G37 Dyno Up on Automobilemag.com 50+ HP
06-10-2007, 09:55 AM
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Originally Posted by tekknikal
so yes to be truly correct you'd have to account for 245/40/19s on the G and 255/35/18s on the 335i..
I am not an expert but, with the G given a larger diameter tire, for a given speed, the transmission (and drive shaft) does not have to turn as much vs. a smaller diameter tire as with the BMW's.
Is this a trade-off design? Tranmission does not have to turn as much = more reliable?
Just guessing.
06-10-2007, 10:22 AM
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Originally Posted by tekknikal
to put it another way, you want to have as much tq as high in your rpm band as possible...which means you want max hp.
Originally Posted by tekknikal
i looked up a dyno for the s2000 and found one here:
http://www.dragtimes.com/2003-Honda-...phs-11765.html
it looks like this:
now, im not familiar with the s2k nor did i do the math but looking at the dyno it appears that tq is not really flat- peak is near 6600rpm on the s2k, so that's where peak acceleration is likely to be. if i had to guess, it must be vtec/cam profile switching that caused that jump. this also causes more tq to be generated at 8krpm vs lower rpms ... so you're right, acceleration would be higher up top than down low, gear for gear...so maybe that explains what you feel?
http://www.dragtimes.com/2003-Honda-...phs-11765.html
it looks like this:
now, im not familiar with the s2k nor did i do the math but looking at the dyno it appears that tq is not really flat- peak is near 6600rpm on the s2k, so that's where peak acceleration is likely to be. if i had to guess, it must be vtec/cam profile switching that caused that jump. this also causes more tq to be generated at 8krpm vs lower rpms ... so you're right, acceleration would be higher up top than down low, gear for gear...so maybe that explains what you feel?
Originally Posted by tekknikal
and yes, torque is a rotational force, so i measured it going into the wheel at the axle. i didnt take the final step of including the wheels to the ground as a force (stripping the distance part of T=F*D) so you're right the #s may be off by a certain amount based on the tires fitted..... so yes to be truly correct you'd have to account for 245/40/19s on the G and 255/35/18s on the 335i..
06-10-2007, 07:36 PM
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Originally Posted by LudwigB
Don't mean to hijack this thread but does anyone know why Infiniti decides to use larger diameter tire than BMW 3's? Smaller diameter would lower the center of gravity which improve corner and handling.
I am not an expert but, with the G given a larger diameter tire, for a given speed, the transmission (and drive shaft) does not have to turn as much vs. a smaller diameter tire as with the BMW's.
Is this a trade-off design? Tranmission does not have to turn as much = more reliable?
Just guessing.
I am not an expert but, with the G given a larger diameter tire, for a given speed, the transmission (and drive shaft) does not have to turn as much vs. a smaller diameter tire as with the BMW's.
Is this a trade-off design? Tranmission does not have to turn as much = more reliable?
Just guessing.
for super sports cars, i think the trend will be 20" wheels with low profile tires at the corners of the car.
06-10-2007, 08:01 PM
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Originally Posted by muscarel
BUt according to your calc, given the same car, 200 lb-ft of torque at 2,000 rpm gives the same acceleration as 200 lb-ft of torque at 8,000 rpm. Same gear, same car. If that is true (ignore CVTs for now), then why even bring high rpm in to this. I think that is my point - ultimately, the rate at which that torque is applied should affect the acceleration. And that is horsepower.
the rate at which torque is applied, HP does matter though. here's how:
you want to go to high rpm (max hp) because even though the rate of acceleration is declining, you're still accelerating, and you're being pushed by more force than you would at any rpm in the next gear (assuming proper tranny design).
Absolutely not. The extra 15 lb-ft of torque (engine) is not what you feel. I've had a nice chunk of time behind the wheel of an S2000. At 3,500 rpm that car has a dead feeling to it. At 8,000 rpm, the thing screams. Waaayyy too much of a difference - it's night and day. The little bump up in torque is not it. So, back to my point above. Where in all this analysis is the rate of torque being applied being accounted for relative to acceleration?
that bump in torque may appear little, but its simply the mathematical equivilent of the above. that's because at such a high rpm, every lbft you can just maintain is really valuable. If you start picking up extra torque at high rpm that has a major impact on your hp, as you see here.
so to answer your quesiton directly, acceleration peaks at 6500rpms, and stays steady with you to about 8k, with the car pulling much harder than it did before 6k rpm.
after the force being applied to the ground max's out (=after peak hp), its time to go to the next gear because (assuming proper gearing) the force being applied to the ground will be equal and better maintained in the next gear.
