Original URL: http://www.theregister.co.uk/2013/01/22/infiniti_m35h_hybrid_sports_saloon/

Review: Infiniti M35h hybrid sports saloon

To infinity and... er... Skelmersdale

By Alun Taylor

Posted in Hardware, 22nd January 2013 12:01 GMT

If you’ve got a little over 40 grand lying about and fancy a four-door hybrid sports saloon then Infiniti - the posh bit of Nissan in a relationship similar to that between Lexus and Toyota - would have you know that the latest M35h is not only the fastest, but also the cheapest car of its type.

Tempting words. After all who wouldn't want a car that can hit 62mph in 5.5 seconds but returns 41mpg over the combined cycle and all for five grand less than the competing product from BMW?

Infiniti M35h

More curves than Gina Lollobrigida

Given that we are talking about here is a large Japanese saloon, at this point it would be usual to have a good old laugh at the exterior styling, but I’m not sure we should. Granted it’s not what I’d call a pretty car, but neither are the current same-sized offerings from BMW, Audi, Mercedes or Lexus.

In terms of visual appeal, Jaguar’s XF puts them all in the shade, but you can’t have a hybrid XF so there’s no real point in making that comparison.

All those curves and lumps must help cleave the air, though. With a coefficient of drag of 0.26, the M35h is the slipperiest member of the M series family and compares well with the 0.25 score of the Toyota Prius.

Under the M35h’s bonnet sits a double overhead camshaft 3.5-litre 24-valve V6 generating 302bhp and 258lb-ft of torque, and an electric motor good for 67bhp (50kW) and 199lb-ft of torque. Combined output of the V6 and electric motor is 268kW, or 359bhp in old money.

Infiniti M35h

The big chrome framed grille is not to everyone's tastes

As is the case with Toyota and Lexus’ hybrids, the petrol engine uses Atkinson-cycle valve timing to trade some loss in power for improved efficiency.

The battery pack, which is tucked away behind the rear seats, is a laminated cell lithium-ion affair with a 1.4kWh capacity and which borrows its basic design from the Nissan Leaf e-car. Technical details aside, the battery pack eats up a whopping 30 per cent of the boot space available in the non-hybrid, 3.7-litre M37 and robs you of the ski slot.

No matter what’s propelling you along the road, the engine, the electric motor or both, the energy is directed to the rear wheels through a seven-speed automatic transmission with a manual override for the more interventionist.

Infiniti’s hybrid system, called Infiniti Direct Response Hybrid (IDRH), uses a single disc-shaped electric motor/generator, two clutches and what is in effect an automatic transmission with the torque converter removed. It’s called a parallel two-clutch, or P2, system and the idea is to offer the best blend of power and efficiency.

Infiniti M35h

Looks good from the side

The first of the two clutches is a dry clutch positioned between the engine and the electric motor. The second is a wet clutch at the rear of the transmission that allows the engine to turn the motor/generator to charge the batteries when the the vehicle is stationary.

Torque of the town

This combination eliminates the need for a torque converter and allows for the full decoupling of the V6 when there is adequate battery charge to drive the car using electricity alone. It also smooths things out during gear changes and when the V6 is being tuned in or out of proceedings.

The drivetrain architecture allows the M35h to run with either just the electric motor or the petrol engine, or a combination of the two. It also saves fuel by automatically switching off the engine when the car is stopped or stopping. In fact, as soon as you start to slow down the M35h usually drops into EV mode. Think stop/start but writ large.

Infiniti M35h drivetrain schematic

The drivetrain

Being modular the IDRH system will eventually find itself in most if not all of Infiniti’s forthcoming models, including presumably the new premium compact that will go into production at Nissan’s Sunderland factory in 2015.

In the M35h, the electric motor serves a triple purpose: as a drive unit, a starter motor, and a generator to recover energy during deceleration and braking. On paper it’s one of the most compact and efficient hybrid system on the market and when it comes to energy recuperation it seems particularly efficient.

Even after deliberate attempts to drain the battery by maximising the EV-only range - the maximum electric-only range is quoted as 1.2 miles but I managed to get over two easily - the battery recovered to a full charge surprisingly quickly. Of course, part of the trick is the engine’s ability to charge the battery directly.

The compact size of the hybrid drive pays dividends when it comes to kerb weight. At 1830kg, the M35h is 95Kg lighter than a BMW ActivHybrid 5 and 80kg lighter than Lexus GS450h. That’s the equivalent of an extra passenger.

Infiniti M35h energy flow

Energy flow 1: driving in EV mode

Once inside the M35h, you’ll search in vain for an ‘EV’ button. In fact, the only obvious e-car giveaways are the green EV light in the tachometer dial and the power/charge gauge.

