Quote:
Originally Posted by KoenG
Yes you can compare. The d has an iron fist between 1700 and 3200rpm, even more than the 328i has, the 320i is clearly lagging here and even not coming close. Concerning gearing, your reasoning is correct, but... I tend to drive within a low to mid rpm band. When you have a shorter transmission, you just go one gear higher sooner and the effect is neutralised. When I observe other drivers, being a passenger now and then, I notice the same behaviour.
I agree that in the same gear acceleration between two speeds, the i can match the d, but in reality, I would be one gear higher at the same speed with the i seen the short gearing. Therefore, the normal driving experience of the 320d is near to the one of the 328i uptil about 3500rpm. Acceleration from standstill is not a good indication since based on power in the highest part of the rpm band.
Everybody knows that a 328i is faster and of course it will lap the ring faster, but that doesn't represent normal driving conditions.
|
Diesel engined cars have longer gearing not because of choice but because of the rev range of the engine. For example, the d redlines at abt 5000rpm whereas the i redlines at 7000rpm, so if u have the same gearing then the d will run out of breath very quickly. U don't change gears at the same revs when driving a petrol engined car vs a diesel engined car, for example if u change gear in a diesel car at 2000rpm then for a petrol car u change gear at 2500rpm. U just need to compare the normal shifting points of the 8AT for both engines - it's more or less in the same gear at the same speeds despite the d shifting up earlier than the i.
Acceleration from standstill is not only abt top end power, it is also abt low end torque, that's why the 20d is not quicker to 100 than 20i (brochure figs:7.3s vs 7.5s). Don't forget at initial step-off (i.e. 1000rpm) the 20d have only got 175Nm of torque to play with, & it takes 750rpm more to reach peak torque of 380Nm. The 20i has peak torque of 270Nm at 1250rpm, & if u extrapolate the power/torque graph of the 20d u'll get 270Nm at around 1300rpm, so at initial step-off the 20d doesn't have an advantage over 20i (there's no comparison with the 28i as it has over 225Nm at 1000rpm, not to mention much higher power output thruout the rev range). Don't say hard acceleration from standstill is no use, u'll need all the speed u have at busy junctions or roundabouts. Fyi, according to Auto Zeitung, the 520i does 0-40, 0-80, 0-100 & 0-120 @ 2.2s, 5.3s, 7.3s & 10.1s respectively. The 320d does it in 1.9s, 5.2s, 7.6s & 11s. Don't forget the 520i is 180kgs heavier than the 320d. U can see the 20i is no slouch compared to the 20d, the difference will be apparent if u drive a manual with lots of constant speed cruising & u like to overtake without changing down. The difference between the 2 is less if it's an automatic as it'll kickdown if u floor the throttle during overtaking.