RENAULT and I won our class in last year’s MPG Marathon – a right ol’ result, it was, after 400 miles’ somewhat steady driving.

But how? All down to the Grand Scenic I drove – fitted with the 1.4-litre TCe ‘downsized’ engine.

In Renault parlance, this is a 2.0-litre power-puncher with 1.6-litre fuel-sipping ability. Tiny turbo, no direct injection, Nissan all-alloy block and plain efficiency. It’s a canny wee thing, alright.

Particularly if you want to drive economically. See, its key characteristic is delivering loads of torque at really low revs – diesel-like revs, in fact. Throughout the entire Marathon, I honestly didn’t exceed 2000rpm. And still managed to summit the 1-in-2 climbs dotted through the route.

That tiny turbo allows this; it spools up fast, which is just what you need for eco driving. Here’s traits I exploited:

•    Responsive to light throttles
•    Ability to select 6th at ridiculously low speeds
•    Linearity when modulating the throttle
•    Turbo doesn’t ‘run away’ from you
•    If you’re genteel, then so will it be

Being eco is about fluid motion. You need to swim along, with not a misplaced stroke, slipping along like an eel. Only with infintesimal control over the fuel being pumped into the engine can you do this.

Tiny turbo engines often produce great figures on the test rig, but plunge in real life, due to the turbo sucking in air like an iron fist, and forcing fuel injection to throw petrol in accordingly. Many people who drive at low revs and in a seemingly eco manner actually get mediocre economy – because of the lack of control the engine seems to have over itself.

None of that with the TCe. If you want to accurately throttle back as far as necessary to maintain pace, you can do. No torque-free gullies to fall into, no risk of being left floundering. It’s almost electric-like in its reponsiveness when you’re taking it steady.

The result of this is 50.3mpg in a 7-seat Grand Scenic. Official.

Wake up with the sun

Oil be: It’s back

RenaultSport past to inspire turbo future

MINI John Cooper S Works returns 58mpg shock.

Yes, indeed. And a real-life shock, as I proved over the weekend.

I wasn’t doing anything particularly special on this 100-mile journey, either. Simply driving steadily up the motorway.

Listening to Radio 5Live. Hearing Eamonn Holmes interview Steve Bruce. Enjoying the sun. Considering the tactile qualities of Alcantara steering wheels. Normal, everyday stuff.

Yes, my right foot was light, but I wasn’t crawling. Yet, at journey’s end, there the remarkable result was. Boldly blinking on the trip computer. 58.6mpg.

This, from a 211hp turbocharged 1.6-litre… petrol engine! Naughty exhausts and all! Pretty jazz, I reckoned. And yet another tick against my turbo engine theory.

That they’re super-economical when you drive them economically. But thirstier than Richard Burton when on it. Disproportionally so. Jekyll and Hyde. And so on.

Car makers know this. And this is why modern turbo petrol engines always do really well on the official test cycle.That’s something conducted in a genteel manner not dissimilar to how I drove last Saturday.

But what’s real in my world, and the world of Euro-MPG test drivers, isn’t in the vast majority of turbo petrol drivers. Hence, the disparity in economy many report.

It’s a theory I’m going to run with, and put to the next engine, err, engineer I meet…

MINI John Cooper S Works photostream on Flickr

MINI prices and the daily heart-flutter

More on Mini’s classic brochure

How cool is this? The Golf GTD. Like a GTI. But green and eco, too. Even PR genii are rarely this on message.

On the eve of the 211PS Golf GTI arriving in the UK, it risks stealing some of that car’s thunder, which is an unusual thing for Volkswagen to do. Why go for that one, when you can get 15mpg more here, and almost as many thrills?

I reckon it’s a bit of a ploy. For, Volkswagen has done this before. The brilliant, iconic Mk2 Golf GTI also spawned a GTD cousin. Again, it was a pretty high-spec diesel for the time: turbocharged, intercooled, properly whizzy by contemporary Ford Escort 1.8 D GL standards.

It had the looks of the GTI, the steering wheel, the dials; the two were really hard to tell apart. Not that you had to bother all that often, mind. See, the Mk2 GTD hardly set the world alight. It struggled to sell.

Blame an unenlightened public. Fuel was cheap. Diesel something for trucks. Wot wud yer want a DEESEL GTI for? Hairshirts, not designer hairgel, came to mind. It lagged, then quietly disappeared.

And the Mk6? Well, it’s got the looks, the steering wheel, the dials… yes, it really is three-quarters of the way to a GTI. Just like the old one. Only, this time, it will sell. The world’s ready for it.

For the record, I’ve listed the big differences here:

•    GTI: Red tartan seats. GTD: Grey tartan seats
•    GTI: Red stripe on the honeycomb grille. GTD: Chrome stripe
•    GTI: GTI badge. GTD: GTD badge
•    GTI: red stitching on the flat-bottom steering wheel. GTD: black stitching…

… get the idea? Of course, instead of the gem-like 2.0-litre turbo petrol, it’s got a common-rail 2.0-litre turbodiesel, producing 168bhp, for 8.1secs to 60mph. That’s a second down on the GTI. More torque makes up for it.

It’s got a quasi-GTI chassis, too – which is available with the very same pneumatic adaptive suspension system. This trick setup is said to work brilliantly. A so-equipped GTD sounds quite a thing.

Indeed, it’s looking so good – and so ‘blink-and-you’ll-miss-it’s-not-a-GTI’ (VW dealers should prepare for the GTI badge orders), that I think the company who invented the GTI may just have reinvented it.

The GTD is, however, preferable, for one reason above all. GTIs have ridiculous twin exhausts poking out of the rear bumper. GTDs have proud, GTI-tradition dual pipes, poking out the left hand side. Just as it should be. None of this two-side nonsense.

