Need some guidance on n2o 928s
07-07-2005, 03:41 PM
#91
Rennlist Member
again, very misleading, however correct. you have to look past some of this to understand what is REALLY happening. thats the reason we are "talking past" each other. By the way, these discussions tend to help some understand more than they knew before, so i have no problem engaging in this kind of discussion (obviously, to a fault!)
anyway, yes, your car will pull hardest in each gear at max torque. HOWEVER, this dances right past the subject. the area under the curve is what you have to look at , AND MOST IMPORTANTLY, the speeds. This means, there is a difference between what is produced by the engine and what is output to the wheels through the gears. it is the main reason i brought up an infinitely variable gear box. if you had one, where would the engine and drivetrain pull the hardest??? CERTAINLY not at max torque, but at MAX HP!!! this is of the things you can bring up to ANYONE and debate it with full confidence. why, because in gearing , you cant just look at peak values, you have to look at the application of torque through the gears over time.
also meaningless is, is the 5250 crossover. now this is purely arbatrary. its based on ftlbs. if it was another unit of torque, the lines may not even cross
now, want proof about hp vs max torque. try to accelerate from 3200rpm to 6000rpm in 3rd gear. (60 to 100mph) Now, try it in 4th gear. 30% less torque to the wheels, even though you are operating more near max torque for more of the curve. (i.e. around 2500RPM TO 4800RPM)
why, HP !!!!!! (and more torque to the wheels at max hp than at max torque) is all based around speed
as far as your last point of "Repeat after me. "It is better to make torque at high rpm than at low rpm, because you can take advantage of *gearing*." :-)" this means, HP!! and more of it. more torque you make at higher rpms means the more hp you are making, and the more torque you can put to the wheels OVER THE OPERATIONAL SPEED RANGE@!!!!
Mk
what was said:
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
"First of all, from a driver's perspective, torque, to use the vernacular, RULES :-). Any given car, in any given gear, will accelerate at a rate that *exactly* matches its torque curve (allowing for increased air and rolling resistance as speeds climb).
Another way of saying this is that a car will accelerate hardest at its torque peak in any given gear, and will not accelerate as hard below that peak, or above it. Torque is the only thing that a driver feels, and horsepower is just sort of an esoteric measurement in that context. 300 foot pounds of torque will accelerate you just as hard at 2000 rpm as it would if you were making that torque at 4000 rpm in the same gear, yet, per the formula, the horsepower would be *double* at 4000 rpm. Therefore, horsepower isn't particularly meaningful from a driver's perspective, and the two numbers only get friendly at 5252 rpm, where horsepower and torque always come out the same.
In contrast to a torque curve (and the matching pushback into your seat), horsepower rises rapidly with rpm, especially when torque values are also climbing. Horsepower will continue to climb, however, until well past the torque peak, and will continue to rise as engine speed climbs, until the torque curve really begins to plummet, faster than engine rpm is rising. However, as I said, horsepower has nothing to do with what a driver *feels*.
You don't believe all this?
Fine. Take your non turbo car (turbo lag muddles the results) to its torque peak in first gear, and punch it. Notice the belt in the back? Now take it to the power peak, and punch it. Notice that the belt in the back is a bit weaker? Fine. Can we go on, now? :-) "
http://vettenet.org/torquehp.html
His summary?
"Repeat after me. "It is better to make torque at high rpm than at low rpm, because you can take advantage of *gearing*." :-)"
If you read on at the above link he goes on to clearly explain how HP works into the equation, and what it 'does'.
Again, the above matches what i've always understood to be the case, just as the link before it does.
Simply stated, i do not agree with your conclusions as i understand them.
Again, i get the distinct feeling we're talking past one another.[/QUOTE]
anyway, yes, your car will pull hardest in each gear at max torque. HOWEVER, this dances right past the subject. the area under the curve is what you have to look at , AND MOST IMPORTANTLY, the speeds. This means, there is a difference between what is produced by the engine and what is output to the wheels through the gears. it is the main reason i brought up an infinitely variable gear box. if you had one, where would the engine and drivetrain pull the hardest??? CERTAINLY not at max torque, but at MAX HP!!! this is of the things you can bring up to ANYONE and debate it with full confidence. why, because in gearing , you cant just look at peak values, you have to look at the application of torque through the gears over time.
also meaningless is, is the 5250 crossover. now this is purely arbatrary. its based on ftlbs. if it was another unit of torque, the lines may not even cross
now, want proof about hp vs max torque. try to accelerate from 3200rpm to 6000rpm in 3rd gear. (60 to 100mph) Now, try it in 4th gear. 30% less torque to the wheels, even though you are operating more near max torque for more of the curve. (i.e. around 2500RPM TO 4800RPM)
why, HP !!!!!! (and more torque to the wheels at max hp than at max torque) is all based around speed
as far as your last point of "Repeat after me. "It is better to make torque at high rpm than at low rpm, because you can take advantage of *gearing*." :-)" this means, HP!! and more of it. more torque you make at higher rpms means the more hp you are making, and the more torque you can put to the wheels OVER THE OPERATIONAL SPEED RANGE@!!!!
