Err,been asked this question in Fast and furious forum,but since i think this is quite a technical subject.
So,i trying to get my answer here
Should be quite useful for us in picking up new car in the future

some existed discussion in FNF forum
http://forum.lowyat.net/topic/1250660

This post has been edited by nujo87: Dec 7 2009, 09:40 AM

torque for sure, got horsepower but no torque like lorry.

depends, are you on a race track or on rally?

in mareasia especially in cities, torque ^^ in highway zoom zoom, hp

swt.. shouldnt this be in FnF?

I think you've got it reversed. Lorry engines typically have lots of torque to move big loads from a standstill but relatively low horsepower as it doesn't need to sustain high speeds.

yup correct..

torque = better acceleration
bhp = higher speed

So i got 1 of my answer tats is torque is for acceleration,n horsepower for topspeed.
Since my driving style is more depend on acceleration(mostly city driving)torque is more important for me i think


Another look like very simple but yet quite technical question i would like to ask
for old mitsu engine(4g18,4g13,4g15)their peak torque come at earlier RPM(2500-4500)

N campro engine(non cps)their peak torque come at later RPM(4000-6000)

Which 1 is more suitable for city driving/city short boost?

N since old mitsu engine can achieve torque peak at low RPM,will it be more FC?becoz no need to REV so high?
So old mitsu engine=Good FC n good boost power at <110km/h driving?

This post has been edited by nujo87: Dec 7 2009, 11:21 AM

You haven't seen how fast lorries can run without their heavy cargo, and how scary is their acceleration.

I think you mean better FC right? FC is "Fuel Consumption", so more FC is worst.
I'm not sure but I think FC should be better due to less RPM meaning less fuel combusted but FC is still highly subjective to driver and car characteristic. Peak torque at lower RPM is definitely better for city driving where there's a lot of start/stop/slowdown/pickup activity.

the mitsu 4g18 engine are better for city driving. this is known for a very long time d. the campro are meant to be driven in a more sporty way. its just the way it was design.

IC,tat means for city driving(mostly lower than 4000RPM),old mitsu engine/earlier torque peak engine r better,rite?
I think i got all my question answered,thx for urs opinion

n next time when im going to pick a car,i should ask for their torque curve graph for deeper understanding to tat car performance,B4 this discussion HP is the only thing i c when comparing car performance

This post has been edited by nujo87: Dec 7 2009, 12:54 PM

4k shift in city is insane lea.. normally is like 2.5k nia

besides i dont think they hav torque curve graph at car showroom besides the generic ones. lookin at the chart is one thing. understanding is another

Based on the description given by wikipedia on horsepower and torque, it looks like your torque is limited by the amount of horsepower that can be produced by the engine. Horsepower is the amount of power which an engine can produce. Torques determines that amount of power available at a given rpm. The amount of power produced due to torque cannot be more than the amount of power produced by the engine. In another word, don't expect a lot of torque from a car with low horsepower.

As long as a car can produce enough power to overcome resistance from friction and air resistance, it will accelerate. Friction and other resistances increases as the speed of a car increases. Having a car with peak torques at high rpms means that it will have a higher top speed as there's more power to overcome friction and air resistance at higher speeds. Having peak torque at lower rpms means having a car the can carry heavier loads but don't expect it to go fast.

A car running at lower rpms will use less fuel compared to one running at higher rpms. So in theory, a car that is running at lower rpms most of the time should consume less fuel. The problem with comparing fuel efficiency based on the running rpm of an engine is that different engines will burn fuel at a different rate at the same rpm.

no one will understand u

Firstly, let us understand the difference between force and torque.

for linear propulsion, the formula is F = m*a where
F = Force exerted on the object
m = mass of object (also known as inertia, i.e. the tendency of a stationary object to resist motion in a straight line) and
a = acceleration

so for a given amount of mass, the higher Force applied, the higher acceleration you get, make sense?

Okay now let us move on Torque. Torque is basically turning force in layman's term with formula T = F*d where
T = Torque
F = Force
d = Distance between point of Force and pivot.

If this is difficult to understand, think of a door. It is easier to open a door when you push it from the knob compared to if you push it nearer to the hinge right? That's torque acting.

Torque is therefore the analog to Force when it comes to rotational propulsion. Car engines derive their power essentially through rotation therefore we rate engines (and electrical motors) based on their Torque, not Force.

