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HORSEPOWER
Let me enlighten some of you engine wizards about horsepower and torque.
When you read magazines and listen to mechanics you start thinking that torque and horsepower are two different measures of an engines power. Well, thats not really so,,,torque and horsepower are related,,,once you draw the torque curve your horsepower curve is set also. Horsepower is time related,,,in other words it depends on the speed of the engine ,, torque is not,,its a set value the engine gives and the RPM is recorded so that horsepower can be calculated. In effect an engine with a lot of torgue has low end horsepower. The reason engineers dont talk much about torque is that you can get whatever torque you want depending on the gear ratio. Want a thousand foot pounds,,,, just gear it down,,,even a ten horsepower engine can give you 1000 foot pounds when its geared down. Engineers need a value that tells you what the engine is capable of doing and horsepower does that. Torque as an output,,,is meaningless unless accompanied by a speed,,thus horsepower. Horsepower = Torgue X RPM / 5252 Thus torque and horsepower are always the same at 5252 rpm. So be careful when you talk about an engine that is torquey,,,,its just an engine with more low end horsepower. Torque is important as an engine output ONLY at the dynamometer because after that we can get any torque we need by gears,,,ok ? Steve Ex -Ford Engineer |
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#2
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HORSEPOWER
"Steve" > wrote in message ... > Let me enlighten some of you engine wizards about horsepower and torque. > When you read magazines and listen to mechanics you start thinking that > torque and horsepower are two different measures of an engines power. > Well, thats not really so,,,torque and horsepower are related,,,once you > draw the torque curve your horsepower curve is set also. Horsepower is > time related,,,in other words it depends on the speed of the engine ,, > torque is not,,its a set value the engine gives and the RPM is recorded so > that horsepower can be calculated. In effect an engine with a lot of > torgue has low end horsepower. The reason engineers dont talk much about > torque is that you can get whatever torque you want depending on the gear > ratio. Want a thousand foot pounds,,,, just gear it down,,,even a ten > horsepower engine can give you 1000 foot pounds when its geared down. > Engineers need a value that tells you what the engine is capable of doing > and horsepower does that. Torque as an output,,,is meaningless unless > accompanied by a speed,,thus horsepower. > Horsepower = Torgue X RPM / 5252 > > Thus torque and horsepower are always the same at 5252 rpm. So be careful > when you talk about an engine that is torquey,,,,its just an engine with > more low end horsepower. Torque is important as an engine output ONLY at > the dynamometer because after that we can get any torque we need by > gears,,,ok ? > Steve > Ex -Ford Engineer Using gears to get torque is bad because it brings down your top speed, and the car runs at higher RPM all the time. Forget Gears. Put a Blower on it, roots or a Keene Bell. |
#3
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HORSEPOWER
Steve wrote:
> Let me enlighten some of you engine wizards about horsepower and torque. > When you read magazines and listen to mechanics you start thinking that > torque and horsepower are two different measures of an engines power. Well, > thats not really so,,,torque and horsepower are related,,,once you draw the > torque curve your horsepower curve is set also. Horsepower is time > related,,,in other words it depends on the speed of the engine ,, torque is > not,,its a set value the engine gives and the RPM is recorded so that > horsepower can be calculated. In effect an engine with a lot of torgue has > low end horsepower. The reason engineers dont talk much about torque is that > you can get whatever torque you want depending on the gear ratio. Want a > thousand foot pounds,,,, just gear it down,,,even a ten horsepower engine > can give you 1000 foot pounds when its geared down. Engineers need a value > that tells you what the engine is capable of doing and horsepower does that. > Torque as an output,,,is meaningless unless accompanied by a speed,,thus > horsepower. > Horsepower = Torgue X RPM / 5252 > > Thus torque and horsepower are always the same at 5252 rpm. So be careful > when you talk about an engine that is torquey,,,,its just an engine with > more low end horsepower. Torque is important as an engine output ONLY at the > dynamometer because after that we can get any torque we need by gears,,,ok ? > Steve > Ex -Ford Engineer > Perhaps I understand why you're an EX Ford engineer after reading that. -- “I intended that "not stupid" be a requirement.” – Seth Breidbart |
