Good Thread about Torque

[SlasherX]

and its meanings:

http://www.v6power.net/cgi-bin/ultimatebb.cgi?ubb=get_topic&f=6&t=000481


Chui, what do you think?

[t2000gts]

some stuff is right and some stuff is wrong but yeah, good thread to help you get the 'feel' for what torque is and how it relates to horsepower :)

my personal method (which is probably blatantly incorrect, but it helps me get the relationship) is that torque is the pull you have at any given RPM. horsepower is just going through the RPMs. i.e, two cars, same horsepower but one has more torque (let's say one has nitrous to get same horsepower as other, but result is more torque as well)...the rpms will go up with the same speed, they'll both have similar MPH in any given 'race', but the one with more torque will pull on the other one. which is why to offset the torque from say an LS1, we'd need a ton of horsepower to increase the RPMs so quickly that we'd pick up speed fast enough to keep their torque from powering them away (and eventually as their torque curve dies off in the top end, it'd come to a point in time where we're going a few mph faster and end up pulling away through sheer speed).

also can be seen in ETs and trap speeds. former is a better indicater of torque and latter is for horsepower (of course if you launch and stuff that throws most comparisons out the window but you get the relationship).

i don't think many people can explain this correctly even if they understand it correctly :D you gotta use parables that're probably wrong (like mine and to an extent, the ones in that post which were hit and miss).

[vvtlikick]

Originally posted by t2000gts
some stuff is right and some stuff is wrong but yeah, good thread to help you get the 'feel' for what torque is and how it relates to horsepower :)

my personal method (which is probably blatantly incorrect, but it helps me get the relationship) is that torque is the pull you have at any given RPM. horsepower is just going through the RPMs. i.e, two cars, same horsepower but one has more torque (let's say one has nitrous to get same horsepower as other, but result is more torque as well)...the rpms will go up with the same speed, they'll both have similar MPH in any given 'race', but the one with more torque will pull on the other one. which is why to offset the torque from say an LS1, we'd need a ton of horsepower to increase the RPMs so quickly that we'd pick up speed fast enough to keep their torque from powering them away (and eventually as their torque curve dies off in the top end, it'd come to a point in time where we're going a few mph faster and end up pulling away through sheer speed).

also can be seen in ETs and trap speeds. former is a better indicater of torque and latter is for horsepower (of course if you launch and stuff that throws most comparisons out the window but you get the relationship).

i don't think many people can explain this correctly even if they understand it correctly :D you gotta use parables that're probably wrong (like mine and to an extent, the ones in that post which were hit and miss). Huh? :confused: This doesn't make sense to me.

In common usage, torque can mean only bottom-end, and power can mean only top-end. But technically, both names apply at all rpm. Power is directly proportional to rpm times torque, so a torquier motor is automatically more powerful (at the same rpm).

Power, both peak and off-peak, is all that matters for performance, period. Torque is meaningless without knowing the rpm. And gearing determines how narrow a powerband you can get away with.

[t2000gts]

Huh? This doesn't make sense to me.

it isn't supposed to ;) that's how i explain it to myself.

i think as long as you get that horsepower is the rate of change of torque which is the potential work from the engine which is usually proportional to the displacement or something like that, i guess you got it.

but understanding the direct end result and the corresponding between the two is harder to explain. my example deals more sorta with horsepower and speed (in mph) and how quick you accelerate with optimum gearing compared to a motor with the same horsepower but more torque. thus the two should be identical, and the only difference between the two in a race would vary depending upon the torque advantage. (and to get this difference in power between identical cars, i'd compare a n/a tuned car to one with nitrous. say a GTS with those TRD internals that makes 230hp compared to a GTS that makes 230hp with nitrous. the latter would end up making more torque too). this is not really a test to distinguish between cars as it is between 'horsepower' you can see and 'torque' you can see.

[GTS LAID]

umm... i know nothing about what these numbers mean in auto talk... but if the meanings were preserved from physics... then brace yourself:

power = rate of energy consumption = j/s
joule = energy
amount of enery in J divided by seconds gives you the Watt .. unit of power measure in rest of automotive world...

