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      02-18-2013, 06:31 PM   #23
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Quote:
Originally Posted by e1000 View Post
They scaled HP and Torque on different scales.

Okay. I see now.
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      02-18-2013, 06:42 PM   #24
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The suspension has a lot to do with it too as mentioned by the tester. It sounds like there was too much squat with the Dinan stage III compared to the stock M3.
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      02-18-2013, 06:54 PM   #25
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Where's Bruce, can't wait 'til he gets a hold of this thread!
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      02-18-2013, 07:08 PM   #26
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Quote:
Originally Posted by M3takesNYC View Post
Its actually the power curve that is meaingful and only looking in the area within the 2-3k RPM's worth of the powerband which the car is in during maximum acceleration. ie. Looking under 6k for the m3 is useless when comparing its full-out performance. Daily driving ability is different but all out performance you look at power under the curve in its powerband which is really 6-6.5k to 8400.

Higher revs does not increase performance because you can stay in the revs for longer as the powerband is simply adjusted quite far to the right in a high-revving car. An F1 car never dips below 17000 RPMS's so its not like the advantage is there because it can sit in second gear from 11k-19k RPMS.

If you compare and bench race a 335, you look at its powerband where its gearing allows it to be during max acceleration which is about 4.5-6.5k RPM's so a span of 2k RPMS roughly. Compare that with the area under the curve of power for the m3 which again is really only a 2k RPM span, so no difference in total number of RPMS available to play with, but rather the effect the RPM's are having on the power output. Within the 6k-8500 RPM range the m3 uses its high-revs coupled to a weaker torque to produce its power which is illustrated by the power curve.

A 335 takes its relatively higher torque (given its power) and uses the lower amount of revs coupled with the higher amount of torque to produce its power curve during those peak 2.5k worth of band. The total area of those 2 curves (power curves) is indicitive of its maximum output during its powerband during maximum acceleration.

Go to youtube and watch an all-out sprint with someone video taping the RPMS's and you notice when all-out a 335 never dips below 4500-5k rpms and the m3 never below 5500-6k. They both only have about 2k-2.5k worth of RPMS to rev through so the m3 is not using more revs to stay in the band longer.
Disagree

The Horsepower and RPM define the torque curve. The amount of torque at a RPM is directly proportional to the force applied at that RPM and that determines your instantaneous acceleration.

It's about the gearing and not so much where they are in the rev range. The Dinan has 450tq/408hp and the M3 has 295tq/414hp. Now the HP is pretty equal, but how does the M3 keep up with the Dinan even though it's torque is much lower? It's absolutely the higher RPM's the M3 is able to produce, which obviously produces it's high HP with relatively low torque.

If you have a race, the Dinan will take a jump, but it will have to shift to second. The M3 is able to stay in first gear much longer and first gear has a higher torque multiplication. Thus the M3 will make more torque at the wheels after the Dinan shifts to second. The M3 should pull even or ahead because it can stay in first gear. The M3 shifts to second, but the Dinan has to shift to third and the M3 can keep up by using it's RPM advantage.

Last edited by HighandDry; 02-18-2013 at 07:44 PM.
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      02-18-2013, 10:40 PM   #27
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Quote:
Originally Posted by HighandDry View Post
Disagree

The Horsepower and RPM define the torque curve. The amount of torque at a RPM is directly proportional to the force applied at that RPM and that determines your instantaneous acceleration.

It's about the gearing and not so much where they are in the rev range. The Dinan has 450tq/408hp and the M3 has 295tq/414hp. Now the HP is pretty equal, but how does the M3 keep up with the Dinan even though it's torque is much lower? It's absolutely the higher RPM's the M3 is able to produce, which obviously produces it's high HP with relatively low torque.

If you have a race, the Dinan will take a jump, but it will have to shift to second. The M3 is able to stay in first gear much longer and first gear has a higher torque multiplication. Thus the M3 will make more torque at the wheels after the Dinan shifts to second. The M3 should pull even or ahead because it can stay in first gear. The M3 shifts to second, but the Dinan has to shift to third and the M3 can keep up by using it's RPM advantage.
I believe that a 335i and M3 have the same 6 speed gear ratios. The final drive however is different. Both cars can pretty much carry the same speed in each gear despite the difference in red line. I don't know if the Dinan car in this test has a modified final drive or not.