06-11-2007, 06:53 AM
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Originally Posted by tekknikal
true...it does give the same acceleration.
the rate at which torque is applied, HP does matter though. here's how:
you want to go to high rpm (max hp) because even though the rate of acceleration is declining, you're still accelerating, and you're being pushed by more force than you would at any rpm in the next gear (assuming proper tranny design).
.
the rate at which torque is applied, HP does matter though. here's how:
you want to go to high rpm (max hp) because even though the rate of acceleration is declining, you're still accelerating, and you're being pushed by more force than you would at any rpm in the next gear (assuming proper tranny design).
.
Originally Posted by tekknikal
in only a few hundred rpm at about 6k, the hp (the rate torque is being applied at) jumps 75%! thats going to feel like night and day!
that bump in torque may appear little, but its simply the mathematical equivilent of the above. that's because at such a high rpm, every lbft you can just maintain is really valuable. If you start picking up extra torque at high rpm that has a major impact on your hp, as you see here.
that bump in torque may appear little, but its simply the mathematical equivilent of the above. that's because at such a high rpm, every lbft you can just maintain is really valuable. If you start picking up extra torque at high rpm that has a major impact on your hp, as you see here.
According to your graph and explanation - In EACH gear - you are ONLY looking at torque times gear multiplication. and from that you are drawing a conclusion about acceleration (that's the whole point of creating the graphs in the first place). The way you did the calc is take the engine torque at the calculated rpm (based on vehicle speed) and multiply by the transmission ratio and then multiply by the final drive ratio. That's it. Nowhere in there is the "rate of torque (horsepower)" taken into account. Therefore, in the S2000 example, your calculation would show torque to the wheels almost the same at 3,000 rpm as it would be at 8,000 rpm. You would show only a slight bump up in torque. Yet we know from experience that these cars literally have NO acceleration at 3,000 rpm and a whole lot at 8,000 rpm (in the same gear). To me, there is the flaw in the torque vs. speed graph. How does your graph account for this?
Now, mind you, after all this I believe BOTH graphs are important. The first graph would need to account for road force rather than torque (you've ignored the effects of tire size). It would then at least show the effects of torque multiplication which the horsepower graph does not show. The horsepower graph does show what the effect of increased rate of torque is - and I think that is just as important. Even though, there is no real "horspower x gear ratio" number - I think it would paint the best picture of all. Showing both the affects of torque multiplication AND the value of sustained torque at high rpm.
06-11-2007, 12:39 PM
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first off, i must say that this has been a good exchange. although both of us have been wrong at times, i think that now we're both very close to getting it right...i think we're now getting very close to saying the same thing...in what ive put below, i believe everything's been pretty much figured out and put together.
ive gone back and edited some of my prior statements to clarify mistakes/accurate statements in red, but we went back and fourth quite a bit. to really see the comparison it was necessary to put it in terms of tire force, not just axle torque, as you suggested. i do hold my ground that gearing doesnt multiply hp and i also maintain my thoughts on the bike/s2k/f1 'argument'. anyway like i was saying i think we're pretty close and i think that its most accurately said as i explain below:
not sure i said that 
the force you put to the ground will be greater at hp peak than at any point in the next gear...and this is what maximizing power is about. i cant address your 8k vs 3k rpm unless you're talking about the s2k...and we've already discussed that.
when you look at the tq vs speed chart, rpm is definitely part of the picture. its what allows it to be the way it is; as speeds increase within each gear, rpms increase. if you couldnt put down tq at a high rpm, your redline would need to be lower. that would also mean you couldnt use the same gearing. so the picture would be very different.
i never said hp wasnt the factor. and i really cant say that b/c hp and tq can be put in terms of each other. as ive said before, you can look at the picture one way OR the other. what ive said before (and maintain) is that i think that a force vs speed graph might be the most intuitive and revealing. (note; since doing everything im about to get into below, i still think the same thing for me, but understand that others may see this different)
if you made the same hp/tq but everything were compressed to lower rpms, your gearing would need to be different...as stated above, the rate of torque/hp is very much present. even though its not obvious per se.
8k rpm would put more force for acceleration than 3k rpms.