Mk
what was said:
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
"First of all, from a driver's perspective, torque, to use the vernacular, RULES :-). Any given car, in any given gear, will accelerate at a rate that *exactly* matches its torque curve (allowing for increased air and rolling resistance as speeds climb).
Another way of saying this is that a car will accelerate hardest at its torque peak in any given gear, and will not accelerate as hard below that peak, or above it. Torque is the only thing that a driver feels, and horsepower is just sort of an esoteric measurement in that context. 300 foot pounds of torque will accelerate you just as hard at 2000 rpm as it would if you were making that torque at 4000 rpm in the same gear, yet, per the formula, the horsepower would be *double* at 4000 rpm. Therefore, horsepower isn't particularly meaningful from a driver's perspective, and the two numbers only get friendly at 5252 rpm, where horsepower and torque always come out the same.
In contrast to a torque curve (and the matching pushback into your seat), horsepower rises rapidly with rpm, especially when torque values are also climbing. Horsepower will continue to climb, however, until well past the torque peak, and will continue to rise as engine speed climbs, until the torque curve really begins to plummet, faster than engine rpm is rising. However, as I said, horsepower has nothing to do with what a driver *feels*.
You don't believe all this?
Fine. Take your non turbo car (turbo lag muddles the results) to its torque peak in first gear, and punch it. Notice the belt in the back? Now take it to the power peak, and punch it. Notice that the belt in the back is a bit weaker? Fine. Can we go on, now? :-) "
http://vettenet.org/torquehp.html
His summary?
"Repeat after me. "It is better to make torque at high rpm than at low rpm, because you can take advantage of *gearing*." :-)"
If you read on at the above link he goes on to clearly explain how HP works into the equation, and what it 'does'.
Again, the above matches what i've always understood to be the case, just as the link before it does.
Simply stated, i do not agree with your conclusions as i understand them.
Again, i get the distinct feeling we're talking past one another.[/QUOTE]
07-07-2005, 03:58 PM
#92
Rennlist Member
I know of bruce augustine. his paper is correct, but misleading as i have mentioned. i sent him a email years ago to clean this paper up as it was being widely misunderstood. no emal back.
however, here is his case for HP. kind of puts things in perspective
remember, you have to look at the entire system and components of accelerating your car faster!
Augustine says in that same link:
The Case For Horsepower
OK. If torque is so all-fired important, why do we care about horsepower?
Because (to quote a friend), "It is better to make torque at high rpm than at low rpm, because you can take advantage of *gearing*.
For an extreme example of this, I'll leave carland for a moment, and describe a waterwheel I got to watch awhile ago. This was a pretty massive wheel (built a couple of hundred years ago), rotating lazily on a shaft which was connected to the works inside a flour mill. Working some things out from what the people in the mill said, I was able to determine that the wheel typically generated about 2600(!) foot pounds of torque. I had clocked its speed, and determined that it was rotating at about 12 rpm. If we hooked that wheel to, say, the drivewheels of a car, that car would go from zero to twelve rpm in a flash, and the waterwheel would hardly notice :-).
On the other hand, twelve rpm of the drivewheels is around one mph for the average car, and, in order to go faster, we'd need to gear it up. To get to 60 mph would require gearing the wheel up enough so that it would be effectively making a little over 43 foot pounds of torque at the output, which is not only a relatively small amount, it's less than what the average car would need in order to actually get to 60. Applying the conversion formula gives us the facts on this. Twelve times twenty six hundred, over five thousand two hundred fifty two gives us:
6 HP.
Oops. Now we see the rest of the story. While it's clearly true that the water wheel can exert a *bunch* of force, its *power* (ability to do work over time) is severely limited.
At The Dragstrip
OK. Back to carland, and some examples of how horsepower makes a major difference in how fast a car can accelerate, in spite of what torque on your backside tells you :-).
http://vettenet.org/torquehp.html
Horsepower is simply an arbitrary(and largely innacurate for that matter) marketing ploy invented by Mr. Watt.
however, here is his case for HP. kind of puts things in perspective
remember, you have to look at the entire system and components of accelerating your car faster!
Augustine says in that same link:
The Case For Horsepower
OK. If torque is so all-fired important, why do we care about horsepower?
Because (to quote a friend), "It is better to make torque at high rpm than at low rpm, because you can take advantage of *gearing*.
For an extreme example of this, I'll leave carland for a moment, and describe a waterwheel I got to watch awhile ago. This was a pretty massive wheel (built a couple of hundred years ago), rotating lazily on a shaft which was connected to the works inside a flour mill. Working some things out from what the people in the mill said, I was able to determine that the wheel typically generated about 2600(!) foot pounds of torque. I had clocked its speed, and determined that it was rotating at about 12 rpm. If we hooked that wheel to, say, the drivewheels of a car, that car would go from zero to twelve rpm in a flash, and the waterwheel would hardly notice :-).