In my opinion, the M3 is able to pull ahead of the 335i mostly because on the greater drivetrain multiplication in each gear, not because it can stay longer in each gear.

Last edited by CanAutM3; 02-18-2013 at 11:18 PM.
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      02-18-2013, 10:57 PM   #28
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Quote:
Originally Posted by Nautik View Post
The Math gurus need to crunch a new formula to rate an engine which incorporates how much power was generated over a given amount of time. Maybe some kind of weighted horsepower figure.
It exists, and it is called "Work".

Work is a force applied over a distance, a form of energy. Power is the rate at which work can be produced (Power = Work / time).

Hence how much power was generated over a given amount of time: Work = Power x Time

The thing is, it will not give you what you are looking for. Power is ultimately the number that represents the ability to produce work over time, i.e. the ability to quickly accelerate a body .

Last edited by CanAutM3; 02-18-2013 at 11:21 PM.
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      02-18-2013, 11:07 PM   #29
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Quote:
Originally Posted by HighandDry View Post
Disagree

The Horsepower and RPM define the torque curve. The amount of torque at a RPM is directly proportional to the force applied at that RPM and that determines your instantaneous acceleration.

It's about the gearing and not so much where they are in the rev range. The Dinan has 450tq/408hp and the M3 has 295tq/414hp. Now the HP is pretty equal, but how does the M3 keep up with the Dinan even though it's torque is much lower? It's absolutely the higher RPM's the M3 is able to produce, which obviously produces it's high HP with relatively low torque.

If you have a race, the Dinan will take a jump, but it will have to shift to second. The M3 is able to stay in first gear much longer and first gear has a higher torque multiplication. Thus the M3 will make more torque at the wheels after the Dinan shifts to second. The M3 should pull even or ahead because it can stay in first gear. The M3 shifts to second, but the Dinan has to shift to third and the M3 can keep up by using it's RPM advantage.
How can you disagree? Simply go to youtube and watch a few videos of flat out acceleration of both cars with a video showing the tachometer. You will see the RPMS on the M never drop below 6k on a full out run therefore RPMS below are of no importance for a flat out run. Since it revs to 8400 you have 2400 useable powerband

Look at a 335 and you see it never drops below 4500 or 5000k. Therefore about 2000-2500 useable powerband.

The M may have a few more revs within its powerband but essentiall both cars powerband is 2500k RPMS wide on full out acceleration.

I like the analogy of the screwdriver screwing in a screw by hand with the force of the turning being torque and the speed at which its turned as the RPM and work being Horsepower which the distance the screw goes over time.

An m3 takes 250 foot pounds of twisting force and applies it at a rate of 6-8400k RPMS which means its 250 foot pounds is being applied at a very fast rate just like someone who can screw in a screw faster.

The 335 takes its X amount of torque and applies it at a rate of 4500-7k which is analogous to turning a screwdriver more slowly but with more force than the M.

Two different methods to produce essentially the same amount of work or acceleration in this case.

Sure gearing matters as well but in this video the gear ratios are so close that its really a non-issue here with the two 6 speeds.
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      02-18-2013, 11:12 PM   #30
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Quote:
Originally Posted by M3takesNYC View Post
Sure gearing matters as well but in this video the gear ratios are so close that its really a non-issue here with the two 6 speeds.
Not sure what you mean by this .

While the gearing for each individual gear might be the same, the overall gear ratios including the final drive is definitely not the same in both cars. It is that difference in gear ratio that allows the M3 to put down more torque at the wheel than a 335i despite having less torque at the crank (in this case here, the M3 probably producing very similar torque at the wheel as the Dinan 335i despite much lower torque at the crank).

Last edited by CanAutM3; 02-18-2013 at 11:21 PM.
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      02-19-2013, 12:03 AM   #31
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The Dinan needs stiffer bushings, would quell all the complaints on the squat off the line and lack of crispness.

2 different cars with two different purposes:
335i=daily drive
M3=weekend drive

Yes you can use either for both, but I'm saying 80% of the time it's easier just owning both.
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      02-19-2013, 12:17 AM   #32
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Quote:
Originally Posted by CanAutM3 View Post
Not sure what you mean by this .