Torque is Force x perendicular dist.i'm assuming the distance in this case is the flywheel dist from the driveshaft cause thats where the 'leverage' takes place...

by the way.. energy or work done is force x parallel dist....

so to get to torque measurements you would need to know the force and the dist. from driveshaft to flywheel.

force can be obtained from (Power*time)/parallel dist. travelled

now the time per revolution depends on the RPM so a proper time conversion would be something like 60/time(in seconds)

so putting it all together:

torque = [ Power*(60/RPM) ] / parallel dist. * perp. dist.

so pretty much everything can be made a constant cause parallel and perp dist dont change in a car.. so its based on power and RPMs + constant.... thats probably where they get it from cause its in line with what vvli said

[vvtlikick]

Here's power and torque mathematically defined for standard units (hp and lbft):

1 lbft = A force of 1 lb applied 1 ft away from the axis of rotation

1 hp = A force of 1 lb applied through a distance of 1 ft over 1 min, but 33,000 times to equal the power of a horse

And if you apply a force 1 ft away from the axis of rotation, you are applying that force through 2pi ft per revolution (the circumference of the circle)

So, Power (in hp) = 2pi × Torque (in lbft) × rpm / 33,000

<img src="http://www.newcelica.org/forums/attachment.php?s=&postid=35124">

[t2000gts]

i think that post was less about the definition of torque/hp than it was about applying that knowledge to engines/cars.

[vvtlikick]

Also, if you know the power at the wheels at all times, you can calculate the acceleration at any time.

Because, power is the rate of energy increase and the kinetic energy of the car is proportional to the square of the speed. KE = &frac12; mass &times; velocity ^{<small>2</small>}. Of course, you have to subtract the energy that is being wasted to friction in the differential(s), tires, axles and air (internal drivetrain losses are already accounted for, because we took the power at the wheels).

[vvtlikick]

Originally posted by t2000gts
i think that post was less about the definition of torque/hp than it was about applying that knowledge to engines/cars. Yeah, but it's can get confusing when people misuse the terms torque and power, so it helps to have a firm mathematical definition.

A way I've found to estimate the width of the powerband of a engine is to look how far apart in rpm its' power and torque peaks are. <i>Generally</i>, a peaky engine will have its' power and torque peaks close together, and a broad powerband engine will have them further apart.

So, a "peaky" GT-S engine has a peakiness factor of 6800 / 7600 = 0.89, while the "broad" powerband Z28 has a factor of 4000 / 5200 = 0.77, and the 360 Modena has a incredibly broad powerband, its' factor is 4750 / 8500 = 0.56.

Of course, the dramatically closer gears of the GT-S eliminate much of its' peakiness compared to the Z28. And the Modena simply has staggering power at all engine speeds.

[t2000gts]

here's an idea for an applicable use of everyone's torque/gearing knowledge and simple multiplication,

how much power can the GTS take (major suspension mods withstanding) before it absolutely gets no traction on launch?

6-speed 1st Gear: 3.166
6-speed Final: 4.529

Est. whp w/NOS = 220
Est. wtq w/NOS = 200 (these are the numbers BryanH said from his nitroused GTS 6speed)...

so 3.166 * 4.529 = 14.34 * 200 = 2867 ft-lbs of torque at the wheels.

the GTS with Nitrous develops peak torque as low as 2000-3000rpm in cases (from BryanH once again) but definitely for sure at around 3500rpm (the first torque peak, thank you VVT-i).

SO, assuming launched @ peak torque...2867 is too much. case in point: 6-speed with 50 shots spinning through first, and most of 2nd (almost up to 60mph). BryanH posted his launch technique with his radials, i forgot it offhand, but it was something convuluted to get a 1.9 60' which netted him that famous 13.12...while larry's 2.3 or 2.4 60'(s) netted him 13.9 but trap speeds that were only 1mph off from Bryan's.

Is this because 2867 is greater than the curb weight of the car? or is that just coincidence?

