I know this thread has been posted before and i kinda got an idea what torque is being that you feel and what gets you off the line. But with all these superchargers and turbos out what really makes the difference? Lets say you have higher HP than torque like most the 3.5 superchargers produce? Or higher torque than HP? What will you notice in both situations? Why is HP even important? Thanks
dejuan7
This is an age old debate and if you really want a better understanding I would suggest just doing and internet search and reading some articles on it since it can get rather lengthy. What you will find out is that both are important along with how and when each is utilized. This should get you started: http://auto.howstuffworks.com/auto-parts/towing/towing-capacity/information/fpte5.htm
Man forgive me but i have no clue what that means. Im just wanting to know the difference in driving a car with a higher HP with lower torque vs. driving a car with higher torque and lower hp. Like if a car has 350 HP with 370tq or 323hp with 280tq.
Cool so lets say something wild like i had 500 hp with only 250tq would that mean it would take longer to get going? lol Then eventually getting fast?
Aw ok now it makes sense. Sorry i know it makes everyone mad when these type of threads are posted. I just wish i knew more about cars besides wanting them to be fast but not knowing the basics of an engine. Maybe in my next life lol
Torque is what gets you moving off the line...horsepower is what keeps you moving, in simple terms. Yes, there is always torque present, just in varying amounts.
Compare to getting a nut or a bolt to loosen, it requires torque on your part to "free" it but once it has been turned, it no longer requires the same amount of torque...simply turning it off the rest of the way is, in a simple way, what horsepower is. Very simple terms... does that make sense?
Horsepower is a product of torque.
Compare to getting a nut or a bolt to loosen, it requires torque on your part to "free" it but once it has been turned, it no longer requires the same amount of torque...simply turning it off the rest of the way is, in a simple way, what horsepower is. Very simple terms... does that make sense?
Horsepower is a product of torque.
As an automotive engineer, I've thought of different ways to explain this, but here's the best way I've found:
Torque is how HARD the engine is turning
RPM is how FAST the engine is turning
Horsepower is nothing more than the product of the two
In other words, an engine spinning twice as fast and half as hard is making the same power as an engine spinning half as fast and twice as hard. Thus, you can get a 2.0L four cylinder in a Honda S2000 to make 240 hp, the same as your average 3.5-4.0L V6, because it produces it's torque so FAST.
Torque and horsepower are related, but are different entities. You can't say an engine has "more torque than horsepower". That would be like saying you had more height than money. The number of one might be higher than the other, but that depends on the units: lb-ft or Nm, hp or kW.
If torque was constant (say, 300 lb-ft), acceleration would be constant in any given gear, but horsepower would be climbing with RPM (100, 200, 300, etc). Torque is what you actually feel, horsepower is a way to take into account the speed it's being delivered at. So, a 300 lb-ft car with 150 hp would accelerate at the same rate in the same gear as an identical car with 300 lb-ft and 300 hp, but for only half as long. The 300hp car would destroy it because it can keep up that given acceleration for twice as long.
Sorry for the windy post, but maybe this helps! My senior design project was a dynamometer, so this is close to my heart.
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Torque is how HARD the engine is turning
RPM is how FAST the engine is turning
Horsepower is nothing more than the product of the two
In other words, an engine spinning twice as fast and half as hard is making the same power as an engine spinning half as fast and twice as hard. Thus, you can get a 2.0L four cylinder in a Honda S2000 to make 240 hp, the same as your average 3.5-4.0L V6, because it produces it's torque so FAST.
Torque and horsepower are related, but are different entities. You can't say an engine has "more torque than horsepower". That would be like saying you had more height than money. The number of one might be higher than the other, but that depends on the units: lb-ft or Nm, hp or kW.
If torque was constant (say, 300 lb-ft), acceleration would be constant in any given gear, but horsepower would be climbing with RPM (100, 200, 300, etc). Torque is what you actually feel, horsepower is a way to take into account the speed it's being delivered at. So, a 300 lb-ft car with 150 hp would accelerate at the same rate in the same gear as an identical car with 300 lb-ft and 300 hp, but for only half as long. The 300hp car would destroy it because it can keep up that given acceleration for twice as long.
Sorry for the windy post, but maybe this helps! My senior design project was a dynamometer, so this is close to my heart.
