Saturday, 22 October 2011

Diesel; What Happened To The Backlash? (Part 1)

A colleague the other day told me of comparison event where he drove a crop of current German Big-Three cars, including the Audi A8. It had been of the 4.2 V8 petrol variety, and he said;

“It needed to be a diesel”.

When quizzed about what he meant, he replied that the V8 didn’t have that low-down urge that a diesel car would have enjoyed. And, unknowingly, he’d just exposed a great truth in how we have come to regard diesel cars.

Diesel cars would be nothing if it wasn’t for the invention of the turbocharger. This fantastic device allows the diesel engine to breathe with bigger lungs and make all of its power potential available for service right across the rev-range. But that rev-range isn’t very broad. Your typical diesel rev-counter is red-lined from four-thousand revolutions up until the dial runs out of space, but there’s little point in the needle spending any time in those reaches of the dial, peak power is usually produced at around the 4K mark and torque peak can be barely above a fast idle.

This, ironically, makes them absolutely ideal for cut-and-thrust city motoring, where the ability to out-drag buses away from the lights is essential lest you find yourself being barged into the wrong lane, or off the road altogether.

Sadly, though, it also makes the diesel engine ideal for the sort of person who always has to be at the head of every queue; the sort of person who absolutely will not wait for the traffic to move at its own pace. This person, his iPhone bursting with vital contacts in the photocopier toner industry, his suit positively glinting in the suburban sunshine, needs his engine power delivered now, now, now.

Whether it be in the city or on the motorway, he’s always there ready to flex the torque of his tax-efficient mid-range car, ready to dispatch dawdlers with a puff of soot. With his automatic gearbox he’s free to simply mash his foot to the floor and go, he doesn’t have to worry about being in the right gear, he doesn’t have to counter any turbo-lag, he can just explode past in a tizzy of wildly thrashing diesel fury.

Diesel cars with automatic gearboxes lend themselves to use by lazy, impatient drivers. My colleague who so badly wanted the low-end surge of a big diesel in his Audi A8 only wanted that so that he could get away from the lights even quicker. That, it would seem, is all that seems to matter today.

What happened to the thrill of driving? On flowing country roads a car with a big, heavy diesel engine can feel a bit like an arrow from a bow; light and slim of fuselage but with a lot of weight at the front. The predilection for ploughing on through corners is usually tempered only by the massive wheels and tyres that all of today cars come with. By comparison, a petrol equivalent typically feels wholly more lithe and delicate.

Look at all of cars I’ve driven in the last year that have felt the most rewarding. The Honda S2000; an obvious choice perhaps, but a car with a thoroughly addictive appetite for revs; the Maserati Quattroporte, who’s exhaust song goes through phases from mellifluous warble to Formula One wail, encouraging you up and down through the gears.

The CLS 350CGi, a car with a powerful petrol engine, feels a bit gutless down the bottom end, but this is only because I’ve driven the diesel model so often. Other than that, the car is a revelation over the diesel. It delivers its creamy power evenly throughout the rev-range, and does so with a sonorous enthusiasm as the tap is opened further.

Neither Ferrari nor Lamborghini have released a diesel, just yet, though I’m sure they will one day. There is no diesel BMW M, either, the M-Sport badged ones don’t count (I’m looking at you, Gary in accounts, with the M-Power badge on the back of your 320D). Audi have done brilliantly with their TDi LeMans race cars, but diesel still doesn’t feature prominently in the enthusiasts car landscape; a fact that has its cause in the way petrol cars drive compared to their oil-fired counterparts.

This is partly because we always loved the way that petrol cars deliver their power progressively; no matter whether carburettored, injected or turbocharged, there’s always something to look forward to somewhere in the rev-range. It might be the peaky excitement of a VTEC, the midrange step of a Saab Turbo or the full-bodied laziness of an old American V8, but somehow every notable petrol engine bubbles with interest and personality.

