in our garage and yes we do have a 2 foot torque wrench. so it was a slight typo.

um no....for teh sake or argument if the force parallel to the distance the torque is zero no matter how hard u push or how far is is. and es i made a mistake, i meant crankshaft, not camshaft

in all my physics classes I've taken (3) and all the automotive books I have (3 textbooks) I was always taught just Force*Distance even though on a rotational basis was always stressed the equation was always just normal distance.

AND: if some dumbass takes a torque wrench and tries to push down on it to turn the bolt they shouldn't even be allowed to ride in a car.

as its been explained already, Force*Distance/Time= power aka torque. what i think hasnt been adiquately explained is how hp is derived from torque
Horsepower = (trorque)(RPM)/5252
as the power is given in rotational form, it is converted back to liniar form when say, you go down the streatch of tarmac
the engine power is lost by
By accelerating the car over a distance in a given amount of time.
Aerodynamic drag on the vehicle.

Rolling friction loss. Some of the energy is dissipated as heat in the gears, torque converter, wheel bearing, and tires.

Inertial losses. It takes energy to speed up a mass. Internal components in the vehicle drivetrain that undergo acceleration draw energy. These components include the pistons/connecting rods changing direction, pulleys, flywheel, transmission shafts, drive shaft, axles, and wheels. The mass of the pistons/connecting rods and valves/springs are always a draw on horsepower. The mass of the rotating components only draw horsepower when the engine increases RPM. Lightening up all of these components will reduce inertial losses, and make the engine less stable. On the plus side, these inertial components, once up to speed, will make your car coast further and can help mileage on the highway. But they hither acceleration so buy aluminum or magnesium rims. =P

so in retrospect, hp is little more then a differnece between torque and rpm.
when looking to buy your next sportscar, look up its torque curve... the flatter the curve, the more linear your accelleration will be, but it wont be a sudden boost of power, but a constant application. some people dont like this, and choose to buy high reving, low torque cars... tho they make decent torque, there is little startoff accelleration (do you really want to try and dump the clutch from 7000 rpms in an S2000?)
my 2 cents

oh dear.....u're so confused. first diesel's have more torque because diesel has more btu/lbm. and secondly diesels ahve higher compression ratios than gas engines, thats why they're so noisy. notice its the stroke that causes the higher compression and hence the torque.

so they should only pull up on a torque wrench ? or maybe only push it sideways ? LMAO.. and since when was mechanical competency a must for being allowed in a car :?:

jeez deth/zevlov lol calm down, we are here to have fun and learn.... so what if we are sometimes wrong...

impressive, then i guess that just negates all 3 year of my mech eng studies then, doesnt it..damn..i wish i had 6 physics/technical books. and you do realize that 'normal to' is the same a 'perpendicular to' right?


where are the pix of your and your dad's cars?

lmao. Engineering is the Shit! no doubt to that. so many posts so quickly, i think ill have a drink!

yes but in the equation it always just said distance that's what I meant by normal distance.

Care to list the textbooks you've got, and what classes you've taken? I am a physics major, and I've taken several University of Michigan Engineering school classes on mechanics in addition to my studies in physics. YOU ARE WRONG. The equation for Torque is force times the perpendicular distance to the axis of motion. That means in a simple case...say a wheel...the perpendicular distance to the point of application of the force...i.e. static friction on the road... would be the same distance as the radius of the wheel. In other cases it does not work out that way. If you want to find the torque on a dipole (something that has a positive electric charge at one end, and a negative one at the other end) in a constant electric field, the sum of the forces on the dipole comes to ZERO, but there is still torque, i.e. the thing will still rotate about its center. The torque is measured at a PERPENDICULAR distance to the center of rotation, from both ends separately. The equation for torque is T = R X F where "X" means "cross product" and the force "F" must be applied at a perpendicular to the lever arm "R". If you would like a more thorough explanation of what torque is, and how to find it, I will be more than happy to look it up in any of my 7 physics textbooks, 3 engineering texts, or even some of my high-level math texts.

