[NoelWatson]

Originally Posted by SO8

IIRC when Autocar tested the 272bhp 330i it was 0.1 to 60 quicker (at 6 secs dead) than a 330d LCI 241bhp (at 6.1)... but nearly a second slower to 100mph at nearer 16 than the 15 secs dead of the LCI 330d.

I saw these figures when I was looking at both before I bought a 330d LCI

Are you definitely sure they tested the N53 330i?

[dxb335d]

Originally Posted by NoelWatson

My friend put his on a few months back and it was a tad under 300 IIRC - dodgy MAF sensor to blame. This is not uncommon apparently according to the chap that owns the rolling road (he owns an E46 M3). That said, I am yet to be convinced that the 330 makes 272 bhp when it has a few miles under its belt.

That sounds like a poor example coupled with a problem.

Maf sensor problem ain't gonna lose it 30-40HP, must be a low power one anyhow.

[NoelWatson]

Originally Posted by dxb335d

That sounds like a poor example coupled with a problem.

Maf sensor problem ain't gonna lose it 30-40HP, must be a low power one anyhow.

I'll get in touch with him and get the before and after numbers.

[dopper99]

Originally Posted by SO8

IIRC when Autocar tested the 272bhp 330i it was 0.1 to 60 quicker (at 6 secs dead) than a 330d LCI 241bhp (at 6.1)... but nearly a second slower to 100mph at nearer 16 than the 15 secs dead of the LCI 330d.

I saw these figures when I was looking at both before I bought a 330d LCI

Talking of Autocar............just looked up the new M5 does 0-100 in 9 secs. now thats quick.

[dxb335d]

Originally Posted by dopper99

Talking of Autocar............just looked up the new M5 does 0-100 in 9 secs. now thats quick.

Is the review in this weeks? I'll have to get that tomorrow!!

9.what mate?

[dopper99]

Originally Posted by dxb335d

Is the review in this weeks? I'll have to get that tomorrow!!

9.what mate?

No, it was in the section at the back of an old Autocar I've got on a M5 with a tested date of 29/12/11 so they must have tested it then.

Was 9.0s dead.
And 0-60 in 4.3s
30-70 in 3.6s

Pretty rapid.

[SteveC]

High torque at lower rpm and high gearing vs. lower torque, higher rpm and lower gearing is very difficult to compare on paper.

Even on the road, comparisons are difficult and will depend on the type of driving.

For example, if we compare 2 cars with similar performance (330i vs 330
d) driven 'normally' in a straight line, (<50% throttle, short shifting), high torque at low rpm will feel and be faster. Driven for maximum performance in a straight line (max throttle, max revs), lower torgue and gearing with high rpm will typically feel and be faster. On a combination i.e real world....the diesel will be faster punching out of the bends but will even eventually be overhauled on the longer straights by the 30i.

So, in normal driving situations on winding roads, the '30d will feel and be considerably quicker. Even driven at 10 10ths, the diesel should still be the quicker o winding roads. Throw in a lot of staights and the 30i will reign in the 'd but realistically only on the racetack, due to the high speeds involved.

[A_P]

Originally Posted by SteveC

So, in normal driving situations on winding roads, the '30d will feel and be considerably quicker. Even driven at 10 10ths, the diesel should still be the quicker o winding roads. Throw in a lot of staights and the 30i will reign in the 'd but realistically only on the racetack, due to the high speeds involved.

I am not arguing your theory of gearing and torque variables. But on what grounds are you saying a 330d which is heavier and has a considerably lower power to weight ratio than a 330i is faster in the twisties?

On what experience or academic qualifications are you basing this on? If you can provide adequate weight to your argument then I will accept your theory.

Also same goes to the other people who havent actually compared the 330i and 330d and also the M3 in real life. I thought the original question on here was based on standard assumed factors.

- all cars producing the manufacturer rated power and torque figures and are machanically sound.
- all factors influencing mechanical grip such a tires, brakes, weather, surface conditions all fixed.
- either same driver or 2 equally competant drivers.

