Rx8 torque
12-24-2008, 03:54 AM
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Rx8 torque
According to spec sheet rx8 has a torque of 165, hp of 235 and 0-60 time of 6.1 second while a honda accord 2000 cc has hp of 160, torque of 156 and does 0-60 in 10 second.
So i am sort of consfused; because how can i car with meagre 165 torque do 0-60 in 6.1 seconds while the other car with the same torque does it in 10 seconds.
Any explanation without flaming me would be nice.
So i am sort of consfused; because how can i car with meagre 165 torque do 0-60 in 6.1 seconds while the other car with the same torque does it in 10 seconds.
Any explanation without flaming me would be nice.
Last edited by HUSSAIN; 12-24-2008 at 04:00 AM.
12-24-2008, 04:07 AM
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According to spec sheet rx8 has a torque of 165, hp of 235 and 0-60 time of 6.1 second while a honda accord 2000 cc has hp of 160, torque of 156 and does 0-60 in 10 second.
So i am sort of consfused; because how can i car with meagre 165 torque do 0-60 in 6.1 seconds while the other car with the same torque does it in 10 seconds.
Any explanation without flaming me would be nice.
So i am sort of consfused; because how can i car with meagre 165 torque do 0-60 in 6.1 seconds while the other car with the same torque does it in 10 seconds.
Any explanation without flaming me would be nice.
Just because one car has more or less torque does not mean it's faster. You have to factor in things such as drivetrain, vehicle weight etc.
12-24-2008, 04:22 AM
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The weight does not add a difference of 4 seconds.
The gear ratio's actually do make a difference because in all probability accord owner has to change to third gear to reach 60 mph and that might account for the difference.
But this means that if we install both car with similiar gear ratios both would be very compatative in a drag race.
Furthermore what more doesn't make sense is that for what little physics i know:
Torque = Force X Displacement = Work
Power= Work Done per Second
So the Torque and power should always be propotional but here :
Accord = 160hp and 160lb-ft
Rx8 = 230hp and 160lb-ft
The gear ratio's actually do make a difference because in all probability accord owner has to change to third gear to reach 60 mph and that might account for the difference.
But this means that if we install both car with similiar gear ratios both would be very compatative in a drag race.
Furthermore what more doesn't make sense is that for what little physics i know:
Torque = Force X Displacement = Work
Power= Work Done per Second
So the Torque and power should always be propotional but here :
Accord = 160hp and 160lb-ft
Rx8 = 230hp and 160lb-ft
Last edited by HUSSAIN; 12-24-2008 at 04:27 AM.
12-24-2008, 04:38 AM
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Torque and horsepower measurements advertised by manufacturers are the peak measurements, taken from a dyno (not at the wheels, mind you, but the... flywheel I think?).
Also, horsepower is determined by torque * RPM / 5252. This is why horsepower = torque at 5252 RPMs. You cannot simply assume a direct ratio because they tend to be measured at very different RPMs (if you look at specifications for vehicles they tend to say something like "250 peak hp at 5.5k RPM" or something similar.)
As Flashwing said, several things determine acceleration. Weight is very important (the Accord is somewhere in the neighborhood of 3600 lbs while our RX-8 is roughly 3000 lbs. Those 600 lbs make a big difference.) The torque/horsepower curve is also important (an engine making 50-100 hp from 0-5k RPM but with a peak of something like 300 hp at 7k RPM is going to be much slower starting out than an engine with a smoother power curve.) You also have to consider drivetrain losses. The Accord could have a much more inefficient transmission that loses far more power than the RX-8 (parasitic loss).
Also, horsepower is determined by torque * RPM / 5252. This is why horsepower = torque at 5252 RPMs. You cannot simply assume a direct ratio because they tend to be measured at very different RPMs (if you look at specifications for vehicles they tend to say something like "250 peak hp at 5.5k RPM" or something similar.)