The formula is then T = I*alpha where
T = Torque
I = moment of inertia (i.e. the tendency of a stationary shaft to resist rotation)\
alpha = angular acceleration

Therefore, it is clear to see that for a given moment of inertia, the higher the Torque to higher the angular acceleration. Makes sense so far? higher angular acceleration means higher straight line acceleration at the wheels.

Hope you find this useful, I am running short of time. Let's save the discussion of Power for another day lol. Cheers!

This post has been edited by onlyforthecars: Dec 7 2009, 06:42 PM

1. Not necessarily. For engines, horsepower is actually derived from torque. It is given by the formula HP=Torque x RPM/5252. Thats why you have diesel engines which can pull heavy weights but dont have high top speed, because they operate at low rpms. Try driving a diesel powered vehicle (eg pickup truck). You will find they have much better low speed acceleration compared to petrol powered vehicles.

2. It is neither very advantageous to have a higher rpm peak torque or a lower rpm one (although for city driving, a low peak, wide torque curve is preferable due to the low speeds involved). What is better is to have a flat torque curve. This means torque is available for a wider range of rpm, i.e your pulling power is spread over more rpm. This is especially noticeable in certain cars having a narrow range, where you have to shift the gears often to keep accelerating.

3. An engine is most efficient at peak torque. At this point, you are getting the most power from your engine compared to fuel being consumed. Your statement that a car running at low rpm would consume less fuel is misleading. Assume 3 identical cars heading to the same destination. 1 fella drives at a very low speed (60kmh=2000rpm), the 2nd guy drives at the speed that matches peak torque (120kmh=4000rpm) while the 3rd guy drives flat out (160kmh=6000rpm). When compared, most likely the 2nd guy will get the best fuel consumption, because he keeps his engine running closest to peak torque. But even this analysis is still subjective, i'm just giving a best case scenario. It would be best to test each car individually to find the point where it gives best FC, but chances are high this will be somewhere near peak torque when at constant speed.

sporty way? there's nothing sporty about the campro... just because it is a small & inferior engine it has to be rev higher..

ermm.. good comparison, but not nessesary... no1 could be having better fc... 2x the rpm doesnt mean 2x d fc..

tl:dr @onlyforthecars.

city driving + carrying loads = torque rules.
high speed blast = bhp rules
genting = torque rules

geddit?

You're being rather unfair to the campro, as i mentioned...it has a lousy torque curve for a engine suitable for city driving. Iinm, it has a slightly higher than average maximum HP for 1.6L class and from what I've seen, its quite good on the highway.
I don't think u understood my analogy. I in fact said that car number 2 (at 4000rpm which is nearest peak torque) would probably get the best FC, simply on the assumption that at peak torque, you get the best power for fuel consumed.

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Added on December 7, 2009, 8:44 pmAgreed. The simplest non-technical explanation anyone can give

This post has been edited by joe_star: Dec 7 2009, 08:44 PM

i think u got me wrong.. wut i meant was tht the torque peak much later at the band.. not earlier like 4g18. btw.. all NA cars need to rev higher to draw out the power.. im not a car idiot..

Lets forget about rpm, torque peak, and engine.

From physic point of view, in layman term:

Torque = ability to carry load
High torque means high load bearing ability. Low load bearing ability means a vehicle will immediately feel sluggish when a load is added.

Horsepower = ability to accelerate[/u]
High horsepower means better acceleration. For a vehicle with same load, high horsepower means it accelerate better.

Ok, now lets get complicated. A vehicle with small torque but huge horsepower has amazing acceleration. But any additional load will make significant impact on its acceleration, because the inability to handle load (due to low torque). For example, motorbike.

Then, a vehicle with huge torque but small horsepower has low acceleration, but excellent load handling. By load handling means, the vehicle won't feel much different when a load is added. For example, bulldozer.

When it comes to good engine management (and driving experience), race car driver generally drive the car at high rpm near peak hp. While truck driver generally drive the vehicle around peak torque.

Now lets take a real scenario. Say a car with peak torque at 4k rpm and peak hp at 6k rpm.

During uphill drive, when engine speed drop below peak torque (say 3k rpm), the engine immediately feel sluggish. Hence we downshift, accelerate (rev) the engine to higher rpm, say to 5k rpm (higher than peak torque). After that, when we shift the gear back, say 4k, we immediately feel the engine power returns.

The sames goes to why tires are more likely to burn (skid) when we accelerate from standstill at peak hp.