While the gearing for each individual gear might be the same, the overall gear ratios including the final drive is definitely not the same in both cars. It is that difference in gear ratio that allows the M3 to put down more torque at the wheel than a 335i despite having less torque at the crank (in this case here, the M3 probably producing very similar torque at the wheel as the Dinan 335i despite much lower torque at the crank).
335i:
Manual gear ratios – I/II/III4.11/2.32/1.54 :1
Manual gear ratios – IV/V/VI/R1.18/1.00/0.85/3.73 :1
Manual gear ratios – Final drive ratio3.23 :1

M3:
BMW M3 6-speed
Gear / Ratio / Max Speed / RPM drop on upshift
1st 4.055 44
2nd 2.396 75 4900
3rd 1.582 113 5600
4th 1.192 150 6300
5th 1.000 179 7000
6th 0.872 205 7300
Final Ratio 3.85

Not really a huge difference. Its not the M3's gearing that gives it a significant advantage but rather its the high RPMS that allow the relatively low amount of torque to be delivered at a rate that is so fast that it matches a larger amount of torque delivered at a slower rate (335).

The difference in first gear for example is a multiplier of 13.2 for the 335 vs 14 for the m3. It gets closer through the gears. That is not neglible but hardly what is making up the difference in torque.

The hardest thing for people to grasp seems to be the effect of RPMS's on horsepower and ultimately torque at the wheels. Think of high RPMS as a way to take a given value of torque and apply the torque more rapidly and at a fast rate which translates into more force delivered to the wheels and thus more torque at the wheels.

Essentially you can take a higher amount of torque and apply it less frequently to accelerate a mass or take a lower torque and apply it at a rate that is much higher to accelerate a mass. This is how the 335 vs m3 works

Last edited by M3takesNYC; 02-19-2013 at 05:09 PM.
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      02-19-2013, 01:12 AM   #33
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Quote:
Originally Posted by M3takesNYC View Post
The hardest thing for people to grasp seems to be the effect of RPMS's on horsepower and ultimately torque at the wheels. Think of high RPMS as a way to take a given value of torque and apply the torque more rapidly and at a fast rate which translates into more force delivered to the wheels and thus more torque at the wheels.

Essentially you can take a higher amount of torque and apply it less frequently to accelerate a mass or take a lower torque and apply it at a rate that is much higher to accelerate a mass. This is how the 335 vs m3 works
Umm, don't know what you're arguing about here, but I believe that everyone agrees on this point.

To say that RPM's don't matter in a flat out run is flat out wrong. 1st gear has a greater torque multiplication, so because of the M's higher RPM range, it can stay in 1st gear longer (which also increases it's HP). That's going to give it greater torque to the wheels and allow it to stay with the Dinan. If the Dinan had significantly less HP, the M would start walking away after 1st gear.

If the M didn't have high RPM's it wouldn't have high HP. If the M redlined at 6500, it's HP would be very low and the Dinan would kill it. So, how can you say RPM's don't matter?
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      02-19-2013, 02:32 AM   #34
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Who said RPM's don't matter? I posted a long explanation of why RPM does matter. Perhaps we are in agreement and saying the exact same thing.

I was saying that the gearing is almost the same between the two and that it is not gearing that is responsible for the performance of the high-revving m3. It is a function of its high rpms which makes it perform
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      02-19-2013, 09:58 AM   #35
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Quote:
Originally Posted by HighandDry View Post
If you have a race, the Dinan will take a jump, but it will have to shift to second. The M3 is able to stay in first gear much longer and first gear has a higher torque multiplication. Thus the M3 will make more torque at the wheels after the Dinan shifts to second. The M3 should pull even or ahead because it can stay in first gear. The M3 shifts to second, but the Dinan has to shift to third and the M3 can keep up by using it's RPM advantage.
Then the Dinan shifts to fourth. Then it heat-soaks and limps to the pits.
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      02-19-2013, 10:09 AM   #36
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Quote:
Originally Posted by M3takesNYC View Post
How can you disagree? Simply go to youtube and watch a few videos of flat out acceleration of both cars with a video showing the tachometer. You will see the RPMS on the M never drop below 6k on a full out run therefore RPMS below are of no importance for a flat out run. Since it revs to 8400 you have 2400 useable powerband

Look at a 335 and you see it never drops below 4500 or 5000k. Therefore about 2000-2500 useable powerband.

