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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Powertrain and Drivetrain Discussions > N54 Turbo Engine / Drivetrain / Exhaust Modifications - 335i > How does all this torque help?



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      04-21-2007, 10:04 PM   #23
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I'm also pretty sure that 12.3 number was achieved with euro launch control which helps quite a bit.
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      04-22-2007, 04:31 AM   #24
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From engine's part, it is the integral of the hp curve that determines the acceleration. Torque slows you down since the transmission parts need to be heavier. Weight is performance car's worst enemy. The more curves and less straight line, the more the weight is an issue.

Last edited by bnj; 04-22-2007 at 05:26 AM.
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      04-22-2007, 06:57 AM   #25
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Quote:
Originally Posted by leftcoastman View Post
While I agree that torque in and of itself isn't enough to determine how fast a car is, I wouldn't say it's so simple to say that torque multiplication is what makes low gear acceleration so rapid.

At low gearing, you are travelling at low speed. Air resistance increases as a square of speed. At higher gears, you're probably going at a high speed, therefore the power necessary to overcome that air resistance (which has been growing as a square) is much higher.
Frictional resistance (air and road) is obviously a factor and it's effect does increase (roughly) to the square of speed. However, a vehicle will accelerate most when wheel torque is greatest.

If you work out the torque at the wheels (multiplying by gear ratios and final drive ratio) then you will see that it is massively higher in 1st gear than 5th or 6th.

There are several small light vehicles which can accelerate to 60 mph very quickly. They are often powered by high revving engines with relatively low levels of torque.

To continue to accelerate as swiftly in the upper gears you need the ability to generate lots of torque at high revs.
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      04-22-2007, 12:53 PM   #26
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Quote:
Originally Posted by needforspeed View Post
Frictional resistance (air and road) is obviously a factor and it's effect does increase (roughly) to the square of speed. However, a vehicle will accelerate most when wheel torque is greatest.

If you work out the torque at the wheels (multiplying by gear ratios and final drive ratio) then you will see that it is massively higher in 1st gear than 5th or 6th.

There are several small light vehicles which can accelerate to 60 mph very quickly. They are often powered by high revving engines with relatively low levels of torque.

To continue to accelerate as swiftly in the upper gears you need the ability to generate lots of torque at high revs.
When it comes to how engine affects acceleration, power during the acceleration defines how fast the car accelerates.

You are kind of right saying that one needs torque at high revs. Torque is power multiplied by time. Thus, you need power x time at high revs (revs is measured as 1/time (revs per time)) -> power x time / time (power multiplied by time divided by time -> power. So torque at high revs is power.

Power is defined as how fast the work is done. The work can be e.g. getting car to 100 mph. How fast this work is done (ceteris paribus) depends on the average power during the acceleration.

You can't avoid having high torque if you have high power as it is closely related to power. However, average power is the measure affecting the acceleration. Power means performance. Torque is luxory and stress to transmission components.
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      04-22-2007, 01:06 PM   #27
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Quote:
Originally Posted by E90ice View Post
I don't understand why there is all this talk about the torque?

How does it help?

E60 M5 500hp and 386 torque:

0-60 - 4.5 sec
1/4 mile - 12.3

E55 AMG 500 hp and 517 torque:
0-60 - 4.5 sec
1/4 mile - 12.4 (Road & Track)

The M5 is just as fast with much less torque than the E55.

So, why alll this talk about the torque? Not trying to flame anything or anyone...just wondering....
High torque means that there is a lot of power also at lower revs. This you can verify also from power curve. However, typically they don't publish power curves e.g. due to the space they take. Thus giving torque and power figures and their respective revs describes the power delivery through the rev range better than power figure alone. So torque is power at low - medium revs. It does not mean a thing in maximum acceleration, since in acceleration you use only high revs since there is more power than in low/mid rev range.

However, it is nice to have power also in low/mid range. I.e. it is nice to have high torque figure.
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      04-22-2007, 01:37 PM   #28
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Quote:
Originally Posted by CokerRat View Post
Horsepower is what ultimately makes a car go fast -- it is a measure of power output. Torque is a measure of how much twist the engine will make... but torque is important in how the curve looks over the whole rpm range. Torque made at higher rpm's allows you to take advantage of gearing so that you get the same acceleration force at the wheels as cars making more torque but at lower rpms.
True, but a piston motor is not designed for torque at high rpms. Torque is simply put, the power of the explosion in the cylinders. It is directly proportional to displacement.

Quote:
Originally Posted by leftcoastman View Post
While I agree that torque in and of itself isn't enough to determine how fast a car is, I wouldn't say it's so simple to say that torque multiplication is what makes low gear acceleration so rapid.

At low gearing, you are travelling at low speed. Air resistance increases as a square of speed. At higher gears, you're probably going at a high speed, therefore the power necessary to overcome that air resistance (which has been growing as a square) is much higher.
Absolutely true. But air resistance does not come into play at speeds less than 100kph at a coefficient of drag of around .3 which I believe our 3 series has. Below that speed, its the inertial resistance where torque is very important.