3k rpms would give someforce, albeit not as much, so you would not have NO acceleration...just not as much. i dont really see a flaw in my graphs regarding this...
agreed that to be completel, it should be force not tq. ive changed it below. but tq multiplication has always been there...and im sorry but i really disagree on the hp * effective gearing because it simply does not exist in that form. it would not be any more revealing, and would only be misleading as a result. the physics on it just doesn't work, as stated before (note-in a sense id say its already there). you can look at the axle tq and derive the same engine hp from it. gearing just doesn't multiply hp though.
consider the following (assuming your average car):
1. for a car to move, a force must be applied.
2. cars use tires to exert a force on the road.
3. to use a tire to exert a force, a torque must be applied to the axle.
4. the only source of that torque is from the car's engine.
5. if you want to know the tq the engine generates vs rpms the engine can run at, dyno charts such as the ones we've been looking at will give you this/
6. the data on the dyno charts indicates the crank hp less drivetrain loss and engine torque, again less drivetrain loss.
7. the tq #s on the dyno charts must be engine tq because the data is derived from horsepower data
8. the transmission does not multiply hp, by the law of conservation of energy. this can be proven by calculating hp from from the tq-hp eqn following #9:
9. the torque is multiplied from the flywheel through the transmission and final drive to ultimately be put down as a force on the road per #2
10. as a result of the above, the max acceleration in any gear will come when force on the road is at maximum. this happens at peak tq.
11. after peak tq, the car's rate of acceleration declines even though work is increasing.
12. the car should be left in the current gear however, because if you want to maximize acceleration, you want to maximize power. if you shift at peak tq you'll be too low in the next gear to utilize effective tq being sent to the ground (or max power), so you should let it go to redline.
13. at redline, just after peak power, you shift because in your next gear you will actually be able to maintain the gearing adjusted tq levels (assuming a proper transmission). this is because although the effective gear ratio will be lower, tq will be higher. as before you're aim is to maximize this (=power) and go to redline again.
the latest charts are below.
i think that with this revision to the tq chart, and the improved accuracy of data both ways, it will become apparent that we're talking about the same thing...and we've both been right on some things and wrong on others.
let me know what you think
ive gone back and edited some of my prior statements to clarify mistakes/accurate statements in red, but we went back and fourth quite a bit. to really see the comparison it was necessary to put it in terms of tire force, not just axle torque, as you suggested. i do hold my ground that gearing doesnt multiply hp and i also maintain my thoughts on the bike/s2k/f1 'argument'. anyway like i was saying i think we're pretty close and i think that its most accurately said as i explain below:
Originally Posted by muscarel
We've all declared tha an exgine has a horsepower curve (vs. rpm) and that that curve is constant regardless of teh gear you are in. Only torque is multiplied by the gear ratios (rpm being reduced in the opposite direction). Your above argument is that the reason you do not shift is "because the horsepower is greater in the current gear versus the next gear" - well, that goes against your own argument about horsepower being constant regardless of which gear you are in. As a result, at 8,000 rpm, your HP is greater than than at 3,000 rpm (in the same gear), so acceleration should be greater. Even though I agree (remember my argument is that horsepower is the test for acceleration, not any torque value absent of rpm), it goes against your own logic (or appears to).
the force you put to the ground will be greater at hp peak than at any point in the next gear...and this is what maximizing power is about. i cant address your 8k vs 3k rpm unless you're talking about the s2k...and we've already discussed that.
when you look at the tq vs speed chart, rpm is definitely part of the picture. its what allows it to be the way it is; as speeds increase within each gear, rpms increase. if you couldnt put down tq at a high rpm, your redline would need to be lower. that would also mean you couldnt use the same gearing. so the picture would be very different.
Whoa, wait a minute - that's my argument - that horsepower is the factor in determining acceleration (hence my repeated request for graph 2). You can't explain my S2000 example using my own logic and then in the same breath say that we should use graph 1 (torque vs speed) as the judge of acceleration.
According to your graph and explanation - In EACH gear - you are ONLY looking at torque times gear multiplication. and from that you are drawing a conclusion about acceleration (that's the whole point of creating the graphs in the first place). The way you did the calc is take the engine torque at the calculated rpm (based on vehicle speed) and multiply by the transmission ratio and then multiply by the final drive ratio. That's it. Nowhere in there is the "rate of torque (horsepower)" taken into account.