As Flashwing said, several things determine acceleration. Weight is very important (the Accord is somewhere in the neighborhood of 3600 lbs while our RX-8 is roughly 3000 lbs. Those 600 lbs make a big difference.) The torque/horsepower curve is also important (an engine making 50-100 hp from 0-5k RPM but with a peak of something like 300 hp at 7k RPM is going to be much slower starting out than an engine with a smoother power curve.) You also have to consider drivetrain losses. The Accord could have a much more inefficient transmission that loses far more power than the RX-8 (parasitic loss).
12-24-2008, 05:00 AM
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The 5.9 to 6.1 second 0-60 time I think is a bit of a quicker time than what the typical RX8 is capable of. You'd have to be power shifting that transmission.
Either way, examining torque numbers alone isn't going to tell you the total performance of a vehicle.
Either way, examining torque numbers alone isn't going to tell you the total performance of a vehicle.
12-24-2008, 06:58 AM
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THIS is why I stopped coming onto forums...
-"You'd have to be power shifting that transmission" to get a 5.9 0-60.
-the 4 cyl. Accord "is somewhere in the neighborhood of 3600 lbs"
Hussain; you're better off searching on the web, the subject is well covered, and you'll find out it isn't just about torque, kinda like it isn't just about trap speeds - two areas where forums often get it wrong...
-"You'd have to be power shifting that transmission" to get a 5.9 0-60.
-the 4 cyl. Accord "is somewhere in the neighborhood of 3600 lbs"
Hussain; you're better off searching on the web, the subject is well covered, and you'll find out it isn't just about torque, kinda like it isn't just about trap speeds - two areas where forums often get it wrong...
12-24-2008, 08:47 AM
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It's a relatively easy explanation, and was basically touched on but not directly stated.
It's the GEARS!! Engine numbers are nice things that marketers can key on, but the GEARS are what makes it get up and go, almost regardless of how much the engine puts out...
Gears are torque multipliers. This is why when you hook up to a dyno, you want to measure it based on the gear that is a 1:1 ratio in the transmission, otherwise, you've got to introduce a calculation to get the torque back to what the engine is really putting out.
Examples:
If your engine puts out 200 lb-ft of torque, and your transmission is a 2:1 ratio, you're actually putting 400 lb-ft of torque to the rear axle. Say you have 3.0:1 gears in the rear axle, and now you're actually putting down 1,200 lb-ft of torque to the ground through the wheels. (not including all the losses that occur due to friction).
But change that transmission ratio a "small" amount to 2.2:1, and now you're actually applying 1,320 lb-ft to the ground, an increase of 10%!!
Better yet, leave the tranmission alone, and change the rear axle ratio from a 3:1 to a 3.7:1, and you've increased torque the ground a whopping 280 lb-ft, to 1,480 lb-ft, an increase of 23%!
In other words, torque ratings at the engine really don't have a whole lot of meaning as far as the acceleration goes, because the GEARS in the transmission and the rear axle are much, much more directly responsible for torque that makes it to the ground, and resultantly, are much more directly responsible for the acceleration of the vehicle.
EDIT:
If you're having a hard time wrapping your head around this concept, picture yourself with a wrench in hand. Say you are strong enough to put out 50 lb of force, straight up (this is your "engine"). Your wrench is 1 ft long (this is your "gear") so you can exert a "whopping" 50 lb-ft of force on that bolt to turn it (this is your total torque to the ground including engine force, transmission & axle ratios).
But say that bolt is stuck as a *****'...needs 400 lb-ft to move it (this is your car's weight) You can either go work out for a few months so you can increase the force comin' out your arm to 400 lbs (turbo, baby!), and get the job done. OR, you can go get a wrench that's 8' long (change the gear ratios) and you get the same 400 lb-ft of torque to the bolt (your wheels on the ground).
There's lots of different ways to get an increase of torque; different car manufacturers do it different ways. Just measuring 1 of the values (engine torque and related horsepower) don't give you an overall picture of how much torque actually gets exerted to the ground by the tires. You gotta' look at it all as a whole. The torque/horsepower rating is virtually meaningless by itself.