But don’t assume this is hybrid-lite. You can travel under electric power at speeds up to 65mph, and in everyday motoring I was surprised to see how often the tacho needle would suddenly drop down to zero even when my foot was still on the throttle pedal.

Such is the refinement of the Infiniti that even with the stereo turned off it’s difficult to tell when the V6 has decided it’s not needed and metaphorically stepped outside for a fag.

On the emissions front, the Infinti screws the global pooch to the tune of 159g/km of CO2. By comparison, the Lexus GS450h returns 141g/km but the Lexus achieves this by using a CVT transmission, something that in my opinion has no place in a car with even vaguely sporting pretensions.

Infiniti M35h energy flow

YEnergy flow 2: the V6 can charge the battery pack directly

The manufacturers’ economy figures as always err on the optimistic side. I covered over 350 miles in my week with the M35h and averaged 33.6mpg. That’s 16.8mpg less than the extra-urban best and 7.3mpg less than the on-paper average.

I should say in the car’s defence that most of the distance I covered was in a style best described as energetic and with the gearbox in Sport mode. You see, in addition to the manual gear selector, the M35h has four driving modes selected by a rotary knob on the centre console: Normal, ECO, Sport and, appositely given the recent weather, Snow.

Inside the Infiniti

Infiniti M35h

Wood and leather all over the place

Infiniti M35h

No e-car or hybrid dashboard silliness here

Infiniti M35h

The touchscreen satnav comes as standard

Infiniti M35h

Snow setting for the car, heated seats for the driver

Infiniti M35h

V6 and hybrid gubbins under bonnet

Speed merchants and tree huggers apply here

The last is for treacherous conditions, while Eco provides the best fuel economy by dialing the throttle response so far back it makes you want to self-harm. Acceleration response sharpens considerably in Normal, while Sport takes things one step further and gingers things up significantly.

Assuming you can live with Eco mode, you can cover around 30 per cent of your distance under electric power. Ater an 18-mile dawdle around Skelmersdale, the EV distance covered showed as 5.6 miles. In Sport mode that figure drops to around 20 per cent, which still isn’t too shabby.

Infiniti M35h

Out on t' moors in Snow mode

Once in Sport, the M35h is a licence-endangeringly fast car. The engine, electric motor and gearbox work in perfect harmony when you put your foot down and conspire to hurl you at the horizon.

Infiniti doesn’t quote any performance numbers other than 0-62 and top speed - a limited 155mph - but by my rough measurements the 50-70 sprint was dispatched in four seconds. Even a Jaguar XFR takes 1.9. That’s the advantage of all that torque the electric motor can dump onto the rear wheels in the blink of an eye.

Performance doesn't come at the expense of civilised behaviour either. The M35h goes about its accelerative feats in an impressively fuss-free way. The seven-speed box moves up and down the gears as smoothly as you could wish for. Even at high revs, the V6 never emits more than a growl.

Get to a corner and an XF will disappear in a cloud of superior handling, but that doesn’t automatically mean I’m saying that the M35h is bad, or even poor in this department.

Infiniti M35h

The back end is a bit bulbous

The electro-hydraulic steering certainly delivered more feedback than I expected and even on bumpy rural B-roads everything felt balanced and composed, even when shod with knobbly winter tyres. It was helped, I suspect, by the battery pack sitting over the rear axle. As per many hybrids, the brakes have a slightly unnatural feel to them but it’s nothing you can’t learn to live with.

The chassis can’t quite match the best from the Germans, let alone Jaguar, but the M35h rides better than any 5 Series I’ve been in. Given the state of the roads in Britain, that’s arguably a more important consideration.

Where the Infiniti scores over the Europeans is with kit and fittings. The well-appointed cabin is mostly made from bits of what used to be a tree and a cow, and you get all the modern toys: electric just-about-everything and an excellent 7-inch touchscreen satnav and infotainment system.

Infiniti M35h

The lithium-ion battery eats into the boot space - but not in a Dreamliner fashion...

It all proved remarkably easy to use too: I only had recourse to the massive handbook once, to try to find out how to permanently disable the forward proximity alert. Sadly, it seems you can’t.

The Reg Verdict

Forty-grand hybrid sports saloons are never likely to be more than rare beasts on our roads, but that doesn’t detract from the Infiniti M35h’s appeal. Even when driven inconsiderately, it’s decently economical. But put your foot down and it shows a very impressive turn of acceleration. It’s cheaper than the direct competition too, and you get more standard kit for your money. ®