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Originally Posted by 42pilot
Quote:
Originally Posted by schaeffs
IMO - That will be because the diesels have excellent torque down low whereas the petrol engines have a better top end. Subjectively this torque gives a great seat of the pants feeling that you are making good progress but the top end whack of the petrol cars more than makes up for it performance wise.
On a side note - the 8 speed ZF box has made the diesel cars even better relatively as they mask the diesels shortcoming top end wise by being able to drop the engine back into that massive torque curve on each upshift. The move from 6 to 8 speeds was a huge improvement in the E70 diesels and that continues and has been nicely refined in the F15.
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I would bet most of our daily driving is right in the sweet spot of a diesel. Even when I owned a 525 hp 500 tq 2600 lb turbo Porsche, I only took it to its sweet spot (above 4500 rpm) on the track or when showing off.
In real world driving, like 0 - 60 or 70 like entering a motorway/freeway, the two engines are nearly identical and I would argue it's really up to the driver. By the numbers, they are essentially the same. If you want to talk about the 1/4 mile, they are identical - torque always trumps HP. So, except for the V8, as far as performance is concerned, the diesel has the edge because of efficiency - there is no masking of the diesel's short-comings because, by the numbers, it really doesn't have any.
Transmission technology and ECU strategy has come a long way in the last 5 years. My F10 550i had an 8 speed and I got great economy. And when I stepped on it, the ECU always chose the right gear for the given RPM/condition. I would never go back to standard transmissions (yikes, can't believe I'm saying that being a track guy since 1989) because you cannot chose the right gear faster than an ECU and you certainly cannot shift faster than an auto. On the track, a paddle shifter is the best option. Again, for street purposes it's the ECU that's doing the real work, admittedly in an excellent ZF package - keeping the diesel or the petrol in sweet spot. Tuning trannys is equally important as the engine now. Push the sport button on our F15 and it will select the right gear for the given RPM and lock the torque converter at a lower RPM. Line pressures are probably higher too which give crisp shifts rather than butter smooth of comfort settings.
The good thing these days is, you can chose a petrol or diesel and not lose performance - it is now completely a personal decision. You can't lose. |
Agree - the Diesel engine is perfectly suited to the usual DD tasks. Whilst not quickest against the stopwatch in a drag race the "roll-on" performance is outstanding - particularly in the M50d - as you rightly say it's that torque that gives what is a heavy car physics bending capabilities!
I've noticed the shift action in sport in the F15 gives the car a perceptible sense that you are changing gears - unlike the comfort setting which is totally smooth - it makes the car feel more sporty in that setting so matches its billing well. It also makes the car feel like one of my other cars in this respect and that has a single clutch robotised manual gear change - racy stuff for a two tonne SUV!!