#4
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HORSEPOWER
WindsorFox > wrote:
> Steve wrote: >> Let me enlighten some of you engine wizards about horsepower and >> torque. When you read magazines and listen to mechanics you start >> thinking that torque and horsepower are two different measures of an >> engines power. Well, thats not really so,,,torque and horsepower are >> related,,,once you draw the torque curve your horsepower curve is set >> also. Horsepower is time related,,,in other words it depends on the >> speed of the engine ,, torque is not,,its a set value the engine >> gives and the RPM is recorded so that horsepower can be calculated. >> In effect an engine with a lot of torgue has low end horsepower. The >> reason engineers dont talk much about torque is that you can get >> whatever torque you want depending on the gear ratio. Want a >> thousand foot pounds,,,, just gear it down,,,even a ten horsepower >> engine can give you 1000 foot pounds when its geared down. Engineers >> need a value that tells you what the engine is capable of doing and >> horsepower does that. Torque as an output,,,is meaningless unless >> accompanied by a speed,,thus horsepower. >> Horsepower = Torgue X RPM / 5252 >> >> Thus torque and horsepower are always the same at 5252 rpm. So be >> careful when you talk about an engine that is torquey,,,,its just an >> engine with more low end horsepower. Torque is important as an engine >> output ONLY at the dynamometer because after that we can get any >> torque we need by gears,,,ok ? >> Steve >> Ex -Ford Engineer >> > > Perhaps I understand why you're an EX Ford engineer > after reading that. > Yeah... sounds like we need to go back to RWHP? Ricers would like that. -- Yeh, I'm a Krusty old Geezer, putting up with my 'smartass' is the price you pay..DEAL with it! |
#5
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HORSEPOWER
"karinhall" > wrote in message ... > > "WindsorFox" > wrote in message > ... >> Steve wrote: >>> Let me enlighten some of you engine wizards about horsepower and torque. >>> When you read magazines and listen to mechanics you start thinking that >>> torque and horsepower are two different measures of an engines power. >>> Well, >>> thats not really so,,,torque and horsepower are related,,,once you draw >>> the >>> torque curve your horsepower curve is set also. Horsepower is time >>> related,,,in other words it depends on the speed of the engine ,, torque >>> is >>> not,,its a set value the engine gives and the RPM is recorded so that >>> horsepower can be calculated. In effect an engine with a lot of torgue >>> has >>> low end horsepower. The reason engineers dont talk much about torque is >>> that >>> you can get whatever torque you want depending on the gear ratio. Want >>> a >>> thousand foot pounds,,,, just gear it down,,,even a ten horsepower >>> engine >>> can give you 1000 foot pounds when its geared down. Engineers need a >>> value >>> that tells you what the engine is capable of doing and horsepower does >>> that. >>> Torque as an output,,,is meaningless unless accompanied by a speed,,thus >>> horsepower. >>> Horsepower = Torgue X RPM / 5252 >>> >>> Thus torque and horsepower are always the same at 5252 rpm. So be >>> careful >>> when you talk about an engine that is torquey,,,,its just an engine with >>> more low end horsepower. Torque is important as an engine output ONLY at >>> the >>> dynamometer because after that we can get any torque we need by >>> gears,,,ok ? >>> Steve >>> Ex -Ford Engineer >>> >> >> Perhaps I understand why you're an EX Ford engineer >> after reading that. >> > Actually: > One horsepower is an estimate of