STOCK GTS 6-speed:

14.34 * 120wtq = 1720 ft-lbs of torque at the wheels.

So...is 1720 enough? or can it run with more power and get traction?


There's another GTS which has better documented figures.

Auto GTS 4-speed 1st Gear: 3.94
Auto GTS 4-speed Final: 3.12

http://subzero.mine.nu/celica/autoGTS_dyno_NOS.jpg (before/after with 50 shot on Zooq's car)...peak wtq = 102.2 before and 160.7 after...peak whp = 136.5 before and 196.2 after...

So, stock Auto GTS:

3.94 * 3.12 = 12.29 * 100 = 1229 ft-lbs of torque at the wheels

a lot lower than the 1720 of the 6-speed, eh? plus first gear runs a few mph higher...so we know 1229 is actually quite a bit lower than the threshold...a lot lower.

Auto GTS w/NOS:

12.29 * 160 = 1966 ft-lbs of torque at the wheels

Zooq has no problems getting traction with the nitrous. He was running 2.4 60' when launching at 2000rpm but with a 3000rpm stall converter and drag radials, he gets consistent 2.1 60'(s).

So...1966 is also quite tolerable. it's only 140ish more ft-lbs than a stock 6-speed.

Zooq has since sprayed a 75 shot (which would put him closer to the 190 wtq number) and reports not much in the way of traction problems.

12.29 * 190 = 2335 ft-lbs of torque at the wheels.

now it gets closer to the 2500lb number! and still not much problem.

Last part...

6-speed GTS 2nd Gear = 2.050
6-speed GTS Final = 4.529

2.050 * 4.529 = 9.28 * 200 = 1857 ft-lbs of torque at the wheels.

Now that's interesting. the 6spd with nitrous still will not have traction up to the second torque peak at 6800rpm in 2nd. why is this? cuz 1st was so crazy it screwed it up so that 2nd takes a while to get traction? Cuz this contradicts the auto GTS with nitrous. Maybe horsepower comes into play? It uses up that 1857 ft-lbs too quick? Interesting to note spraying nitrous, a 6-speed's 2nd will pull harder than then a stock 6-speed's 1st!

things i don't know:

is there a 'magical' number where the car suddenly loses traction? probably not. but how far is the range? over 100ft-lbs? i think a safe bet would be 2500 ft-lbs of torque at the wheels for pushing the limit when it comes to manageable power and traction in a FWD GTS, but is it just coincidence that's the car's curb weight?

i think too many people overlook the gearing needs when talking about turboing or supercharging or whatnot. let's take this further, instead of changing the gearing, can you change the power levels as needed to push towards 2000+ ft-lbs of torque in each gear? (obviously not, gears are not as tall as first and you'd need like a 900hp car or something, but as much as possible)? sounds like 2nd gear might be an issue

whatever you guys know, lemme know. i'm kinda stuck at this point.

[vvtlikick]

Originally posted by t2000gts
...

is there a 'magical' number where the car suddenly loses traction? probably not. but how far is the range? over 100ft-lbs? i think a safe bet would be 2500 ft-lbs of torque at the wheels for pushing the limit when it comes to manageable power and traction in a FWD GTS, but is it just coincidence that's the car's curb weight?

...Mathematically, the radius of 205/50-16 tires is about 1.003ft, so the torque at the wheels becomes force at the road when divided by this number (2500lbft / 1.003ft = 2492lb), and a Celica with driver and gas only weighs a little more than this.

And if the force the drivewheels exert on the pavement is equal to the weight of you car, you will accelerate at 1g. However, it takes a serious amount of traction to channel that much force. Only slicks on RWD or sticky tires on AWD will get you to 1g (FWD dragster, too?).

I don't know what the peak aceleration possible for a FWD car is in general, or a Celica in particular. For the Celica maybe like 0.65g on normal street tires?