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All things truly equal; vehicle, torque, weather, conditions, driver, etc, the higher hp car will always win.
Remember, you can trade RPM for torque and vice-versa with gearing, but HORSEPOWER IS FIXED. In other words, if car A has 400 hp and 300 lb-ft of torque, it will beat an identical sized car B with 300 hp and 300 lb-ft of torque in one of two ways:
Car A can have the same gear ratio as Car B. In this case, they will initially accelerate at the same rate, but Car A will be able to keep it up longer while Car B has to shift to a higher gear since it runs out of RPM. Car A will pull away.
Car A can have more gear ratio, making the torque at the tires greater than Car B but maintain it up to the same speed. It will accelerate faster right off the bat, and shift at the same speed.
So you can get a tiny 4 cylinder to make 400 hp, but it will have to rev very high and be geared very low, and that makes for a BAD driving experience (noisy, jumpy, bad gas mileage, etc). Having good low-end torque is MUCH more fun and usable. If it can ALSO keep it up into higher revs, you have a great engine. Long live the HEMI.
Remember, you can trade RPM for torque and vice-versa with gearing, but HORSEPOWER IS FIXED. In other words, if car A has 400 hp and 300 lb-ft of torque, it will beat an identical sized car B with 300 hp and 300 lb-ft of torque in one of two ways:
Car A can have the same gear ratio as Car B. In this case, they will initially accelerate at the same rate, but Car A will be able to keep it up longer while Car B has to shift to a higher gear since it runs out of RPM. Car A will pull away.
Car A can have more gear ratio, making the torque at the tires greater than Car B but maintain it up to the same speed. It will accelerate faster right off the bat, and shift at the same speed.
So you can get a tiny 4 cylinder to make 400 hp, but it will have to rev very high and be geared very low, and that makes for a BAD driving experience (noisy, jumpy, bad gas mileage, etc). Having good low-end torque is MUCH more fun and usable. If it can ALSO keep it up into higher revs, you have a great engine. Long live the HEMI.
In basic terms, torque is low end power, horespower is more for high end. At the track you can have a the same E/T with the same car with both combinations, but one will have a higher trap (MPH) in the 1/4. MPH in the 1/4 shows hp, my Father's TT Vette ran a 12.0 with a junk 60' sandbagging it the whole way at 140mph.
Yes, prior discussion on torque and hp was assuming sufficient traction. You're right, as soon as you throw a traction limitation into the equation, it changes significantly. Your dad's TT Vette had way more torque than the tires could handle. If you had super sticky slicks, the time would be much lower, but the speed wouldn't change as much.
If you sat on the starting line roasting the tires for 5 seconds, it would affect your ET by 5 seconds, but you still have the same distance to hit the trap speed. That's why they say trap speed is a better indicator of power, because it's less dependent on traction.
If you sat on the starting line roasting the tires for 5 seconds, it would affect your ET by 5 seconds, but you still have the same distance to hit the trap speed. That's why they say trap speed is a better indicator of power, because it's less dependent on traction.
In the charger you are going to want alot of torque to get you off the line.Torque is what sets you back in your seat off the line.Which is actaully HP in a low gear.HP is the power a giving engine produces(at the crank or wheel).Gearing is used to produce desired torque.A lower gear will get the RPM's up to max HP faster which produces the max torque quicker,as the car speeds up the engine rmp's increase in a somewhat equal amount which reduces the strain on the engine.
Also when you are driving down the road and you down shift and punch it,that force on your body is torque and as the force lessens you are switching from torque to HP.
I'm probably the only one who understands what I just wrote.
An example my charger has 350 HP at the crank and weighs 4000 plus.
My previous car was a 90 daytona torbo which had 249 HP(I never confirmed that)and weighed alot less.
With the chargers extra weight and more torque launches really push you in the seat where the light weight less torque daytona launched easy but got to the RPM HP pretty quick.
Ok I'm done babbling
Also when you are driving down the road and you down shift and punch it,that force on your body is torque and as the force lessens you are switching from torque to HP.
I'm probably the only one who understands what I just wrote.
An example my charger has 350 HP at the crank and weighs 4000 plus.
My previous car was a 90 daytona torbo which had 249 HP(I never confirmed that)and weighed alot less.
With the chargers extra weight and more torque launches really push you in the seat where the light weight less torque daytona launched easy but got to the RPM HP pretty quick.