It's the GEARS!! Engine numbers are nice things that marketers can key on, but the GEARS are what makes it get up and go, almost regardless of how much the engine puts out...
Gears are torque multipliers. This is why when you hook up to a dyno, you want to measure it based on the gear that is a 1:1 ratio in the transmission, otherwise, you've got to introduce a calculation to get the torque back to what the engine is really putting out.
Examples:
If your engine puts out 200 lb-ft of torque, and your transmission is a 2:1 ratio, you're actually putting 400 lb-ft of torque to the rear axle. Say you have 3.0:1 gears in the rear axle, and now you're actually putting down 1,200 lb-ft of torque to the ground through the wheels. (not including all the losses that occur due to friction).
But change that transmission ratio a "small" amount to 2.2:1, and now you're actually applying 1,320 lb-ft to the ground, an increase of 10%!!
Better yet, leave the tranmission alone, and change the rear axle ratio from a 3:1 to a 3.7:1, and you've increased torque the ground a whopping 280 lb-ft, to 1,480 lb-ft, an increase of 23%!
In other words, torque ratings at the engine really don't have a whole lot of meaning as far as the acceleration goes, because the GEARS in the transmission and the rear axle are much, much more directly responsible for torque that makes it to the ground, and resultantly, are much more directly responsible for the acceleration of the vehicle.
EDIT:
If you're having a hard time wrapping your head around this concept, picture yourself with a wrench in hand. Say you are strong enough to put out 50 lb of force, straight up (this is your "engine"). Your wrench is 1 ft long (this is your "gear") so you can exert a "whopping" 50 lb-ft of force on that bolt to turn it (this is your total torque to the ground including engine force, transmission & axle ratios).
But say that bolt is stuck as a *****'...needs 400 lb-ft to move it (this is your car's weight) You can either go work out for a few months so you can increase the force comin' out your arm to 400 lbs (turbo, baby!), and get the job done. OR, you can go get a wrench that's 8' long (change the gear ratios) and you get the same 400 lb-ft of torque to the bolt (your wheels on the ground).
There's lots of different ways to get an increase of torque; different car manufacturers do it different ways. Just measuring 1 of the values (engine torque and related horsepower) don't give you an overall picture of how much torque actually gets exerted to the ground by the tires. You gotta' look at it all as a whole. The torque/horsepower rating is virtually meaningless by itself.
Last edited by RX8-Frontier; 12-24-2008 at 08:59 AM.
12-24-2008, 08:55 AM
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the rx8 is faster because of the rotary's ability to hold its torque for a longer period of time(9k rpms) which equals more power ....so while in gear it can continue to accelerate to 9k rpms while the honda accord is limited o 6.5k rpms....if the honda accord engine were able to hold torque longer then it too would accelerate faster...... like the honda s2000 which aslo has ~160 ft lbs of torque but a higher rev limit and does 0-60 in 5.5 sec
Last edited by chancejat; 12-24-2008 at 12:10 PM.
12-24-2008, 08:58 AM
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Everyone knows that, Torque is a measure of rotational energy, and we all know piston engines only go up and down. So really, only rotary engines make torque at all, as piston engines make up and down motions.
People who talk about piston engines having torque are just ignorant.
/why so serious?
People who talk about piston engines having torque are just ignorant.
/why so serious?
12-24-2008, 09:29 AM
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THIS is why I stopped coming onto forums...
-"You'd have to be power shifting that transmission" to get a 5.9 0-60.
-the 4 cyl. Accord "is somewhere in the neighborhood of 3600 lbs"
Hussain; you're better off searching on the web, the subject is well covered, and you'll find out it isn't just about torque, kinda like it isn't just about trap speeds - two areas where forums often get it wrong...
-"You'd have to be power shifting that transmission" to get a 5.9 0-60.