[t2000gts]

ah! that makes tons of sense, thanks!

the auto GTS weighs 2582 and zooq probably is no more than 150lbs (he's not some big hulking guy)...2750 let's say if he has other junk in there.

and he has drag radials. 18 inch wheels. i don't remember offhand how big those were...you know what kind of 18s fit on the GTS?

so if they increase his peak acceleration to .70-.75g maybe? while lower the ft-lbs @ wheels number... and the 1g number would be 2750 so he's a ways off there...

does this mean that if larry just threw another 200lbs of weight into the car he'd get better traction on launch?

also, if i used my GTech to get some G readings when flooring it from a stop, would these be close to the real peak acceleration of my car as is?

[GTS LAID]

Yes your figures are very close t2000 because the torque level arm is indeed about 1 ft. so you're not far off even when you dont incorporate it. Only thing you forget about is that the car is 60/40 and .6 of the weight is on the front...

once the car lauches (that instant) the trick is to calculate the weight transfer to the back.. which you can do using those physics of racing articles and that'll tell you how much weight on the fronts you can use for accelerating the car... Which is why VVT said that you'd need RWD... those f*ckers get most traction AFTER the launch...

[t2000gts]

oh yeah i totally forgot about weight transfer...those *******s...

it doesn't matter if you add weight to the front, it'll get transferred to the back? or not all of it will get transfered (so to get 20 lbs on front when launching you'd need to put like 200 or something?)...the auto tranny is heavier (about 80 lbs)...

ALSO...how does tire pressure affect traction? i know lowering it helps at the track for better launches but hinders trap speeds...why? is there any way to use tire pressure to actually make wheel spin easier? case in point. my auto GTS' best 60' at the track was 2.668...with nitrous it'd be 2.4x...the car bogs horribly when i launch. i dump the brake at 2000rpm and there's like a pause before the speedometer starts to go up (big 2000-3000rpm bog)...would overinflated tires make spinning them easier? (and would this hurt or help trap speeds) my accord wagon (4 cyl, 1993) when launched at 1800-2000rpm spins the tires like crazy and the rpms jump to 3500 while the tires are spinning instantly. no bog. then it pauses and picks up slowly @ 3500. i know that thing would rape my auto GTS off the line, but if i could launch like that, it'd definitely be a lot closer if not at 2.4 60' already. (i think it's a 2.2l engine in the acccord? explains the torque).

[vvtlikick]

Adding weight is always a bad idea for performance.

However, if you have to add 20lbs to FWD car at the dragstrip, you would want to add it all low at the front. The reason you add it low is to lower the center of gravity to reduce weight transfer.

Conversely, if you were removing 20lbs you would want to remove it all from the rear top for the similar reasons. But weight removed anywhere would be a benefit.

[vvtlikick]

As for tire pressure, I like to think each car/tire combo has a single optimum pressure for straight-line traction during acceleration, which can be different than the optimum pressure for cornering or braking.

And in the case of the stock GT-S tires, 32psi is higher than optimum for straight line traction. So we lower the front pressure, but this increases rolling resistance, which robs power (but the higher traction at the launch is worth the price). I don't think the pressures we tend to run are low enough to mess up the gearing appreciably, but I might be wrong.

We raise the rear pressure, since the rears are just dead weight on a FWD car and the higher pressure will reduce rolling resistance of the rears.

[t2000gts]

nice, on top of the lack of power and lack of launch capability i got an extra 80 lbs near the bottom of the front. i don't like traction. :(

if i increased tire pressure in front, would that reduce rolling resistance too? so should i run 40 in all tires or something to launch easier or what? 40 in front, 32 in back? (the disproportion in tire pressures with 40 in front 32 in back would increase the effect to get the front tires to spin easier?)

i'm basically going for the opposite everyone else goes for when launching at a track.

also removing spare tire/jack and back seats would help a lot then wouldn't it since it's all from the rear?

[vvtlikick]

Just from adjusting tire pressure, I don't think you'd be able to get enough wheelspin in a automatic Celica to avoid getting bogged down. But trial-and-error is the only way to truly know.

So I'd probably aim for the reduced rolling resistance of high pressure tires all-around.

As for reducing weight by removing the spare and seats, that's always a benefit, and since it's rearward weight, its' removal shifts the balance of the car forward onto the drivewheels, which is good at the dragstrip. My 6spd seemed to gain about 0.2s and 2mph from similar weight reduction.