Therefore, in the S2000 example, your calculation would show torque to the wheels almost the same at 3,000 rpm as it would be at 8,000 rpm. You would show only a slight bump up in torque. Yet we know from experience that these cars literally have NO acceleration at 3,000 rpm and a whole lot at 8,000 rpm (in the same gear). To me, there is the flaw in the torque vs. speed graph. How does your graph account for this?
3k rpms would give someforce, albeit not as much, so you would not have NO acceleration...just not as much. i dont really see a flaw in my graphs regarding this...
Now, mind you, after all this I believe BOTH graphs are important. The first graph would need to account for road force rather than torque (you've ignored the effects of tire size). It would then at least show the effects of torque multiplication which the horsepower graph does not show. The horsepower graph does show what the effect of increased rate of torque is - and I think that is just as important. Even though, there is no real "horspower x gear ratio" number - I think it would paint the best picture of all. Showing both the affects of torque multiplication AND the value of sustained torque at high rpm.
consider the following (assuming your average car):
1. for a car to move, a force must be applied.
2. cars use tires to exert a force on the road.
3. to use a tire to exert a force, a torque must be applied to the axle.
4. the only source of that torque is from the car's engine.
5. if you want to know the tq the engine generates vs rpms the engine can run at, dyno charts such as the ones we've been looking at will give you this/
6. the data on the dyno charts indicates the crank hp less drivetrain loss and engine torque, again less drivetrain loss.
7. the tq #s on the dyno charts must be engine tq because the data is derived from horsepower data
8. the transmission does not multiply hp, by the law of conservation of energy. this can be proven by calculating hp from from the tq-hp eqn following #9:
9. the torque is multiplied from the flywheel through the transmission and final drive to ultimately be put down as a force on the road per #2
10. as a result of the above, the max acceleration in any gear will come when force on the road is at maximum. this happens at peak tq.
11. after peak tq, the car's rate of acceleration declines even though work is increasing.
12. the car should be left in the current gear however, because if you want to maximize acceleration, you want to maximize power. if you shift at peak tq you'll be too low in the next gear to utilize effective tq being sent to the ground (or max power), so you should let it go to redline.
13. at redline, just after peak power, you shift because in your next gear you will actually be able to maintain the gearing adjusted tq levels (assuming a proper transmission). this is because although the effective gear ratio will be lower, tq will be higher. as before you're aim is to maximize this (=power) and go to redline again.
the latest charts are below.
i think that with this revision to the tq chart, and the improved accuracy of data both ways, it will become apparent that we're talking about the same thing...and we've both been right on some things and wrong on others.
let me know what you think
Last edited by tekknikal; 06-11-2007 at 01:05 PM.
06-11-2007, 09:38 PM
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Originally Posted by FenixL1P
how come this only gets nearly 10-15 ft-lbs more torque to the wheels than my late 02 6spd maxima???... (255hp/240ft-lb)
this means that the g37 is applying more torque and doing it 'faster'....this is another way of saying that its making much more power. and, because it revs higher and produces such good tq at high rpms, it can also use more agressive gearing.
06-14-2007, 01:52 PM
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Originally Posted by tekknikal
first off, i must say that this has been a good exchange. although both of us have been wrong at times, i think that now we're both very close to getting it right...i think we're now getting very close to saying the same thing...in what ive put below, i believe everything's been pretty much figured out and put together.
ive gone back and edited some of my prior statements to clarify mistakes/accurate statements in red, but we went back and fourth quite a bit. to really see the comparison it was necessary to put it in terms of tire force, not just axle torque, as you suggested. i do hold my ground that gearing doesnt multiply hp and i also maintain my thoughts on the bike/s2k/f1 'argument'. anyway like i was saying i think we're pretty close and i think that its most accurately said as i explain below:
not sure i said that
the force you put to the ground will be greater at hp peak than at any point in the next gear...and this is what maximizing power is about. i cant address your 8k vs 3k rpm unless you're talking about the s2k...and we've already discussed that.
when you look at the tq vs speed chart, rpm is definitely part of the picture. its what allows it to be the way it is; as speeds increase within each gear, rpms increase. if you couldnt put down tq at a high rpm, your redline would need to be lower. that would also mean you couldnt use the same gearing. so the picture would be very different.
i never said hp wasnt the factor. and i really cant say that b/c hp and tq can be put in terms of each other. as ive said before, you can look at the picture one way OR the other. what ive said before (and maintain) is that i think that a force vs speed graph might be the most intuitive and revealing. (note; since doing everything im about to get into below, i still think the same thing for me, but understand that others may see this different)
if you made the same hp/tq but everything were compressed to lower rpms, your gearing would need to be different...as stated above, the rate of torque/hp is very much present. even though its not obvious per se.