Ok I'm done babbling
OK, Hears my .02....On the dyno sheet I had done before heads and cam..this is stock w/just bolt-ons w/CMR tune..You will see lots of bottom end torque at say 2200rpm-all the way to say 4900-5100rpms...HP was way low until say 3500rpm until say 5800...This is good, you want lowend torque to get our sleds going, then the HP takes over and finishes the job at the higher rpms...BTW, the stock cam does a great job with lowend torque with a good CMR tune........OK, I'm done
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Okay you gear heads and engineer types... this is a great learning thread... now advance it up a notch..
Add what different gear ratio ( High/Low) coupled with tire size does for you torque\HP wise getting you down the track at a good click so even a DUMMY like me can understand.
Add what different gear ratio ( High/Low) coupled with tire size does for you torque\HP wise getting you down the track at a good click so even a DUMMY like me can understand.
The "shorter" the tire gets, the more it acts like increased gear ratio.
For the really anal explanation...(I warned you)
For example, if a tire is 24" tall, it's about 12" (or one foot) from the center of the wheel (where torque is applied) to the contact patch where it is converted to linear force to accelerate the vehicle (F=ma).
If the engine makes 350 lb-ft of torque average over some RPM range, you then x by 3.59 first gear ratio x 3.06 rear gear ratio x 75% efficiency (or so). This would be 2880 lb-ft of torque to the tire. If the tire has exactly 12" (or one foot) of radius, it comes out to 2880 lbs of force at the tire contact patch. A taller tire will reduce the force, but give a higher linear speed for a given RPM. Trading RPM for torque or vice versa... just like gear ratio!
Now, in this example, because a Charger weighs 4300 lbs with driver, it would be capable of accelerating at about 0.67 g's (2880 lbs of force / 4300 lbs of weight). That is, IF the tire can hold it. If so, you hook. If not, you spin. As an aside, if the tire has a coefficient of friction of 1.0, the Charger would have to have 67% of it's weight on the rear tires under acceleration to sustain 0.67 g's. Sticky tires can have more than 1.0 coefficient of friction, and obviously loose suspensions will allow more rearward weight transfer.
The trick is to match gear ratio to engine to tire holding power. Do it right and you'll have a perfect combination.
By the way, some of you guys are talking like torque is completely different than hp. Torque is a COMPONENT of hp, RPM being the other. They are different, but related.
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For the really anal explanation...(I warned you)
For example, if a tire is 24" tall, it's about 12" (or one foot) from the center of the wheel (where torque is applied) to the contact patch where it is converted to linear force to accelerate the vehicle (F=ma).
If the engine makes 350 lb-ft of torque average over some RPM range, you then x by 3.59 first gear ratio x 3.06 rear gear ratio x 75% efficiency (or so). This would be 2880 lb-ft of torque to the tire. If the tire has exactly 12" (or one foot) of radius, it comes out to 2880 lbs of force at the tire contact patch. A taller tire will reduce the force, but give a higher linear speed for a given RPM. Trading RPM for torque or vice versa... just like gear ratio!
Now, in this example, because a Charger weighs 4300 lbs with driver, it would be capable of accelerating at about 0.67 g's (2880 lbs of force / 4300 lbs of weight). That is, IF the tire can hold it. If so, you hook. If not, you spin. As an aside, if the tire has a coefficient of friction of 1.0, the Charger would have to have 67% of it's weight on the rear tires under acceleration to sustain 0.67 g's. Sticky tires can have more than 1.0 coefficient of friction, and obviously loose suspensions will allow more rearward weight transfer.
The trick is to match gear ratio to engine to tire holding power. Do it right and you'll have a perfect combination.
By the way, some of you guys are talking like torque is completely different than hp. Torque is a COMPONENT of hp, RPM being the other. They are different, but related.
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ZZ, excellent description. For advanced studies, you can start playing with gearing to cross the 1/4 mile line 10 feet before the vehicle shifts into the next gear. Shifting drops you way down in the power band, and there's the loss in power during the shift.