That it also does 53mpg and emits 39g/km less CO2 is but the icing on the cake. Eight-tenths a GTI’s driving talent? Given how brilliant CJ here tells me that car is, it sounds like a pay-off well worth making.

Volkswagen was ahead of the game with the original GTD. The world wasn’t ready for a hot diesel hatch. Now, it is. This June, hot hatch hot cakes will be diesel-powered, mark my words…

Porsche makes cranky Cayenne cool

Secrets of the new Toyota Prius

What I learnt… from Autocar, 11 March 2009

I was honoured to speak with the chief engineer of the new Toyota Prius, Akihiko Otsuka, at the Geneva Motor Show recently. Honoured, because the young dude is quite a guy.

Oozing enthusiasm for the Prius, his groundedness and sheer enthusiasm wowed me. We’re close in age, he and I, and I really felt how ‘here and now’ he is. Think everything that’s dynamic and invigorating about modern Japan, for an idea of his approach.

This whirlwind of ideas shows in the new car, which really is quite something. Official fuel economy of the current one doesn’t always carry through to reality, I said. Unbowed, he admitted so – a key target of the new car was to improve on this.

He told his team to benchmark against the Volkswagen Golf 1.9 TDI – not the default 2.0 TDI, which is a fair bit less efficient. Quite a challenge, as I know how economical that engine can be. But Otsuka ‘beat it’.

A new approach to body design helped here – he allowed the aerodynamic engineers to work with clay models, ‘despite the expense’. This is unheard of in the car industry, where stylists normally hold sway. But, getting aerodynamics engineers so closely involved in the shape means the drag factor is a startling 0.25. An old Mini, by way of comparison, is 0.56….

However, while the hybrid gear is the big deal, he admits that this contributes only half to the overall 14 percent economy improvement. The other 7 percent?

‘Low rolling resistance tyres, aerodynamics and other energy improvement methods.’ The same, in other words, as employed on a VW BlueMotion, Volvo DRIVe, Ford ECOnetic, SEAT Ecomotive…

This fact brings home the law of diminishing returns. And the scale of the challenge car makers face in making cars continually more green.

I have an absolute mass of information from the discussion, which I’m using to write a piece for Automotive Engineer magazine. Overall, though, meeting Otsuka-san was quite something. In a month or so’s time, we’ll be finding out if his car is as good.

Diesel has devoured the bulk of car maker development budgets in recent years.

It’s been a quick and dirty way for them to reduce parc CO2 emissions. Petrol’s been left lagging. Fiat’s helping it catch up, and giving us a new acronym in the process. MultiJet for diesel, meet MultiAir for petrol.

As the company that invented common rail injection, now de rigueur for diesel, MultiAir is thus maybe quite significant (not least because it’s not as dirty as diesel). But what on earth is it?

A way to make petrol engines 25 per cent more fuel efficient, that’s what. God knows, they need it. Geneva was the first signs that development budgets are switching to petrol. How they’ve some catching up to do. The weediest 1.2 Grande Punto can’t even average 48mpg. The zappy 90bhp 1.3 turbodiesel? Nearly 63mpg. Plus 20g/km less CO2. That’s a big difference (circa 25 per cent in fact), even if the problem is that you do pay for it.

Now then. How it works. Fiat told me that if you want to enhance diesel performance and emissions, you need to control how much fuel you inject into the cylinders. It’s down to how accurately you can do this, too.

For petrol, though, the trick is to play with not the fuel, but the air being injected.

Normal engines have a ‘dumb’ intake valve. This can only open or close. How much air goes into the cylinders depends on the throttle valve, further up the air supply chain. This is (says Fiat) wasteful. What you should be doing is controlling the intake values themselves, electronically. At source, rather than further up the chain, so to speak. How to do it cheaply, though? That’s what’s been keeping car companies busy, apparently, since the 1980s.

Fiat’s solved this. MultiAir is easy, cheap, variable valve actuation, giving full independent control over what the intake valve does. Hurrah. Diesel eco without the diesel cost, plus cheaper fuel to boot. This is big stuff. But this realisation didn’t come before I’d interpreted a tech-heavy press release…

Eventually, I found out MultiAir uses a piston connected to the intake valve. It’s moved by a cam, but the clever part comes because it’s connected via a hydraulic chamber. A solenoid valve controls this. This can have two states – open or closed. Now, then:

• Solenoid closed? Oil behaves a like a solid body. Intake valves do what the mechanical cam says.

• Solenoid open? Bingo: intake valves decoupled from intake camshaft! They close instead under valve spring action. (This is why Fiat also fitted a hydraulic ‘brake’, for soft and controlled valve closing…)

So, what tricks does it offer? Well, the solenoid is always closed for maximum power. But for low-rev torque, independent operation comes in. It opens near the end of the cam profile, meaning the values close early – trapping as much air in the cylinders as possible.

However, for part load, it opens much earlier, which does all sorts of clever things to airflow. This boosting torque. Or, it can be opened later, boosting ‘higher-in-cylinder’ turbulence. These two modes, called ‘MultiLift’, can be deployed in the same stroke, which is the really, really clever part. And which is why it’s taken so long for the ECU engineers to map…

It’s not just for petrol, either. Potentially, it reduces diesel NOx emissions by 60 per cent, and taking 40 per cent of unburned hydrocarbons out of cold start emissions. Indeed, Fiat says that this is just the start. MultiAir could even see petrol and diesel engines unified, rather like Mercedes and VW are proposing with DiesOtto.

The first MultiAir will be a 1.4 Alfa Romeo later this year. Fiat will also fit it to its new two cylinder engine, coming to the 500 in 2010.

No need to hedge bets on the fuel of the near-future, then. Seems it’ll be a bit of both…