As i know the horsepower constantly increase when RPM roll up,n normally would achieve peak HP at 6-7K RPM.
Is tat means for fastest acceleration,we should drag to 6-7k RPM b4 shift to higher gear?

For example:
we drag the 1st gear to 7k RPM to archieve Peak Horse power,
Then shift up to 2nd gear n the RPM dropped to 5k RPM,then we drag again to 7k RPM to Peak horse power,
N repeat n repeat...
So in this way we can maintain the peak HP,n btw Fastest acceleration?

I dun think all these make sense,torque is the force to twist the wheel/tyre,meaning torque high=faster acceleration,
Peak HP should be the total force created at by the car wheel at maximum RPM,meaning a metric for topspeed.

This post has been edited by nujo87: Dec 8 2009, 12:47 AM

out of topic: no leh.. for city campro sucks because u have to rev it high.. get torque only after so much revving... for highway also it sucks because @ 120km/h it has to be rev high also... so it is totally =.=" this kind of tech is around 20 years old already, even if it has valve tech which provides flatter torque curve... newer tech are like those by vw... small turbo charged engines.. good fc good performance... tdsi fsi

no no.. d best fc is obtain by the fastest speed at the highest gear reachable by the peak torque... knowing just the speed and rpm wont tell much

i didnt say u r a idiot also.. dun get offended... me n u just trying to share... ok, i get what u r trying to convey... but if u were to compare d 3 cays then maybe car no. 2 not nessesary get d best fc.. but i get what u mean about d torque band

horsepower depends on rpm because hp depends on speed which depends on wheel speed...if the torque is high, but the wheel spins then actual hp will be less because d wheel is losing traction.. unless u r talking about dyno hp.. am i right?

ermm.. for the example it depends on the car... whether is it na/turbo.. gear ratios/torque curves,top speed... the best i believe for na sporty cars (eg integra) (from personal experience) is to rev to max, shift and it will drop to just slightly below max torque.... it depends on d gear ratios...



i believe what you say is true... that's what i learned during dynamics

Then blame the transmission not the engine Poor pairing of transmission with engine will make any engine no matter how good perform poorly
I thought that was pre-assumed from my analysis I gave the speed as an example to show where the savings comes from, when you go faster, u spend les time on the road running the engine

no leh.. their transmission no prob.. just that they follow d wrong trend... they still think techs like vvti, vtec vvtc are d best around... so hard spend so much $$$ for their cps then they realise oops... there's a better tech around owned by vw...

An old article I read that debated shifting at peak torque vs shifting at max HP explained it this way:
1. Say you shift at peak torque, when you go to the next higher gear, your engine torque now is lower than what you had earlier because it is revving at lower rpm. The engine has to climb up the torque mountain again, thus giving poorer acceleration
2. As you know, the torque usually peaks at around 2000-4000rpm and then starts dropping. Now if you shift at max HP or redline, you will definitely be shifting to an rpm where your torque is higher than it was before. The acceleration will be better.

Conclusion: always shift close to max power to obtain best acceleration

cps not that bad also if you ever try b4, the performance have a drastic improvement compared to campro without cps.

and transmission does matter alot. first generation gen2 with automatic gearbox just simply lower the gear when u approach a slightly downhill, and when u floor the acceleration pedal it takes much longer time to lower the gear. dun you think it ll affect the performance and fuel consumption alot.

hahah.. out of topic la bro..

but d world is no longer playing with valve timing anymore... that was like 20-30 years ago... now compare it with the fsi and tsi engines... superior fc & performance for small engines... or even hybrids

lol... that 1 is gearbox prob... not design prob... so they design it with a lousy gearbox is a diff story

Lets say for car 1,torque peak at 2500RPM,and slowly drop from 2.5k-4k,n a drastic drop after 4k.
Which way should be better?

1)drag to 4k RPM n then shift to higher gear,n it should drop back to 2-3k RPM.

2)drag to 6k RPM(closest to MAX HP)then only shift gear,n should be dropped to 4-5k RPM.

he already explained that the best would to rev it as high as the engine is designed to..

Seriously do u guys think,if i go to a car showroom,do i have the RIGHT to ask for their engine torque curve/HP curve chart?
Or any other way to know a car engine performance more detail?

Buy car not = buy something in pasar le

This post has been edited by nujo87: Dec 8 2009, 01:56 PM

they should have it... unless u r looking for local cheap cars... eg from peroduas... why bother

If Sir Isaac Newton is still alive, he would have been struck with heart attack after reading the postings in this thread. If only electric motor has been discovered back then this question wouldn't have been asked int he first place. Where efficiency is high, often greater than 0.9 this issue is a matter of dust. Absolutely bin material if you asked me.

