[ChrisMWard]

Originally Posted by silverbmwz3

JonMad> what did you mean by "real world, std diesel faster anyway blah blah etc"

The only thing that bugs me with diesel is the noise when it first starts up. There seem to be a lot more around than 335i, the diesel is becoming more tempting now.

I wouldn't worry about the noise, go drive one, it will blow your 325i off the planet.

Regards

Chris

[silverbmwz3]

Chris> Thanks. I did drive one, at the weekend. Loved it, didn't push it as I had the dealer with me (p'raps I should have) but was definitely quick. Just the taxi noise on startup that put me off, but I guess that's only 1% of the journey !!!

[silverbmwz3]

Need for speed> I don't get this torque business....surely if the 335i is faster 0-60, 50-70 or whatever then it's faster ?

[NFS]

Originally Posted by silverbmwz3

Need for speed> I don't get this torque business....surely if the 335i is faster 0-60, 50-70 or whatever then it's faster ?

Torque is the measureable rotational force which creates acceleration. You can ignore horsepower for the time being.

A vehicle will always accelerate hardest when torque at the wheels is highest. Torque at the wheels is a function of engine torque for a given speed multiplied by the effects of gearing.

BMW don't post in gear acceleration times for the 335d because it is only available as an auto. But it's in gear times WILL be faster than the 335i's, just as the in gear times for the 330d are faster than the 330i (in fact the 320d's are faster than the 330i).

This happens because turbo diesel engines create lots of torque, much more than petrol engines. Therefore most of the time, if you are cruising in a sensible gear - say at 70mph in 5th - the available wheel torque in a diesel will be greater than in a petrol car. That means it will accelerate harder in that gear - hence the in gear times.

The petrol car has an advantage though. It makes torque higher in it's rev range (which means it has higher horsepower). So in a 335i you would be able to drop to a lower gear than the diesel and hence multiply your torque.

So petrol cars ARE quicker, but only if you keep the revs high (in the powerband). You can't do this practically on the road, so in many situations diesels are quicker.

Great explanation here:

http://craig.backfire.ca/pages/autos/horsepower

[silverbmwz3]

Are you a rocket scientist NFS ? Or a BMW engineer. C'mon. Which ?

[NFS]

Originally Posted by silverbmwz3

Are you a rocket scientist NFS ? Or a BMW engineer. C'mon. Which ?

I'm a BMW anorak.

Before I got my first diesel (320cd) I decided I had to understand what these 'torques' meant and why everyone said diesels were quick.

So I educated myself.

[RockIt]

Originally Posted by ChrisMWard

I wouldn't worry about the noise, go drive one, it will blow your 325i off the planet.

Regards

Chris

But it depends what you want from a car. For me the engine note and revs are crucial in terms of the 'fun' factor. This may be because I'm used to driving cars that thrive on revs, but heart rules head whan it comes to the crunch. The diesel may have the torque, but it just doesn't do it for me as an all round driving experience. For some people it's definitely what they want and that's great. We can't all be the same. But for me the petrol engine appeals to the senses much more immediately. I love the sound of the engine as it reaches 7000rpm and as I'm used to a car that needed lots and lots of revs to get the most out of the engine, I have no problem revving the nuts off the BMW and enjoy doing so whenever possible! (Sod the increased fuel bill and environmental 'impact'...I pay enough road tax to ease the conscience!)

[NFS]

Originally Posted by RockIt

But it depends what you want from a car. For me the engine note and revs are crucial in terms of the 'fun' factor. This may be because I'm used to driving cars that thrive on revs, but heart rules head whan it comes to the crunch. The diesel may have the torque, but it just doesn't do it for me as an all round driving experience. For some people it's definitely what they want and that's great. We can't all be the same. But for me the petrol engine appeals to the senses much more immediately. I love the sound of the engine as it reaches 7000rpm and as I'm used to a car that needed lots and lots of revs to get the most out of the engine, I have no problem revving the nuts off the BMW and enjoy doing so whenever possible! (Sod the increased fuel bill and environmental 'impact'...I pay enough road tax to ease the conscience!)

Funnily enough I totally agree - which is why I bought a 330i

[silverbmwz3]

I think if I could be bothered to wait til probably July for a spec'd 335i I would but I'm very tempted to find a 335d ready/coming soon.

[RockIt]

Originally Posted by needforspeed

Funnily enough I totally agree - which is why I bought a 330i

[JonMad]

I sure miss the induction roar of my old 306 Rallye as it revved rounnd to 7500.

[RockIt]

Originally Posted by JonMad

I sure miss the induction roar of my old 306 Rallye as it revved rounnd to 7500.

I actually miss my rotary engine as it redlined at 9000 and beeped to let you know that it was time to change gear!

[JonMad]

ZiM should be here in a bit, I reckon, talking about his old Integra Type R

[ChrisMWard]

Originally Posted by RockIt

But it depends what you want from a car. For me the engine note and revs are crucial in terms of the 'fun' factor. This may be because I'm used to driving cars that thrive on revs, but heart rules head whan it comes to the crunch. The diesel may have the torque, but it just doesn't do it for me as an all round driving experience. For some people it's definitely what they want and that's great. We can't all be the same. But for me the petrol engine appeals to the senses much more immediately. I love the sound of the engine as it reaches 7000rpm and as I'm used to a car that needed lots and lots of revs to get the most out of the engine, I have no problem revving the nuts off the BMW and enjoy doing so whenever possible! (Sod the increased fuel bill and environmental 'impact'...I pay enough road tax to ease the conscience!)

