[alpinewhite3]

I've been wondering about this, can someone please give a technical explanation ? Is it cause of the gearing or b/c peak torque occurs at 2750?

[KungFuJoe]

Peak torque at 2750RPMs. Torque = acceleration.

Which brings up another question. I've never driven a G35, but it seems most people seem to think it accelerates faster (or at least FEELS faster). Torque is what you feel...but the G35 doesn't reach it's peak torque until 4800RPMs. Of course it has more torque than the 330. Is there anywhere to find HP and torque curves for both cars?

[KungFuJoe]

BTW...I also drive a 95 integra gs-r, which I've had for 9 years. It has max torque of 128ft/lbs at 6200RPMs!

Of course, with an 8200RPM redline, it just keeps pulling and pulling...

[E90Fleet]

Originally Posted by KungFuJoe

Torque = acceleration.

If that were true a 320d would be faster than a 325i, which it aint

[Paul330d]

HP = acceleration, torque = pick-up

[crex]

It doesnt accelerate fast, but it is peppy.

[Robin_NL]

Just take a look at the 2006 F1 cars. Only 2.4 litres(V8) with 700+BHP @ 19000rpm and maybe 270Nm @ 12000(dunno exactly)

HP + revs + gearing +weight + traction I think.

[Broken1]

Originally Posted by E90Fleet

If that were true a 320d would be faster than a 325i, which it aint

Torque is the force applied in a turning motion. I.e. it's the feeling of "pull" when accelerating a car - as it's the force acting on the crankshaft from the piston, which "pulls" the car forward.

Power is force x speed. Therefor, power is the ability of the engine to change the torque into speed. (*Howstuffworks.com: If you were pushing on something with a force of 1 N, and it moved at a speed of 1 m/s, your power output would be 1 watt.)

This is why a 320d feels more powerfull than a 325i BUT the 325i is acutally FASTER than a 320d. The 320d gives you more pull, but the 325i is better at converting that pull into speed.

[Saintor]

Originally Posted by agent0986

I've been wondering about this, can someone please give a technical explanation ? Is it cause of the gearing or b/c peak torque occurs at 2750?

It is because of HP and gearing. Torque is just not determinant for acceleration over a range of RPM.

[David328M-Sport]

the 330 accellerates fast because of the right mix between power, torque, engine displacement and bmw's experience.

the engine does not have to drive as many auxiliary items as in previous models so it can convert the gains to the rear wheels.

being a bmw, the chassis dynamics come into play as does the aerodymamics of the car. take a look at the underside of the car when an opportunity arises. you will be impresed at how well it has been constructed to reduce drag.

the valvetronic system on the new n52 engine helps as well as the lightweight construction of the engine.

it really is a combination of many things that make the 6 cylinder e90 cars as flighty as they are.

[RD Sport]

Here are some numbers for reference.

320d 163hp@4000rpm, 251lb-ft@2000
0-100km/h 8.3s
Acceration 80-120km/h in 4th gear: 6.7s, 5th gear: 8.5s, 6th gear: 11.3s
topspeed: 225km/h

325i 218hp@6500rpm, 184lb-ft@2750-4250rpm
0-100km/h 7.0s (Faster than 320d)
Acceration 80-120km/h in 4th gear: 7.5s (slower than 320d), 5th gear: 9.5s (slower than 320d), 6th gear: 12.4s(slower than 320d)
topspeed: 245km/h (faster than 320d)

By looking at these numbers. I think you really can't say which one is faster. It really depends on the situation. If running at topspeed, of coz 325i is faster but if they are pulling from 80km/h upward, the 320d will be the winner

[Robin_NL]

Originally Posted by RD Sport

Here are some numbers for reference.

320d 163hp@4000rpm, 251lb-ft@2000
0-100km/h 8.3s
Acceration 80-120km/h in 4th gear: 6.7s, 5th gear: 8.5s, 6th gear: 11.3s
topspeed: 225km/h

325i 218hp@6500rpm, 184lb-ft@2750-4250rpm
0-100km/h 7.0s (Faster than 320d)
Acceration 80-120km/h in 4th gear: 7.5s (slower than 320d), 5th gear: 9.5s (slower than 320d), 6th gear: 12.4s(slower than 320d)
topspeed: 245km/h (faster than 320d)

By looking at these numbers. I think you really can't say which one is faster. It really depends on the situation. If running at topspeed, of coz 325i is faster but if they are pulling from 80km/h upward, the 320d will be the winner

From 80kmh THRU gears(shifting at 6600/7000 and for the 320d @ 4000/4200rpm) the 325i will be quicker because of the 55BHP difference. If you don't want to shift and stay in 4th gear the 320d will win. The car with the most HP and driven properly will be fastest.

[RD Sport]

Originally Posted by Robin Hood

From 80kmh THRU gears(shifting at 6600/7000 and for the 320d @ 4000/4200rpm) the 325i will be quicker because of the 55BHP difference. If you don't want to shift and stay in 4th gear the 320d will win. The car with the most HP and driven properly will be fastest.