Thanks PD..I try, rackin my old brain from college days, have to think about this...OK..James, so you want to go with a smaller rim, with smaller tire height, Now, you run into a problem that may hurt you, as you know, 3rd gear is the sweet spot for our cars,..I can't remember the gear ratio for third in the tranny, but anyway, I know you don't hit 4th now as your highest trap speed is 122....You haven't shifted into 4th yet, and I know your engine is high revin, but you might have to think about the possiblity of it hitting 4th during a run with the smaller dia. tires and rims, now your bac down in the power band, I don't know the ratio for 4th, but I think it's pretty long....It looks like you might try it and see what the engine feels like at that shift point.....I have a question.....You hit 4th in the TT chally, how did the 4th shift point feel???..something to think about......Hey PD, I just remembered what you said....same point....I just reread James post, and if you go to 3.23 gears instead of 3.55...uummmm...and keep the smaller tires and rims.....Might work...Hey
CHGR hemi...that sound about right???...where is the shift point for fourth in your car James??
CHGR hemi...that sound about right???...where is the shift point for fourth in your car James??
Just remember you want to accelerate as hard as you can as EARLY as you can in the race, even if you shift into 4th the last bit of the run. Very little is done at that point in the race.
If the tires can hold it, give them as much torque as they'll hold!
If two cars are identical but one has 3.23's and one has 3.06's, AS LONG AS THE TIRES CAN HOLD IT, the 3.23 car will get out of the hole faster and establish an early lead, which it should never lose, even if it shifts to 4th for the last second or so. The other car, even in 3rd at the end of the run, won't be able to make up the difference it lost at the start.
If you plot acceleration vs. speed and/or distance, you'll see what I mean.
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If the tires can hold it, give them as much torque as they'll hold!
If two cars are identical but one has 3.23's and one has 3.06's, AS LONG AS THE TIRES CAN HOLD IT, the 3.23 car will get out of the hole faster and establish an early lead, which it should never lose, even if it shifts to 4th for the last second or so. The other car, even in 3rd at the end of the run, won't be able to make up the difference it lost at the start.
If you plot acceleration vs. speed and/or distance, you'll see what I mean.
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For tire size, yes torRed you have the right idea. Tall tires act like tall gear ratio. Short tires act like short gear ratio.
For gear ratio specifically dejuan, the 3.5 uses a 3.64 rear gear ratio. This is how much it multiplies torque coming out of the transmission (which has already multiplied engine torque depending on what gear it's in). In other words, the 3.5 makes 250 lb-ft of torque. First gear is 2.84, rear gear ratio is 3.64. So to the tires you take 250 lb-ft x 2.84 x 3.64 x 75% (since the trans and rear gear are not 100% efficient) = 1938 lbs-ft to the tire. Because the tire radius is about 1 ft, it's 1938 lbs of force at the tire acting on the car to accelerate it.
If the tires can hold that force, you'll accelerate at about 0.47 g's (1938 lbs of force / 4100 lbs of weight for a 3.5 Charger with driver). If not, you would spin. Lowering the gear ratio (increasing the number) to, say, 4.10, will multiply torque that much more and accelerate that much harder, but it will shift into 2nd at a lower vehicle speed since you hit redline sooner. Again, with gear ratios you trade torque for RPM or vice versa.
So to answer your question, lower gear ratios (higher numbers) are BETTER for accleration if the tires can take it, but worse for RPM. It depends on what you want.
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For gear ratio specifically dejuan, the 3.5 uses a 3.64 rear gear ratio. This is how much it multiplies torque coming out of the transmission (which has already multiplied engine torque depending on what gear it's in). In other words, the 3.5 makes 250 lb-ft of torque. First gear is 2.84, rear gear ratio is 3.64. So to the tires you take 250 lb-ft x 2.84 x 3.64 x 75% (since the trans and rear gear are not 100% efficient) = 1938 lbs-ft to the tire. Because the tire radius is about 1 ft, it's 1938 lbs of force at the tire acting on the car to accelerate it.
If the tires can hold that force, you'll accelerate at about 0.47 g's (1938 lbs of force / 4100 lbs of weight for a 3.5 Charger with driver). If not, you would spin. Lowering the gear ratio (increasing the number) to, say, 4.10, will multiply torque that much more and accelerate that much harder, but it will shift into 2nd at a lower vehicle speed since you hit redline sooner. Again, with gear ratios you trade torque for RPM or vice versa.
So to answer your question, lower gear ratios (higher numbers) are BETTER for accleration if the tires can take it, but worse for RPM. It depends on what you want.
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