Who thinks they understand the difference between Tq and horsepower....
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Originally Posted by power2weight
[engineer]
As far as gearing is concerned, you may notice that you can half the speed of any shaft, and under the same input conditions double the torque. The HP figure however, will remain unchanged. Another free-body diagram would show this nicely. As an engine revs several times through the power band over its pass down a 1/4 mile, peak acceleration is found when the TQ numbers are highest (without accounting for traction, aero drag).[/engineer]
As far as gearing is concerned, you may notice that you can half the speed of any shaft, and under the same input conditions double the torque. The HP figure however, will remain unchanged. Another free-body diagram would show this nicely. As an engine revs several times through the power band over its pass down a 1/4 mile, peak acceleration is found when the TQ numbers are highest (without accounting for traction, aero drag).[/engineer]
you were right, until this paragraph (and you are still half-right).
peak acceleration at any given speed occurs at the POWER PEAK, not the torque peak.
peak acceleration in any given gear happens at the torque peak.
the way to get the MOST acceleration out of a car with CVT is to hold the engine at the power peak, not the torque peak.
a way i have for years paraphrased something you said in your post:
gearing can compensate for torque. there is no compensation for horsepower, thus horsepower is ultimately the limiting factor of acceleration. not torque.
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Originally Posted by Frank
Wussy! Having an excessive amount of torque in the low band is what makes a car/bike fun. You just never know what's going to happen when you stomp that pedal or twist that grip.
Having an excessive amount of torque in the low band is also necessary when you have a 4500lb Cadillac. Powerband from 500rpm to 3500rpm kicks ass! 2.14 ring gear and 0.68 overdrive inna house!
Having an excessive amount of torque in the low band is also necessary when you have a 4500lb Cadillac. Powerband from 500rpm to 3500rpm kicks ass! 2.14 ring gear and 0.68 overdrive inna house!
if the torque is NEEDED to move a 4500lbs car, it's not really excessive, is it.
it's all relative. a 4500 lbs cadillac will need more low-end torque for tractability than a 1200 lbs formula car.
the intent of the vehicle is a factor too. most 1200 lbs formula cars don't start from a standstill often (especially given that MOST formula car races involve a sprint race format with a rolling start). i am sure cadillacs see their fair share of red lights.
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Originally Posted by shadowboy
if the torque is NEEDED to move a 4500lbs car, it's not really excessive, is it.
it's all relative. a 4500 lbs cadillac will need more torque for tractability than a 1200 lbs formula car.
it's all relative. a 4500 lbs cadillac will need more torque for tractability than a 1200 lbs formula car.
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Once again, USABLE power... IE 1000 RWHP Supra running 12.X but at 120 mph.
Torque doesnt come on soon enough in the powerband, and also why a mustang can run a 12.X but at@105 mph, where the torque comes on early and makes it accelerate and use the torque for 5000 rpms not just 1000rpms like the Supra(not saying ALL supras or ALL Mustangs but all SRT-4s run 11s, math that!)
Torque doesnt come on soon enough in the powerband, and also why a mustang can run a 12.X but at@105 mph, where the torque comes on early and makes it accelerate and use the torque for 5000 rpms not just 1000rpms like the Supra(not saying ALL supras or ALL Mustangs but all SRT-4s run 11s, math that!)
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Originally Posted by En-GLaived
Once again, USABLE power... IE 1000 RWHP Supra running 12.X but at 120 mph.
Torque doesnt come on soon enough in the powerband, and also why a mustang can run a 12.X but at@105 mph, where the torque comes on early and makes it accelerate and use the torque for 5000 rpms not just 1000rpms like the Supra(not saying ALL supras or ALL Mustangs but all SRT-4s run 11s, math that!)
Torque doesnt come on soon enough in the powerband, and also why a mustang can run a 12.X but at@105 mph, where the torque comes on early and makes it accelerate and use the torque for 5000 rpms not just 1000rpms like the Supra(not saying ALL supras or ALL Mustangs but all SRT-4s run 11s, math that!)
A car running low ETs and low traps is coming out of the hole good while a car with the same ET and a higher MPH is spinning.
In your example, if the Supra ran slow because of it's narrow powerband it would also have shit for trap speeds as well.
That's oversimplifying things alot, but it's the basic idea.
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Originally Posted by NegativeGeForce
I think having a good amount if displacment, and then having a very good topend works well taking a car through the turns off boost gently, and them stomping it in the straights with maximum topend power.
A large amount of displacment would work in a track car, but would require more care with the power.
Drag cars work best with larger dislacment because you can control the launch better with alot of torque...unlike a boosted small engine witch requires brake boosting or slipping the clutch to get any good of a launch.
From a roll, a larger displacment engine wont perform as well as a topend machine because you have the lower powerband of the v8 wich is more suited for a fast launch vs the topend machine that likes its power in the higher revs and speeds.
