We em­bed with the dev team that put the rear-drive venom in Stinger

Wheels (Australia) - - Contents -

AUSSIE chas­sis tun­ing of Kia’s rear-drive Stinger be­gins not in the flow­ing climbs of the Great Di­vid­ing Range, but deep in­side Kia’s vast test­ing fa­cil­ity in Namyang, a two-hour bus haul from South Korea’s cap­i­tal, Seoul.

It’s the self-con­tained func­tion­al­ity of a prov­ing ground that makes them so de­sir­able. Here, you bolt in a new set of com­po­nents, drive out the door and, a few min­utes later, you’re flat out on the ride and han­dling cir­cuit, un­em­cum­bered by traf­fic and free of speed lim­its. And you have un­lim­ited ac­cess to a heads-cram­bling num­ber of com­peti­tor ve­hi­cles.

As has been the case since 2010, pas­sion­ate rally driver and tal­ented automotive en­gi­neer Graeme Gam­bold is Kia’s go-to sus­pen­sion guy. Gam­bold and his chas­sis de­vel­op­ment crew be­gin by plug­ging swathes of de­sign data – front and rear cen­tre-of-grav­ity height, wheel­base, track widths, roll-cen­tre heights, sprung and un­sprung weights – into a VDA (Ve­hi­cle Dy­nam­ics Anal­yser) com­puter sim­u­la­tion pro­gram to es­tab­lish a kine­matic base­line. And not just for the Stinger, ei­ther. The Kore­ans have com­pre­hen­sive data on ev­ery Euro­pean bench­mark you care to name, hav­ing an­a­lysed the com­pe­ti­tion in painstak­ing de­tail. Not the cur­rent rear-drive Com­modore, how­ever.

“We haven’t looked at Com­modore”, ad­mits Gam­bold. “Not be­cause we don’t feel that Com­modore is im­por­tant, but it means noth­ing to these guys [at Namyang]. If we find an is­sue, it’s much bet­ter to com­pare it against some­thing that they know. And Euro­pean stuff is usu­ally the bench­mark; in this case the C-class or 4 Se­ries.”

The Aussies are re­stricted to a small num­ber of tune­able com­po­nents. In the case of Stinger, it’s four front springs and four rear springs for both the four­cylin­der and V6, three front anti-roll bars and three rear anti-roll bars each, as well as a range of damp­ing rates and steer­ing tunes. Gam­bold sim­ply has to make it work.

Six months be­fore on-sale, Stinger is al­ready too far down its de­vel­op­ment path for the Kore­ans to ap­prove any tun­ing part out­side the off-the-shelf stuff avail­able in Namyang’s work­shops. Says Gam­bold: “We don’t play with kine­matic ge­om­e­try – arm lengths, roll-steer co­ef­fi­cients, bump steers – be­cause we trust and work with the data that the car is pre­sented with. That stuff is ve­hi­cle de­sign, not ve­hi­cle tun­ing. If there’s a big prob­lem, then we’ll iden­tify it and ne­go­ti­ate it, and there have been a cou­ple of times where we’ve been suc­cess­ful in or­ches­trat­ing change on kine­matic de­sign. But, gen­er­ally speak­ing, we work with what we’re given. [The Kore­ans] do enough bench­mark­ing of other ve­hi­cles to know what they’re do­ing”.

Job One is form­ing a base tune to take back to Aus­tralia. In Korea, it’s chiefly springs, anti-roll bars and some damper tun­ing. Back home, it’ll be dampers and steer­ing, in­clud­ing pa­ram­e­ters of the ECS (Electronically Con­trolled Sus­pen­sion) adap­tive damp­ing sys­tem and three lev­els of steer­ing weight. “We’ll just build max­i­mum/min­i­mum stuff here, and then hope­fully by the end of the week, get it into a win­dow where we’re happy that’s our start point back in Aus­tralia,” says Gam­bold.

What he’s cer­tain of, how­ever, is that the do­mes­tic (Korean) sus­pen­sion tune of the V6 won’t work for Aus­tralian roads. “Be­fore I’ve driven it, I can tell you now I won’t par­tic­u­larly like it. Firstly, it’s go­ing to pitch be­cause the front is too soft. Its roll-cou­ple dis­tri­bu­tion [the rel­a­tive roll stiff­ness be­tween front and rear] for a rear-wheel car is too neu­tral, so it’s go­ing to lift the in­side rear wheel a fair bit so it’ll prob­a­bly have poor trac­tion,” Gam­bold says.

“Even though they’re happy with it in their coun­try and it suits their driv­ing styles, I know that for Aus­tralia it won’t work. We have a lot of fo­cus on pitch­ing be­cause we drive down coun­try roads at 100 kays and if you’ve got a car that’s por­pois­ing, you’ll no­tice it. Here [in Korea], you won’t. They like it be­cause it gives them a bit of a luxo feel, an undamped feel, a bit of pitch, but we don’t like that.”