8k rpm would put more force for acceleration than 3k rpms.
3k rpms would give someforce, albeit not as much, so you would not have NO acceleration...just not as much. i dont really see a flaw in my graphs regarding this...
agreed that to be completel, it should be force not tq. ive changed it below. but tq multiplication has always been there...and im sorry but i really disagree on the hp * effective gearing because it simply does not exist in that form. it would not be any more revealing, and would only be misleading as a result. the physics on it just doesn't work, as stated before (note-in a sense id say its already there). you can look at the axle tq and derive the same engine hp from it. gearing just doesn't multiply hp though.
consider the following (assuming your average car):
1. for a car to move, a force must be applied.
2. cars use tires to exert a force on the road.
3. to use a tire to exert a force, a torque must be applied to the axle.
4. the only source of that torque is from the car's engine.
5. if you want to know the tq the engine generates vs rpms the engine can run at, dyno charts such as the ones we've been looking at will give you this/
6. the data on the dyno charts indicates the crank hp less drivetrain loss and engine torque, again less drivetrain loss.
7. the tq #s on the dyno charts must be engine tq because the data is derived from horsepower data
8. the transmission does not multiply hp, by the law of conservation of energy. this can be proven by calculating hp from from the tq-hp eqn following #9:
9. the torque is multiplied from the flywheel through the transmission and final drive to ultimately be put down as a force on the road per #2
10. as a result of the above, the max acceleration in any gear will come when force on the road is at maximum. this happens at peak tq.
11. after peak tq, the car's rate of acceleration declines even though work is increasing.
12. the car should be left in the current gear however, because if you want to maximize acceleration, you want to maximize power. if you shift at peak tq you'll be too low in the next gear to utilize effective tq being sent to the ground (or max power), so you should let it go to redline.
13. at redline, just after peak power, you shift because in your next gear you will actually be able to maintain the gearing adjusted tq levels (assuming a proper transmission). this is because although the effective gear ratio will be lower, tq will be higher. as before you're aim is to maximize this (=power) and go to redline again.
the latest charts are below.
i think that with this revision to the tq chart, and the improved accuracy of data both ways, it will become apparent that we're talking about the same thing...and we've both been right on some things and wrong on others.
let me know what you think
ive gone back and edited some of my prior statements to clarify mistakes/accurate statements in red, but we went back and fourth quite a bit. to really see the comparison it was necessary to put it in terms of tire force, not just axle torque, as you suggested. i do hold my ground that gearing doesnt multiply hp and i also maintain my thoughts on the bike/s2k/f1 'argument'. anyway like i was saying i think we're pretty close and i think that its most accurately said as i explain below:
not sure i said that
the force you put to the ground will be greater at hp peak than at any point in the next gear...and this is what maximizing power is about. i cant address your 8k vs 3k rpm unless you're talking about the s2k...and we've already discussed that.
when you look at the tq vs speed chart, rpm is definitely part of the picture. its what allows it to be the way it is; as speeds increase within each gear, rpms increase. if you couldnt put down tq at a high rpm, your redline would need to be lower. that would also mean you couldnt use the same gearing. so the picture would be very different.
i never said hp wasnt the factor. and i really cant say that b/c hp and tq can be put in terms of each other. as ive said before, you can look at the picture one way OR the other. what ive said before (and maintain) is that i think that a force vs speed graph might be the most intuitive and revealing. (note; since doing everything im about to get into below, i still think the same thing for me, but understand that others may see this different)
if you made the same hp/tq but everything were compressed to lower rpms, your gearing would need to be different...as stated above, the rate of torque/hp is very much present. even though its not obvious per se.
8k rpm would put more force for acceleration than 3k rpms.
