Raising the compression?

[Fusion Ed]

Ok to put it very very simply.

Torque is the TURNING force of an engine.

Power is well.... the amount of POWER an engine produces, which simply put is the amount of torque x the rpm its doing it at.

Ultimately power is what makes a car move. Yes people will try and claim its torque. But you could have 1000lb ft of torque and zero power. Example: Your doing up a head stud with a torque wrench, the wrench clicks to say 60lb ft, your still putting on the 60lb/ft but the bar is not moving. Hence you have torque, but no power as no effective work is being done.
On the other hand you could in theory have a 1lb engine spinning very very very very fast and producing 1000bhp. Once you had geared that down via a gearbox to a usefull speed then obviously you then get a slower RPM and torque.

Another way to look at it is: An engine with high power but low torque breathes well and typically revs higher and makes its power higher than say an engine with high torque but low bhp, which when revved hard would feel strangled and lethargic.

Make sense ?!

Ed

 

[pulsarboby]

bigger pistons, bigger cams, headwork, stroker crank will all help give a higher torque reading!

you hit the nail on the head andy when you said 'breathing' the better the engine can breaths and can emitt the gases then the better torque reading you will get i think

 

[Fusion Ed]

just an idea on that torque figure from wrc:
2.0 L, 300 bhp @ 5250 rpm
Torque 580 Nm @ 3500 rpm

Odd how people mix up imperial with metric measurements. Should be power as KW and Torque as Nm, or power as BHP and Torque as LB/ft.

Anyway: 580 N/m = 427.73 lb/ft.

 

[Fusion Ed]

bigger pistons, bigger cams, headwork, stroker crank will all help give a higher torque reading!

you hit the nail on the head andy when you said 'breathing' the better the engine can breaths and can emitt the gases then the better torque reading you will get

A torque graph relates directly to the air flow graph of an engine.

If an engine breathes best BELOW 5252 RPM then the torque will be higher than the BHP.
If an engine breathes best ABOVE 5252 RPM then the BHP will be higher than the Torque.

Therefore a better breathing higher RPM engine will ****ALWAYS***** have a higher BHP reading than Torque.

Power produced ignoring a few factors of efficiency is directly related to fuel consumption for a given AFR. So simply put more fuel used = more power = more energy produced = faster car as it has more energy to use.

Torque is not the be all and end all.

Thankfully we have gearboxes, so are high power figures can the be geared down to produce even more torque at a given road speed/gear than compared to a car with more torque/less power, which would certainly be slower.

 

[fubar andy]

Interesting!

So for instance if I lighten my engine components quite a bit: crank, pistons rods, flywheel, then that would attribute to a lower torque level than say a similar spec'd engine yet with no lightening?

 

[pulsarboby]

aah i see! i stand corrected on that one then i always thought it was the other way round.

so if say you had a close ratio box such as a rb box would the torque be higher than a standard box or lower using the same engine?

 

[fubar andy]

If an engine breathes best BELOW 5252 RPM then the torque will be higher than the BHP.
If an engine breathes best ABOVE 5252 RPM then the BHP will be higher than the Torque.

Just out of interest (without trying to sound retarded)

If I wanted more lbft than bhp, would what be involved to change that?

*edit just noticed some of Bob's post...

 

[Fusion Ed]

No,

You would see an apparent higher torque level at the flywheel as less energy is used to spin the engine up during changes in rate of RPM and so more of it becomes useful to do other work, like move your car instead.

In reality however energy would = the same assuming friction losses remain equal.

Ed

 

[Fusion Ed]

aah i see! i stand corrected on that one then i always thought it was the other way round.

so if say you had a close ratio box such as a rb box would the torque be higher than a standard box or lower using the same engine?

You have to consider the torque at the wheels vs the wheel RPM or cars MPH to really get a clear picture.

You either have comparisons with flywheel figures or comparisons with wheel figures.

You sometimes hear the term tractive effort from dynos etc. Thats effectively torque at the wheels.

Now if you say had a pulsar with high bhp lower torque and the close box, it would be much quicker than a pulsar with a high torque low bhp and long ration box.

If you had say an infinite great ratio box, power would win EVERY TIME over a car regardless of torque measurements.

 

[Fusion Ed]

Just out of interest (without trying to sound retarded)

If I wanted more lbft than bhp, would what be involved to change that?

*edit just noticed some of Bob's post...

Um simply put, stick a small turbo on the car and cane the nuts off it.

You would go slower than another pulsar that had more power however and less torque, as the one with more power could stay in the higher gears for longer, thus have an average higher torque @ wheels.

 

[pulsarboby]

still dont fully understand!

let me put it another way. if car had say 300bhp and was running on say 15'' rims with standard box, then you removed the standard box and fitted a close ratio unit.
then in 0-60 times which would be the fastest and which box would run the higher torque reading given the same engine, wheels?

 

[fubar andy]

At the end of the day my bhp is healthy enough, plenty of air getting in/out of there and it drags my fat ass around tracks with ease, yet when I looked at my lbft it was much lower than I expected, hence my query!

 

[Fusion Ed]

still dont fully understand!

let me put it another way. if car had say 300bhp and was running on say 15'' rims with standard box, then you removed the standard box and fitted a close ratio unit.
then in 0-60 times which would be the fastest and which box would run the higher torque reading given the same engine, wheels?

0-60 are tricky, reason is as depending on box you have to change either two or three times, so although say getting to 50 mph would be quicker on the close ration box it would possibly loose to the long ratio one due to having to change gear again, if you were to ignore gear change times then the 0.60 would be quicker on the close ratio unit.

Trouble with the example above is were comparing the same engine with different boxes, so the power remains the same, so although one can accelerate quicker its ultimate top speed etc will be the same (if not limited by gear box ratios)

Another thing which throws a spanner in the works in trying to understand torque and power is the following: Consider this carefully:

In any one gear, the rate of acceleration is at its GREATEST at the point of peak torque, not peak power.

However in order to achieve the overall best rate of acceleration you need to use peak power coupled with a suitable gearbox ratio that will make more use of that power where you need it. Than using the power available at the point of peak torque, thus ending with an overall greater amount of tractive effort at the wheels.

Get it!!? lol

 

[1ad1]

All sounds very complicated to me guys. as long as it goes like stink who cares.

 

[stumo]

JP will be along in a min.....he knows everything.............

 

[Boooooost]

yeah about **** all ....

 

[stumo]

*sniggers*

 

[paz]

Another question then, why is it that turbo diesel cars (I'm thinking particularly VAG stuff here) have massive torque figures compared to their BHP?

If you chip the 130bhp diesel engine, you get something like 180bhp but 250lb/ft torque. Why is that when a lot of our pulsars have c300bhp and 250lb/ft (just an example, not accurate figures- however on most cars the bhp is higher than the torque)?

Also torquey cars seem to pull harder, why is that?

Finally, I know that WRC cars are restricted in terms of BHP, but what is the advantage to the massive torque figures that they turn out? I guess that may in part answer my second questions.

Cheers - interesting stuff.

Paz

 

[GTIR-LOZ]

i guess as diesels rev to about 6000rpm all the power is lower down so giving a high torque figure

bhp is how fast the car goes the torque is how fast the car feels (i just made that up sounds good though!!)

http://www.pumaracing.co.uk/POWER1.htm this is a good link

as is www.pumaracing.co.uk as a whole

 

[gtir_pimp]

bhp is top end power and torque is low end power isnt it? whats your bhp and torque figure fubarandy? mine are the same 290bhp and 290lbft. standard turbo. but with the bigger turbos they can achieve high bhp but no as much torque. bhp is more for drag racers and torque more for rallying isnt it?