On a road course or autox circuit, the same weight reduction would promote understeer at the handling limit, but the lighter car would have a higher handling limit and be faster even with the understeer.

[GTS LAID]

Wait VVT i thought that reducing the weight in the back is a better recipe for oversteer cause when you brake hard the wight T-fer gives you much better grip on your turning tires.... and so by removing the rear weight you in effect lift the back higher (rotate around center of axis) and therefore lose traction faster in the back...

Also on a side note.. I put the APR strut bar in my car and tightened all the bolts like a mother f*cker... do you guys think that its strong enough to actually throw off my camber if the bar is holding the whole thing in tight...

By the way road test review shows much more understeer with strut bar... I'm assuming its not because of the car but because of my hightened confidence level... I also rotated my worn out tires to the back for the first time since i got the car... I notice more drift in hard cornering but its equal between the front and the back, esp if i hold steady on the brakes while in the turn...

unfortunately its raining today here in jersey so I wont be doing any testing today.

Another question for you guys... this is on my sisters lexus though.. i was replacing the brake pads today (4 wheel disc) and I had a little trouble compressing the first 2 pistons with my c-clamp, so i unscrewed the little reservoir screw and let so fuid drain out... Now thats not even the stupid part... when i got to the back ones the caplier is only held on by one bolt and the other the caplier simply rotates around, I didnt know this though and I ended up actaully unscrewing the brake line itself. I put it back on when i noticed the fluid but a little had leaked out already. My question to anyone who's done their own brakes b4 is how do you tell if theres air in the lines.. right now the levels are topped off under the hood and the pistons are all the way in cause the brakes are brand new, but theres still a latency distance in the pedal where i feel like I'm compressing air (could be my imagination too)... and if I do have air how do i get it out... (how do i bleed and replace the whole thing to make sure theres no air in there)..

Thanks in advance for your help.

[vvtlikick]

Boy, We've gotten way off topic here :D.

But anyway...

GTS LAID, when I said removing rear weight would promote understeer, I was simply basing this on the fact that cars with more weight-bias to the front tend to understeer. I suppose it could behave differently than this simple generalization states, but I don't know for sure.

As for the strut bar, I don't know. I do remember SCC took advantage of the "slack" in their Celica's strut mounting holes, to gain some free camber.

And as for bleeding the brakes, I've never done it. But if there's gas bubbles in the lines, I believe it would manifest as a mushy brake pedal.

[t2000gts]

i think if you brake hard under most circumstances you'll experience oversteer

[SlasherX]

WOW. you guys are funny to watch, fighting each other with teh calculus. hehe..good thread :) still trying to make sense of it all.

BTW--weight transfer rules! :p

[Chui]

The article is a rehash of an excellent article dealing with the same topic. It's okay except for this glaring error in concept:

Now, one reason rotaries have lower torque peaks then, say, V8's is because of the amount of rotating mass. The more mass to rotate, the more torque you will have. Think about it, what will have a tendancy to keep rolling if you push on it slightly, a billiard ball, or a bowling ball? The bowling ball, the bowling ball has more moving mass, therefore it requires more of a force to stop. The same is true for an engine. If you are in gear and let off the gas, you slow down. You slow down because the friction of the road is slowing down your tires, therefore slowing down your engine. If you have a 4-cylinder, then the road will slow you down pretty rapidly. If you have a V8, then the road won't slow you down as quickly because there is more rotating mass for the road to have to slow down and it won't slow you as quickly. Back to rotaries, they have less rotating mass than a V8 because they have fewer parts, therefore less torque.

I dunno where he's coming from here. He's thinking about inertia, but he's got it backwards. The lower the inertia the easier it is to rev the engine, thus the quicker the engine will rev which results in quicker acceleration.

I wouldn't put too much into his knowledge of bhp and torque.

[pensfan83]

Hey guys, I don't have anything to add except I can actually understand some of this now because I'm taking physics :D Keep the discussion going.