3k rpms would give someforce, albeit not as much, so you would not have NO acceleration...just not as much. i dont really see a flaw in my graphs regarding this...
agreed that to be completel, it should be force not tq. ive changed it below. but tq multiplication has always been there...and im sorry but i really disagree on the hp * effective gearing because it simply does not exist in that form. it would not be any more revealing, and would only be misleading as a result. the physics on it just doesn't work, as stated before (note-in a sense id say its already there). you can look at the axle tq and derive the same engine hp from it. gearing just doesn't multiply hp though.
consider the following (assuming your average car):
1. for a car to move, a force must be applied.
2. cars use tires to exert a force on the road.
3. to use a tire to exert a force, a torque must be applied to the axle.
4. the only source of that torque is from the car's engine.
5. if you want to know the tq the engine generates vs rpms the engine can run at, dyno charts such as the ones we've been looking at will give you this/
6. the data on the dyno charts indicates the crank hp less drivetrain loss and engine torque, again less drivetrain loss.
7. the tq #s on the dyno charts must be engine tq because the data is derived from horsepower data
8. the transmission does not multiply hp, by the law of conservation of energy. this can be proven by calculating hp from from the tq-hp eqn following #9:
9. the torque is multiplied from the flywheel through the transmission and final drive to ultimately be put down as a force on the road per #2
10. as a result of the above, the max acceleration in any gear will come when force on the road is at maximum. this happens at peak tq.
11. after peak tq, the car's rate of acceleration declines even though work is increasing.
12. the car should be left in the current gear however, because if you want to maximize acceleration, you want to maximize power. if you shift at peak tq you'll be too low in the next gear to utilize effective tq being sent to the ground (or max power), so you should let it go to redline.
13. at redline, just after peak power, you shift because in your next gear you will actually be able to maintain the gearing adjusted tq levels (assuming a proper transmission). this is because although the effective gear ratio will be lower, tq will be higher. as before you're aim is to maximize this (=power) and go to redline again.
the latest charts are below.
i think that with this revision to the tq chart, and the improved accuracy of data both ways, it will become apparent that we're talking about the same thing...and we've both been right on some things and wrong on others.
let me know what you think
I agree with all of your points, but you are still answering alot of questions that I am not asking.
I understand that you will always put down more force in 1st gear than you would in 2nd gear. Short shifting doesn't work. No one is disputing that. I am trying to apply all this theory to real life. My argument is about an S2000, that has for all intents and purposes a flat torque curve and a linear horspower curve. Forget about shifting. Talking about one specific gear with a set transmission ratio and final drive ratio. For instance, the 1st gear ratio of an S2000 is 3.1. The final drive raito is 4.1. According to the calc:
at 3,000 rpm, the car's engine puts out 115 lb-ft of torque. The torque to the wheels is - 115 x 4.1 x 3.1 = 1,461 lb-ft
at 8,000 rpm, the car's engine puts out 130 lb-ft of torque. The torque to the wheels is - 130 x 4.1 x 3.1 = 1,652 lb-ft.
The difference is there mathematically (13% more torque), but minor compared to the actual driving experience. The acceleration from experience is exponentially different at 3,000 rpm as it is at 8,000 rpm in any 1 gear. That's what I am looking for an explanation on. The acceleration is not just 13% more - it's multiples of that. You must drive the car to understand what I am talking about. Anyone here with an S2000 that can back this up?
If you can explain that last part, I am set. Thanks for your patience.
By the way, it's pretty scary how your force vs speed graph chanegd once you entered the tire information. Now, it is evident (assuming the graphs are right) that the 335 will still be much faster than the G37 (at least up to 90 mph).
Last edited by muscarel; 06-14-2007 at 01:54 PM.
06-14-2007, 03:10 PM
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Originally Posted by chilibowl
The G37 with a lightweight flywheel, a 3.9 Final Drive, High flow cats, drag radials, and I believe it can be a high 12 second car.
06-14-2007, 04:58 PM
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Originally Posted by chilibowl
The G37 with a lightweight flywheel, a 3.9 Final Drive, High flow cats, drag radials, and I believe it can be a high 12 second car.
the other problem is that most g-drivers are not racers. so if the answer isnt obvious/decisive, we probably wont know for a long time.
06-14-2007, 07:53 PM
#254
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I dont suppose a reasonable comparison would be the E42 M3 and its convertible variant. Both are rated at 330hp, 262lbs/ft. Very similar to the g37's figures, which are probably actually higher based on the new SAE-ratings.