The M may have a few more revs within its powerband but essentiall both cars powerband is 2500k RPMS wide on full out acceleration.
Doesn't matter that the revs don't drop below 6K after it reaches redline. It still has to start at 1K.
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      02-19-2013, 12:30 PM   #37
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Quote:
Originally Posted by M3takesNYC View Post
Not really a huge difference. Its not the M3's gearing that gives it a significant advantage but rather its the high RPMS that allow the relatively low amount of torque to be delivered at a rate that is so fast that it matches a larger amount of torque delivered at a slower rate (335).
Hum, not entirely right.

Gearing has a direct impact on how torque at the flywheel is converted to torque at the wheels. And it is torque at the wheels that accelerates the car.

What gives the M3 the advantage is the combination of gearing and torque produced at high RPM.

Quote:
Originally Posted by M3takesNYC View Post
The difference in first gear for example is a multiplier of 13.2 for the 335 vs 14 for the m3. It gets closer through the gears. That is not neglible but hardly what is making up the difference in torque.
The final drive of the M3 is 3.846 compared to 3.080 for the 335i (you should check your numbers, they don't seem right). This is a 25% advantage in every gear, which is considerable. The fact that the M3 produces power high in the RPM range allows it to use the shorter gearing.

The maximum speed in each gear for the 335i and the M3 are quite similar. However, because of the gearing, the torque produced by the M3's engine is multiplied 25% more than the torque produced by the 335i's engine, yielding higher torque at the wheels. This is what allows the M3 to accelerate faster even if it has less torque at the flywheel.

Quote:
Originally Posted by M3takesNYC View Post
The hardest thing for people to grasp seems to be the effect of RPMS's on horsepower and ultimately torque at the wheels. Think of high RPMS as a way to take a given value of torque and apply the torque more rapidly and at a fast rate which translates into more force delivered to the wheels and thus more torque at the wheels.

Essentially you can take a higher amount of torque and apply it less frequently to accelerate a mass or take a lower torque and apply it at a rate that is much higher to accelerate a mass. This is how the 335 vs m3 works
A good way to illustrate the relationship of torque, RPM and power is to consider a gearbox. The power at the input and output of the gearbox is the same (assuming no losses in gearbox). However the torque is directly impacted by the ratio of the gearbox. Let's take a 2:1 ratio gearbox as an example at which you input 200lb-ft at 5000RPM. This translates to 190hp (200x5000/5252). The output spins at 2500RPM (2:1 ratio) and the torque produced is doubled to 400lb-ft. The power produced however is the same, 190hp (400x2500/5252).

Last edited by CanAutM3; 02-19-2013 at 04:48 PM.
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      02-19-2013, 03:00 PM   #38
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Quote:
Originally Posted by LarThaL
Quote:
Originally Posted by Nautik View Post
Said best right here.

The best way horsepower vs torque was explained to me was: "Horsepower = Torque * Engine Speed"

And as far as performance of the M3 engine, it certainly is under-rated if you just look at the peak power of it. It is very smooth and delivers that power over a much longer period of time.

The Math gurus need to crunch a new formula to rate an engine which incorporates how much power was generated over a given amount of time. Maybe some kind of weighted horsepower figure.
The exact formula is hp =(torque in lb-ft * rpm)/5250. If you look at ALL power and torque graphs, they all cross around 5250 rpm. This is where power in hp and torque in lb-ft are numerically the same.
My 5.9 liter cummins diesel redlines at 3150 rpm. I guess I'll never know about 5250 rpm. But it's torque curve is flat from about 1500 rpm to the top.
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      02-19-2013, 08:06 PM   #39
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Quote:
Originally Posted by CanAutM3 View Post
Hum, not entirely right.

Gearing has a direct impact on how torque at the flywheel is converted to torque at the wheels. And it is torque at the wheels that accelerates the car.