I do not have a degree in fluid mechanics. or vehicle development. My grounds are experience. I owned a E46 M3 prior to the 330i and have raced my friends 330d.

[BanziBarn]

Originally Posted by dopper99

No, it was in the section at the back of an old Autocar I've got on a M5 with a tested date of 29/12/11 so they must have tested it then.

Was 9.0s dead.
And 0-60 in 4.3s
30-70 in 3.6s

Pretty rapid.

I can vouch for the fact that the M5 is massively rapid! Awesome bit of kit.

[ALF_E90]

Originally Posted by SO8

IIRC when Autocar tested the 272bhp 330i it was 0.1 to 60 quicker (at 6 secs dead) than a 330d LCI 241bhp (at 6.1)... but nearly a second slower to 100mph at nearer 16 than the 15 secs dead of the LCI 330d.

I saw these figures when I was looking at both before I bought a 330d LCI

Some reliable 0-100 times (the performance metric I always look at the most when comparing performance) ought to be the answer to this question. I am not sure about those ones though - I have seen early E90 330's around the 16seconds dead mark, in fact ISTR slightly below. A full second difference to 100 either way seems unlikely, I would suspect the 330i should be a few tenths quicker. Torque is pretty meaningless in this sort of thing - power, weight, gear ratios and drag will make it or break it. Revs and the wider meaningful power band of the NA car ought to win it - race engine manufacturers try hard to simply add revs to an engine as the effect of more revs is similar to that of more power. The Honda F1 guys talked about this back in the V10 days.

My 156GTA SW was 250bhp / 1490kg and they regularly posted low to mid 15's to 100. A 272bhp N53 330 ought to be much the same - with a RWD advantage, more power, but slightly more weight and I suspect wider spaced ratios.

[SO8]

Originally Posted by NoelWatson

Are you definitely sure they tested the N53 330i?

Fairly sure - as I was looking to buy at the time.

FWIW I have owned a 330i and now have a 330d LCI and other than the noise I don't really see there is much difference as far as I can recall. They just do it differently ... the 'i' sounds great ... but the 'd' does about 10+mpg more.

Both gain speed effortlessly above 60mph ... but the 'i' has a lovely noise.

Personally in these times, despite the fact that the 'i' is fairly frugal given what it is + has low tax (the 272 one) I went for the 'd' ... partly also because I have had the 'i' anyway

Either is great - and after 14 months with a 330d the only thing missing is the noise ... certainly not the performance !

[SteveC]

Originally Posted by Awfully_Polite

I am not arguing your theory of gearing and torque variables. But on what grounds are you saying a 330d which is heavier and has a considerably lower power to weight ratio than a 330i is faster in the twisties?

On what experience or academic qualifications are you basing this on? If you can provide adequate weight to your argument then I will accept your theory.

Also same goes to the other people who havent actually compared the 330i and 330d and also the M3 in real life. I thought the original question on here was based on standard assumed factors.

- all cars producing the manufacturer rated power and torque figures and are machanically sound.
- all factors influencing mechanical grip such a tires, brakes, weather, surface conditions all fixed.
- either same driver or 2 equally competant drivers.

I do not have a degree in fluid mechanics. or vehicle development. My grounds are experience. I owned a E46 M3 prior to the 330i and have raced my friends 330d.

Driven 'normally', the 'd' will spend most of the time in the fat part of its torque curve, whereas the 'i' will require 1 or 2 down shifts to get there(which no longer constitutes 'driven normally'). At say 60 mph in 5th or 6th gear, the 'd' makes far more power than an 'i' based on ((torque * revs) / 5252), which is reflected in the in-gear acceleration times, which are considerable better for the 'd'.
To prove mathematically, you'd need to decide on a particular speed and gear, look up both cars' revs at that speed (gearing), look up torque values (torque) for the revs, apply the above formula to calculate horsepower, then divide by weight to give the power to weight ratio for given revs. Torque and bhp curves for particular engines give you part of this information, but you need to add vehicle weight and gearing to complete the equation.