P.S. "Normal" is another word for "perpendicular"

If your asking about the Physics books I sold those after I took the class in High School and the Automotive books are Automotive Engine Rebuilding, Automotive Engineering, Automotive Brake Assemblies those are the only ones I still have.
and we covered your P.S. comment
And I know what torque is and I know how to figure it out but the simple equation is just Force*Distance.

Yes, the simple equation is FD, but it doesn't make any sense to use it, as in any reasonable application it's far too inaccurate to be of any use.

So how 'bout some pics, I'll post some of mine if you post some of yours.

pics of what?

obviously your classes werent very advanced if they;re just definign torque as force* distance. if you look at more advanced texts its usually written as Fxd which as vanquish covered is not the same as F.d or F*d or as F.dsin(theta)

WHERE ARE THE PIX!

dont be ignorant....well actually u already are...so at least dont be stupid! pix of you and your dad's cars! you postem and if they're real i'll drop this whole argument

well for a couple of reasons I couldn't do that right now if I wanted to and it definitely wouldn't be to please your sorry ass. 1. I'm not even in the same state as my House and 2. not all my dad's cars are kept at our house right now. And like I posted somewhere else once the snow stops and i bring the car's up to our house I will take pics of them and the new Installs on the Camaro. So you will just have to fuckin wait won't you but that shouldn't stop Vansquish.

As for your comment about the Camshafts vs. the Crankshaft, you're right in that case, but your facts are still a bit screwed up. Long-block engines do not by nature have more torque or higher compression. It is something of a coincidence that the large portion of industrial and commercial diesel engines use an inline long-block configuration. However, it is not the block length but the compression, which has more to do with the stroke (and method of aspiration) of the engine than anything else. This would not come from the length of the crankshaft, it would come from the eccentricity of its nodes. The more eccentric, the farther the piston will travel in the cylinder, and the higher the compression ratio can be, and therefore the more torque the engine can produce. Diesels tend to have very high compression ratios compared to gasoline engines, that's where the torque tends to come from, as well as the fact that diesel is a more efficient fuel (more btu/L).

Poor guy, you keep slandering another member of JW.

so u're telling me u're away from home, but u have 2 cars and you didnt take either of them with you? what about that sweet evo u got for xmas? i'm guessing its stored safely at home, and the thunderbird is in storage, and you decided not to take any cars to school so you could save money cuz u're a starving student or something like that right?

actually I'm in Sacramento for the weekend at My Uncle's house.

so u can have pix up on monday then?

PS you flew to sacramento for the weekend? i'm guessing your uncle has an amazing car collection too, but its all in storage too right?

I smell fire :D

god, i wish my dad or myself had a "car collection" oh well....
torque->hp->misinformation->argument->car pic arguments
LMAO
this really is funny, but hell, chill out zev

fire? where?! :roll: let me go put it out w/ my carbon fibre/kevlar fire extinguisher! oh wait..its in storage..damn....

Zevlol you lying bastard.

1st- How in the fuck did you get 500bhp on a fucking Thunder Bird? I dont see modified anywhere so it gotta be stock. And it has 500bhp? Or is it a special one off like your daddys Maxime Elite Edition? Where in the fuck did he get an Elite Edition Maxima? Im sure he got it straight from the Nissan factory.


Now to questions

How do you turn of yaw control in your EVO?

And what tranny are you running on that Drag Strip Camaro of yours?

And I see your mother drives a 20th aniversiry golf. That car has a manual transmission, and I got a feeling that your mother would not want to drive a stick around a city like Chicago.


And while your at it, make sure you stop and think about the load of amphibian shit that is going to come out of your mouth the moment you read this post ya fucking wanker!

aaa

Is it me, or did zevlov get owned?

And Zevlov, before you even think of posting anything. Make sure you got some explanations for that computer you got which is running 2x500gb hdd.

Ohhh and Zevlov, how did you manage to Major In Arts at 18? Im sure your a gifted child and finished high school at 14...........

Ouch... and I thought arguements I got into recently were getting outta hand.


*On a side note: I too would like to see some car pics.. Just outta curiousity..