What gives the M3 the advantage is the combination of gearing and torque produced at high RPM.



The final drive of the M3 is 3.846 compared to 3.080 for the 335i (you should check your numbers, they don't seem right). This is a 25% advantage in every gear, which is considerable. The fact that the M3 produces power high in the RPM range allows it to use the shorter gearing.

The maximum speed in each gear for the 335i and the M3 are quite similar. However, because of the gearing, the torque produced by the M3's engine is multiplied 25% more than the torque produced by the 335i's engine, yielding higher torque at the wheels. This is what allows the M3 to accelerate faster even if it has less torque at the flywheel.

A good way to illustrate the relationship of torque, RPM and power is to consider a gearbox. The power at the input and output of the gearbox is the same (assuming no losses in gearbox). However the torque is directly impacted by the ratio of the gearbox. Let's take a 2:1 ratio gearbox as an example at which you input 200lb-ft at 5000RPM. This translates to 190hp (200x5000/5252). The output spins at 2500RPM (2:1 ratio) and the torque produced is doubled to 400lb-ft. The power produced however is the same, 190hp (400x2500/5252).
All of this is sort of correct, and not to pick on you, but you don't really have to mess with torque and gearing in order to determine acceleration - although you can. In your second paragraph ypu said "What gives the M3 the advantage is the combination of gearing and torque produced at high RPM."

This is true - but torque at rpm is what makes power, and it's really power that governs how fast a car can accelerate from any given speed. In fact, and I've said this several times before, but this time I'll shout it so folks back there in the cheap seats can hear:

ALTHOUGH YOU CAN DO THE CALCULATIONS IN ORDER TO DETERMINE TORQUE AT THE DRIVE WHEELS, AT ANY GIVEN SPEED IT'S POWER THAT GOVERNS ACCELERATION AND YOU DON'T HAVE TO BOTHER WITH EITHER TORQUE OR GEARING. POWER IS THE SHORTHAND IN THIS CALCULATION, AND IF YOU TAKE ANY TWO CARS ROLLING ALONG SIDE BY SIDE (and ignoring possible differences in wind and rolling resistance, rotational inertia, etc.), THE CAR MAKING BETTER POWER TO WEIGHT AT THAT INSTANT WILL BEGIN PULLING AWAY, REGARDLESS OF TORQUE OR GEARING.

OK, I feel better now. Thanks.

Bruce
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      02-19-2013, 09:47 PM   #40
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Quote:
Originally Posted by bruce.augenstein@comcast. View Post
All of this is sort of correct, and not to pick on you, but you don't really have to mess with torque and gearing in order to determine acceleration - although you can. In your second paragraph ypu said "What gives the M3 the advantage is the combination of gearing and torque produced at high RPM."

This is true - but torque at rpm is what makes power, and it's really power that governs how fast a car can accelerate from any given speed. In fact, and I've said this several times before, but this time I'll shout it so folks back there in the cheap seats can hear:

ALTHOUGH YOU CAN DO THE CALCULATIONS IN ORDER TO DETERMINE TORQUE AT THE DRIVE WHEELS, AT ANY GIVEN SPEED IT'S POWER THAT GOVERNS ACCELERATION AND YOU DON'T HAVE TO BOTHER WITH EITHER TORQUE OR GEARING. POWER IS THE SHORTHAND IN THIS CALCULATION, AND IF YOU TAKE ANY TWO CARS ROLLING ALONG SIDE BY SIDE (and ignoring possible differences in wind and rolling resistance, rotational inertia, etc.), THE CAR MAKING BETTER POWER TO WEIGHT AT THAT INSTANT WILL BEGIN PULLING AWAY, REGARDLESS OF TORQUE OR GEARING.

OK, I feel better now. Thanks.

Bruce
Fully agree

Read my first post in this thread, it is pretty much what I said

Quote:
Originally Posted by CanAutM3 View Post
This has been debated to death. Peak torque by itself is pretty much a meaningless number. As a single number, peak power provides a much better appreciation of an engine's capability to accelerate a car. Especially when comparing power to weight.
It is also the point I was trying to bring through with the gearbox example.

I guess you need to read the whole thread to understand why we ended up in the gearing discussion...