Regards, Joey

p.s: Torque and power are (almost) flip sides of the same coin. They are entwined entities.

This post has been edited by Joey Christensen: Dec 8 2009, 05:22 PM

dun care la wut the theory is.. pedal to metal = win

What exactly is the point of your reply? where does this connect with the importance of torque or horsepower in a vehicle?

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Added on December 8, 2009, 8:36 pmpedal to metal = hole in pocket

This post has been edited by joe_star: Dec 8 2009, 08:36 PM

Hmm, I have to disagree with you. (No offense, but this is what phd section is all about: argument and discussion ) In fact, motor is a perfectly good example of how engine can be so different. I'll drop the efficiency factor, since this is a discussion about torque and horsepower.

Torque
Torque is the resultant of inertia x angular acceleration.

Horsepower
Horsepower (or power) is the rate of energy release. High horsepower means high rate of energy release. Like explosion.
-----------------------------------------------------------------------------------

Motor
Motor has a constant (or near constant) torque with respect to RPM. Torque depends on voltage. While its power (or horsepower) depends on current draw (assume constant voltage). A motor with low resistance has high power rating. Motor power rating is also constant (due to constant resistant).

For example, take table fan. Without the blade, when we turned it on, the motor spin to its maximum speed almost immediately. And when we put on the blade, (higher inertia), the motor take some times to reach its maximum speed. Probably you also notice that fan with blade does not spin as fast as without. This is because air resistance increase as the speed increase. My last post use the assumption of fixed torque and power over the range, i.e. like a motor. Or more precisely, the instantaneous response (if you take dynamic, you know what I mean).

Engine
Engine, on the other hand has variable torque and horsepower. This is because its power input varies. (Motor has fixed power supply). Everyone knows engine runs due to small explosion in combustion chamber. And this combustion is not limited. (because someone "pedal to metal ").

In layman term, with fix fuel supply (maintain pedal position), a vehicle can travel at 100km/h (2500 rpm) on straight road, or 120km/h (3000 rpm) going downhill, or 70 km/h (2000 rpm) going uphill. Despite the different in speed and rpm, the engine actually consume same amount of fuel (in reality this might varies a bit, but this assumption is still generally true). What happen is that, the engine require less fuel to produce same amount of torque (during downhill) or more fuel during uphill.

Horsepower, on other hand, is the ability of the engine to response to fuel supply. (rate of energy release). An engine with high horsepower has the ability to response immediately to fuel, thus able to change its torque. By the chart, it simply means the ability to rev. If you notice, a car rpm increase faster when it approach peak hp, and fastest at peak hp. (We are unlikely to admit that it is fastest at peak hp. This is because hp drop after the peak hence it appear slow). Engines with VTEC, VVTI, CPS has higher peak hp at high rpm, this means driver will observe that the acceleration is highest when it reach peak hp.

What happen to campro engine, it has relatively acceptable hp chart (higher rate of energy release), which means angular acceleration (the speed rpm needle increase) is fairly constant. Because horsepower means the ability to change its torque, looking from the graph (campro), at 2000-3500 rpm, it means the ability to decrease its torque. This also mean it is less efficient in this interval. No wonder why campro owner complain about sluggish engine response. This effect is magnified during uphill. The dip in torque means it require even more fuel than other vehicle to carry itself uphill.

Back to motor, its high torque, low horsepower means it is good for road cruising, at constant speed. While for acceleration, the high horsepower engine comes in. The next generation of hybrid car will see the evolution of small cc engine (with high horsepower) and high torque motor.

How it is implemented, that require a new chapter of applied physic.

All this theory is good. but if u cant apply. its all just talk and no meaning...

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Added on December 9, 2009, 10:28 amPlease refer to my post script. It's already has it's meaning there and then.

Regards, Joey

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Added on December 9, 2009, 10:30 am

I wouldn't take it too far. Torque is the only thing that a driver feels, and horsepower is just sort of an esoteric measurement in that context.