Maybe I will rent a 325i next year when I go to Europe and try it. I had a 320d this year. It really surprise me how quick it is. 0-100km/h in 7.9s and 0-200km/h in 30s which I tested by myself

[Durbrain]

Originally Posted by Robin Hood

From 80kmh THRU gears(shifting at 6600/7000 and for the 320d @ 4000/4200rpm) the 325i will be quicker because of the 55BHP difference. If you don't want to shift and stay in 4th gear the 320d will win. The car with the most HP and driven properly will be fastest.

Exactly.

HP correlates best with average acceleration.
Torque correlates best with instantaneous acceleration.

Instantaneous acceleration at one point in the RPM range is useless information (ie max torque). You also need to know i) its instantaneous acceleration at other points in the RPM range & ii) how large an RPM range the engine has.

HP takes into account all of the above and is thus the key value.

All those ppl who say "diesels accelerate better at speed than petrols" are wrong. Driving for maximum acceleration, a 325i will always outaccelerate a 320d no matter what the starting speed.

Of course, if we limit the 'race' to 4th gear - the 320d will win. But that's not fair. If the 325i was really trying, he would downshift to 3rd (or even 2nd) and make use of the torque multiplication of the lower gear + the extended rev range of the petrol engine. The 320d doesn't have this option because it already ran out of puff at 4000rpm and thus can't downshift.

Diesels will only win races if both drivers are lazy and refuse to downshift.

HP rules!

[Broken1]

Originally Posted by Durbrain

Diesels will only win races if both drivers are lazy and refuse to downshift.

In a real-world situation...with two normal drivers: If the 325i and 320d are driving next to eachother at 80km/h in 4th, and they both decide to "take-off" and race at the same time, the 320d will be gone before the 325i driver has completed his downshift.

I've tried this with a friend of mine, who is probably a better driver than me in his E90 325i. He was the one "counting" and even had the advantage of knowing when he was going to say go. As he downshifted, I just put foot... I stayed infront of him. You lose time doing the downshift.

[Paul330d]

Just to broaden the discussion & drag in 330i owners...

0-100km/h
330i: 6.3
330d: 6.7

80-120km/h in 4th
330i: 6.6
330d: 5.0

(BMW figures for 2WD cars with manual transmission).

[RD Sport]

Originally Posted by Paul330d

Just to broaden the discussion & drag in 330i owners...

0-100km/h
330i: 6.3
330d: 6.7

80-120km/h in 4th
330i: 6.6
330d: 5.0

(BMW figures for 2WD cars with manual transmission).

330d Quick yet saves fuel

[RD Sport]

Originally Posted by Broken1

In a real-world situation...with two normal drivers: If the 325i and 320d are driving next to eachother at 80km/h in 4th, and they both decide to "take-off" and race at the same time, the 320d will be gone before the 325i driver has completed his downshift.

I've tried this with a friend of mine, who is probably a better driver than me in his E90 325i. He was the one "counting" and even had the advantage of knowing when he was going to say go. As he downshifted, I just put foot... I stayed infront of him. You lose time doing the downshift.

Yes indeed! The time for downshift=no power. So it's very difficult to judge which one is faster in real world driving situtation. If they are both on the race track, the 320d will eat dust period............

[visor]

Originally Posted by Durbrain

Exactly.

HP correlates best with average acceleration.
Torque correlates best with instantaneous acceleration.

Instantaneous acceleration at one point in the RPM range is useless information (ie max torque). You also need to know i) its instantaneous acceleration at other points in the RPM range & ii) how large an RPM range the engine has.

HP takes into account all of the above and is thus the key value.

Good points.

From previous discussions on this topic, the total areas under the torque and hp curves are more important than peak torque and hp for acceleration.

Putting it another way, it is much better to have slightly lower hp/tq if it's available flatter across the whole rev range than to have a peaky engine with a higher hp/tq at only 1 or 2 points in the rev range. Pit the 330i against the G35 and you'll understand why.

Plus, there're other factors also, like weight, gearing, traction.

[haulin79]

Torques versus Power? Who cares!! You always want more of both

[RD Sport]

Originally Posted by haulin79

Torques versus Power? Who cares!! You always want more of both

yes, indeed! Power and tq are never enough

[thebigman]

Originally Posted by Broken1

In a real-world situation...with two normal drivers: If the 325i and 320d are driving next to eachother at 80km/h in 4th, and they both decide to "take-off" and race at the same time, the 320d will be gone before the 325i driver has completed his downshift.

I've tried this with a friend of mine, who is probably a better driver than me in his E90 325i. He was the one "counting" and even had the advantage of knowing when he was going to say go. As he downshifted, I just put foot... I stayed infront of him. You lose time doing the downshift.

Indeed Broken1, one of the great advantages of diesel engines is that you have the power right where you need it in everyday driving, particularly useful for short overtaking bursts.