Toyota TRD Aurion 3500S 2007 Review

Now this is an engine! Toyota Racing Development's supercharged 3.5-litre V6 is brilliant. There's fat torque - as expected from a sizeable six with a belt-drive blower - which, multiplied by high revs, naturally equals big power. No reason, then, to doubt the 241kW and 400Nm claims.

But numbers, while important, aren't the whole story. A dyno doesn't measure what makes this Australian-developed package truly impressive - attributes like responsiveness and refinement. Lazing down the freeway, with only light pressure on the throttle pedal, you probably wouldn't guess that there was a supercharger under the bonnet. But push a little harder and you'll wake the boosted beast. Thrust grows in precise proportion to pressure on the throttle, and a cultured, mechanical snarl grows in intensity as the tacho needle accelerates through its arc. But even nearing the redline, the V6 never emits the irritating whine typical of many supercharged engines.

None of this has happened by accident. It has taken years, and millions, to make the TRD Aurion what it is. And you can sense immediately where the time and money went.

This isn't the first time I've driven a TRD Aurion, but it is my first time behind the wheel of the finished product. It's more than 12 months since my first sworn-to-secrecy briefings on the car, which covered every aspect of the program. In Toyota Style Australia's studio, the designers who penned the exterior's additions and chose the interior's decorations explained their work. Then there was a visit to Harrop Engineering, where the precision components needed to join Eaton supercharger to Toyota V6 were cast and machined. More recently, I've joined chassis development engineers for test sessions on both road and racetrack. And I've carefully listened to the Toyota Australia TRD engine guys explain the difficulties they faced and overcame ... and even understood a little of it.

Now, at last, I'm driving a TRD Aurion that has the correct suspension, engine, brakes, seats and steering wheel. And all in the same car! The vehicle from August 2006, for example, combined not-quite-finalised suspension settings with a rev-limited, low-power engine. The TRD Aurion I'm now driving is called T2, signifying it's the second in a batch of trial-build cars assembled in February '07. And it somehow seems to sense it has an opportunity to make a good first impression.

On the freeway heading south-east out of Melbourne, the engine stands out most. Mainly because it's so damned quiet in this undemanding environment. But the creamy quality of the TRD Aurion's six-speed automatic also impresses when a surge of acceleration is required. Yes, it's exactly the same transmission as the regular Aurion. No, there isn't a manual option, and nor is one planned. Neither of these facts is an issue, as this is a truly outstanding automatic. Sensitively and sensibly responsive, its shifts in 'D' are nicely timed and suavely executed. Its only obvious flaw is a back-to-front pseudo-manual mode, same as the regular Aurion. While I disagree, some drivers claim pushing the lever forward to upshift and back to downshift feels more natural to them. Maybe, but it means working against the g-forces when accelerating and braking. Significantly, I have never met a racing driver who thinks forward to upshift and back to downshift makes sense.

Maybe the manual-mode shift direction will be an issue tomorrow, at Phillip Island, where we'll spend time on one of the world's great racetracks. In the meantime, there's time to explore the TRD Aurion's personality on public roads. Peeling off the bayside highway, we point T2's nose towards the verdant hills.

This is more like it. There are long, if lumpy, straights, high-speed sweepers, sharp climbs, and descents packed with tight bends. It's a mix that includes just about everything a driver will encounter on Australian rural roads.

Again the blown V6 shines. This time for the vigour and precision of its response to throttle. From the driver's seat, TRD's 0-100km/h claim of 6.1 seconds (recorded with only the driver aboard), seems reasonable. Accelerating out of slower second- and third-gear corners, the sustained strength of the supercharged surge is damned impressive. Near the grip limit through faster bends, where throttle influences the car's balance and trajectory, the telepathic accuracy of the engine's response to fine variations in pedal pressure is simply luscious. This is one characteristic where supercharger will beat turbocharger every time.

And the TRD Aurion stops every bit as well as it goes. The greater diameter of its 19-inch wheels means it can accommodate larger discs and more capable calipers, and the system delivers great power and feel. While the pedal is firm, it's not unyielding, and there's a nicely linear relationship between pedal pressure and travel, and the rate of deceleration. As well as being easy to modulate, there's not a hint of fade.