BTW, what I said is not "sort of correct", it is correct period

Last edited by CanAutM3; 02-19-2013 at 10:23 PM.
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      02-19-2013, 10:17 PM   #41
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LOL

True, HP is always king, but IF you want to figure out the instantaneous acceleration than torque will give you that.

Force determines your acceleration and torque is directly proportional to force for that RPM.

F=M*A

Work=F*DIstance or F=Work/Distance

Therefore Acceleration=Work/(M*Distance) or something like that

As Bruce said, Power to weight ratio is the key.

Last edited by HighandDry; 02-19-2013 at 10:23 PM.
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      02-19-2013, 10:44 PM   #42
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Quote:
Originally Posted by HighandDry View Post
LOL

As Bruce said, Power to weight ratio is the key.
We can start getting in much more complex discussions here. While it is true that power to weight is a key figure here (I said so myself). To be more precise, it is "available power" to weight that should be considered.

Let me explain. At lower speeds, drag is relatively low. So not much of the total power is used to overcome drag. However, as the speed increases, more and more power is used to overcome drag. The power required to overcome aero drag actually increases with the cube of speed.

What this means is that at higher speeds, a car with more hp might out accelerate a car that has a better absolute power to weight ratio.

To illustrate, let's assume two cars with the same aero characteristics (Cd and frontal area). One weighs 4000lb with a 400hp engine. The other, 2000lb with a 250hp engine. The second car has the better power to weight ratio 8 vs 10 lb/hp. So the second car will pull on the first at lower speeds.

However at a higher speeds, (lets assume a speed at which 200hp is required to overcome drag) the first car still has 200hp of "available power" for acceleration whereas the second one is only left with 50hp. In this case the first car would pull on the second (20 vs 40 lb / available hp).

The point I am trying to make: power to weight is king at lower speeds. Utlimate power is king at higher speeds

Last edited by CanAutM3; 02-20-2013 at 10:58 AM.
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      02-19-2013, 11:51 PM   #43
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Fully agree

Read my first post in this thread, it is pretty much what I said



It is also the point I was trying to bring through with the gearbox example.

I guess you need to read the whole thread to understand why we ended up in the gearing discussion...

BTW, what I said is not "sort of correct", it is correct period
You're right. It really wasn't incorrect, but what I was thinking about at the time I typed that was the rotational inertia thing that negates some of that extra torque at the drive wheels advantage you spoke of. As soon as you accelerate, poof!, you start paying at the rotational inertia window. Stiffer gearing, pay more.

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      02-20-2013, 12:28 AM   #44
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Originally Posted by CanAutM3 View Post
We can start getting in much more complex discussions here. While it is true that power to weight is a key figure here (I said so myself). To be more precise, it is "available power" to weight that should be considered.

Let me explain. At lower speeds, drag is relatively low. So not much of the total power is used to overcome drag. However, as the speed increases, more and more power is used to overcome drag. The power required to overcome aero drag actually increases with the cube of speed.

What this means is that at higher speeds, a car with more hp might out accelerate a car that has a better absolute power to weight ratio.

To illustrate, let's assume two cars with the same aero characteristics (Cd and frontal area). One weighs 4000lb with a 400hp engine. The other, 2000lb with a 250hp engine. The second car has the better power to weight ratio 8 vs 10 lb/hp. So the second car will pull on the first at lower speeds.

However at a higher speeds, (lets assume a speed at which 200hp is required to overcome drag) the first car still has 200hp of "available power" for acceleration whereas the second one is only left with 50hp. In this case the first car would pull on the second (20 vs 40 lb / available hp).

The point I am trying to make: power to weight is king at lower speeds. Utlimate power is king at higher speeds
Great note. Those of us who misspent our youth way back when often learned this the hard way, when we were able to easily dust a Caddy or Lincoln off the line, but then had to watch helplessly as he steadily began reeling us in, and then just kept motoring away.

A nit: The power necessary to overcome aero drag actually increases with the square of speed. You get to keep the cube, however, because the need for power increases in a linear way as speeds climb. That is, ignoring aero and rolling resistance, you'll need five times the power to accelerate at the same rate at 100 mph as you needed at 20.

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