Hyundai spares no suspense

Stung by the success of its smaller sibling’s local tuning efforts and harsh media criticism of its sub-standard i45 sedan back in 2010, Hyundai has embarked on one of the most comprehensive chassis development programs ever seen in Australia

This week’s facelifted Elantra is the latest evidence of a multi-million-dollar chassis localisation program established by Hyundai Motor Company Australia in the wake of the ill-fated i45 launch, which marked a turning point in the company’s model development process.

Changes to the now-discontinued i45’s suspension for the 2011 model year failed to address its inherent steering rack rattle and kickback problems, and the all-new ix35 compact SUV arrived too soon after that for HMCA to make significant changes to its underdone chassis.

But every passenger model released since 2010 -- except the soon-to-be-replaced i20 -- has undergone a comprehensive six-month local ride/handling program, including the all-new i30 and Santa Fe in 2012 and the recently facelifted Elantra and ix35.

Motoring.com.au was embedded in the ‘Australianisation’ schedule for latter late last year and can confirm the investment easily eclipses well-publicised efforts undertaken for Kia by Gambold Engineering Services, which is headed by accomplished chassis tuner Graeme Gambold and has undertaken consultancy work for brands including Toyota.

The ix35 program is unusual because it comes at midlife facelift time rather than a full model changeover, but Hyundai Australia says it takes any opportunity to enhance a vehicle and can initiate its own changes to any model at any time.

Not unlike the localisation programs Holden previously subjected its imported Korean models to, Hyundai’s exhaustive Australian ride/handling regime conducts development testing of all steering and suspension components.

However, unlike Toyota, Holden and Ford, in the absence of an Australian proving ground Hyundai carries out most of its tuning in urban, suburban and rural roads in and around its Sydney base.

Hyundai says that will continue to be the case following the establishment of a new engineering centre at Germany’s famous Nurburgring, which aims to improve the base chassis performance of most Hyundai models.

The Australian team’s brief is to identify the combination of spring, damper, rollbar, bump stop and electric steering calibration settings that best suits local conditions, before those components are fitted at the Korean factory.

In some cases the Australian chassis set-up is also applied to Hyundai models in other countries. For example, South Africa’s Elantra has adopted the Aussie suspension tune, our Accent tune goes to Russia and China takes our suspension tune for the Santa Fe butmakes small changes to suit different engines sold there.

Hyundai won’t say exactly how much it invests in Australian chassis tuning, but the eight-man localisation team, based at HMCA’s HQ in the Sydney suburb of Macquarie Park, includes four full-time Hyundai staffers and four contractors.

It is overseen by HMCA’s product planning manager Andrew Tuitahi, a former Toyota Australia product planner and club racer who is the team’s chief test driver and signs off all local projects, while the engineering is led by HMCA’s senior product engineering manager Heeloong ‘Wongy’ Wong.

The brains behind the outfit are Philip Rodgers, the former team manager of Subaru’s Australian Rally Championship program who established Captec, the company that supplies the team with software and hardware, and renowned engineering consultant David Potter.

A former rally driver with 25 years of test driving experience, the France-based Brit wrote his Oxford University bachelor of engineering thesis on monotube damper design and has also worked in Formula One, IndyCar and world rallying.

Apart from helping engineer the E36 BMW M3 and a number of Renault Sport models, Potter has worked with a range of European touring car teams including Subaru, Vauxhall, Honda, Mitsubishi, Ford, Peugeot, Nissan, Volkswagen and BMW.

He continues to be a consulting engineer in the design and development of suspension for production, motorsport and military vehicles and he’s contracted by HMCA to analyise suspension kinematics, predict spring and damper rates, reanalyse the data and then specify final spring and damper valving specs.

Potter works closely with Young Chul Park, the R&D manager for South Korean damper manufacturer Mando, which (along with Sachs) supplies Hyundai with shock absorbers built to Potter’s specifications.

Out first taste of the of the MY14 ix35 comes mid-way through the program, in which the car is driven back-to-back alongside direct competitors including the Mazda CX-5 and Volkswagen Tiguan over an urban loop and a typically twisty country road loop through the Kuringai National Park.

The same loops are used by every car, replicating their performance at identical speeds over the same lumps, bumps, potholes, cambers, cat’s eyes, broken bitumen, manhole covers and the sort of country roads that 30 per cent of Hyundai buyers encounter.

Data from 35 sensors -- including a MoTec data-logger to cross-check road speed and position via GPS, a three-axis g-force senor in the middle of the car, accelerometers and potentiometers at each wheel to track the rate of body roll, pitch and yaw -- is logged at a rate of 1000 times per second and sent wirelessly back to Potter in real time.

The software Potter developed as part of his thesis (and later sold to Ohlins) dramatically increases the speed of suspension development because it negates the need to physically test each parameter independently.