One of the reasons the brakes feel so good is that the tyres selected for the TRD Aurion deliver great grip. Naturally, the Dunlop SP Sport Maxx tyres also deliver impressive cornering power. On busted-up Australian bitumen, more importantly, the low-profile Dunlops won't bust your arse. Despite a 35 percent aspect ratio, the rubber rides pretty well - it's firmly disciplined, but the TRD Aurion's suspension rounds off the sharp bumps quite nicely, thank you.

Handling? Well, the TRD feels much more alive, more eagerly agile than an Aurion Sportivo. While the springs and dampers for the TRD Aurion are stiffer and firmer, the chief reason for the change in character is a simple alteration to the rear suspension geometry. Seems to work, too - the TRD Aurion feels sweetly balanced front-to-rear, and answers steering wheel inputs promptly.

Despite this, the steering is the car's weakest link dynamically. The engine's torque makes itself felt when accelerating hard - the steering wheel squirms and tugs - but it's distracting rather than dangerous, and could be tamed if the traction control system was more appropriately calibrated. The TRD uses the regular Aurion chassis electronics without modification, and the system allows a surprising amount of wheelspin before it intervenes. If it acted earlier, the squirm and tug would be lessened. The steering's other issue is tramlining on rutted roads, especially when braking. Nevertheless, it does deliver a sense of connection, and has reasonably consistent and appropriate weighting.

Next day, on Phillip Island, the steering isn't a major issue. On a smooth and grippy racetrack, it's much, much calmer. There are two impressions I take away from laps in T2, the car I drove on the road, and the old C18, an instrumented engine and chassis development reference car.

Firstly, the brakes just don't give up. Racetracks can make road car brakes that feel good disappear in a puff of smoke, but these stay strong and consistent for laps at a time.

Secondly, the car's grip is serious. Through the long left-hander onto Phillip Island's straight, I steal a glance at the most interesting meter in the C18, and see it sustaining more than 1g lateral force

It takes serious provocation for the TRD Aurion to develop any attitude. In the safe environment of a closed circuit, I'm able to establish that the car will briefly, but satisfyingly, tighten its line if you give it a hint with wheel and throttle. The standard electronic stability system intervenes, of course, but the TRD's grip means such events are rare.

Perhaps the best measure of its ability is the 1min 59sec lap cut by Neal Bates in another car at Phillip Island that day. The rally champ's primary task is to record some videotape for the launch in the black TRD Aurion T11, but he seems equally interested in nailing a good time. It takes a number of laps, but he finally bags a sub-2min time. This, I'm told, is a good result for a front-drive road car.

While a little track cred will enhance the TRD Aurion's image, its ability on a circuit isn't the most appealing thing about this car. What I'm most impressed by is the cohesion and completeness it exudes. It's a harmonious whole. Its design, outside and in, accurately conveys its dynamic abilities. And the driving experience, with the exception of the steering, aligns nicely with the car's restrained and (dare I say it) tasteful styling. It's a fine first effort from Toyota Oz's tiny TRD outfit.

ENGINE DEVELOPMENT
Supercharging was a key element of the TRD Aurion plan, right from the start. It was chosen for the 2004 Camry V6-based, high-performance TSO-1 concept, and the team liked what it measured. The Roots-type, belt-drive Eaton blower easily upped the 3.0-litre V6's outputs by 44kW and 45Nm, to 185kW and 324Nm. But raw numbers weren't the only attraction. TRD also found the relative simplicity of supercharging, compared with turbocharging, very appealing. Fewer pieces and simpler plumbing means installing a mechanically-driven blower is much easier.

While Toyota PR people turned out press releases that avoided mentioning the exact max power target for the TRD Aurion, the engine development guys were always aiming for 240kW. To help them get it, TRD needed partners. Harrop Engineering was a natural. Already the distributor for Eaton superchargers in Australia, the company was also equipped to cast and machine the unique components required to supercharge the 3.5-litre 2GR-FE V6. TRD also needed an engine development, calibration and testing partner. Orbital, the West Australian powertrain development specialist, was chosen.

Then the difficulties began...

There wasn't an issue with the Harrop components. The Oz-made inlet manifold, blower body, blower drive, and new front engine plate (with pulleys and tensioners for the serpentine blower drive belt) went together without trouble. But the prototype engine fell short of the desired power output.

