Why does the Volkswagen Golf GTI ‘burb?
All petrolheads know the distinctive sound of a VW Golf GTI DSG shifting at speed. In fact, here in SA the engine note made when that DSG box swap cox at lightning speed is known as ‘burpa’, and has become somewhat of a motoring culture phenomenon.
But does a DSG transmission work and why does the GTI’s engine ‘burp’?
Best of both worlds
A Direct-Shift Gearbox (DSG) is a newer type of automatic transmission that was first seen in racing cars manufactured by Porsche, but it was VW that made DSG a household name.
Like a conventional automatic transmission, a DSG uses fixed gear ratios to ensure an engine is running at its most efficient r/min depending on the speed.
But unlike these ‘normal’ automatic gearboxes, a DSG effectively mates two gear sets (one with odd gears 1-3-5 and the other with even gears 2-4-6) and two clutches to allow for pre-selection of gears and a seamless swap between them.
It offers a best-of-both-worlds scenario, giving you the ease of driving you get from a normal automatic gearbox with only a brake and accelerator pedal, along with the control of a manual gearbox without the need of having to use a clutch pedal.
Furthermore, because of how a DSG works, there’s no loss of power during up shifts thanks to the preselection of the next gear or other gear set, and shifts are much faster than the normal sort of selection in a manual gearbox.
DSGs allow for both manual and automatic modes, with gear selection happening in around eight milliseconds with most drivers almost unaware of the gears even changing.
Science behind the noise
In a traditional manual transmission, when you shift gears, you lift off the throttle slightly to allow the revs to stabilise and drop slightly while engaging the next gear.
For the DSG, VW came up with the concept of retarding ignition timing at the crucial moment of the gear change, effectively mimicking the act of lifting off the throttle. However, fueling and valve timing remain unaffected under this programming set-up.
This results in excess fuel being deposited into the combustion chamber, remaining unignited. When the next gear is engaged, ignition of the fuel is resumed via the spark plugs, and the excess fuel in the combustion chamber and exhaust manifold ignites creating that lovely ‘burpha’ sound.
VW were the original pioneers of this set-up, but since then it has caught on and gained massive popularity for the aural theatre it provides. Manufacturers now rig their dual clutch set-ups for prolonged ignition retardation to create all sorts of false bangs and pops on up shifts – case in point Mercedes-Benz and the A45 AMG.