the power a standard workhorse can exert: > 550 ft.lbs/sec. Before applying any formula, we must first identify the > units of torque on you engine. Torque may be listed as foot-pounds or as > Newton-meters. As you made no specification, I will assume you automobile > specifications use foot-pounds. > > The power exerted by a rotating object is the torque it exerts multiplied > by > the speed at which it rotates. In standard English units, this would be > foot-pounds multiplied by radians/second. It is a special property of > radians that allows this product to be foot-pounds/second: a radian is a > distance around an arc divided by the length of the radius (feet per > foot). > > We start with 1 horsepower. We want to get to (foot-pounds)x(rpm). > 1 hp = 550 ft-lbs/sec = 550 (ft-lbs)x(rad/sec) > 1 rad/sec = 60 rad/min > = 33,000 (ft-lbs)x(rad/min) > 1 revolution=2(pi)radians > > 1 rpm = 2(pi) rad/min > 1 hp = 5252 (ft-lbs)(rpm) > > As for source of rpms, that varies from moment to moment. The number of > rpms will probably be greatest in the lowest gears. When rpms get too > great, a vehicle is usually shifted to a higher gear and a lower rpm for > the > motor. The torque tends to be greater in lower gears, when the car is > trying to speed up. Once at cruising speed, all the engine needs to do is > keep the car moving. > > Look at the greatest rpm listed on the scale of your tachometer. Use this > as a reasonable maximum. Multiply this by your engine's greatest torque. > This is an estimate of your vehicle's maximum horsepower. Actual value > can > vary with speed, with how well oiled the car is, even with humidity. > Now, I'm confused. lol So explain to me how a car like the 5.0 can have 300lbs of tq and 225 horse. Yet the new ones have 305(?)lbs and 300 horse. Since the torque is the same, why is the hp different? The rotating speed? Does this make any sense...? lol Brad |
#6
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HORSEPOWER
RPM. Note the following specs...
1992 stock 5.0L V8: Horsepower: 225 hp @ 4200 rpm Torque: 300 ft-lbs. @ 3200 rpm 2005 stock 4.6L V8: Horsepower: 300 hp @ 5750 rpm (1550 RPM higher) Torque: 320 ft-lbs. @ 4500 rpm (1300 RPM higher) Don't let the formula intimidate you. HP is simply proportional to Torque X RPM, and therefore HP rises rapidly as RPM increases. Note this is why a "flat torque curve" still results in a rising HP curve. Note the 5252 is a constant based on James Watt's definition of "horsepower", a term he coined to help people relate to the power generated by the new fangled steam engine which was taking over the duties of plow animals. Also note that this 5252 constant results in HP always equaling Torque at 5252 RPM, which is why the dyno curves always cross at this point (this means HP is always LESS than Torque below 5252 RPM & always GREATER than above 5252 RPM.) The multiplied result is how a high-rev'ing Ferrari or Lamborghini V12 can produce upwards of 500 hp and "just" 300 ft-lbs of Torque--that is 300 ft-lbs at 8750 RPM! While it's true gearing (and tire size) can determine the RPM the engine will spin at, it's not easily to build a mass-produced V8 or V6 that can rev that high without self-destructing. Also, it would be impractical to expect most drivers to shift 8, 10 or 15 gears (although big rigs have 10 and the new Lexus LS has an 8 speed auto!); therefore automobile engines are designed to produce reasonable "low-end torque", or good torque at low RPM, as well as torque at a reasonably high RPM, which results in high HP. A flat torque curve from 2000 to 5000 or 6000 RPM is considered a good thing for a passenger car. The way I describe Torque and HP to my kid is...imagine 2 runners; one with strong legs but a long, slow stride and the other can pump his legs very fast. The 1st runner has lots of low-end Torque, but not a lot of HP due to the slow stride ("RPM"). He's like a tractor, he could push your car out of a ditch, but despite even stronger legs, cannot run as fast as the 2nd runner. The 2nd runner's fast stride (high RPM) enables him to have a very high top speed. In other words, his fast moving legs provide enough power to enable him to cover a great distance in a short period of time (distance ÷ time = velocity.) Is that clear? Therefore a typical