Ex­hausts: the Af­ter­mar­ket

It’ s no longer just about mak­ing more noise– the after mar­ket-ex­haust in­dus­try has come such along way that even big-name car mak­ers now queue up for its war es

Evo - - INTERVIEW - by Brett Fraser

EXHAUSTSAND THE af­ter­mar­ket: why bother? Man­u­fac­tur­ers now ex­pend tens of thou­sands of hours and mil­lions of pounds de­vel­op­ing their per­for­mance cars to a high state of tune, and the ex­haust sys­tem is crit­i­cal to that process. Can the af­ter­mar­ket re­ally do bet­ter?

Well, the af­ter­mar­ket ex­haust in­dus­try has come a long way since the days when it sim­ply cre­ated nice shiny sys­tems out of stainless-steel tubes, said they’d last for­ever and give you lots more horse­power, and en­sured they made plenty of noise to drown out the sound of of­ten empty prom­ises. Rep­utable af­ter­mar­ket firms to­day have to com­ply with EC reg­u­la­tions con­cern­ing sound lev­els, ex­haust-gas emis­sions and man­u­fac­tur­ing standards, and em­ploy uni­ver­si­tye­d­u­cated engineers to op­er­ate so­phis­ti­cated de­sign soft­ware to cre­ate their prod­ucts.

The goal of any af­ter­mar­ket ex­haust sys­tem is, you’d think, to hurry the ex­haust gases away from the com­bus­tion cham­bers quicker than the orig­i­nal-equip­ment (OE) sys­tem can man­age. The faster the ex­haust gas is evac­u­ated, the sooner a fresh fuel-air mix can be in­jected, and the more power and torque can be pro­duced. To this end, af­ter­mar­ket sys­tems try to fol­low a neater, straighter path from man­i­fold to tailpipe, and cour­tesy of more la­bo­ri­ous and costly bend­ing and weld­ing pro­cesses, the in­ter­nal sur­face of their pipework is smoother, for unim­peded gas-flow. They also fea­ture ex­pen­sive high- flow cat­alytic con­vert­ers, and their si­lencers breathe more freely.

And yet few af­ter­mar­ket man­u­fac­tur­ers make a song and dance about power-in­crease claims, even those such as the Slove­nian maker Akrapovic, or the UK’S Mill­tek Sport, both of which are also heav­ily in­volved in mo­tor­sport. Akrapovic does men­tion a 14bhp boost to the power out­put of the BMW M2 by us­ing its re­place­ment down­pipe and sports cat, but you have to read a long way through the prod­uct de­scrip­tion to dis­cover that fact. It’s as though the in­dus­try is ner­vous that any in­creases may not be re­peat­able.

Quick­sil­ver’s man­ag­ing di­rec­tor, Paul God­dard, is equally coy about high­light­ing power im­prove­ments, and claims his clients have other pri­or­i­ties. ‘Cus­tomers with ex­pen­sive sports cars tend to be

ex­tro­verts with an emo­tional at­tach­ment to their cars,’ he says. ‘To them, sound qual­ity is crit­i­cal; their car is al­ready quick enough. So our sys­tems are tuned to em­pha­sise and am­plify the au­ral sen­sa­tions of the ex­haust. Sound helps you judge your car’s per­for­mance.’

That last com­ment is par­tic­u­larly per­ti­nent in an era where down­sized en­gines with tur­bocharg­ers are be­ing crit­i­cised for weak au­ral per­for­mance – the Porsche 718 se­ries is a prime ex­am­ple. Af­ter­mar­ket si­lencers can help re­store some of the roar emerg­ing from the tailpipes, and tur­bocharged en­gines can re­spond well to af­ter­mar­ket down­pipes used in tan­dem with sports cats, with (again, largely un­spec­i­fied) im­prove­ments to power and torque.

The in­creas­ing pop­u­lar­ity of ‘switch­able’ ex­hausts, which al­low cars to meet noise con­straints in ur­ban ar­eas but achieve the full ban­zai out on the open road, are test­ing the in­ge­nu­ity of af­ter­mar­ket engineers. Not least be­cause the con­trols for these sys­tems can be deeply in­ter­linked with the rest of a car’s elec­tron­ics. Mill­tek is work­ing on a valve ar­range­ment that opens pro­gres­sively rather than turn­ing on and off, and Quick­sil­ver has de­vel­oped a sys­tem of ‘bal­ance’ pipes that are brought into play de­pend­ing on en­gine speed and throt­tle open­ing, cre­at­ing a smoother change in tone (DB11 sys­tem pic­tured, left). Mean­while, Akrapovic has put con­trol of valves witch­ing in the fin­ger­tips of the driver, with a wire­less push-but­ton.

Whereas stainless-steel sys­tems were once the pre­serve of the af­ter­mar­ket, they’re now far more com­mon­place as an OE fit­ment, so the af­ter­mar­ket has had to move on to new things. Stainless steel does still fea­ture in their brochures but is of higher-grade metal, while the tubes them­selves fea­ture thin­ner walls to re­duce weight. In re­cent years, though, ti­ta­nium has come to the fore for light­weight sys­tems, spear­headed by Akrapovic, which has an in-house ti­ta­nium foundry (and whose Ti hard­ware for the Fer­rari 488 GTB is pic­tured above).

Ti­ta­nium yields mas­sive weight sav­ings, par­tic­u­larly for si­lencers – a ti­ta­nium si­lencer for the Audi R8 can trim 30kg from a 45kg OE item.

The tech­nol­ogy and ex­pe­ri­ence avail­able to the ma­jor af­ter­mark etex­haust man­u­fac­tur­ers have now caught the eye of main­stream car mak­ers, some of which are call­ing in this out­side help. Porsche, for in­stance, had Akrapovic de­velop the OE sys­tem for the 997 GT3, and Volk­swa­gen re­cently an­nounced a col­lab­o­ra­tion with the com­pany for a ti­ta­nium sports ex­haust for the Golf R – it’s 7kg lighter than the stan­dard sys­tem. Akrapovic is also a mo­tor­sport part­ner to BMW and col­lab­o­rated with Audi on its World En­durance Cham­pi­onship cam­paign. Quick­sil­ver, Mill­tek and oth­ers also have man­u­fac­turer mo­tor­sport con­nec­tions.

So, the in­dus­try has turned full cir­cle, with the af­ter­mar­ket mak­ers now not merely be­ing tol­er­ated by car man­u­fac­tur­ers, but in some in­stances be­ing em­braced.

It’s as though the in­dus­try is ner­vous that any claimed power in­creases may not be re­peat­able

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