On the other hand, twelve rpm of the drivewheels is around one mph for the average car, and, in order to go faster, we'd need to gear it up. To get to 60 mph would require gearing the wheel up enough so that it would be effectively making a little over 43 foot pounds of torque at the output, which is not only a relatively small amount, it's less than what the average car would need in order to actually get to 60. Applying the conversion formula gives us the facts on this. Twelve times twenty six hundred, over five thousand two hundred fifty two gives us:
6 HP.
Oops. Now we see the rest of the story. While it's clearly true that the water wheel can exert a *bunch* of force, its *power* (ability to do work over time) is severely limited.
At The Dragstrip
OK. Back to carland, and some examples of how horsepower makes a major difference in how fast a car can accelerate, in spite of what torque on your backside tells you :-).
Originally Posted by m21sniper
http://vettenet.org/torquehp.html
Horsepower is simply an arbitrary(and largely innacurate for that matter) marketing ploy invented by Mr. Watt.
07-07-2005, 04:07 PM
#93
Banned
Thread Starter
"again, 500hp cars, one with 250ftlbs, the other with 500ftlbs, which one is faster????? both woiuld be identical as far as accelerative forces."
In simplified terms that's because the torque peak in the 500/500 car is going to come much, much lower in the RPM band than the 500/250 car(ie the 500/500 will produce it's peak torque at 5250rpm, vs the 500/250 having a torque peak of 10,500rpm) and the 500/500 vehicle will therefore have a much more narrow torque curve. If the 500lb-ft of torque came at a comparable RPM wrt the 500/250, then the 500/500 would have double the HP- 1000.
The 500/500 engine would have twice the pulling capacity vs the 500/250 however, and twice the accelerative force at it's torque peak than the 500/250 engine would, but it has a much more narrow torque band(meaning the 500/500 will spend far less time at or near it's torque peak vs the 500/250) which allows the 500/250 to keep up.
Ie, the 500/250 engine is producing it's peak power at a much higher RPM, denoting a much wider and more useful(for racing) power band.
However, the 500/500 would be far superior for a street car wrt general drivability issues.
Now if we had a 750/500 engine the only difference between it and the 500/500 would be that the 750/500 makes it's peak torque at a much higher RPM(7950rpm vs 5250rpm), thereby giving it a much broader torque curve than the 500/500 possesses. Both would possess an identical peak accelerative force, but the 750/500 would spend a much greater amount of time near it's torque peak than the 500/500 does, giving the 750/500 a clear advantadge in average accelerative force.
If you like, HP is merely a measurement of when exactly an engine makes it's peak torque.
In simplified terms that's because the torque peak in the 500/500 car is going to come much, much lower in the RPM band than the 500/250 car(ie the 500/500 will produce it's peak torque at 5250rpm, vs the 500/250 having a torque peak of 10,500rpm) and the 500/500 vehicle will therefore have a much more narrow torque curve. If the 500lb-ft of torque came at a comparable RPM wrt the 500/250, then the 500/500 would have double the HP- 1000.
The 500/500 engine would have twice the pulling capacity vs the 500/250 however, and twice the accelerative force at it's torque peak than the 500/250 engine would, but it has a much more narrow torque band(meaning the 500/500 will spend far less time at or near it's torque peak vs the 500/250) which allows the 500/250 to keep up.
Ie, the 500/250 engine is producing it's peak power at a much higher RPM, denoting a much wider and more useful(for racing) power band.
However, the 500/500 would be far superior for a street car wrt general drivability issues.
Now if we had a 750/500 engine the only difference between it and the 500/500 would be that the 750/500 makes it's peak torque at a much higher RPM(7950rpm vs 5250rpm), thereby giving it a much broader torque curve than the 500/500 possesses. Both would possess an identical peak accelerative force, but the 750/500 would spend a much greater amount of time near it's torque peak than the 500/500 does, giving the 750/500 a clear advantadge in average accelerative force.
If you like, HP is merely a measurement of when exactly an engine makes it's peak torque.
07-07-2005, 04:08 PM
#94
Rennlist Member
sorry, you cant believe everything you read. mechanical air moving devices with 21hp driving them are WAY more than any truck will use. like i said, the cooling needs of our 928s can be done with 300watts. even doubled, or even trippled, its way above the driven fan air flow, and still less than 2hp. want further proof. look at the fans they use at dyno shop. 2-5 hp and when they turn on they make my car idle funny! and can practically blow the hood off the car.. (ie, a lot of air flow).
think of an utral light. those planes are usually only 10hp engines and the thrust will practically knock you over.