As soon as you add variables like driving style (gear selection and throttle setting), precise calculations fly out the window and you're back to making inferences.

[NoelWatson]

Originally Posted by NoelWatson

I'll get in touch with him and get the before and after numbers.

297 before, 325 after

[NoelWatson]

Originally Posted by SteveC

which is reflected in the in-gear acceleration times, which are considerable better for the 'd'.

IIRC, the in gear times are measured when the engine is already under load. It would be interesting to see the different between the i and the d if the cars started a given acceleration measurement at a steady speed - we could then see the effect of turbo lag

[SteveC]

Originally Posted by NoelWatson

IIRC, the in gear times are measured when the engine is already under load. It would be interesting to see the different between the i and the d if the cars started a given acceleration measurement at a steady speed - we could then see the effect of turbo lag

The primary causes of turbo lag are inertia, friction, and compressor load. A certain exhaust flow is required through the turbine to overcome inertia and friction while the compressor must be revolving at a certain speed in order to exceed its boost threshold and generate pressure.

At steady speed, there will still be a flow of exhaust gases through the turbine to overcome friction and inertia and the compressor will be rotating well above its boost threshold, so turbo lag will not be an issue.

I believe that the characteristic delay most attribute to turbo lag on flooring the throttle is in fact due to the automatic transmission, since the same delay is completely absent in the MT.

[NoelWatson]

Originally Posted by SteveC

The primary causes of turbo lag are inertia, friction, and compressor load. A certain exhaust flow is required through the turbine to overcome inertia and friction while the compressor must be revolving at a certain speed in order to exceed its boost threshold and generate pressure.

At steady speed, there will still be a flow of exhaust gases through the turbine to overcome friction and inertia and the compressor will be rotating well above its boost threshold, so turbo lag will not be an issue.

I believe that the characteristic delay most attribute to turbo lag on flooring the throttle is in fact due to the automatic transmission, since the same delay is completely absent in the MT.

How do you know the flow of exhaust gases will be sufficient at steady state speed for the turbo to be well above its threshold? Are you suggesting that BMW have managed to eradicate lag?

[SteveC]

Originally Posted by NoelWduce significant turnatson

How do you know the flow of exhaust gases will be sufficient at steady state speed for the turbo to be well above its threshold? Are you suggesting that BMW have managed to eradicate lag?

Think of the exhaust gases and the turbo like a hose pipe. A low flow down a large pipe gives no pressure, no force....but place you thumb over the end of the pipe to constrict the outlet and the pressure increases, producing a forceful jet of water capable of doing work (blasting off dirt for example).

Turbos in exhaust streams are the same. A small turbo will constrict the exhaust flow and spin up quickly, producing boost at low revs. However the same small turbo will constrict exhaust flow at high revs, limiting performance. A large turbo on the other hand will produce good boost at high revs but lacks the exhaust pressure at low revs to produce boost, so will introduce significant turbo lag (friction, inertia, compressor boost threshold). Modern turbo-diesels, like the 330d's, employ variable-geometry to allow a single turbo to be efficient at both high and low rpm. At low rpm, the vanes nearly close which directs and speeds up the relatively small volume of exhaust over the turbocharger turbine -- like putting your thumb over the end of the hose. The increased exhaust velocity accelerates the turbine harder, which decreases turbo lag. At high rpm, the vanes open to allow the larger volume of exhaust gas to pass over the turbine nearly unimpeded at the appropriate velocity, ensuring unresticted high end performance.

Future BMW motors, expecially high performance M cars will employ multiple turbos, at least one of which will be driven by an electric motor in order to produce boost independently of exhaust flow. Clever stuff

So to answer your question, am I suggesting that BMW has managed to eradicate turbo lag I would say yes....with their multiple- and variable-geometry turbo designs, BMW engines suffer from insignificant amount of turbo-lag off idle and virtually non at the critical 50-60 mph level, where instant response is essential.