[RACEM4TE]

My question in the title, lets say a porsche 911 turbo it has 580 HP/ 780 Torque why cant it have 750HP/ and 580 torque?

[Fundguy1]

Depends where you are making the power on the torque curve. If you make the power early like a truck engine you have lots or torque, low hp. If you make it at high rpms like mustang gt350, e9x m3, etc, gou have higher hp, lower torque numbers. Generally in cars higher torque than hp = better acceleration, especially from a launch, higher hp than torque = higher top speed. Turbo cars also suck from launch due to lag, which is why turbos like to race after moving instead of from a stop. Muscle cars are usually torque monsters. Ferraris and exotics hp cars. The 911 in question must be brutal accelerating.

[antych]

I think you need to go back to school and learn about units. Your question makes no sense. There's no such thing as 580 torque and you can't compare two different things measured in different units. It's like saying that 780 litres of milk is more than 580 meters of rope.

[overcoil]

I'm not an engineer nor particularly bright but the problem with the original question is that horsepower and torque are two different types of classifications of energy. And engine designers can choose to design engines to have maximum horsepower or maximum torque greater or lesser then the other. And they can design that at different points on an RPM table how horsepower and torque rise and fall almost independent of the other.

Certainly with artificial charging of the intake and fuel efficiency - getting the car up to cruising speed as efficiently as possible and other factors, you may see trends in the figures such as many cars having higher torque then horsepower - but I'm not convinced that is the case.

antych I was posting while you were posting and wouldn't have responded if had known of your post

[Fundguy1]

Originally Posted by antych

I think you need to go back to school and learn about units. Your question makes no sense. There's no such thing as 580 torque and you can't compare two different things measured in different units. It's like saying that 780 litres of milk is more than 580 meters of rope.

Yes and no. Torque is thrust. Hp is torque x rpm basically. So depending on your torque curve, if you make your torque early in the rpm range, you will have higher torque numbers and a good launch. If you make the torque later in the curve, you will make higher hp numbers and have power later after you're moving. Ideally you want a flat torque curve so you have the thrust evenly over a broad range of rpms. My 335i e93 is like that. Flat torque curve, 675 rwhp, 650 rwtq. Also, remember torque is different at the engine than at the wheels. The drivetrain typically leaches 10-20% of the power. Rotating mass, transmission type, etc. Reduce a car makers engine numbers by 15% or so to see about what rwhp/rwtq are for comparisons.

[Fundguy1]

A good example of this in action was the 440 six pack vs the 426 hemi. The 440 was a brutal torque monster with low end power. A stoplight warrior. The hemi was a higher reving engine made for high end torque for nascar racing. In the quarter they produced similar results but they raced completely differently. The 440 would launch ahead at the start and halfway the hemi would start to reel it in. Past a quarter mile the hemi would dominate. Hope this helps.

[Fundguy1]

Originally Posted by Lobb

Torque at the flywheel is not a very helpful measure. One must consider gearing, or more accurately the thrust at the wheels. Thus manufacturers of diesel cars will market the big torque numbers to gullible punters.

Correct, which is why I put my rwhp/rwtq numbers and pointed that out. Also some engines have short spikes of power, so their numbers are big but they don't have usable power throughout the full rpm range, so motors with smaller flatter numbers could actually be faster as they have more power for longer amounts of rpm.

[antych]

You can debate the torque curve etc. but you can't compare those numbers with each other. The apparent difference is accidental and depends on units used. If that 780 was in Nm, then converted to lbf⋅ft it becomes 575, so it's less than 580 now, which could also be metric or imperial hp, or kW. It would get higher or lower depending which country's measurement system you pick.

[F32Fleet]

Originally Posted by RACEM4TE

My question in the title, lets say a porsche 911 turbo it has 580 HP/ 780 Torque why cant it have 750HP/ and 580 torque?

Depends on the engine configuration, tuning, and fuel type.

For example

E90 335d (US) 265 hp / 425 ft lb tq, sequential turbo, diesel
E90 M3 414 hp / 295 ft lb tq naturally aspirated, gasoline

[Fundguy1]

Originally Posted by antych

You can debate the torque curve etc. but you can't compare those numbers with each other. The apparent difference is accidental and depends on units used. If that 780 was in Nm, then converted to lbf⋅ft it becomes 575, so it's less than 580 now, which could also be metric or imperial hp, or kW. It would get higher or lower depending which country's measurement system you pick.

Yes, I was considering the numbers to be a comparison using the same units from the same country. The original question was why was the torque a higher figure than the jorsepower and not the other way around. Since hp is torque times rpm, they are entirely related. So i was explaining why sometimes one was higher, sometimes the other.

[Fundguy1]

Originally Posted by F32Fleet

Depends on the engine configuration, tuning, and fuel type.

For example

E90 335d (US) 265 hp / 425 ft lb tq, sequential turbo, diesel
E90 M3 414 hp / 295 ft lb tq naturally aspirated, gasoline

In this case, the diesel torque comes on right away in the rpms then fades away. This is why dielels are ideal for heavy vehicles to get things moving. The m3 the torque is low until you get the rpms up which is why it doesnt really get moving until 5000 rpm. Since the torque is at higher rpm, the hp is high. Good for autobahns but not stoplight races.

[GuidoK]

Originally Posted by antych

You can debate the torque curve etc. but you can't compare those numbers with each other. The apparent difference is accidental and depends on units used. If that 780 was in Nm, then converted to lbf⋅ft it becomes 575, so it's less than 580 now, which could also be metric or imperial hp, or kW. It would get higher or lower depending which country's measurement system you pick.