While the ability to simulate suspension behaviour has short-cut testing by around 80 per cent, the team works within a development ‘corridor’ specified by the Korean R&D department and based on simulations that take into account body rigidity, durability and production requirements.

Nevertheless, the new ix35 tune includes revisions to all components except bushings because they’ve already been subject to durability testing, with a focus on damping because of its tuneability.

“We operate within the parameters the makers set, but a damper is infinitely variable,” says Potter. “Of course valving has a limit but compared to rigid components it’s like choosing from a lolly jar.

“There are parts of cars that we’d like to address but it’s not always possible given the components available and the window in which we’re working.

“All suspension tuning involves some sort of compromise; our job is to get the best out of what is available.”

All suspension tuning involves compromise in a cause-and-effect way, since firmer springs reduce body roll and pitch but also ride comfort, softer springs enhance the ride but reduce stability, thicker front roll bars promote understeer but thicker rear bars promote oversteer, stiffer dampers enhance body control but contribute to body ‘shake’. And then there’s fine-tuning like wheel camber and toe angles.

“Manufacturers invest a lot of time and money to achieve the best balance,” says Potter. “No single component can be altered in isolation without affecting the rest of the package.”

When it comes to a small family SUV like the ix35, suspension needs to be soft enough to absorb suburban speed bumps but hard enough to cart whole families and their luggage on long trips and even tow.

Because firm springs improve handling and stability, the HMCA team starts with the heaviest springs possible based on suspension geometry, vehicle weight and weight distribution, and – because larger stabiliser bars mask feedback -- the lightest roll bar possible.

Far from arriving at a single optimum spring, damper and roll bar combination, however, the suspension development team has to take into account different tyre brands, sizes and compounds, the different weight distributions of petrol and diesel and 2WD and AWD models, laden and unladen vehicle weighs, and maximum towing capacity.

We arrive to take part in testing damper build #6 for the base petrol ix35 2WD, which is 30 per cent more compliant than before, but it’s already clear the original ix35’s brittle ride quality has been made more supple on coarse-chip road surfaces and more compliant on typical rural road irregularities, without increasing body roll or pitch.

Before we return to HQ, Potter has not only acquired and interpreted the telemetry data via graphs on his laptop, but specified new damping shim stacks (which control the internal flow of oil and therefore stiffness under both compression and rebound strokes, at both low and high speeds) in the shocks, which are already built and ready for installation.

Potter and Tuitahi swap notes after the drive and the latter’s seat-of-the pants assessment confirms the changes Potter has pre-empted. In this case it’s extra compression damping and less rebound damping for the front shocks, which are replaced before the ix35 test mule hits the road again.

Potter says it’s an old rule of thumb that shock absorbers should be three times firmer on rebound than under compression using a 70-profile tyre (in which the sidewall height is 70 per cent of its width), but lower-profile tyres can require as much as a 50/50 damping split.

But although the ix35’s ride/handling is much improved, its steering remains reluctant to self-centre, slow to react and remote in feedback.

That’s because the team is concerned only with suspension this week; next week it will work on improving the steering to match the new suspension tune. Changes to the car’s electric steering – including specific settings for the Comfort, Normal and Sport modes -- are applied by altering the system electronic control unit (ECU).

By the time we return two weeks later, the team has settled on the ix35 2WD’s suspension calibration after 12 front and 24 rear shock rebuilds and the difference is marked in every respect – especially its more planted feel over road corrugations.

Similarly, the move to faster 32-bit computer processing, rather than the original ix35’s 16-bit system, combines with a tighter steering ratio (2.83 turns lock-to-lock versus 2.99), makes the steering quicker to respond to driver input and better equipped to communicate what the front wheels are doing on any given road surface.

Potter believes the changes made to the ix35 make it an even better all-round package than the CX-5, putting it on par with some of the world’s best small SUVs, and there’s no doubt the latest ix35’s vastly improved high-speed damping control made it more composed over a wider variety of roads than the two cars against which it was benchmarked.

“The new suspension covers all surfaces and situations; the more the road deteriorates, the more competent the ix35 feels,” he said, adding that the best-tuned vehicles aren’t always European ones.

“The Germans don’t do supple suspension. They have a different rationale as to how a car should handle. They work well in Germany, where they are tested on the autobahns, less so on secondary roads that aren’t as smooth.

“Properly tune a car for Australian roads and it will work well everywhere.”

Most people will notice the MY14 ix35’s new front-end styling, but far more effort has gone into making its chassis a match for any car in its class.

Chassis dynamics were once the Achilles heel of budget-priced Hyundai models, but with a local tuning program that’s more extensive than most of its Japanese and European rivals, the ambitious Korean car-maker looks set to deliver ride, handling and value in equal measures.

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