Tenacious D

For decades Mazda dedicated itself to proving a rotor, not a piston, makes for a better internal combustion engine. The high-revving rotary experiment has been spectacular to watch. Now, while Mazda may have temporarily shelved its revolutionary rotary engine program along with RX-8 production, via a US racing series, the company’s rebellious spirit lives on.

Being ‘eccentric’ is a critical quality in Mazda’s corporate thinking – so important that Mazda is willing to walk away from half a century of rotary engine development and racing to explore a new direction. Remember, it was Mazda in 1991 that won LeMans with a shrieking quad-rotor engine, a triumph as remarkable and counter-establishment as are Audi’s more recent LeMans wins with its diesel engines.

And there’s a connection here: Mazda – LeMans – Diesel. Indeed, with those three words Mazda has plotted a radical shift in its motorsport strategy. The future for the brand is diesel and the company has focussed its efforts for the time being on endurance racing via the United States Grand-Am Series. In the background (quiet) plans exist to return to LeMans with corporate support and privateer entries.

The Mazda Grand-Am racer shown hereabouts might be low, lean and mean but some of you are literally commuting daily with the same engine block and cylinder-head in your Mazda3 or 6 turbodiesel.

The rules that govern Grand-Am racing state that the engine block and cylinder-head must be standard components. Mazda claims its racer features something like 51 per cent OEM engine components – that is, more than 280 parts carry production part numbers. The three major exceptions are crankshaft, connecting rods and pistons.

The same determination applied to developing the rotary engine into a race winning powerplant has been redirected into the Grand-Am program. Mazda is now focused on proving a high-performance diesel is an excellent alternative to petrol and may possibly be a viable alternative to other so-called green technologies.

“We realise we do things differently at Mazda,” said John Doornan, Director of Motorsports Mazda North American Operations.

“And we’re different for very good reasons. We believe there is a direct link between Mazda’s racing program and the customer.”

In other words, Mazda victories will somehow make diesel sexy. In the United States, at least, the Mazda brand, not Honda, is synonymous with racing and associated with all those key words marketers love: responsive, fun to drive, sporty. But diesel, at least to American ears, is still a dirty word.

Doornan says Mazda within a few months will be the only Japanese marque with a diesel engine offered in the USA. But this diesel-racing program reaches far beyond the borders of the US. Australia and Europe will see Mazda introduce a wider range of turbo-diesel engines in most of its model ranges from the next-generation Mazda2 upward. The latest 2.2-litre turbodiesel engine Australians are offered in the new-egneration 6 is the pointy end of the D revolution.

MAZDA BORN AND BRED
Free from control of (previous) headmaster Ford, the new aluminium 2.2-litre turbocharged diesel engine is all Mazda. Not badge engineered and borrowed, Mazda assembles the diesel alongside petrol engines.

Senior Advisor at Mazda NA, Jay Amestoy, points out why this is significant.

“We didn’t need to invest in a new diesel manufacturing plant nor install a new diesel production line.

“We anticipate strong growth for diesel in the United States, and producing petrol and diesel engines on the same production line in Japan gives us the ability to balance volumes to meet customer desire for diesel.”

Aside from the pricey European luxury brands, only Volkswagen offers an affordable diesel option in American showrooms. Doonan and Amestoy both mention Chevrolet’s recent launch of the mid-sized Cruze with diesel (at $US25,695), but to settle their nerves they turned to Mazda dealers who also own a Volkswagen franchise.

“They’ve been teaching us a lot about the buyer who wants diesel and how to sell the benefits of diesel,” said Doonan. “We’re very confident.”

Indeed, there’s now less risk than ever in offering diesel alongside petrol in showrooms in Los Angeles, London or Melbourne, especially when Mazda is without a viable petrol hybrid, plug-in hybrid or electric drivetrain offering. Diesel is Mazda’s ‘green’ alternative for the time being.

ROAD TO RACE TRANSITION
In the land of Stars and Stripes, maybe the stars have aligned for diesel. For all the same positive reasons – power, torque, fuel efficiency and clean emissions – diesel transitions from road car to race car with amazing dexterity. And, in the case of the Mazda SpeedSource Grand-Am racing 6, with a whopping 298kW at 4600rpm and 610Nm at 4000rpm...

And you can discard those old ‘rotary’ earplugs... This turbo diesel at full song is, well, humming. You actually hear more wind whistle off the deck spoiler than bark out the exhaust.

A peripheral ported 20B turned decibels into painful darts and fired them through your forehead, but this 2.2-litre turbo diesel at full anger sounds as placid as Placido Domingo. The rotary faithful (if they can still hear) won’t like this at all.

“Inside the car you hear a little gear noise and you hear the two turbos spool up and that’s about it,” driver Tristan Nunes told motoring.com.au.

“We heard the rotary but the diesel is so quiet. That’s why we have the highly visible shift lights in the cockpit.”