The simple truth, though, is that I’m wrong to champion petrol in this highfalutin’ way, because we’ve changed the way we drive. The masses out there on the roads are in competition with each other in any number of ways, badge prestige, number of gadgets fitted to your car, and even for the very space on the road you drive in.
We’ve become less interested in the upper reaches of the tachometer, simply because we hardly ever get to visit it. Our daily battle happens in fifth or sixth gear, and between 65 and 95mph; the battle of the outside two lanes of the motorway. Here, you don’t need an engine with personality, you need lot of immediately delivered clout to use when thrusting yourself between lanes, squeezing into gaps. A turbodiesel fits the bill perfectly; small wonder then that the Passats and A4s that sit in these 90mph traffic jams all have TDi badges sparkling on their bottoms. Diesel Passats keep churning away at must-get-to-McDonalds-Before-They-Stop-Serving-Egg-McMuffins velocities all day long.

Over any faster increment a petrol car would come out on top. From a standing start, providing it’s allowed to rev properly, the petrol equivalent is rarely any slower than the diesel. In fact, petrol cars are generally better for outright acceleration than diesels because you don’t have to keep changing gear all the time. But the outside lane battle only calls for a surge of power; the ability to lunge forward, and diesels are better at that due to their turbo-exaggerated torque reserves.

A few years ago it was claimed that there would be an anti-diesel backlash, and it simply hasn't materialised. Will it ever? Will people become fed up with having to change DPF filters the whole time as well as paying ten pence a litre more for their fuel? Does the number of fairly recent, eight-to-ten year old diesels being prematurely scrapped for reliability reasons have any bearing on the diesels' continuing popularity? And what about the environmental effect of the extra nitrogen oxide that diesel exhaust spits out, will that tempt people to hang their derv pumps up? Probably not. Companies will still issue diesels as company cars for as long as the tax advantages make it worthwhile.

As it happens, todays diesels are better than they've ever been before. Emissions are at an all time low, refinement has been improved hugely and performance has been transformed. But they are still completely different to petrols in their driving experience. How do you take your power; all served up in one lump, or measured and released evenly? Efficient and businesslike or thrilling and highly-strung? It seems that you still have to choose between derv or verve.

I, honestly, have no great downer on diesels. They certainly have their place in the world and, if I was doing the mileage, I'd have one as my main car, no problem, so long as I can have a second car with a proper rev-range and a nice exhaust sound to balance things out.

To read Part 2 of "What Happened To The Backlash?" Please click here.


  1. "Diesel cars would be nothing if it wasn’t for the invention of the turbocharger."

    Have you tried any naturally aspirated diesels?
    I've owned and test driven VW Golfs with the 1Y 1.9 diesel and Citroen ZXs and a Rover 218D with the n/a XUD, they're quite pleasant, surprisingly nippy with an even spread of power and compare well with the 1.4 petrol versions.

    The current appetite for diesel powered cars is bonkers, often just to save a few quid a year on car tax.
    Diesels still fail to make sense financially unless you have an old one running on waste vegetable oil...

  2. Hi Anonymous! Yep, including the n/a XUD in a 306, Isuzu 1.7 in an Astra and, while they compare well in day-to-day driving, I'd still pick the 1.4 petrol if I was spending all day tackling my favourite B-road!

    The turbocharger comment was vis-a-vis todays traffic and the mass of todays cars. I don't think diesel would be practical today without forced induction for power / packaging / emmissions reasons.

  3. Just a note that BMW have looked at producing a 550M Diesel which is an actual 'M' car.. which will be exciting to say the least- it will have 3 turbos (you can never have enough) and will produce somewhere in the region of 500-550 bhp .. down on the petrol version but torque will be up considerably... im sure this will deliver immense power all the way through the range.. and with 4 wheel drive i am sure it will manage to get that power down (just) - surely this will be enough to sway any 'petrol' loyal supporters!

  4. Hi "M", Yep, rumours have been circulating for a while but BMW have been coy about how the "M" branding will work. You're right though, could be another step in our complete transition to petrol...

    Read Part Two of "What Happened To The Backlash?"