-the 4 cyl. Accord "is somewhere in the neighborhood of 3600 lbs"
Hussain; you're better off searching on the web, the subject is well covered, and you'll find out it isn't just about torque, kinda like it isn't just about trap speeds - two areas where forums often get it wrong...
12-24-2008, 10:09 AM
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the rx8 is faster because of the rotary's ability to hold its torque for a longer period of time(9k rpms) which equals more power ....so while in gear it can continue to accelerate to 9k rpms while the honda is limited o 6.5k rpms....if the honda engine were able to hold torque longer then it too would accelerate faster...... like the honda s2000 which aslo has ~160 ft lbs of torque but a higher rev limit and does 0-60 in 5.5 sec
I don't know what S2000 you're looking at, but the ones I've seen redline at 8,500-9,000RPMs..
http://en.wikipedia.org/wiki/Honda_S2000#Specifications
12-24-2008, 10:11 AM
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If you are serious about wanting to know why, then I seriously suggest that you read this thread: https://www.rx8club.com/series-i-major-horsepower-upgrades-93/what-makes-so-hard-get-big-hp-numbers-152449/
The subject is regarding making more power in the 8, but in the process there are many good explanations about what power actually means.
Simply put however, it isn't the peak HP/TQ numbers that you quote, but how long each of those cars can hold near those numbers, as well as the gearing involved. The RX-8's torque curve is very flat, which means that it is producing close to the same amount of torque the entire time spent across the rev range. The Accord's torque curve is likely very bubbled, so it is only getting it's published peak torque for a portion of the time. So we can hold our torque for most of every gear, and our RPMs are higher which means we can hold our gears longer, where-as the Accord can only hold it's torque briefly, the rest of the time it is pushing significantly less torque. It is the "Area under the curve" way of looking at it.
For a simple layman's experiment to feel the difference, pay attention to how long you feel the pull in the 8 under full acceleration, and then take a ride/drive in an accord or other car of similar numbers, and pay attention to how long you feel the pull in those cars.
Though you have the wrong car if you are paying attention to acceleration times. That isn't what this car was designed for, and although it does it respectably, it will never do it well enough to really draw attention. Unless maybe Mazda designs a 5 liter rotory engine...what's that? 8 rotors?
The subject is regarding making more power in the 8, but in the process there are many good explanations about what power actually means.
Simply put however, it isn't the peak HP/TQ numbers that you quote, but how long each of those cars can hold near those numbers, as well as the gearing involved. The RX-8's torque curve is very flat, which means that it is producing close to the same amount of torque the entire time spent across the rev range. The Accord's torque curve is likely very bubbled, so it is only getting it's published peak torque for a portion of the time. So we can hold our torque for most of every gear, and our RPMs are higher which means we can hold our gears longer, where-as the Accord can only hold it's torque briefly, the rest of the time it is pushing significantly less torque. It is the "Area under the curve" way of looking at it.
For a simple layman's experiment to feel the difference, pay attention to how long you feel the pull in the 8 under full acceleration, and then take a ride/drive in an accord or other car of similar numbers, and pay attention to how long you feel the pull in those cars.
Though you have the wrong car if you are paying attention to acceleration times. That isn't what this car was designed for, and although it does it respectably, it will never do it well enough to really draw attention. Unless maybe Mazda designs a 5 liter rotory engine...what's that? 8 rotors?
12-24-2008, 10:14 AM
#17
The AP1 (older models) had their redline set to 9000, whereas the others I believe are 8250-8500..
That is what Chance was saying, because of the higher redline, they have a faster 0-60 than the accord which has nearly the same amount of torque. He wasn't implying that the S2K redlined at 6500.
That is what Chance was saying, because of the higher redline, they have a faster 0-60 than the accord which has nearly the same amount of torque. He wasn't implying that the S2K redlined at 6500.
12-24-2008, 10:39 AM
#18
What people tend to forget is that the torque numbers are *peak* torque.