There isnt such a thing as the fastest all around car in the world. The super cars of the world can get easily wipped by the high displacment drag cars of today...likewise I wanna see a drag car go against a ferrari on a curcuit.
Thats why theres a million different cars and engines...not everone llikes to drag race, not everyone likes to road race, and some people just want to fucking get to work without worrying
A large amount of displacment would work in a track car, but would require more care with the power.
Drag cars work best with larger dislacment because you can control the launch better with alot of torque...unlike a boosted small engine witch requires brake boosting or slipping the clutch to get any good of a launch.
From a roll, a larger displacment engine wont perform as well as a topend machine because you have the lower powerband of the v8 wich is more suited for a fast launch vs the topend machine that likes its power in the higher revs and speeds.
There isnt such a thing as the fastest all around car in the world. The super cars of the world can get easily wipped by the high displacment drag cars of today...likewise I wanna see a drag car go against a ferrari on a curcuit.
Thats why theres a million different cars and engines...not everone llikes to drag race, not everyone likes to road race, and some people just want to fucking get to work without worrying
damn good explanation man. damn nice supra too
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People have already covered the hp vs tq thing pretty well, hmm, gearing and powerband.
The gearing is there to allow the engine to operate in its peak powerband at different speeds. If there was no gearing, the engine would have to start accelerating the car from idle and slowly work its way up until hitting the top speed at redline. If the car was geared to cruise at 80 it would be impossibly slow off the line, if it was geared to accelerate you'd have drive down the interstate at 7k rpm. With gearing you can put more torque down at lower speeds and still turn acceptable rpms at higher speeds, and you can accelerate using close to peak power at any point in the speed range by selecting the proper gear, whereas there would only be one point in the speed range where that was true without gearing.
The best setup for gearing is one that allows you to accelerate while staying as close to the power peak as possible with each gear change. For something like the quarter mile, It should be set up so that the gear you end the quarter mile in is just tall enough to give you headroom for your trap speed, with the appropriate ratio changes between gears to keep the engine as close to peak power as possible. In road racing other considerations would come into play, you'd want the gearing to give you useful upshift and downshift options in the speed range you'll be in most often, and considerations on not getting caught out in certain corners might change the gear ratios you'd choose. There's got to be a lot more to this one, but I can only guess at it because I have no experience with it.
The wider the peak powerband of the engine, the better, but gearing can make up for a narrow powerband. As long as the powerband is wide enough that you can stay close to the peak without dropping to an area with dramatically less power on a shift, you're good. The problem with a lot of dyno queens is that they have too peaky a powerband- like turbo supras that make 800hp but only from 7-8k rpm. It would require more gears than will fit in their gearbox to keep the engine in a powerband that narrow and all that shift time would add up. Depending on the max operating rpm of the engine, usually a 3k rpm range near peak power is good enough to keep it in the power with the stock tranny on cars that come from the factory with a 7k or higher redline, on cars with a 6k redline like a lot of domestics it may be 2500 rpm or even less. Depending on the power curve, the fastest way down the track may be shifting after the power peak while the power is dropping- it all depends on the gear ratios. You have to look at the power the engine makes and figure out shift points to put down the most average power down the length of the track.
The gearing is there to allow the engine to operate in its peak powerband at different speeds. If there was no gearing, the engine would have to start accelerating the car from idle and slowly work its way up until hitting the top speed at redline. If the car was geared to cruise at 80 it would be impossibly slow off the line, if it was geared to accelerate you'd have drive down the interstate at 7k rpm. With gearing you can put more torque down at lower speeds and still turn acceptable rpms at higher speeds, and you can accelerate using close to peak power at any point in the speed range by selecting the proper gear, whereas there would only be one point in the speed range where that was true without gearing.
The best setup for gearing is one that allows you to accelerate while staying as close to the power peak as possible with each gear change. For something like the quarter mile, It should be set up so that the gear you end the quarter mile in is just tall enough to give you headroom for your trap speed, with the appropriate ratio changes between gears to keep the engine as close to peak power as possible. In road racing other considerations would come into play, you'd want the gearing to give you useful upshift and downshift options in the speed range you'll be in most often, and considerations on not getting caught out in certain corners might change the gear ratios you'd choose. There's got to be a lot more to this one, but I can only guess at it because I have no experience with it.
The wider the peak powerband of the engine, the better, but gearing can make up for a narrow powerband. As long as the powerband is wide enough that you can stay close to the peak without dropping to an area with dramatically less power on a shift, you're good. The problem with a lot of dyno queens is that they have too peaky a powerband- like turbo supras that make 800hp but only from 7-8k rpm. It would require more gears than will fit in their gearbox to keep the engine in a powerband that narrow and all that shift time would add up. Depending on the max operating rpm of the engine, usually a 3k rpm range near peak power is good enough to keep it in the power with the stock tranny on cars that come from the factory with a 7k or higher redline, on cars with a 6k redline like a lot of domestics it may be 2500 rpm or even less. Depending on the power curve, the fastest way down the track may be shifting after the power peak while the power is dropping- it all depends on the gear ratios. You have to look at the power the engine makes and figure out shift points to put down the most average power down the length of the track.
