The barrage of (what I think is) ill-founded criticism over my Audi's DIY boost control system ("From the Editor") that I received a few months ago made me watch even more closely than ever the car's digital boost gauge. Every time I drove the S4, I looked at the boost in the different gears, the absolute peak boost, and so on. This showed that basically the system was performing just as I had written; perhaps a touch more top-end boost variation than I had originally stated (though still far less than the factory electronic system gave) but, yes, on the money. I might add that I haven't made even one adjustment to the valve positions - or carried out any other changes - since the initial set-up.
And I absolutely relish all of that new-found mid-range grunt - remember, the measured acceleration improved by no less than 17 per cent with the fitting of the new boost control, even with the peak boost level unchanged! That improvement in acceleration was achieved at full throttle, the normal way of measuring performance variations. But I now realise that I should have included in the article some part-throttle boost and acceleration curves, because that's where by far the biggest improvement is found.
I just love the shove in the back that now comes with quite small throttle openings. And I must get quite a lot of shoves because the fuel consumption is way, way up! Yes, where previously I could average 10-11 litres/100km around town in my normal mix of driving, since I fitted the boost controller, that has skyrocketed to 12-13 - and sometimes even 14 - litres/100km. Because you see, whereas before to get any strong boost in the midrange you had to kick-in the full-throttle overboost scenario (which I did rarely), now - even when you're casually but quickly driving - you can be running 0.5 Bar at one-third throttle!
It gives the car an effortless, torquey feel. No-one, but no-one, would believe that there is only 2.2 litres of engine capacity up front, especially when you look at the size of the car. But the change in fuel consumption is probably one reason that Audi engineers set-up their boost control like that - a significant real world fuel economy gain was made by the approach that they took. Of course, there's nothing to stop me using smaller throttle openings and getting back that economy - nothing at all.
Well, there is one thing. I just revel in that grunt....
Truly, I simply wouldn't have believed that the immense change in the car's character was possible with just a different boost control system. (If you want to read more about this system go to "The Audi's DIY Boost Control - Part 1")
Isn't it odd how we come to accept as 'natural' some things that really aren't at all? Driving the Solectria electric Daewoo a few weeks ago ("The Solectria DW Electric Car") showed how every day we think nothing of operating the brakes in a way which is simply silly.
When you step on the brake pedal in a normal car, you use foot pressure to modulate the degree of retardation that is achieved. Not foot movement, but the amount of pressure that is applied. The difference between half pressure and full pressure might be only a few millimetres of pedal travel - it's how strongly you're pushing, not how far the pedal is travelling, which is the feedback to the person controlling the car. So what's wrong with that, you ask?
Well, how many other controls in the car work like that?
There are certainly two major controls which are not at all similar in the way in which they operate. Imagine if the steering was operated simply by pressure. The harder you turned the wheel right (not actually moving it much, just tugging it right) the sharper the corner the car turned. Sounds silly? It would be - because our current steering systems respond to the much more feedback-rich aspect of travel, rather than pressure. Ditto the throttle - it responds to how far the pedal is moved, not how hard it is pushed.
And driving the electric Daewoo - which had a regenerative braking system that responded to pedal travel, rather than pedal pressure - was a revelation. Suddenly you could modulate with precision the degree of retardation being experienced. The subtleties of varying braking by tiny amounts became natural; you could change the stopping point by a few centimetres if you so desired. And if you find that difference over a normal brake pedal hard to imagine, think of what the accelerator in a conventional car would be like if it operated just on pressure - ie, you had to stand on it to get full affect. After all, that's what you have to do with the brake pedal...
In the electric Daewoo it became a delight to modulate the regen braking so that you came to a halt at precisely the right point on the road - without ever touching the 'blunt instrument' hydraulic brakes. Initially it took me a while to figure it out - just what was so nice about slowing down in this car? Then I realised that using the regen brakes was literally the opposite of using the accelerator...
The reason that the brake pedal in conventional cars is stupidly designed is historical - it's been about displacement of fluid in a cylinder, rather than a direct control of the rate of deceleration. But the advent of fully electronically controlled braking system throws off that shackle - it's now technically possible to change the degree of deceleration on the basis of brake pedal travel, rather than pressure. On paper, the DaimlerChrysler Sensotronic system ("Sensotronic Brake Control" ) should be able to do it with ease. In fact, that system is apparently capable of taking this approach when it is in its 'traffic jam' mode - slowing the car automatically as you lift the accelerator pedal.
And if (when?) brake pedal travel becomes the norm for operating the brakes, you can be sure that no one will mourn the passing of the old system. After all, I became a convert in just one day of driving...