21hp in that paper is probably an error, knowing what i do know about fans and air flow. they probably ment to write 2.1 hp.
MK
think of an utral light. those planes are usually only 10hp engines and the thrust will practically knock you over.
21hp in that paper is probably an error, knowing what i do know about fans and air flow. they probably ment to write 2.1 hp.
MK
Originally Posted by m21sniper
"yes, dont get confused on the scales used. they are talking about military applications and much larger vehicles."
Actually, they specifically discuss the Ford Excursion with a 325hp 6.0L diesel, and they mention specifically that it has has 28.5HP electronically controlled viscous clutch fan, which is the primary reason i linked to it.
http://64.233.167.104/search?q=cache...ient=firefox-a
Actually, they specifically discuss the Ford Excursion with a 325hp 6.0L diesel, and they mention specifically that it has has 28.5HP electronically controlled viscous clutch fan, which is the primary reason i linked to it.
http://64.233.167.104/search?q=cache...ient=firefox-a
07-07-2005, 04:09 PM
#95
Banned
Thread Starter
The last few posts makes it quite clear that we're on the same page....and have been all along.
Still had a lot of fun though.
Can we talk nitrous now?
LOL...
Still had a lot of fun though.
Can we talk nitrous now?
LOL...
07-07-2005, 04:14 PM
#96
Rennlist Member
nope? both cars with a similar shaped hp curve (or torque curve) would accelerate exactly the same. and get this, this will blow the minds of all the "torquies" out there. nether one will ever touch their peak torques in a race. both cars will launch, and end up well above max torque and run to redline(passed even max HP) so that both cars will operate at as near max HP as possible. MEANING, if you have a 5000rpm max hp you would shift at 6000rpm providing you had a 2000rpm drop at the next gear and a perfect bell shapped curve around max HP. (lets assume that both cars have this same shaped curve) the high reving 250ftlb car would have max HP at 10000rpm and have to shift at 11,000rpm to keep its operating range, maximizing the most hp under the curve.
both would have identical torque to the driven wheels at any speed. (same gear boxe ratio spreads )
what-cha think now?
MK
both would have identical torque to the driven wheels at any speed. (same gear boxe ratio spreads )
what-cha think now?
MK
Originally Posted by m21sniper
"again, 500hp cars, one with 250ftlbs, the other with 500ftlbs, which one is faster????? both woiuld be identical as far as accelerative forces."
In simplified terms that's because the torque peak in the 500/500 car is going to come much, much lower in the RPM band than the 500/250 car(ie the 500/500 will produce it's peak torque at 5250rpm, vs the 500/250 having a torque peak of 10,500rpm) and the 500/500 vehicle will therefore have a much more narrow torque curve. If the 500lb-ft of torque came at a comparable RPM wrt the 500/250, then the 500/500 would have double the HP- 1000.
The 500/500 engine would have twice the pulling capacity vs the 500/250 however, and twice the accelerative force at it's torque peak than the 500/250 engine would, but it has a much more narrow torque band(meaning the 500/500 will spend far less time at or near it's torque peak vs the 500/250) which allows the 500/250 to keep up.
Ie, the 500/250 engine is producing it's peak power at a much higher RPM, denoting a much wider and more useful(for racing) power band.
However, the 500/500 would be far superior for a street car wrt general drivability issues.
Now if we had a 750/500 engine the only difference between it and the 500/500 would be that the 750/500 makes it's peak torque at a much higher RPM(7950rpm vs 5250rpm), thereby giving it a much broader torque curve than the 500/500 possesses. Both would possess an identical peak accelerative force, but the 750/500 would spend a much greater amount of time near it's torque peak than the 500/500 does, giving the 750/500 a clear advantadge in average accelerative force.
If you like, HP is merely a measurement of when exactly an engine makes it's peak torque.
In simplified terms that's because the torque peak in the 500/500 car is going to come much, much lower in the RPM band than the 500/250 car(ie the 500/500 will produce it's peak torque at 5250rpm, vs the 500/250 having a torque peak of 10,500rpm) and the 500/500 vehicle will therefore have a much more narrow torque curve. If the 500lb-ft of torque came at a comparable RPM wrt the 500/250, then the 500/500 would have double the HP- 1000.
The 500/500 engine would have twice the pulling capacity vs the 500/250 however, and twice the accelerative force at it's torque peak than the 500/250 engine would, but it has a much more narrow torque band(meaning the 500/500 will spend far less time at or near it's torque peak vs the 500/250) which allows the 500/250 to keep up.
Ie, the 500/250 engine is producing it's peak power at a much higher RPM, denoting a much wider and more useful(for racing) power band.
However, the 500/500 would be far superior for a street car wrt general drivability issues.
Now if we had a 750/500 engine the only difference between it and the 500/500 would be that the 750/500 makes it's peak torque at a much higher RPM(7950rpm vs 5250rpm), thereby giving it a much broader torque curve than the 500/500 possesses. Both would possess an identical peak accelerative force, but the 750/500 would spend a much greater amount of time near it's torque peak than the 500/500 does, giving the 750/500 a clear advantadge in average accelerative force.