Regards, Joey



This post has been edited by Joey Christensen: Dec 9 2009, 10:30 AM

u pick it out of the text book ar? what you say is true.. that's what i am trying to explain... but u clear a lot of things up

however at the ending, bear in mind that doesnt take into acc of static acc... it is only after there's some movement the last paragraph applies.. that's why it is motor as motor has less static resitance, not engine... but the title is car

Getting more confused....
More layman's term pls

This post has been edited by nujo87: Dec 9 2009, 12:05 PM

It had already been noted that both properties are connected, but which has bearing on actual driving was the question at hand
Now you have said it. But might i add that horsepower ultimately determines how fast you can go.

Torque is what powers you out of corners. Brake horse power (Bhp) is what keeps you going on the straight once you've established momentum. Torque and power, in terms of measurements of an engine system's performance, are measuring completely different things.

Basically, if you want to outrun the Polis DiRaja Malaysia (PDRM) you really want a powerful engine + some nut driving skills, if you want to pull your friend out of a "longkang", then a high torque engine would be helpful.

Regards, Joey

This post has been edited by Joey Christensen: Dec 9 2009, 01:08 PM

[bleah, did not read the last few posts, ignore this

This post has been edited by kev da man: Dec 9 2009, 01:41 PM

Let's just say my work require me to be familiar with it. (Does that means I can publish book already? ) Motor has high starting torque, (because it has constant torque curve). While engine has zero starting torque. Which is why we have a motor starter for all engine. Starter motor provide the torque to initiate the rotation in engine, but if engage with gear, it can't maintain the engine rotation because of huge load. Joey mention about motor, hence I try to explain how it is different than engine.

I think it's hp that power a vehicle out of corner, and torque is what keeps us going on straight. Brake horsepower, is different that horsepower. Indeed, horsepower and torque is inter-related. By definition, horsepower is derived from torque. But with engine, the ability to manipulate its input (fuel, in this case), and the torque/power curve makes it unique and difficult to explain.

Lol. Until now still can't agree over Torque and Power?

In super layman terms, Torque is rotating force and power is how fast you take to do a certain amount of work.

A layman example would be, when you try and unscrew a bottle cap, torque is how much rotating force needed by your hands to unscrew it and power is just how fast you can unscrew it. (may not be 100% accurate but it gives a rough idea).

So for engines, Torque is the amount of rotating force the engine can provide to propel the car from standstill and Power is the how fast the engine can propel the car.

So higher Torque means the engine can propel the car to a given speed in a shorter time (Acceleration) and Power determines the maximum speed the car can achieve.

Power is derived from Torque.

The most super basic analogy i can think of is:

Power is how fast you can run.
Torque is how fast it takes you to get fast. (sorry might sound a lil cacat here haha but hope you get my drift).

Hope this helps.

This gives me the idea of being ignorant is good. For example: Takumi Fujiwara with his ignorance in how a car works.

Anyway, there are mathematical ways to explain, there the graphical way to explain it and last but not least, there are words to describe it too.

HP = Torque x RPM ÷ 5252 (If you realised when you are comparing a few charts, you'll notice that the two entities will be intersecting at 5252 RPM) It's a bit weird but it's all there is to it. Note that at 5252 RPM, torque and HP are equal.

Regards, Joey

p.s: From my rusty science knowledge understanding, torque is measured while power is calculated.

This post has been edited by Joey Christensen: Dec 10 2009, 10:12 AM

OK, let me try this on a more layman's term.

When a person lifts a dumbell with his hand, the maximum weight he can lift is the torque, while HP is calculated by (the weight of the dumbell multiply by the distance of the motion) and divided by seconds.

So guys, is that true?

yes.. that's true... very good explanation.. but errr... what happens if the guys carries the weight which is not maximum?

That means he hasn't reached his maximum torque.
That's why in performance statistic the attributes would be 'maximum torque'.

For city driving torque is more important.
btw Torque and Power is interrelated.

Power = torque X speed


It's like you can carry 4 buckets of water to your house but can only do it once a day OR you can carry 2 buckets of water to your house but you do it twice a day. High Torque low speed or low torque high speed but both produces the same amount of Horsepower.

well,i think after this discussion we did learned more about torque n horsepower for car engine.
Hope this lil knowledge will help us out in picking new car in the future

IMHO i prefer low RPM torque power more than High RPM torque power,
becoz usually i wont drag my engine more than 3500RPM,coz very noisy n drink more petrol.

N i oso noticed some ENGINE not really as power as they stated in the performance sheet.
For example their stated Peak torque is on 150NM@4500rpm(example)
while most of the time,their average torque r much lower than the PEAK TORQUE stated,becoz their torque curve fluctuated very much
So do research more on ur potential new car