Also a torque number is easily multiplied by a gearbox for example (which is basically a torque converter).
You can multiply torque (which is a force) virtually infinately, but you cant multiply power.
Also you can write torque easily in Ncm

[Vigilante375]

Like it was mentioned before. It comes down to the engine and fuel type.

You won't find many petrol (gasoline) engines making more tq than hp. They can be close to the same numbers at times. But you'll find a lot of diesel engines making more tq than hp. Since diesel engines great for pulling or pushing heavy objects since they can make so much pulling or pushing force.

is there a specific car that you're talking about?

[NickyC]

Horsepower sells cars, but you drive torque. ;D

[insanecoder]

First off these numbers are usually peak
and the two numbers may peak at different parts of the RPM curve
torque is the rotational force you apply to the shafts
hp is the rate of work which directly related to torque at a given rpm
And for those in the know its the curve or path of how you get there ie a combo of the sustained torque & rpm
so for example if your peak torque at 580 ftlb @ 6791 RPM your hp is your 750horses

[Stubbie Blue]

It's just the way the equation works out:

hp = torque (lb-ft) x rpm / 5252

If an engine produces peak torque below 5252 rpm, the peak hp will be lower than the torque in lb-ft. e.g. most diesels.

If it produces peak torque at or around 5252 rpm, the peak hp will be close to the torque number. Most engines are like this.

If it produces peak torque above 5252 rpm, the peak hp will be higher than the torque number. Usually high-revving, small displacement NA sports cars are like this.

[Fundguy1]

Originally Posted by Stubbie Blue

It's just the way the equation works out:

hp = torque (lb-ft) x rpm / 5252

If an engine produces peak torque below 5252 rpm, the peak hp will be lower than the torque in lb-ft. e.g. most diesels.

If it produces peak torque at or around 5252 rpm, the peak hp will be close to the torque number. Most engines are like this.

If it produces peak torque above 5252 rpm, the peak hp will be higher than the torque number. Usually high-revving, small displacement NA sports cars are like this.

Exactly. So going back to original Porsche example, the torque probably peaks at around 4000

[FogCityM3]

This. Pretty much all you need to know about how power is produced for a given engine and in comparing various ways of producing power (through high torque or through high revs).

The S65 is so different because for a high revving engine, peak torque occurs at a relatively low RPM (3900) compared to peak bhp at 8,300+ rpm. That is an rpm power band spread of over 4,400 rpm, which is incredible and only achieved by a few engines in production automotive history.

Compare this to the Voodoo engine in the Shelby GT350, where peak torque is at 4750 rpm and peak bhp is at 7500 rpm (8250 redline). That is a power band spread of 2750. Even assuming you could make the same or more power at 8250 as you could at 7500 rpm, that's still only a spread of 3500 rpm.

Get the M3 tuned, and it is producing peak power at 8600 rpm, resulting in a power band rpm spread of 4600+!!

Originally Posted by Stubbie Blue

It's just the way the equation works out:

hp = torque (lb-ft) x rpm / 5252

If an engine produces peak torque below 5252 rpm, the peak hp will be lower than the torque in lb-ft. e.g. most diesels.

If it produces peak torque at or around 5252 rpm, the peak hp will be close to the torque number. Most engines are like this.

If it produces peak torque above 5252 rpm, the peak hp will be higher than the torque number. Usually high-revving, small displacement NA sports cars are like this.

[rainfall]

If you're talking about US units (HP and lb-ft), then the numerical values are similar in the value

for example, a MK6 gti has ~200hp and ~200 lb-ft of torque
The Mk7 gti got more torque than it got power because the compression that the turbo is giving to the engine is bigger.

You can typically find more torque on turbocharged engines with high boost or in large engines with low RPM limiter (like the 5.7L Dodge Challenger with 375 hp /410 lb-ft of torque an a 5600 rpm rev limiter)

p.s. I think the others already bashed you enough saying that torque and power are two completely different things ,right

[trey100]

Originally Posted by Stubbie Blue

It's just the way the equation works out:

hp = torque (lb-ft) x rpm / 5252

If an engine produces peak torque below 5252 rpm, the peak hp will be lower than the torque in lb-ft. e.g. most diesels.

If it produces peak torque at or around 5252 rpm, the peak hp will be close to the torque number. Most engines are like this.

If it produces peak torque above 5252 rpm, the peak hp will be higher than the torque number. Usually high-revving, small displacement NA sports cars are like this.

The formula is correct but a car's torque can peak below 5252 and still have a higher HP number. Depends on how that torque falls off as RPMs rise. For instance if you have a car that "peaks" at 406 lb ft at 1850 rpm but still has 375 lb ft or torque at 7,500 rpm, then in that case

HP = 375 x 7500/5252 which is 535 HP.

You can't look at torque and HP at 2 different RPMs and compare them. They are happening at different points. To calculate HP across the rpm range, you look at the torque throughout the rpm range and calculate the corresponding HP at each rpm. Graphing that gives you the HP curve.

This is why HP and torque curves always intersect at 5252 rpm. Regardless of the torque value the equation will always give you a HP equal to the torque value.

An S2000 has a relatively flat torque curve all the way up high in the rpm range. Therefore the horsepower curve is close to a line in shape compared to say an M3 that has a drop off in torque up high and therefore has a rounded off hp curve.

[GuidoK]

Do you guys know why lb ft is (physically) a wrong measurement of torque?

[RACEM4TE]

Originally Posted by GuidoK

Do you guys know why lb ft is (physically) a wrong measurement of torque?

I was talking About Nm not ib-ft