If you like, HP is merely a measurement of when exactly an engine makes it's peak torque.
07-07-2005, 04:25 PM
#97
Rennlist Member
see my inserts>>>>>>>>> lots of errors below:
>>>>>>>>>>>>>>>>>>no, HP is a unit of measure of power. work over time. engine's peak torques are inconsequential. its all about peak HP and again, area under the HP curve used over the operational range. (ie speed range) AGAIN, give me an infinitely variable gear box, and the engine would run right at max HP and stay there until the end of the run, never seeing max torque on the engine
Mk
Originally Posted by m21sniper
"again, 500hp cars, one with 250ftlbs, the other with 500ftlbs, which one is faster????? both woiuld be identical as far as accelerative forces."
In simplified terms that's because the torque peak in the 500/500 car is going to come much, much lower in the RPM band than the 500/250 car(ie the 500/500 will produce it's peak torque at 5250rpm,
>>>>>>>>>>>>>>>>>>>>5250 doesnt mean peak torque happens. most 5000rpm peak hp car will have max torque in the 4000rpm range.
vs the 500/250 having a torque peak of 10,500rpm)
>>>>>>>>also, the 10000rpm PEAK HP car would then have its peak torque at 8000rpm.
and the 500/500 vehicle will therefore have a much more narrow torque curve. If the 500lb-ft of torque came at a comparable RPM wrt the 500/250, then the 500/500 would have double the HP- 1000.
>>>>>>>>>>>>>>>as we said, both cars have 500hp. this is a real comparison, as there are engines like this.
The 500/500 engine would have twice the pulling capacity vs the 500/250 however,>>>>>>>>>>>>>>>no, the SAME!!!
and twice the accelerative force at it's torque peak than the 500/250 engine would,
>>>>>>>>>>>>>no, the same all the way around. same same same. all th same as it comes out the rear wheels. DUE TO THE SAME HP!
but it has a much more narrow torque band(meaning the 500/500 will spend far less time at or near it's torque peak vs the 500/250) which allows the 500/250 to keep up.
>>>>>>>no, same also. same range, and both will not be near max torque, but near max HP.
Ie, the 500/250 engine is producing it's peak power at a much higher RPM, denoting a much wider and more useful(for racing) power band.
>>>>>>>>>no, same width of power band
However, the 500/500 would be far superior for a street car wrt general drivability issues.
>>>>>>>>>>>>>now, you have something due to aversion of most folks to rev their cars out. high rpms make for forces in the trannie that can make for harder shifting, etc. but this is beyond the point
Now if we had a 750/500 engine the only difference between it and the 500/500 would be that the 750/500 makes it's peak torque at a much higher RPM(7950rpm vs 5250rpm), thereby giving it a much broader torque curve than the 500/500 possesses. Both would possess an identical peak accelerative force, but the 750/500 would spend a much greater amount of time near it's torque peak than the 500/500 does, giving the 750/500 a clear advantadge in average accelerative force.
>>>>>>>>>>>>>>>>there are plenty peak torque engines that have USELESS torque in the 3500rpm range (like a DEVEK stroker) if both cars have the same hp, they will accelerate the same in race conditions. most likely, in our cars, from 5000rpm to 6500rpm. however, in street applications, its nice to have this engine torque, however, accelerative torque to the wheels is usually the same if the curves uptop are close.
If you like, HP is merely a measurement of when exactly an engine makes it's peak torque.
In simplified terms that's because the torque peak in the 500/500 car is going to come much, much lower in the RPM band than the 500/250 car(ie the 500/500 will produce it's peak torque at 5250rpm,
>>>>>>>>>>>>>>>>>>>>5250 doesnt mean peak torque happens. most 5000rpm peak hp car will have max torque in the 4000rpm range.
vs the 500/250 having a torque peak of 10,500rpm)
>>>>>>>>also, the 10000rpm PEAK HP car would then have its peak torque at 8000rpm.
and the 500/500 vehicle will therefore have a much more narrow torque curve. If the 500lb-ft of torque came at a comparable RPM wrt the 500/250, then the 500/500 would have double the HP- 1000.
>>>>>>>>>>>>>>>as we said, both cars have 500hp. this is a real comparison, as there are engines like this.
The 500/500 engine would have twice the pulling capacity vs the 500/250 however,>>>>>>>>>>>>>>>no, the SAME!!!
and twice the accelerative force at it's torque peak than the 500/250 engine would,
>>>>>>>>>>>>>no, the same all the way around. same same same. all th same as it comes out the rear wheels. DUE TO THE SAME HP!
but it has a much more narrow torque band(meaning the 500/500 will spend far less time at or near it's torque peak vs the 500/250) which allows the 500/250 to keep up.