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Originally Posted by Jordan Y.
People have already covered the hp vs tq thing pretty well, hmm, gearing and powerband.
The gearing is there to allow the engine to operate in its peak powerband at different speeds. If there was no gearing, the engine would have to start accelerating the car from idle and slowly work its way up until hitting the top speed at redline. If the car was geared to cruise at 80 it would be impossibly slow off the line, if it was geared to accelerate you'd have drive down the interstate at 7k rpm. With gearing you can put more torque down at lower speeds and still turn acceptable rpms at higher speeds, and you can accelerate using close to peak power at any point in the speed range by selecting the proper gear, whereas there would only be one point in the speed range where that was true without gearing.
The best setup for gearing is one that allows you to accelerate while staying as close to the power peak as possible with each gear change. For something like the quarter mile, It should be set up so that the gear you end the quarter mile in is just tall enough to give you headroom for your trap speed, with the appropriate ratio changes between gears to keep the engine as close to peak power as possible. In road racing other considerations would come into play, you'd want the gearing to give you useful upshift and downshift options in the speed range you'll be in most often, and considerations on not getting caught out in certain corners might change the gear ratios you'd choose. There's got to be a lot more to this one, but I can only guess at it because I have no experience with it.
The wider the peak powerband of the engine, the better, but gearing can make up for a narrow powerband. As long as the powerband is wide enough that you can stay close to the peak without dropping to an area with dramatically less power on a shift, you're good. The problem with a lot of dyno queens is that they have too peaky a powerband- like turbo supras that make 800hp but only from 7-8k rpm. It would require more gears than will fit in their gearbox to keep the engine in a powerband that narrow and all that shift time would add up. Depending on the max operating rpm of the engine, usually a 3k rpm range near peak power is good enough to keep it in the power with the stock tranny on cars that come from the factory with a 7k or higher redline, on cars with a 6k redline like a lot of domestics it may be 2500 rpm or even less. Depending on the power curve, the fastest way down the track may be shifting after the power peak while the power is dropping- it all depends on the gear ratios. You have to look at the power the engine makes and figure out shift points to put down the most average power down the length of the track.
The gearing is there to allow the engine to operate in its peak powerband at different speeds. If there was no gearing, the engine would have to start accelerating the car from idle and slowly work its way up until hitting the top speed at redline. If the car was geared to cruise at 80 it would be impossibly slow off the line, if it was geared to accelerate you'd have drive down the interstate at 7k rpm. With gearing you can put more torque down at lower speeds and still turn acceptable rpms at higher speeds, and you can accelerate using close to peak power at any point in the speed range by selecting the proper gear, whereas there would only be one point in the speed range where that was true without gearing.
The best setup for gearing is one that allows you to accelerate while staying as close to the power peak as possible with each gear change. For something like the quarter mile, It should be set up so that the gear you end the quarter mile in is just tall enough to give you headroom for your trap speed, with the appropriate ratio changes between gears to keep the engine as close to peak power as possible. In road racing other considerations would come into play, you'd want the gearing to give you useful upshift and downshift options in the speed range you'll be in most often, and considerations on not getting caught out in certain corners might change the gear ratios you'd choose. There's got to be a lot more to this one, but I can only guess at it because I have no experience with it.
The wider the peak powerband of the engine, the better, but gearing can make up for a narrow powerband. As long as the powerband is wide enough that you can stay close to the peak without dropping to an area with dramatically less power on a shift, you're good. The problem with a lot of dyno queens is that they have too peaky a powerband- like turbo supras that make 800hp but only from 7-8k rpm. It would require more gears than will fit in their gearbox to keep the engine in a powerband that narrow and all that shift time would add up. Depending on the max operating rpm of the engine, usually a 3k rpm range near peak power is good enough to keep it in the power with the stock tranny on cars that come from the factory with a 7k or higher redline, on cars with a 6k redline like a lot of domestics it may be 2500 rpm or even less. Depending on the power curve, the fastest way down the track may be shifting after the power peak while the power is dropping- it all depends on the gear ratios. You have to look at the power the engine makes and figure out shift points to put down the most average power down the length of the track.
very well said.
one caveat though..
top fuel drag cars don't have gear ratios. they are direct drive (just a clutch & differential).
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The answer to your question is sqrt(pi)
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Originally Posted by shadowboy
you were right, until this paragraph (and you are still half-right).
peak acceleration at any given speed occurs at the POWER PEAK, not the torque peak.
peak acceleration in any given gear happens at the torque peak.
peak acceleration at any given speed occurs at the POWER PEAK, not the torque peak.
peak acceleration in any given gear happens at the torque peak.
HP just means that the TQ is available at a high enough RPM to push the car to high speeds and multiply to ludicrous torque in low gear.
F = m * a, where F = TQ in the case of a car.
