bhp/torque
What do you want to know? Torque is how hard something is turned whereas horse power is work done.
This may help:
This may help:
So, let's put this theoretical F1 car on the rolling road.
We wind it up until we have overcome the volumetric and combustion inefficiencies caused by the big valves/big ports/long-duration wide-overlap high-lift cams, and bingo! we've got it "on cam".
Let's plot a torque graph. Obviously crap up to roughly "on cam". Remember this is "strength" we're measuring. Now we're getting a roughly consistent combustion pressure, the stroke is constant, as are the number of cylinders. We would hope to see a flatish line on our graph, up until the point we can't breath enough air in, and combustion pressures drop off. The highest point on this graph is Torque, measured in pounds/feet or newton metres. Most tuners will be more interested in width of the flatish bit of the graph than the peak figure.
Now it's time to measure BHP on our F1 car.
We won't get any serious power til we're in the Torque band, then all hell breaks loose!
Let's Guess and say we're "on cam" at 15,000rpm.
We've got 10 cylinders of 300cc each, running at full efficiency, pushing the crank round with a leverage of whatever, at the rate of (and this is the important bit) 75,000 pulses of power per minute.
Squeeze that pedal up a bit to 16,000rpm (you'll need ear defenders), that is now 80,000 pulses per minute.
At the 18,000rpm redline we're packing 90,000 power pulses per minute!
So the higher we push our peak efficiency up the rev range, we cannot fail to make more BHP, purely because we're getting more power pulses per minute.
We wind it up until we have overcome the volumetric and combustion inefficiencies caused by the big valves/big ports/long-duration wide-overlap high-lift cams, and bingo! we've got it "on cam".
Let's plot a torque graph. Obviously crap up to roughly "on cam". Remember this is "strength" we're measuring. Now we're getting a roughly consistent combustion pressure, the stroke is constant, as are the number of cylinders. We would hope to see a flatish line on our graph, up until the point we can't breath enough air in, and combustion pressures drop off. The highest point on this graph is Torque, measured in pounds/feet or newton metres. Most tuners will be more interested in width of the flatish bit of the graph than the peak figure.
Now it's time to measure BHP on our F1 car.
We won't get any serious power til we're in the Torque band, then all hell breaks loose!
Let's Guess and say we're "on cam" at 15,000rpm.
We've got 10 cylinders of 300cc each, running at full efficiency, pushing the crank round with a leverage of whatever, at the rate of (and this is the important bit) 75,000 pulses of power per minute.
Squeeze that pedal up a bit to 16,000rpm (you'll need ear defenders), that is now 80,000 pulses per minute.
At the 18,000rpm redline we're packing 90,000 power pulses per minute!
So the higher we push our peak efficiency up the rev range, we cannot fail to make more BHP, purely because we're getting more power pulses per minute.
Originally Posted by Stavros
And if anyone says "bhp sells cars, torque wins races" and truly believes it, they are cocks 
PS- Im rubbish at explaining, so wont try
PS- Im rubbish at explaining, so wont try
PS - I'm rubbish at explaning to so i'll shut up.
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PassionFord Post Whore!!
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From: Exeter
There is quite a good write up on this in the latest Practical Performance Car.
I will try my best....
Basically, Imagine a really stiff wheel on a vertical post. (ie the flywheel)
Now imagine a bar fixed to this wheel in order to turn the wheel that is say one foot long. Now imagine putting one pound of pressure on the bar in an attempt to turn the wheel. This would be one Pound per Foot of pressure (ie 1 lb/ft). So if you applied 10 lbs of weight on the end of the same bar, then you then have 10 lb/ft of load.
Now this is important - note that the above has not yet turned our wheel.
Techincally, that means that no work has been done (sad isnt it!) Even if you struggle with it all day with lots more weight - if it doesnt move, then it is not a measurement of work.
Work is the measurement of how far it moves. If you manage to move one pound 33,000 ft in one minute, then you have acheived work, and more specifically, one Horse Power!.
One Horse Power = moving one pound 33,000 feet.
In an engine, the movement is round and round, rather than in a straight line! As such we talk about revolutions (also known as RPM!)
So now you have the torque from the flywheel, and the amount it moves in a given amount of time frame. This gives you the engine horse power!
Power is a result of torque.
So what is Break Horse Power?
This is simply the torque of an engine measured by a tool called an engine brake. What the machine does is effectively try to stop the engine from turning, and then measures how much effort it takes to slow the engine down. When the engine can no longer accelerate, but also does no longer deccelerate, then you have a reading that provides you with a measurement of the engine torque. The BHP is then a calculation based on the the rest!
Clear as mud!
JJ
I will try my best....
Basically, Imagine a really stiff wheel on a vertical post. (ie the flywheel)
Now imagine a bar fixed to this wheel in order to turn the wheel that is say one foot long. Now imagine putting one pound of pressure on the bar in an attempt to turn the wheel. This would be one Pound per Foot of pressure (ie 1 lb/ft). So if you applied 10 lbs of weight on the end of the same bar, then you then have 10 lb/ft of load.
Now this is important - note that the above has not yet turned our wheel.
Techincally, that means that no work has been done (sad isnt it!) Even if you struggle with it all day with lots more weight - if it doesnt move, then it is not a measurement of work.
Work is the measurement of how far it moves. If you manage to move one pound 33,000 ft in one minute, then you have acheived work, and more specifically, one Horse Power!.
One Horse Power = moving one pound 33,000 feet.
In an engine, the movement is round and round, rather than in a straight line! As such we talk about revolutions (also known as RPM!)
So now you have the torque from the flywheel, and the amount it moves in a given amount of time frame. This gives you the engine horse power!
Power is a result of torque.
So what is Break Horse Power?
This is simply the torque of an engine measured by a tool called an engine brake. What the machine does is effectively try to stop the engine from turning, and then measures how much effort it takes to slow the engine down. When the engine can no longer accelerate, but also does no longer deccelerate, then you have a reading that provides you with a measurement of the engine torque. The BHP is then a calculation based on the the rest!
Clear as mud!
JJ
PassionFord Post Whore!!
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From: Exeter
Originally Posted by Carlsworth
There is quite a good write up on this in the latest Practical Performance Car.
there is a white bmw 320 turbo in there somewhere that im sponsoring
there is a white bmw 320 turbo in there somewhere that im sponsoring
If it is, it sounds like quite an impressive conversion - M535i engine into an E30 with a turbo on a custom manifold - Developing good power on low boost!
JJ
DEYTUKURJERBS
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From: North Korea
spot on, though how much it matters is depending how much you value drivability and how widely spaced your gears are.
for pure razzing tits outa a car with closely spaced gears its just whats at the top end of the revs that counts, but on a daily driver thats no fun.
thats why ive never liked highly tuned small n/a engines, unless the car is stupidly light.
for pure razzing tits outa a car with closely spaced gears its just whats at the top end of the revs that counts, but on a daily driver thats no fun.
thats why ive never liked highly tuned small n/a engines, unless the car is stupidly light.
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Joined: May 2003
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From: Stockport, Cheshire
Originally Posted by Stavros
spot on, though how much it matters is depending how much you value drivability and how widely spaced your gears are.
for pure razzing tits outa a car with closely spaced gears its just whats at the top end of the revs that counts, but on a daily driver thats no fun.
thats why ive never liked highly tuned small n/a engines, unless the car is stupidly light.
for pure razzing tits outa a car with closely spaced gears its just whats at the top end of the revs that counts, but on a daily driver thats no fun.
thats why ive never liked highly tuned small n/a engines, unless the car is stupidly light.
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