Barry

Volkswagen fart noise

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I’m sure everyone has heard it, when some VWs change gear, there is a fart noise from the exhaust, especially noticeable on Golfs and Sciroccos. 

Someone asked me to explain it today, this is the best I could come up with. 

These cars run a DSG gearbox. This means direct shift gearbox. It runs with 2 clutches but you drive it like an auto. It’s basically a semi auto gearbox with no clutch pedal. 

During gearchanges, the spark is temporarily retarded but fuel is unaltered. This results in some unburnt fuel getting dumped into the exhaust system where it is ignited by the heat of the exhaust system, causing the fart noise you hear. 

But isn’t that just a pointless exhaust noise in an attempt to sound cool and down with the kids? Next thing the car will be doing the floss dance from fortnite?

No.

The ECU is deliberately retarding the timing during gearchanges. Why? Because it cuts torque levels for a split second. This reduces stress levels on the gearbox and twin clutch system which increases reliability. We all know DSG gearboxes are unreliable (mainly due to the mechatronic system) so every little helps. If you have to endure a car with a case of flatulence, just remember it’s the manufacturer trying to save you a gearbox rebuild.

 

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You are right about the unreliability of these gearboxes- in fact, the one developed by Ford was such a pile of crap that they gave up on trying to work out the bugs. Instead, they just gave it up as a bad idea and abandoned their use altogether.  

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4 hours ago, desertdude said:

An answer to a question no one ever asked ! lol

Totally unwanted comment, even with lol

Thanks @Barry for sharing this info on DSG autobox, so that many won't fall for it per their marketing campaign as a twin clutch bla bla god-like tech.

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