I can understand perfectly what you are saying and I had a similar opinion many years ago, my first car was a 550kg Mini that ran 100BHP at the wheels at nearly 8000RPM and I loved it. I raced cars for 15 years at up to international level and now I feel my days of tearing around like a hooligan have passed. I like a car that's relaxed, goes like shit off a shovel when you want it to, is quiet and easy to drive. We had an M3 and it was great but it was tiring to drive and hard work in town and had nowhere near the torque of the 330 diesel that replaced it.

I guess I'm just getting old.

Regards

Chris

[JonMad]

Originally Posted by ChrisMWard

I raced cars for 15 years at up to international level

Oooh, tell us more... (if you want to, of course)

[RockIt]

Originally Posted by ChrisMWard

I can understand perfectly what you are saying and I had a similar opinion many years ago, my first car was a 550kg Mini that ran 100BHP at the wheels at nearly 8000RPM and I loved it. I raced cars for 15 years at up to international level and now I feel my days of tearing around like a hooligan have passed. I like a car that's relaxed, goes like shit off a shovel when you want it to, is quiet and easy to drive. We had an M3 and it was great but it was tiring to drive and hard work in town and had nowhere near the torque of the 330 diesel that replaced it.

I guess I'm just getting old.

Regards

Chris

I can appreciate what you're saying Chris. I don't like to think of myself as a 'hooligan'...but I do like to drive in a spirited fashion at times. And I did catch myself talking to my wife about getting a 'sensible' car some time in the future... That will be a long time in the future I think, because I've still got to own a Porsche 911. It's one of my promises to me, so it's simply got to happen

Cheers

[mjh93sa]

Originally Posted by silverbmwz3

Need for speed> I don't get this torque business....surely if the 335i is faster 0-60, 50-70 or whatever then it's faster ?

It's made a bit complicated by the standard autobox on the 335d. Like for like there's not a lot in it, less than half a second with the autobox to 60 (5.8 / 6.2) according to official figures.

Now comes the interesting bit...
335i 50-75 in 4th = 5.3
330d 50-75 in 4th = 5.0
So in gear the 330d gives away a whole turbo and still out accelerates the 335i (just).

Now the technical bit...
Basically Torque is a measure of turning force. Power is related to torque and engine speed. Power = Torque x rpm.

So for a given engine speed the engine with the most torque will be producing the most power and so acceleration at that point. Now as we know a diesel is great at generating low down torque, but this tails off at high rpm. Therefore at low revs the power being produced by a diesel will generally be more than that being produced by a similar petrol engine. Or a smaller engine will be as quick as a larger one (ie Paddy's 320d vs Beauforty's 330i )

So how does this effect the 335i / 335d? The 335i has a ridiculously flat torque curve and generates a max torque of 400Nm from 1300 - 5000 rpm. The 335d generates more than 400Nm of torque from some 1200 - 4500 rpm (according to the brochure curve). So at these revs the power generated will be more than the 335i can generate.

But... the 335i can keep pulling to higher revs and so although it doesn't generate as much torque it can produce more power (by using high revs). But by then the diesel has hooked up the next gear to use it's superior torque to counter the petrol's superior revs.

[mjh93sa]

Damn. Took too long thinking and typing, where did all those posts come from?

[silverbmwz3]

So 50-70 the 335d will be quicker than 335i ?

[mjh93sa]

It'll depend on the gearbox and how it's driven.

Hypothetically if they both started at about the same revs and stayed in gear (with the same gearing) then the diesel would be quickest as it has more torque. More torque = more acceleration.

But the petrol can use more revs to generate a higher power output. So if the petrol drops a gear or two more than the diesel and gets those revs up it may be at an advantage, but shifting takes time.

But in the real world the 335d has an auto so it's going to kick down and do it's best to give you the maximum acceleration possible. A 335i auto will do the same and almost certainly drop to an even lower gear to maximise power. We would need proper figures and curves, or some tests to determine if or by how much it would be faster. However, I would go out on a limb and say that in the real world a manual 335i will be slower. Potentially the direct drive, fewer transmission losses and so on put it at a theoretical advantage. But... it would need a driver that will select the right gear, shift perfectly and generally operate like a robot. With practice and a disdain for the mechanical welfare of the car it's possible, but I wouldn't like to be that harsh on my car.

[ChrisMWard]

You shouldn't really be worried about what gear your in as this clouds the situation a bit because the two cars have quite different final drive ratios. As has been correctly stated a cars rate of acceleration will be highest at the RPM its engine develops maximum torque. However there is another factor in acceleration and that is weight. My 400cc bike would spank our M3 to about 70 but after that the M3 would start to gain and over a quarter of a mile would have it. After about 100mph aerodynamics start to have an effect as well.

What would be more interesting to see though would be a torque versus road speed graph which would explain things visually a bit more easily especially for those markets that don't have the 335d.

Regards

Chris

[Raggie]

Originally Posted by RockIt

I actually miss my rotary engine as it redlined at 9000 and beeped to let you know that it was time to change gear!

Like wise.. I traded the RX8 for the BM.. and I'm starting to miss it..

as good as this car is.. I just can't get it round the bends as fast

Wish I could have kept both..