Analysis revealed that the problem was caused by the M90 blower, which was pushing hot air into the manifold. Compressing air naturally results in a temperature rise. In a diesel engine, for example, high compression results in temperatures hot enough to ignite fuel when it's injected. The temperature of the air exiting the engine's blower wasn't that hot, of course, but 100°C at high revs was reducing air density enough to effectively limit power.

While the chassis development team worked on with rev-limited, low-power versions of the supercharged V6, the engine team looked for solutions. An intercooler was the obvious answer to their power problem, but finding room for it wasn't easy.

With under-bonnet space already tight, slipping a liquid-to-air intercooler between blower body and manifold was problematic. Installing an intercooler, the team also realised, meant a redesign of the engine's fuel delivery rails. This they were keen to avoid, for reasons of cost and engine assembly ease.

Still, by September '06, the TRD engine development team had an intercooled version of the supercharged V6 ready for testing. Early results were promising. The proto engine delivered 231kW on one of Orbital's dynamometers, with clear potential for more.

But work on the intercooled engine was abandoned after Eaton and Harrop made a presentation to TRD on its next-gen TVS (Twin Vortices Supercharger) blower family. With four-lobe rotors and 160 degrees of twist - in contrast to the three-lobe, 60-degree design of its M90 supercharger - the TVS looked like it could do what TRD wanted. While the TVS also brought advances like compactness and quieter operation, the blower's most appealing feature was its greater efficiency and promised reduction in output air temperature.

It didn't take long for Harrop to turn out a prototype blower housing to accommodate the new TVS rotors. By October a TVS engine was running. The TRD engine development team saw manifold air temp reduced to 80°C, and 230kW, with this first try. Their 240kW goal was in sight - and without an intercooler.

A period of painstaking calibration work development followed. TRD senior development engineer James Cathcart, for example, was sent to Orbital's facility to work his way through a series of blower drive pulleys that varied in diameter in 1mm steps.

Engine calibration was followed by testing, including a 100-hour test at wide-open throttle and 6400rpm on an Orbital engine dyno. Hot-weather testing in Australia, plus cold-weather and high-speed testing in Japan, followed.

It was only in April that Harrop was able to supply sets of final production supercharger components. Using these parts, the engine's peak power and torque figures of 241kW and 400Nm were established. So, too, was its Euro IV emissions level compliance and very impressive 10.9L/100km official government fuel consumption test result.

But perhaps the most impressive thing about the supercharged V6 is the way that it meshes harmoniously with the remainder of the car. TRD, clearly, is determined to make sure its cars are much more than a bunch of accessories and add-ons hanging out together.

And more than any other part of the TRD Aurion, this supercharged engine convinces you they can do it.

INTERIOR DESIGN
Front seats, steering wheel and shifter knob are the big statements inside the TRD Aurion, although the rear seat and doors are also re-trimmed with fabrics to match. While the front seats use the same frame as a standard Aurion, redesigned padding is aimed at providing support when cornering. Colour is cleverly used to emphasise the seats' supportive bolstering.

Toyota Style Australia's initial steering wheel design for the TRD Aurion tried hard - too hard - to establish a link with Formula One. The oversize thumb bumps, weird variations in rim thickness, and flat bottom were all too much. The chassis engineering team didn’t like it, and neither did rally champ and Toyota driver Neal Bates. Facing a chorus of objections, the designers came up with a much plainer - but more finger friendly - design.

EXTERIOR DESIGN
Quite obvious, when you think about it, that TRD should look to Formula One for stylistic inspiration for its supercharged Aurion. After all, Toyota doesn't have a long and storied history of successful competition in Australia's premier touring car categories. Unlike the performance divisions of Holden and Ford, the TRD name doesn't come encumbered with any need for its products to appeal to the, um ... unsophisticated tastes of V8 Supercar fans. Aiming instead for an audience that would appreciate high-tech and refinement, referencing F1 seemed smarter, even if Toyota's red and white F1 cars are more often seen in sand traps than taking the chequered flag.

Considering TRD's aspirations for its first car, there's some irony in the fact that the Aurion's exterior is the work of a former Ford Australia designer. Englishman Lee Moran was hired by Toyota Style Australia chief Paul Beranger in 2005, and went straight to work on Aurion TRD.

