Quote:
Originally Posted by logiclee
The M135i produces peak torque from just 1250rpm, the ZF8HP gearbox has lower gearing and different mapping than the diesel variants. Even in eco pro there's not many situations where you'd have less than 1250rpm.
It's torque at the wheels that accelerate a car though not at the engine.
The diesel 330d has around 24% more "Peak" torque but the diesel auto's have a 20% taller final drive and the 330d has peak torque over a much smaller rev range than the M135i. (330d 560NM 2000rpm to 2750rpm)(M135i 450NM 1250rpm to 5000rpm)
That means in any given gear the torque reaching the wheels is only 4% higher in the 330d and only for a very narrow rpm band. The M135i has the the advantage of using it's torque earlier in the rev range and for much longer in each gear.
Cheers
Lee
|
You're completely right about the torque at the wheels, but after many years of thinking this over and over again... I guess this is not necessarly relevant. Of course, in second gear at 1500rpm, the torque difference is levelled out like you calculate correctly, but the 330d will also drive faster at same rpm then! In your reasoning your reference is 'in the same gear', but I guess it should be 'at the same speed and rpm'.
When you extrapolate and compare a Fiat 500 with a Veyron, you don't mentally compare same gear acceleration, you will compare the 80 to 120mph. The Veyron will do this in 3rd gear, the Fiat will do this in 5th gear. It doesn't matter the Fiat partially compensates his lack of engine output with lower gearing in his 3rd gear since you won't be using it.
Now you'll state that the wider rpm range of the M135i allows comparable gear selection wrt 330d, and yes that's also true. But that's on the circuit. When you drive in normal traffic and care for some fuel efficiency, you'll go to highest comfortable gear... and then, you open the trap where the diesel wins. With my driving style (relaxed with short bursts of excessive torque), this trap is open 99% of the time and I guess I'am not alone.