>>>>>>>no, same also. same range, and both will not be near max torque, but near max HP.
Ie, the 500/250 engine is producing it's peak power at a much higher RPM, denoting a much wider and more useful(for racing) power band.
>>>>>>>>>no, same width of power band
However, the 500/500 would be far superior for a street car wrt general drivability issues.
>>>>>>>>>>>>>now, you have something due to aversion of most folks to rev their cars out. high rpms make for forces in the trannie that can make for harder shifting, etc. but this is beyond the point
Now if we had a 750/500 engine the only difference between it and the 500/500 would be that the 750/500 makes it's peak torque at a much higher RPM(7950rpm vs 5250rpm), thereby giving it a much broader torque curve than the 500/500 possesses. Both would possess an identical peak accelerative force, but the 750/500 would spend a much greater amount of time near it's torque peak than the 500/500 does, giving the 750/500 a clear advantadge in average accelerative force.
>>>>>>>>>>>>>>>>there are plenty peak torque engines that have USELESS torque in the 3500rpm range (like a DEVEK stroker) if both cars have the same hp, they will accelerate the same in race conditions. most likely, in our cars, from 5000rpm to 6500rpm. however, in street applications, its nice to have this engine torque, however, accelerative torque to the wheels is usually the same if the curves uptop are close.
If you like, HP is merely a measurement of when exactly an engine makes it's peak torque.
Mk
07-07-2005, 04:26 PM
#98
Rennlist Member
NOS!!!! love it. got to get some for the HOLBERT car! maybe ill fill the roll cage with NOS and plumb it!
ask away
MK
ask away
MK
Originally Posted by m21sniper
The last few posts makes it quite clear that we're on the same page....and have been all along.
Still had a lot of fun though.
Can we talk nitrous now?
LOL...
Still had a lot of fun though.
Can we talk nitrous now?
LOL...
07-07-2005, 04:31 PM
#99
Banned
Thread Starter
"sorry, you cant believe everything you read. mechanical air moving devices with 21hp driving them are WAY more than any truck will use. like i said, the cooling needs of our 928s can be done with 300watts. even doubled, or even trippled, its way above the driven fan air flow, and still less than 2hp. want further proof. look at the fans they use at dyno shop. 2-5 hp and when they turn on they make my car idle funny! and can practically blow the hood off the car.. (ie, a lot of air flow).
think of an utral light. those planes are usually only 10hp engines and the thrust will practically knock you over.
21hp in that paper is probably an error, knowing what i do know about fans and air flow. they probably ment to write 2.1 hp.
MK"
It's an official US Gov't DoD report, i highly doubt it has any typographical errors in it.
Further, if you read the paper it's obvious they meant 28.5 hp(read the summary in the expedition portion of the findings, part 7.0, they not only repeat the HP savings for each component removed, but also convert them to Newton meters and tally up the complete savings in parasitic loss).
It's a safe bet that whatever you and i know about parasitic loss, the DoD knows about oh.....1000x more.
think of an utral light. those planes are usually only 10hp engines and the thrust will practically knock you over.
21hp in that paper is probably an error, knowing what i do know about fans and air flow. they probably ment to write 2.1 hp.
MK"
It's an official US Gov't DoD report, i highly doubt it has any typographical errors in it.
Further, if you read the paper it's obvious they meant 28.5 hp(read the summary in the expedition portion of the findings, part 7.0, they not only repeat the HP savings for each component removed, but also convert them to Newton meters and tally up the complete savings in parasitic loss).
It's a safe bet that whatever you and i know about parasitic loss, the DoD knows about oh.....1000x more.
07-07-2005, 04:49 PM
#100
Banned
Thread Starter
"no, HP is a unit of measure of power. work over time. engine's peak torques are inconsequential(emphasis added). its all about peak HP and again, area under the HP curve used over the operational range."
HP is not a measure of absolute power, torque is.
HP is a measure of force applied over time. Specifically 1 hp is the ability to lift 33,000lb 1 foot in 1 minute(or any applicable combination thereof).
As far as peak torque being completely inconsequential, you are completely wrong, as i have amply demonstrated with several links now. Links which you call 'misleading', but to me, there is nothing misleading about them at all. They are very, very clear in what they are saying, and i find no problem with their conclusions. Indeed, they mimic what i learned in trade school, and they mimic everything i've ever heard anyone knowledgeable in the subject state.
"AGAIN, give me an infinitely variable gear box, and the engine would run right at max HP and stay there until the end of the run, never seeing max torque on the engine"
Infinitely variable transmissions already exist. Subaru introduced them in 1989(Justy). It's called a CVT(Continuously variable transmission), and is chain driven.
http://auto.howstuffworks.com/cvt9.htm
BTW, CVTs do not work like you think they do.(check out the RPM to speed graphic in the above link).