In­deed, the do­mes­tic-mar­ket V6 chas­sis set-up feels a bit wrong. Its back end, in par­tic­u­lar, feels like it’s on a

It’s no se­cret that Al­bert Bier­mann, Hyundai-kia’s high­per­for­mance de­vel­op­ment chief, thinks there’s some head­room in the Stinger. “In Detroit he was very keen to say that there is more in this car… he has a vi­sion for where he wants it to go,” says Kia’s Aussie PR boss, Kevin Hep­worth. Gam­bold agrees: “It’s a car that Bier­mann spoke about. He wants to build to [ M3, C63, et al] level, and I would too, but the parts bin isn’t there at the mo­ment.” And what does Gam­bold think would make the ideal hot Stinger? “My per­sonal view is that they would be best to just hot the V6 up.”

dif­fer­ent page to the front, while the rear wheels lack pur­chase and pro­duce too much wheel­spin when you push the car hard on chal­leng­ing sur­faces.

In com­par­i­son, the ini­tial Aussie tune feels far more co­he­sive, if still a bit un­der­steery – es­pe­cially when backto-backed with bench­mark­ing ve­hi­cles, which in­clude a BMW 428i xdrive Gran Coupe and an Audi A5 1.8TFSI Sport­back, as well as a BMW M4 and Mercedes-amg C63 S sedan to ex­pe­ri­ence the other ex­treme. We deem the 428i the most rel­e­vant for com­par­i­son, with its softer rear end, pointier steer­ing, and over­all dy­namic su­pe­ri­or­ity to the (old-gen) A5.

At­ten­tion then turns to the Stinger four, and Gam­bold thinks the do­mes­tic tune isn’t bad. “Their fi­nal tune is the same hard parts as we want… and when we drove it we were re­ally happy with it.” But pushed hard in the lane-change, the Stinger four un­der­steers strongly, un­like the much sharper 428i. Lim­ited by spring choice, Gam­bold opts for a smaller front anti-roll bar and has asked the on-site en­gi­neers from damper sup­plier Mando to re­build the 2.0T’s rear dampers with re­duced re­bound and in­creased com­pres­sion to lessen the un­der­steer by “hold­ing the rear end up”. In­stead of inertly fol­low­ing the front, Gam­bold wants the Stinger’s rear end to play a con­tribut­ing role in point­ing the nose into a cor­ner.

Two days of fet­tling later, Gam­bold is much hap­pier with the V6. “We’ve in­creased the rear shock ab­sorber rate quite a bit, so when you turn now it rolls in and you feel the back set­tle; you know that you’ve got that grip. It doesn’t un­der­steer as much as it did, ei­ther.”

Back in Syd­ney, the tun­ing team’s dead­line is just as tight. When I head out to Kia’s head of­fice work­shop, they’re de­ter­min­ing the con­trol strat­egy for the ECS dampers. “We’re look­ing at steer­ing an­gle, brake pres­sure, ac­cel­er­a­tion po­si­tion, lat­eral G-force, ve­hi­cle speed, the mode switch the driver has se­lected, body G-force, and wheel G-force,” says Gam­bold. “And from those in­puts, the so­le­noid valve gets a logic from the map that we build. We’ll ex­trap­o­late the Euro­pean high-speed data, and we can play with a lot of things – roll, pitch, bounce, slow roll, fast roll, hard brak­ing, give it squat to help trac­tion...”

I leave the white GT V6 in the pits and head out in the red 2.0T with fixed dampers. It doesn’t have its Aussie steer­ing cal­i­bra­tion, mean­ing it’s a lit­tle numb and overlight at the helm, but its chas­sis feels very keen on the sin­u­ous, chal­leng­ing roads snaking through Syd­ney’s Kuringai Na­tional Park. For com­par­a­tive pur­poses, we bring along a BMW 420i Coupe. The au­to­matic Beemer proves pleas­ant but colour­less – just like the Stinger 2.0T’s engine.

Back at Kia HQ, I de­liver my feed­back on the four’s very sharp turn-in. “I don’t typ­i­cally like that feel”, says Gam­bold. “I don’t like a fast rear yaw re­sponse, so if it’s do­ing that then we’ll prob­a­bly tame it a bit. But then you can tame a lot of that with the power steer­ing tune.”

And so the fine-tun­ing goes right to the wire. At the pointy end, it’s all about fi­ness­ing. “Hours and hours of driv­ing up and down on the same piece of road, chang­ing num­bers,” says Gam­bold. It’s much more men­tally chal­leng­ing than it sounds. But thanks to the en­gi­neers’ un­wa­ver­ing pa­tience, per­sis­tence, and pas­sion, our Stinger gets to be the best in the world.



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