Login






BMW Garage  BMW Meets  Register  Search  Today's Posts  Mark Forums Read 

BMW 3Series (E90 E92) Forum
>
Which is Quicker?


05242012, 05:34 AM  #45  
Private
0
Rep 83
Posts 
Quote:


Appreciate
0

05242012, 05:57 AM  #46  
The Tarmac Terrorist
459
Rep 29,325
Posts
Drives: 997.2 GT3
Join Date: Mar 2007
Location: ''Fandango Towers''

Quote:
Maf sensor problem ain't gonna lose it 3040HP, must be a low power one anyhow.
__________________
997.2 GT3


Appreciate
0

05242012, 06:03 AM  #47 
Private
0
Rep 83
Posts 

Appreciate
0

05242012, 04:49 PM  #48  
Major General
1189
Rep 8,110
Posts 
Quote:


Appreciate
0

05242012, 04:58 PM  #49  
The Tarmac Terrorist
459
Rep 29,325
Posts
Drives: 997.2 GT3
Join Date: Mar 2007
Location: ''Fandango Towers''

Quote:
9.what mate?
__________________
997.2 GT3


Appreciate
0

05242012, 06:02 PM  #50  
Major General
1189
Rep 8,110
Posts 
Quote:
Was 9.0s dead. And 060 in 4.3s 3070 in 3.6s Pretty rapid. 

Appreciate
0

05252012, 01:01 AM  #51 
Major
29
Rep 1,137
Posts 
The figures themselves don't tell you a lot
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. 
Appreciate
0

05252012, 02:15 AM  #52  
Lieutenant Colonel
25
Rep 1,698
Posts 
Quote:
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. 

Appreciate
0

05252012, 03:47 AM  #53 
Lieutenant Colonel
60
Rep 1,800
Posts 
I can vouch for the fact that the M5 is massively rapid! Awesome bit of kit.
__________________
Black 330d E90 LCI M Sport Saloon Auto. Privacy Glass, Cream Leather, 6FL, IDrive/Nav/Bluetooth, Alpine hifi upgrade.

Appreciate
0

05252012, 05:28 AM  #54  
Second Lieutenant
10
Rep 280
Posts 
Quote:
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. 

Appreciate
0

05252012, 06:24 AM  #55 
Captain
14
Rep 739
Posts 
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 ! 
Appreciate
0

05272012, 04:00 AM  #56  
Major
29
Rep 1,137
Posts 
Quite simply
Quote:
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. 

Appreciate
0

05272012, 08:10 AM  #58 
Private
0
Rep 83
Posts 
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

Appreciate
0

05272012, 09:40 AM  #59  
Major
29
Rep 1,137
Posts 
Quote:
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. 

Appreciate
0

05272012, 11:35 AM  #60  
Private
0
Rep 83
Posts 
Quote:
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? 

Appreciate
0

05282012, 03:28 AM  #61  
Major
29
Rep 1,137
Posts 
BMW Turbos
Quote:
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 turbodiesels, like the 330d's, employ variablegeometry 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 variablegeometry turbo designs, BMW engines suffer from insignificant amount of turbolag off idle and virtually non at the critical 5060 mph level, where instant response is essential. 

Appreciate
0

Bookmarks 
Thread Tools  Search this Thread 