The M3 does 4.8 & low 13's? And it weighs just under 3500lbs.. Its convertible variation takes a hit because of its weight (a little over 3700 lbs), putting out numbers I believe around 5.4 & mid-upper 13's.
I know its not completely apples to apples, but based on what we know I think it should be reasonable to expect the G37 to put out performance #'s between the M3 and its convertible.. or in other words, low 5's and probably mid 13's. My guess that is...
The M3 does 4.8 & low 13's? And it weighs just under 3500lbs.. Its convertible variation takes a hit because of its weight (a little over 3700 lbs), putting out numbers I believe around 5.4 & mid-upper 13's.
I know its not completely apples to apples, but based on what we know I think it should be reasonable to expect the G37 to put out performance #'s between the M3 and its convertible.. or in other words, low 5's and probably mid 13's. My guess that is...
06-15-2007, 12:00 AM
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Originally Posted by muscarel
I agree with all of your points, but you are still answering alot of questions that I am not asking.
I understand that you will always put down more force in 1st gear than you would in 2nd gear. Short shifting doesn't work. No one is disputing that. I am trying to apply all this theory to real life. My argument is about an S2000, that has for all intents and purposes a flat torque curve and a linear horspower curve. Forget about shifting. Talking about one specific gear with a set transmission ratio and final drive ratio. For instance, the 1st gear ratio of an S2000 is 3.1. The final drive raito is 4.1. According to the calc:
at 3,000 rpm, the car's engine puts out 115 lb-ft of torque. The torque to the wheels is - 115 x 4.1 x 3.1 = 1,461 lb-ft
at 8,000 rpm, the car's engine puts out 130 lb-ft of torque. The torque to the wheels is - 130 x 4.1 x 3.1 = 1,652 lb-ft.
The difference is there mathematically (13% more torque), but minor compared to the actual driving experience. The acceleration from experience is exponentially different at 3,000 rpm as it is at 8,000 rpm in any 1 gear. That's what I am looking for an explanation on. The acceleration is not just 13% more - it's multiples of that. You must drive the car to understand what I am talking about. Anyone here with an S2000 that can back this up?
If you can explain that last part, I am set. Thanks for your patience.
By the way, it's pretty scary how your force vs speed graph chanegd once you entered the tire information. Now, it is evident (assuming the graphs are right) that the 335 will still be much faster than the G37 (at least up to 90 mph).
I understand that you will always put down more force in 1st gear than you would in 2nd gear. Short shifting doesn't work. No one is disputing that. I am trying to apply all this theory to real life. My argument is about an S2000, that has for all intents and purposes a flat torque curve and a linear horspower curve. Forget about shifting. Talking about one specific gear with a set transmission ratio and final drive ratio. For instance, the 1st gear ratio of an S2000 is 3.1. The final drive raito is 4.1. According to the calc:
at 3,000 rpm, the car's engine puts out 115 lb-ft of torque. The torque to the wheels is - 115 x 4.1 x 3.1 = 1,461 lb-ft
at 8,000 rpm, the car's engine puts out 130 lb-ft of torque. The torque to the wheels is - 130 x 4.1 x 3.1 = 1,652 lb-ft.
The difference is there mathematically (13% more torque), but minor compared to the actual driving experience. The acceleration from experience is exponentially different at 3,000 rpm as it is at 8,000 rpm in any 1 gear. That's what I am looking for an explanation on. The acceleration is not just 13% more - it's multiples of that. You must drive the car to understand what I am talking about. Anyone here with an S2000 that can back this up?
If you can explain that last part, I am set. Thanks for your patience.
By the way, it's pretty scary how your force vs speed graph chanegd once you entered the tire information. Now, it is evident (assuming the graphs are right) that the 335 will still be much faster than the G37 (at least up to 90 mph).
hmm..well ultimately, i may not be able to link what i've come up with via physics with the perceived degree to which you experience a feeling....
I'm not sure how to make such a link- maybe people pick up on power more so than just a force? maybe this is because people have a hard time gauging the degree of acceleration they're under? im not sure... but i do know that the 15% increase in tq at the top of the rpm band will definitely get the kind of performance that you observe in an S2k. Is that what's felt? Or are people better at telling the rate that tq is being applied at (power- which sees a much larger % increase)? I can't say for sure.
I've driven a S2000. Not for very long, but I remember the pull up top. Maybe the HP graph is what people "feel"? Regardless, I think both graphs are telling a similar story.... from different points of view.