Mustang GT owner really wants POWER--high Torque at high RPM--not just gobs of Torque. Low end torque is great for initial acceleration off-the-line, or simply smoking your tires; however HP is what determines top speed, as well as how much distance can be covered in each gear. At 3200 RPM, both the 5.0 & 4.6 generate about 180 hp & 300 ft-lbs; at 4200 RPM, the 5.0 peaks at 225 hp (at a falling 281 ft-lbs torque), while the 4.6L still-climbing torque results in 260 hp. Beyond 5000 RPM, the stock 5.0L simply starts to "run out of steam," well before the much higher rev'ing stock 4.6L. In fact, though torque begins to drop off after 4500 RPM, the muliplied result allows HP to continue to climb (recall that its number becomes even higher than torque beyond 5252 rpm). Thus the 4.6L can produce 300 hp at 5750 RPM, despite making "only" 274 ft-lbs at this engine speed. In other words, the 4.6L is a damn good engine...which is why it was named one of "Ward's 10 Best Engines" for 2006. BradandBrooks wrote: > "karinhall" > wrote in message > ... > > > > "WindsorFox" > wrote in message > > ... > >> Steve wrote: > >>> Let me enlighten some of you engine wizards about horsepower and torque. > >>> When you read magazines and listen to mechanics you start thinking that > >>> torque and horsepower are two different measures of an engines power. > >>> Well, > >>> thats not really so,,,torque and horsepower are related,,,once you draw > >>> the > >>> torque curve your horsepower curve is set also. Horsepower is time > >>> related,,,in other words it depends on the speed of the engine ,, torque > >>> is > >>> not,,its a set value the engine gives and the RPM is recorded so that > >>> horsepower can be calculated. In effect an engine with a lot of torgue > >>> has > >>> low end horsepower. The reason engineers dont talk much about torque is > >>> that > >>> you can get whatever torque you want depending on the gear ratio. Want > >>> a > >>> thousand foot pounds,,,, just gear it down,,,even a ten horsepower > >>> engine > >>> can give you 1000 foot pounds when its geared down. Engineers need a > >>> value > >>> that tells you what the engine is capable of doing and horsepower does > >>> that. > >>> Torque as an output,,,is meaningless unless accompanied by a speed,,thus > >>> horsepower. > >>> Horsepower = Torgue X RPM / 5252 > >>> > >>> Thus torque and horsepower are always the same at 5252 rpm. So be > >>> careful > >>> when you talk about an engine that is torquey,,,,its just an engine with > >>> more low end horsepower. Torque is important as an engine output ONLY at > >>> the > >>> dynamometer because after that we can get any torque we need by > >>> gears,,,ok ? > >>> Steve > >>> Ex -Ford Engineer > >>> > >> > >> Perhaps I understand why you're an EX Ford engineer > >> after reading that. > >> > > Actually: > > One horsepower is an estimate of the power a standard workhorse can exert: > > 550 ft.lbs/sec. Before applying any formula, we must first identify the > > units of torque on you engine. Torque may be listed as foot-pounds or as > > Newton-meters. As you made no specification, I will assume you automobile > > specifications use foot-pounds. > > > > The power exerted by a rotating object is the torque it exerts multiplied > > by > > the speed at which it rotates. In standard English units, this would be > > foot-pounds multiplied by radians/second. It is a special property of > > radians that allows this product to be foot-pounds/second: a radian is a > > distance around an arc divided by the length of the radius (feet per > > foot). > > > > We start with 1 horsepower. We want to get to (foot-pounds)x(rpm). > > 1 hp = 550 ft-lbs/sec = 550 (ft-lbs)x(rad/sec) > > 1 rad/sec = 60 rad/min > > = 33,000 (ft-lbs)x(rad/min) > > 1 revolution=2(pi)radians > > > > 1 rpm = 2(pi) rad/min > > 1 hp = 5252 (ft-lbs)(rpm) > > > > As for source of rpms, that varies from moment to moment. The number of > > rpms will probably be greatest in the lowest gears. When rpms get too > > great, a vehicle is usually shifted to a higher gear and a lower rpm for > > the > > motor. The torque tends to be greater in lower gears, when the car is > > trying to speed up. Once at cruising speed, all the engine needs to do is > > keep the car moving. > > > > Look at the greatest rpm listed on the scale of your tachometer. Use this > > as a reasonable maximum. Multiply this by your engine's greatest torque. > > This is an estimate of your vehicle's maximum horsepower. Actual value > > can > > vary with speed, with how well oiled the car is, even with humidity. > > > > Now, I'm confused. lol > > So explain to me how a car like the 5.0 can have 300lbs of tq and 225 horse. > Yet the new ones have 305(?)lbs and 300 horse. Since the torque is the > same, why is the hp different? The rotating speed? Does this make any > sense...? lol > > Brad |
