probably does make it faster, just because it can be kept in the torque peak more of the time - especially for a diesel.
.......
Fully realise that for a diseasal ...... is the Lexus diesal?
So why don't all cars have just one gear Andy D?
A shorter single gear will accelerate quicker than a single longer gear.
Take my track bike. Cbr600 road bike. First race, flag drops and they all fwaarck off into the distance, the bikes dog slow. Why? They've all geared their bikes to the track. Lower or shorter gearing on the final drive sprockets. We haven't had time to sort our gearing and it's still stock at the manufactures top speed orientated figures.
But next race we have sorted the gearing and it's holding it's own into turn one.
So clearly we have a quicker accelerating bike yes? (don't argue, we just do
)
So put that bike back on the road with the same final drive gearing and it's a mare. Tops out at too high rpm, and the top speed is about, oh I don't know, let's say it's 1/7th less than it was. So how do we keep the acceleration, but achieve a higher top speed? As a manufacturer, you add another gear. Or even two depending on your engines power out put and a whole load of other factors such as comfort for instance. Because changing gear on a bike geared for Mallory Park at wot, is not a comfortable experience let me tell you. It's quick fire changes all the way.
Your smart isn't faster compared to a four speed omega.( although might just be quicker than a pram
) Your 6 geared smart is faster compared to another smart with with, say, 4 or 5 gears. Which just proves the point.
If it had 5 gears it would either have slower acceleration to the same top speed. Or the same acceleration, but loose the final part of the speed range that gives you the original top speed. Assuming 6th is not an overdrive or something equally gay.
See?