The numbers tell the story. In race tune, the twin turbocharged diesel engine idles smoothly at 1500rpm before generating a massive 610Nm at 3250rpm and holding the torque curve virtually flat to 4400rpm. The first LED shift light flickers at 4500rpm, more lights at 4750 and ‘Christmas’ at 5000...

“You’re just banging through the gears,” said Nunes. “It all happens so quickly.”

Described as compound turbocharging, a primary large turbocharger boosts into a small secondary turbocharger. Whereas Mazda’s standard 2.2-litre turbo-diesel engine produces 5.5 to 6psi boost (above atmospheric), the racing engine sees 45 to 50psi boost above atmospheric.

A unique, high-grade diesel fuel (see box story) is injected directly into the combustion chamber at around 2200 bar (32,000psi). Nothing unique here, except the high fuel pressure and high volume puts a huge strain on the injection pump.

Sylvain Tremblay, principle engineer for the Grand-Am program, claims that the engine sacrifices 73Nm to spin the fuel pump. By way of comparison, the current Mazda2 makes peak torque of 135Nm!

TRACKING SUCCESS
With wins will come the love. Three Mazda6 turbo-diesel racers debuted at the Rolex 24 Hours at Daytona in January this year but their race ended early with piston issues due to overheating and serious harmonics problems in the common-rail fuel injection system. Other issues have surfaced through the debut season, and most have duly been solved.

As motoring.com.au visits the Grand-Am effort at California’s Laguna Seca circuit late in the season, one of the 6s tears apart its driveshaft just before the famous Corkscrew corner. The steel tubing ripped like paper, a telling symptom of how differently this turbodiesel engine delivers its massive torque compared to a rev-happy rotary.

Tremblay has seen it happen a few too many times. He and a team of engineers and technicians at SpeedSource based in Florida are responsible for development of the 2.2-litre turbodiesel engine for motorsport.

“It is very different from the three-rotor 20B engine,” he says.

“We’re solving problems we never experienced with the rotary.”

And he’s trying to negotiate through a maze of regulations being set by Grand-Am series promoter, NASCAR, which has never before sanctioned a diesel engine for competition.

Tremblay and NASCAR are both feeling their way in the dark. Tremblay credits Bosch as being a welcomed source of knowledge.

“Bosch worked with Audi on its diesel LeMans program, and Bosch has shared a few secrets with us about injector design and injector phasing. Audi, though, won’t share any information with us.”

How and when fuel is precisely injected into the combustion chamber is important to a diesel engine. It is critical to a highly strung racing diesel engine.

The standard Mazda diesel engine uses five-stage injection phasing. Tremblay admits to testing from three-stage to seven-stage phasing, and then only smiles.

“I will say that we use post injection phasing.”

To explain, additional fuel is injected during the exhaust stroke which ignites to create more exhaust pressure to spin the turbochargers faster. An anti-lag in effect but without the crackling backfire of a WRC rally car.

Post injection reduces lag but doesn’t eliminate it.

“Oh, there’s lag,” says Nunes.

“Compared with the 20B... I’m on the throttle way before the apex trying to guess it all right. If I get it wrong, there’s a lot of power oversteer to deal with.”

Mazda with the turbo-diesel Mazda6 sedan earned its first Grand-Am class victory at Road Atlanta in April. But burning the midnight oil, so to say, and winning the long day at Daytona in January 2014 remains the goal.

From there, Mazda will put its diesel racing technology to the ultimate test of endurance – LeMans! We’re looking forward to being there...

Sunoco supplies all fuels – petrol and diesel – to the US Grand-Am Championship; however, the diesel tipped into the fuel tank of the Mazda6 is not the same stuff grandad used in the old John Deere. Not even close. Indeed, while Sunoco will not comment about the fuel’s chemistry, it’s clear from the silence that diesel ain’t diesel.

Supplied to Sunoco and manufactured by Dynamic Fuels at a refinery in Louisiana, a main ingredient is commonly found standing in a farmyard. Not soybean, not corn but this diesel is concocted from the animals that eat corn and soy.

According to the Dynamic Fuels website, the company has developed a process to create high-grade, clean diesel using animal fats from chicken, pork and beef. The animal fat is claimed to improve the ignition properties of this type of ‘clean’ diesel and is the reason why the 2.2-litre diesel in the Mazda6 does not clatter and rattle.

Given these characteristics, the cetane rating of 70 is much higher than average pump diesel.

And for those of us who breathe for a living, the lack of black smoke and a dirty tailpipe are proof of clean combustion.

As a racing fuel, it has other beneficial qualities beyond the diesel you pump from the bowser. It is almost colourless and can easily be mistaken for petrol, a reason why the refuelling cans are clearly marked ‘diesel’. It doesn’t foam up either so it can be poured into the racecar’s tank very quickly.

Audi, during its highly successful LeMans diesel racing program, relied on Shell Oil to create a racing fuel for its V12 and V10 engines.

Shell answered with a high-performance diesel refined using a technology known as GTL (gas-to-liquid) diesel – a process which uses natural gas instead of animal fats as a key ingredient.

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