#7
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HORSEPOWER
Jeff:
Gotcha. This was VERY imformative. I think we all learned something here. So, one more question... We all know we can add heads and an intake, etc, say with a kit from any major manufacturer, and increase the 5.0s horsepower to, say, 300 horse. But, what did we really do when we made these changes? How do these parts change the horsepower on the engine, since the crank is still spinning the same, isn't it? This is very cool. Thanks for sharing your knowledge. Brad "Jeff" > wrote in message oups.com... RPM. Note the following specs... 1992 stock 5.0L V8: Horsepower: 225 hp @ 4200 rpm Torque: 300 ft-lbs. @ 3200 rpm 2005 stock 4.6L V8: Horsepower: 300 hp @ 5750 rpm (1550 RPM higher) Torque: 320 ft-lbs. @ 4500 rpm (1300 RPM higher) Don't let the formula intimidate you. HP is simply proportional to Torque X RPM, and therefore HP rises rapidly as RPM increases. Note this is why a "flat torque curve" still results in a rising HP curve. Note the 5252 is a constant based on James Watt's definition of "horsepower", a term he coined to help people relate to the power generated by the new fangled steam engine which was taking over the duties of plow animals. Also note that this 5252 constant results in HP always equaling Torque at 5252 RPM, which is why the dyno curves always cross at this point (this means HP is always LESS than Torque below 5252 RPM & always GREATER than above 5252 RPM.) The multiplied result is how a high-rev'ing Ferrari or Lamborghini V12 can produce upwards of 500 hp and "just" 300 ft-lbs of Torque--that is 300 ft-lbs at 8750 RPM! While it's true gearing (and tire size) can determine the RPM the engine will spin at, it's not easily to build a mass-produced V8 or V6 that can rev that high without self-destructing. Also, it would be impractical to expect most drivers to shift 8, 10 or 15 gears (although big rigs have 10 and the new Lexus LS has an 8 speed auto!); therefore automobile engines are designed to produce reasonable "low-end torque", or good torque at low RPM, as well as torque at a reasonably high RPM, which results in high HP. A flat torque curve from 2000 to 5000 or 6000 RPM is considered a good thing for a passenger car. The way I describe Torque and HP to my kid is...imagine 2 runners; one with strong legs but a long, slow stride and the other can pump his legs very fast. The 1st runner has lots of low-end Torque, but not a lot of HP due to the slow stride ("RPM"). He's like a tractor, he could push your car out of a ditch, but despite even stronger legs, cannot run as fast as the 2nd runner. The 2nd runner's fast stride (high RPM) enables him to have a very high top speed. In other words, his fast moving legs provide enough power to enable him to cover a great distance in a short period of time (distance ÷ time = velocity.) Is that clear? Therefore a typical Mustang GT owner really wants POWER--high Torque at high RPM--not just gobs of Torque. Low end torque is great for initial acceleration off-the-line, or simply smoking your tires; however HP is what determines top speed, as well as how much distance can be covered in each gear. At 3200 RPM, both the 5.0 & 4.6 generate about 180 hp & 300 ft-lbs; at 4200 RPM, the 5.0 peaks at 225 hp (at a falling 281 ft-lbs torque), while the 4.6L still-climbing torque results in 260 hp. Beyond 5000 RPM, the stock 5.0L simply starts to "run out of steam," well before the much higher rev'ing stock 4.6L. In fact, though torque begins to drop off after 4500 RPM, the muliplied result allows HP to continue to climb (recall that its number becomes even higher than torque beyond 5252 rpm). Thus the 4.6L can produce 300 hp at 