Moran's ideas included reducing the size of the grille, and adding emphasis to the bumper line below it. The bottom part of the TRD Aurion's large front bumper is where the designer was able to incorporate stylistic links to F1. Moran sought to do this not just by echoing some of the curving forms seen on GP cars, but also emphasising the joins with colour. He adopted a similar approach with the rear bumper. "It seemed like a notion no-one else was looking at," Moran remembers.

His ideas were refined until there were just two design themes. Both were incorporated into the same full-size clay model, split 50/50 down the centreline. The final design, developed as a hybrid of Moran's two themes, was further refined.

Once TSA had completed its design work, the TRD Aurion body parts then had to be tested. In a Toyota wind tunnel in Japan, the car's 0.30 co-efficient of drag was confirmed. The tunnel also failed to reveal any wind noise issues with the new, TRD Aurion-specific parts. But some prototype pieces failed to score a pass mark when subjected to heat and vibration tests. While the rocker mouldings and bootlid spoiler were okay, the front and rear bumpers distorted in heat. Mounting redesign work on the front bumper, and the adoption of plastic with better heat-resistance properties were required to solve the problems.

Everything was ready in March, the same month a confirmation-build TRD Aurion was subjected to an offset barrier crash test to ensure it met the standard of ADR73. Production finally began in June, with subcontractor Prodrive building four cars a day in the assembly cells of its new facility close to Toyota's factory in the Melbourne suburb of Altona. So, with another ironic twist, a name associated with World Rally Championship success is responsible for building TRD's Formula One-inspired car.

CHASSIS DEVELOPMENT
Extensively tested on racetracks and public roads in Australia, as well as Toyota's Shibetsu proving ground in Japan, the TRD Aurion's dynamics have been carefully honed. And, yes, it is a sharper drive than a regular Aurion Sportivo. Although the car has all the expected alterations to springs, dampers and anti-roll bars, it's a relatively small and inexpensive change to the geometry of the rear suspension that contributes most to its superior sense of agility.

A standard Aurion has a small degree of rear-wheel toe-in, desirable for stability when cornering. Reducing the TRD Aurion's rear toe angle to near zero has a marked effect on its eagerness to change direction. Before, the 10mm lower suspension, stiffer springs, more disciplined dampers and re-rated anti-roll bars just weren't quite doing enough.

At an August 2006 test session on public roads east of Melbourne, the development TRD Aurion had lots of grip and benign handling. But next day, at Winton racetrack near Benalla in country Victoria, it had senior development engineer Marcus Umlauff shaking his head. The ex-Ford Australia chassis expert knew the car should feel more agile, more satisfying. A post-lunch discussion lead to adjustments to the TRD Aurion's rear suspension, reducing the toe-in to half the standard car's value.

"It was a big improvement," confirmed Umlauff after a few laps of Winton. Toyota Australia chassis engineer Paul Diamandis agreed: "The rear wheels were now contributing to the cornering equation."

There's no mistaking the car's eagerness to respond to steering wheel inputs, or its sweet sense of mid-corner balance. But it's the steering system itself that is perhaps the TRD's greatest dynamic weakness. Using the same steering rack as a standard Aurion, it's no more direct. This is a minor issue in comparison to the squirm and tug that can be felt when accelerating hard in lower gears. Tramlining under brakes can also be felt.

Umlauff acknowledges that changes could have been made to quell these symptoms. But when you're delivering the hefty torque of a supercharged V6 through the front wheels, the range of options is limited. Getting rid of torque steer also means getting rid of road feel, and the TRD Aurion is the kind of car that needs to deliver a genuine sense of connection. Given the need for compromise, the TRD chassis team seem to have made a wise choice.

No criticism of the brakes, however, developed in partnership with Australian specialists PBR. The objective of the TRD engineers was for the brakes to meet the standard devised by respected German car magazine Auto Motor und Sport, whose test duplicates a descent of a European mountain pass, and is notoriously tough. The 19-inch wheels selected for the TRD Aurion meant larger, ventilated, discs could fit, 325mm up front and 310mm at the rear (a standard Aurion has solid rear discs). Uprated calipers complete the package, which delivers excellent pedal feel, wonderfully progressive braking, and superb fade resistance.

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