Most piston engines have a narrow power band with a torque curve that spikes up at one point. Rotary engines have a much flatter torque curve: it's fairly linear and increases all the way to the redline.
A piston engine will snap your head back, briefly. A rotary engine will push you back a little, and then keep on pushing you back all the way to the redline. They accelerate in different ways, which is why the 8 can be quick with a peak torque number that would be horrible for a piston engine.
Most piston engines have a narrow power band with a torque curve that spikes up at one point. Rotary engines have a much flatter torque curve: it's fairly linear and increases all the way to the redline.
A piston engine will snap your head back, briefly. A rotary engine will push you back a little, and then keep on pushing you back all the way to the redline. They accelerate in different ways, which is why the 8 can be quick with a peak torque number that would be horrible for a piston engine.
12-24-2008, 11:00 AM
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the rx8 pushes you back??? lol jk
Also factor in the fact that its a rear wheel drive vehicle with limited slip vs. a front wheel drive with an open differential. There is a second right there
Also factor in the fact that its a rear wheel drive vehicle with limited slip vs. a front wheel drive with an open differential. There is a second right there
12-24-2008, 12:09 PM
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The AP1 (older models) had their redline set to 9000, whereas the others I believe are 8250-8500..
That is what Chance was saying, because of the higher redline, they have a faster 0-60 than the accord which has nearly the same amount of torque. He wasn't implying that the S2K redlined at 6500.
That is what Chance was saying, because of the higher redline, they have a faster 0-60 than the accord which has nearly the same amount of torque. He wasn't implying that the S2K redlined at 6500.
12-24-2008, 05:31 PM
#24
here is a 2000 honda accord ex coupe. im actually pretty impressed, kudos to honda for the pretty flat torque curve. (also for not lying about hp numbers, unlike mazda. we all know the rx8 has 215hp, not 232hp.)
from: http://www.dragtimes.com/Honda-Accor...slip-6214.html
and actually, the 2000 accord coupe only weighs 2900lbs. so it gets a bonus here.
gearing is also very important. i bet you (for the ease of driveability) that the transmission of this honda goes out to about 20mph in standard driving for first gear. what do we get? 12-14mph for standard driving. that means we'll accelerate faster, but we'll run out of first gear faster too.
honda makes people movers.
gearing makes a lot of difference in acceleration. if you put the rx7 transmission (which has slightly longer gears) into the rx8, your 1/4 mile time will drop .3 seconds. why? because you dont have to shift into 4th right before the finishline. but in the 1000', the rx8 transmission will beat the rx7 transmission.
but we're talking 0-60. and i know we can hit 60mph in 2nd gear. if the accord can hit 60mph in 2nd gear, it wont lose anything with a gear change. but it will suffer from the longer gears. so it will have longer acceleration times.
acceleration really comes down to gearing and vehicle weight.
edit: also read this
http://www.yawpower.com/tqvshp.html
from: http://www.dragtimes.com/Honda-Accor...slip-6214.html
and actually, the 2000 accord coupe only weighs 2900lbs. so it gets a bonus here.
gearing is also very important. i bet you (for the ease of driveability) that the transmission of this honda goes out to about 20mph in standard driving for first gear. what do we get? 12-14mph for standard driving. that means we'll accelerate faster, but we'll run out of first gear faster too.
honda makes people movers.
gearing makes a lot of difference in acceleration. if you put the rx7 transmission (which has slightly longer gears) into the rx8, your 1/4 mile time will drop .3 seconds. why? because you dont have to shift into 4th right before the finishline. but in the 1000', the rx8 transmission will beat the rx7 transmission.
but we're talking 0-60. and i know we can hit 60mph in 2nd gear. if the accord can hit 60mph in 2nd gear, it wont lose anything with a gear change. but it will suffer from the longer gears. so it will have longer acceleration times.
acceleration really comes down to gearing and vehicle weight.
edit: also read this
http://www.yawpower.com/tqvshp.html
Last edited by kersh4w; 12-24-2008 at 05:33 PM.