5750 RPM, despite making "only" 274 ft-lbs at this engine speed. In other words, the 4.6L is a damn good engine...which is why it was named one of "Ward's 10 Best Engines" for 2006. BradandBrooks wrote: > "karinhall" > wrote in message > ... > > > > "WindsorFox" > wrote in message > > ... > >> Steve wrote: > >>> Let me enlighten some of you engine wizards about horsepower and > >>> torque. > >>> When you read magazines and listen to mechanics you start thinking > >>> that > >>> torque and horsepower are two different measures of an engines power. > >>> Well, > >>> thats not really so,,,torque and horsepower are related,,,once you > >>> draw > >>> the > >>> torque curve your horsepower curve is set also. Horsepower is time > >>> related,,,in other words it depends on the speed of the engine ,, > >>> torque > >>> is > >>> not,,its a set value the engine gives and the RPM is recorded so that > >>> horsepower can be calculated. In effect an engine with a lot of torgue > >>> has > >>> low end horsepower. The reason engineers dont talk much about torque > >>> is > >>> that > >>> you can get whatever torque you want depending on the gear ratio. > >>> Want > >>> a > >>> thousand foot pounds,,,, just gear it down,,,even a ten horsepower > >>> engine > >>> can give you 1000 foot pounds when its geared down. Engineers need a > >>> value > >>> that tells you what the engine is capable of doing and horsepower does > >>> that. > >>> Torque as an output,,,is meaningless unless accompanied by a > >>> speed,,thus > >>> horsepower. > >>> Horsepower = Torgue X RPM / 5252 > >>> > >>> Thus torque and horsepower are always the same at 5252 rpm. So be > >>> careful > >>> when you talk about an engine that is torquey,,,,its just an engine > >>> with > >>> more low end horsepower. Torque is important as an engine output ONLY > >>> at > >>> the > >>> dynamometer because after that we can get any torque we need by > >>> gears,,,ok ? > >>> Steve > >>> Ex -Ford Engineer > >>> > >> > >> Perhaps I understand why you're an EX Ford engineer > >> after reading that. > >> > > Actually: > > One horsepower is an estimate of the power a standard workhorse can > > exert: > > 550 ft.lbs/sec. Before applying any formula, we must first identify the > > units of torque on you engine. Torque may be listed as foot-pounds or > > as > > Newton-meters. As you made no specification, I will assume you > > automobile > > specifications use foot-pounds. > > > > The power exerted by a rotating object is the torque it exerts > > multiplied > > by > > the speed at which it rotates. In standard English units, this would be > > foot-pounds multiplied by radians/second. It is a special property of > > radians that allows this product to be foot-pounds/second: a radian is > > a > > distance around an arc divided by the length of the radius (feet per > > foot). > > > > We start with 1 horsepower. We want to get to (foot-pounds)x(rpm). > > 1 hp = 550 ft-lbs/sec = 550 (ft-lbs)x(rad/sec) > > 1 rad/sec = 60 rad/min > > = 33,000 (ft-lbs)x(rad/min) > > 1 revolution=2(pi)radians > > > > 1 rpm = 2(pi) rad/min > > 1 hp = 5252 (ft-lbs)(rpm) > > > > As for source of rpms, that varies from moment to moment. The number of > > rpms will probably be greatest in the lowest gears. When rpms get too > > great, a vehicle is usually shifted to a higher gear and a lower rpm for > > the > > motor. The torque tends to be greater in lower gears, when the car is > > trying to speed up. Once at cruising speed, all the engine needs to do > > is > > keep the car moving. > > > > Look at the greatest rpm listed on the scale of your tachometer. Use > > this > > as a reasonable maximum. Multiply this by your engine's greatest > > torque. > > This is an estimate of your vehicle's maximum horsepower. Actual value > > can > > vary with speed, with how well oiled the car is, even with humidity. > > > > Now, I'm confused. lol > > So explain to me how a car like the 5.0 can have 300lbs of tq and 225 > horse. > Yet the new ones have 305(?)lbs and 300 horse. Since the torque is the > same, why is the hp different? The rotating speed? Does this make any > sense...? lol > > Brad |
#8
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HORSEPOWER
BradandBrooks wrote:
> Jeff: > > Gotcha. This was VERY imformative. I think we all learned something here. > > So, one more question... > > We all know we can add heads and an intake, etc, say with a kit from any > major manufacturer, and increase the 5.0s horsepower to, say, 300 horse. > But, what did we really do when we made these changes? How do these parts > change the horsepower on the engine, since the crank is still spinning the > same, isn't it? > An IC engine is an air pump. Whatever you do to pump more air through the engine will increase the resulting power (assuming you keep the optimal fuel:air ratio and don't blow the engine). Superchargers and turbos increase the air pressure at the engine inlet and, therefore, increase the air flow, resulting in more power -- sometimes *lots* more power. Better heads reduce the resistance to air flow through the engine and, therefore, increase the air flow (mostly at higher RPM), resulting in higher max. RPM and more high-RPM power, but little impact on the low-end. Better exhaust systems decrease the back-pressure on the engine outlet and, therefore, increase the air flow; generally resulting in modest increases in power for a street car. -- Cheers, Bob |
#9
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HORSEPOWER
Thanks very much for all this and taking the time to answer.
Brad "Bob Willard" > wrote in message . .. > BradandBrooks wrote: > >> Jeff: >> >> Gotcha. This was VERY imformative. I think we all learned something here. >> >> So, one more question... >> >> We all know we can add heads and an intake, etc, say with a kit from any >> major manufacturer, and increase the 5.0s horsepower to, say, 300 horse. >> But, what did we really do when we made these changes? How do these parts >> change the horsepower on the engine, since the crank is still spinning >> the same, isn't it? >> > > An IC engine is an air pump. Whatever you do to pump more air through the > engine will increase the resulting power (assuming you keep the optimal > fuel:air ratio and don't blow the engine). > > Superchargers and turbos increase the air pressure at the engine inlet > and, > therefore, increase the air flow, resulting in more power -- sometimes > *lots* > more power. Better heads reduce the resistance to air flow through the > engine > and, therefore, increase the air flow (mostly at higher RPM), resulting > in higher max. RPM and more high-RPM power, but little impact on the > low-end. > Better exhaust systems decrease the back-pressure on the engine outlet > and, > therefore, increase the air flow; generally resulting in modest increases > in > power for a street car. > -- > Cheers, Bob |
#10
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HORSEPOWER
The MOD that makes the most increase of HP would be the Camshaft. The cam
opens and closes the valves. So if you install a camshaft with higher lift and longer duration, you are allowing more air/fuel to enter the combustion chamber, thus more Torque/HP, and usually a higher redline. Heads & intake will help in boosting Torque & HP, but installing a larger cam will usually yield better results. Just remember, the more duration of the cam, the more lopey it will be. If you intend to drag race, here's something to consider. Pick a combination that will start building torque around the RPM you intend to launch the car at. If you are going to launch at let's say 4000 rpm's, you don't want your torque to peak until after you have already launched. If you build allot of torque before your launch RPM, then your going to need slicks (M/T ET Drags or equivalent) so you don't spin off the line. Allot of people make the mistake of building torque down too low, then wonder why they can't get traction at the drag strip. But to answer your question, what you've actually done was raise the upper RPM limit, thus more HP. 66StangMan "BradandBrooks" > wrote in message newsRKhh.497057$1T2.361236@pd7urf2no... > > So, one more question... > > We all know we can add heads and an intake, etc, say with a kit from any > major manufacturer, and increase the 5.0s horsepower to, say, 300 horse. > But, what did we really do when we made these changes? How do these parts > change the horsepower on the engine, since the crank is still spinning the > same, isn't it? > > Brad |
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