RPM increases steadily from idle with vehicle speed, and the vehicle hits it's redline at max vehicle speed. A CVT DOES NOT hold the engine at it's HP(or torque) peak at all times....that's simply not how a CVT works.
Believe me, i've worked on a few of them.
Further, acceleration is at it's greatest at the torque peak, end of story. If you disagree, you are quite misinformed.
HP is not a measure of absolute power, torque is.
HP is a measure of force applied over time. Specifically 1 hp is the ability to lift 33,000lb 1 foot in 1 minute(or any applicable combination thereof).
As far as peak torque being completely inconsequential, you are completely wrong, as i have amply demonstrated with several links now. Links which you call 'misleading', but to me, there is nothing misleading about them at all. They are very, very clear in what they are saying, and i find no problem with their conclusions. Indeed, they mimic what i learned in trade school, and they mimic everything i've ever heard anyone knowledgeable in the subject state.
"AGAIN, give me an infinitely variable gear box, and the engine would run right at max HP and stay there until the end of the run, never seeing max torque on the engine"
Infinitely variable transmissions already exist. Subaru introduced them in 1989(Justy). It's called a CVT(Continuously variable transmission), and is chain driven.
http://auto.howstuffworks.com/cvt9.htm
BTW, CVTs do not work like you think they do.(check out the RPM to speed graphic in the above link).
RPM increases steadily from idle with vehicle speed, and the vehicle hits it's redline at max vehicle speed. A CVT DOES NOT hold the engine at it's HP(or torque) peak at all times....that's simply not how a CVT works.
Believe me, i've worked on a few of them.
Further, acceleration is at it's greatest at the torque peak, end of story. If you disagree, you are quite misinformed.
07-07-2005, 04:58 PM
#101
Three Wheelin'
I would think it would be hugely annoying to drive a CVT equipped car if it was at near redline all the time. Not my idea of relaxing at all.
Interesting reading you two.
Interesting reading you two.
07-07-2005, 05:13 PM
#102
Banned
Thread Starter
"nope? both cars with a similar shaped hp curve (or torque curve) would accelerate exactly the same. and get this, this will blow the minds of all the "torquies" out there. nether one will ever touch their peak torques in a race. both cars will launch, and end up well above max torque and run to redline(passed even max HP) so that both cars will operate at as near max HP as possible."
First of all, in order to achieve engine redline then by definition you are going to hit(then pass) your torque peak. End of story. No room for interpretation.
"MEANING, if you have a 5000rpm max hp you would shift at 6000rpm providing you had a 2000rpm drop at the next gear and a perfect bell shapped curve around max HP. (lets assume that both cars have this same shaped curve) the high reving 250ftlb car would have max HP at 10000rpm and have to shift at 11,000rpm to keep its operating range, maximizing the most hp under the curve."
Except that both cars WILL NOT EVER have a similar torque or power curve, by their already defined operating RPM ranges(idle to about 6000rpm vs idle to about 11,000rpm) it's completely impossible.
At 5250rpm the 500/500 will be producing double the torque than the 500/250 is ever capable of producing AT ANY POINT IN IT'S RPM RANGE.
That my friend, is not subject to debate.
"both would have identical torque to the driven wheels at any speed. (same gear boxe ratio spreads )"
Wrong. Tell me Mark, at what engine speed will the 500/250 EVER produce 500ft-lbs of flywheel torque? These cars are geared identically. That means that at it's torque peak in top gear(let's assume a 1:1) the 500/500 will deliver 2000lbs-ft of torque (assuming no parasitic loss and a 4:1 final drive ratio) to the rear wheels, whereas the 500/250 can at no point match that level of power in top gear with the same final drive ratio. The 500/250 will deliver a maximum of 1000lb-ft of torque at it's torque peak with a 4:1 final drive ratio...exactly half that of the 500/500 powered car.
what-cha think now?"
I think you're either pulling my leg...or you're crazy.
First of all, in order to achieve engine redline then by definition you are going to hit(then pass) your torque peak. End of story. No room for interpretation.
"MEANING, if you have a 5000rpm max hp you would shift at 6000rpm providing you had a 2000rpm drop at the next gear and a perfect bell shapped curve around max HP. (lets assume that both cars have this same shaped curve) the high reving 250ftlb car would have max HP at 10000rpm and have to shift at 11,000rpm to keep its operating range, maximizing the most hp under the curve."
Except that both cars WILL NOT EVER have a similar torque or power curve, by their already defined operating RPM ranges(idle to about 6000rpm vs idle to about 11,000rpm) it's completely impossible.
At 5250rpm the 500/500 will be producing double the torque than the 500/250 is ever capable of producing AT ANY POINT IN IT'S RPM RANGE.
That my friend, is not subject to debate.
