You can never be sure until the historical context is established by time, but I think that right now (in Australia at least) we're seeing turbocharging really dropping in relevance in new performance cars. Of course, if you simply count the number of OE turbo cars being sold, that's an obvious statement - the glory days were in the early and mid-Nineties, not now.
But in terms of impact on the performance car scene, it's only this year that things have really started to move sideways.
Take the Impreza WRX. Although it's one of our all-time favourite cars, the '01 model is a real letdown. Not only is the goggle-eyed model no faster than the previous cars, but after a drive of a modified one, the lack of real progress was brought home very sharply. In terms of its responsiveness, the EJ20 flat four used in the cars has never been really good, but this car - fitted with new engine management, exhaust, filter and a very slightly larger than standard turbo - was at least a decade old in how it drove. There was little or nothing in performance below 4000 rpm, then it came onto boost with an impact that probably increased torque by 50 per cent over just a few hundred rpm, and then it was at the redline a paltry three thousand rpm later.
In Subaru's armoury where is base model variable cam timing, the variable inlet manifold - or the twin turbos? Ah yes, the Liberty B4 has two turbos, doesn't it? But even that engine drives far more poorly (with a distinct drop in torque between the two boost curves) than (say) a near ten-year-old Supra twin turbo.
Unfortunately, the WRX engine is now aging very fast - whereas once the sheer traction and performance of the car were enough to allow a potential buyer to overlook the engine deficiencies, now the technology of other cars is simply racing ahead.
And not just under the bonnet, too. The car that I drove had been fitted with a sophisticated aftermarket suspension - from the acknowledged brilliant DMS coil-over struts to fully adjustable sway bars, a front anti-lift kit and other good bits. It's handling? Not all that good!
As it had been set up, it had typical viscous coupled four-wheel drive power understeer, able to be relieved only by a sharp lift-off which would bring the tail out a little. But under power in tight corners it was never neutral....
The workshop appeared very surprised by my criticisms, but to give them their due soon had the car up on the hoist again, adjusting the rear bar and rear dampers. On the road the car was then a little better - at least now it didn't understeer so much under power in tight stuff. However, the basic deficiencies of the old driveline technology remained: early power-on understeer and late power-off oversteer.
Constant four-wheel drive cars with Torsen centre diffs are much more responsive to throttle input variations, while cars like the Nissan Skyline GT-R (the later models where they sorted out the four-wheel drive software) are simply far more neutral.
But the real killer is when you bring into the discussion the Lancer Evos 6 and 7. Compared with the current WRX - even one equipped with a very good aftermarket suspension - they simply walk all over the Subaru. And I am not alone in that opinion - off the record, the proprietor of a major Subaru modification workshop confided to me that if he had the choice between a (much more expensive) Evo Lancer or a Subaru WRX for his personal road car, he's always take the Mitsubishi...
It's a pity, but I think that history will look back at the '01 performance Subarus - both WRX and B4 - and suggest that both were indicative more of Subaru dropping the ball rather than advancing the turbo cause. And since Subaru has been the company more responsible than anyone else in the last decade for pushing to prominence turbo performance cars in this country, that's a damn' shame.
And it's not as if other technologies are standing still. Other manufacturers are incorporating new technologies into their NA engines which give them flat torque curves combined with high rpm - a characteristic that allows for excellent power production while still giving instant throttle responsive. With advanced lean cruise capabilities, coated pistons, and air/fuel ratios at maximum throttle which can be much leaner than safely used in forced aspirated engines, the fuel consumption advantage of turbo engines is also starting to be pulled back.
After all, even very cheap cars like the Toyota Echo now run variable cam timing, although the most sophisticated of cam timing systems (altering steplessly both the intake and exhaust cams) is currently confined only to expensive cars. But the use of variable intake systems is common, while sophisticated knock control systems have led to compression ratios rising and rising. (But that's not to say that the current NA engines are all wonderful: I am prepared to bet that the engines which in one step change their valve lift - giving a dreadful two stage torque curve - will be soon regarded as pretty bodgy. I mean, would you put up with a turbo engine that suddenly jumped in boost pressure at one rpm....?)
It's also significant that highly efficient cars like the Toyota Prius and the Honda Insight do not use turbocharging - although in terms of pure thermodynamic efficiency, turbocharging can be used to produce better results than traditional naturally aspirated engines. Whether it's for packaging, cost or engineering reasons, AFAIK not one manufacturer is putting a turbo under the bonnet of their clean, green and increasingly mean machines.
Those manufacturers applying turbocharging to their performance cars are now falling into two distinct camps - small turbos to boost mid-rpm response, and large turbos to give higher peak power. Of course, there are shades of grey in between, but that's largely the demarcation. Sequential twin turbos - a technology proven highly effective as long as ten years ago on the Mazda Cosmo triple rotor and aforementioned Supra - must simply be too expensive to implement on mass consumption cars. Two turbos working in parallel? Also becoming very rare on new cars.
So the odd situation is developing that a technology which can deliver outstanding cruise fuel consumption, unbelievable kilowatt-per-engine-kilogram figures, and very high mid-range torque outputs, appears to be fading from the new car scene.
However, it?s certainly not all gloom and doom for turbo lovers. In fact, breakthrough turbo technologies are now being tested by a very major OE turbocharger manufacturer which could revolutionise the application of turbos to engines ? developments likely to make ball bearing turbos look quite trivial. And in this issue we've brought you the first tech story on these amazing developments.
Christmas has come and gone, but I still think it's worthwhile sharing this wonderful Christmas card with you. Sent to us by highly respected UK automotive engineering company Ricardo, it shows the company's in-house procedures for developing a more sophisticated, mechanised and radio-controlled range of reindeer....
Here the all-wheel drive, mild hybrid 42V/diesel model of reindeer can be seen being fuelled, while two reindeers - about to lose their jobs - look on in horror.
However, while the prototype works just fine, Father Christmas is having some difficulties learning how to drive it....
Once Santa gets the hang of it, though, he should be able to make speedy progress, as this aerodynamic simulation study makes clear. Those areas of flow separation behind the head and, er, bum, might need to be cleared up a bit though.
If you look closely you'll also see a reindeer crash testing computer simulation, reindeer automated manual transmission CAD design being carried out, elves having problems delivering drinks and staying in their chairs, and a very special Ricardo software mouse and mousepad.