Quote:
Originally Posted by bnj View Post
From engine's part, it is the integral of the hp curve that determines the acceleration. Torque slows you down since the transmission parts need to be heavier. Weight is performance car's worst enemy. The more curves and less straight line, the more the weight is an issue.
+1.

Quote:
Originally Posted by bnj View Post
When it comes to how engine affects acceleration, power during the acceleration defines how fast the car accelerates.

Power is defined as how fast the work is done. The work can be e.g. getting car to 100 mph. How fast this work is done (ceteris paribus) depends on the average power during the acceleration.

You can't avoid having high torque if you have high power as it is closely related to power. However, average power is the measure affecting the acceleration. Power means performance. Torque is luxory and stress to transmission components.
Well said.

Torque has nothing to do with speed. At high rpms, its the motor's volumetric efficiency; how fast it can fill the cylinders with air and then expell it; that is power. Power is the only thing that will yield the fastest speed. With that said, the speeds at which most people will drive their cars, torque will still dominate. Around 250kph and higher, its all power.

AMG motors are much better suited for a street car and the speeds at which a street car will see. BMW motors really shine at high load, high rpms, and high speeds. Its not a matter of respect or power for money; AMG's and BMW M's are just different cars. Unless BMW changes its philosphy, M cars will never beat a Powerful Merc on the streets.

Last edited by homerunball; 04-22-2007 at 01:58 PM.
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      04-22-2007, 02:51 PM   #29
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Stock for Stock...
Check this out, my friend:

http://videos.streetfire.net/categor...1D2A2488DA.htm




Quote:
Originally Posted by purplewidow View Post
actually if you have been reading m5 owners are getting spanked by e55 e63 cls 55 cls63 cl55 cl63 s55 and soon to be s63 ....the torque allows for power throughout the power band...i another note i couldn't even keep up with a 335 in the s55 cause of how nimble it is...mercs are great in a straight line but weaving in and out of traffic better suits a small car...but if there was no traffic and i could just gunn it no 335 with a procede or not could catch me....the s55's torque is crazy powerful!!!! people are getting 4.1 0-60 and late 11's on the quartes in the s600 which is supposed to be slower than a 63 or 55....it's crazy just wish AMG's could handle as well as they pull and there steering was as good as bmw....there would be no competition for merc then they would own...but i gotta say i see a hell of a lot more cls, cl, s, and e class amg's than i see m5's and m6's...bmw's big mistake was making the car solely for the smg...what car company offers just the shitty smg even though europe loves it america hates it...then they come out with an even crappier 6sp and it is soooo crappy cause the car was never designed for it in the first place....i am shocked at how shitty the m5 is and how the options for it in terms of trani's suck ass.... no one want's to get there ass handed to them by a merc and in the s55 which is an 03' i rock the shit out of them on the highway, where 90% of the owners have fun with there car...on a track the m5 hands down will kill an amg but damn do they suck in a straight line comparison....i know europe loves the smg and it suites there mountainous driving style more but here in most parts of the US where people own m5's and amg's they aren't concerned with the car beating the merc on a track...they care about real life and comfort and the amg's just kill the m's for that reason....all this talk aout 420 hp and only 289 torque in the new m3....the new merc is gonna have aroung 480 in both the clk has i believe more than 500ft/lbs of torque at least 480...this will make it suck ass on a track cause it will just keep pealing out after a turn which is why bmw relies more on revs and hp to make power than torque....hence why the bmw will win on a track and the merc on the highway
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      04-22-2007, 03:35 PM   #30
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Quote:
Originally Posted by E90ice View Post
Stock for Stock...
Check this out, my friend:

http://videos.streetfire.net/categor...1D2A2488DA.htm

Not that Video. That video has caused alot of debate on mbworld. All the times posted on dragtimes and other videos don't match the outcome. The US cars have a crippled launch control. Same day same track 12.50-60 for the M5 , 12.17 to 12.33 for the e55. Just what some people have witnessed at a track event.
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      04-22-2007, 03:40 PM   #31
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Quote:
Originally Posted by E90ice View Post
I don't understand why there is all this talk about the torque?

How does it help?

E60 M5 500hp and 386 torque:

0-60 - 4.5 sec
1/4 mile - 12.3

E55 AMG 500 hp and 517 torque:
0-60 - 4.5 sec
1/4 mile - 12.4 (Road & Track)

The M5 is just as fast with much less torque than the E55.

So, why alll this talk about the torque? Not trying to flame anything or anyone...just wondering....
Firstly E55's have 469HP not 500 only the E63 has 500hp. Secondly the M5 has a 7-speed transmission and the E55 has 5-speeds.All that tourqe you really feel from a low speed roll more then anything.I used to have CL55 and it had 500hp and 516tq and the inertia you feel pushing you back is more intense then in an M5
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      04-22-2007, 03:52 PM   #32
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my buddy just trade his SL 55 for a new m5 and says the m5 feels faster
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      04-22-2007, 07:31 PM   #33
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Quote:
Originally Posted by scalbert View Post
This is an old write up but one of the better simplistic explanations I have seen.

Horsepower and Torque

A Quick quote:
Thats simplistic, I feel like an absolute idiot now
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