"both would have identical torque to the driven wheels at any speed. (same gear boxe ratio spreads )"
Wrong. Tell me Mark, at what engine speed will the 500/250 EVER produce 500ft-lbs of flywheel torque? These cars are geared identically. That means that at it's torque peak in top gear(let's assume a 1:1) the 500/500 will deliver 2000lbs-ft of torque (assuming no parasitic loss and a 4:1 final drive ratio) to the rear wheels, whereas the 500/250 can at no point match that level of power in top gear with the same final drive ratio. The 500/250 will deliver a maximum of 1000lb-ft of torque at it's torque peak with a 4:1 final drive ratio...exactly half that of the 500/500 powered car.
what-cha think now?"
I think you're either pulling my leg...or you're crazy.
07-07-2005, 05:14 PM
#103
Rennlist Member
ONLY IN a particular gear. Now it feels like im beating my head against the wall.
over all greatest acceleation through gears will not operate an engine at peak torque at all. this is known. agree?
Mk
over all greatest acceleation through gears will not operate an engine at peak torque at all. this is known. agree?
Mk
Originally Posted by m21sniper
"
Further, acceleration is at it's greatest at the torque peak, end of story. If you disagree, you are quite misinformed.
Further, acceleration is at it's greatest at the torque peak, end of story. If you disagree, you are quite misinformed.
07-07-2005, 05:22 PM
#104
Banned
Thread Starter
"over all greatest acceleation through gears will not operate an engine at peak torque at all. this is known. agree? "
The momentary peak of absolute accelerative force occurs precisely at the point of maximum torque delivery, ie, the torque peak.
From the link i posted earlier:
"Another way of saying this is that a car will accelerate hardest at its torque peak in any given gear, and will not accelerate as hard below that peak, or above it. Torque is the only thing that a driver feels, and horsepower is just sort of an esoteric measurement in that context. 300 foot pounds of torque will accelerate you just as hard at 2000 rpm as it would if you were making that torque at 4000 rpm in the same gear, yet, per the formula, the horsepower would be *double* at 4000 rpm. Therefore, horsepower isn't particularly meaningful from a driver's perspective, and the two numbers only get friendly at 5252 rpm, where horsepower and torque always come out the same."
Average acceleration is not the same as peak momentary acceleration though, that much we agree on....and that's what allows the 500/250 engine to run dead even with the 500/500 engine because the 500/250 has a greater average accelerative force.
However, at their absolute torque peaks, the 500/500 will deliver exactly double the accelerative force in G's than the 500/250 will.
That's simple physics.
The momentary peak of absolute accelerative force occurs precisely at the point of maximum torque delivery, ie, the torque peak.
From the link i posted earlier:
"Another way of saying this is that a car will accelerate hardest at its torque peak in any given gear, and will not accelerate as hard below that peak, or above it. Torque is the only thing that a driver feels, and horsepower is just sort of an esoteric measurement in that context. 300 foot pounds of torque will accelerate you just as hard at 2000 rpm as it would if you were making that torque at 4000 rpm in the same gear, yet, per the formula, the horsepower would be *double* at 4000 rpm. Therefore, horsepower isn't particularly meaningful from a driver's perspective, and the two numbers only get friendly at 5252 rpm, where horsepower and torque always come out the same."
Average acceleration is not the same as peak momentary acceleration though, that much we agree on....and that's what allows the 500/250 engine to run dead even with the 500/500 engine because the 500/250 has a greater average accelerative force.
However, at their absolute torque peaks, the 500/500 will deliver exactly double the accelerative force in G's than the 500/250 will.
That's simple physics.
07-07-2005, 05:32 PM
#105
Banned
Thread Starter
"NOS!!!! love it. got to get some for the HOLBERT car! maybe ill fill the roll cage with NOS and plumb it!
ask away"
Earlier you mentioned you used a nitrous works system. It would be helpful to me to know which one(they seem to make 5 or 6 different systems), because i'd like to use the same exact setup you did, if at all possible.
I figure the devil that you know is far superior to the devil that i don't.
I've only ever juiced one car, a carburated 350 Chevy which is a vastly different application than an EFI Porsche,
so i'd like to go with a proven performing system that actual 928 users have had success with.
So question 1 is, what Nitrous works system specifically did you use?
Also, what device did you use to achieve suitable timing retard?
Thanx man, i really appreciate any help you can offer me on this topic, because Nitrous systems are something i don't know much about.
ask away"
Earlier you mentioned you used a nitrous works system. It would be helpful to me to know which one(they seem to make 5 or 6 different systems), because i'd like to use the same exact setup you did, if at all possible.
I figure the devil that you know is far superior to the devil that i don't.
I've only ever juiced one car, a carburated 350 Chevy which is a vastly different application than an EFI Porsche,
so i'd like to go with a proven performing system that actual 928 users have had success with.
So question 1 is, what Nitrous works system specifically did you use?
Also, what device did you use to achieve suitable timing retard?
Thanx man, i really appreciate any help you can offer me on this topic, because Nitrous systems are something i don't know much about.