Diesel turbo noise with decat

corkgsxr

Iv had it myself where you remove the dpf and cat and there is a increase in turbo noise. But what do they do to make the really loud noise. Cant figure it.

Seems mostly passats

colm_mcm

The orgasmic pigeon sound?

The Dagda

Dump valve?

jimgoose

The Dagda wrote: »

Dump valve?

That's "Phsss". Here we have "Whooo", which is the wastegate. Diesels don't use dumpvalves.

corkgsxr

Ya the iv just kicked a owl noise every gear change.

Why is it so loud on some of them what have they done

Supergurrier

Flocks of pigeons trapped in the boot.

Someone call the ISPCA

Mycroft H

Take the cat out and shove a pigeon in there...

dgt

Straight pipe will give you one epic pigeon calling experience, esp on a modern vnt setup....

That noise is caused by the turbulence of the wastegate closing under lift off of the throttle, made worse sometimes by a butterfly valve on the intake. Either way no dump valve or what not causing the iconic coooooo. Silencers and cats are normally engineered to iron this sound out, hence remove one and it becomes more noticeable

Hence why my daily driver never went coooooo, I sealed the wastegate shut

Cee-Jay-Cee

Go into your local car accessory/tuning place and ask for a set of pigeon pipes...wink while your asking. They'll know what you mean, then just stand there looking intelligent.

Gazzmonkey

colm_mcm wrote: »

The orgasmic pigeon sound?

LMFAO

In Donegal we called it the pooing derv!

Chimaera

The loud cooing sound comes from the removal of the resonator and silencer. From what I've heard/seen it's mainly VNT turbos that do this as the vanes snap open on lift-off. Wastegates snap shut and send all the exhaust through the bypass which is quieter.

GTE

One positive about having a 90hp TDI is that going anywhere is generally using all the loud pedal. I don't know if the accelerator position as an influence on the turbo action rather than revs, but for whatever reason, my wastegate TDI makes a pretty daycent "tsss" sound when changing up the gears and in general is good and loud with the window down, sunny evening driving.

Life is all about the little pleasures, especially for a sound designer. :P

Bpmull

My golf does it a bit if you drive it on in 2nd or 3rd. They come like that but it only does it some of the time and not like the ones which are really loud every gear change. But they do do it a certain amount even from the factory. When I test drove the golf when buying it I thought it had a dump value but it didn't. Now in fairness it's slight enough compared to the modified ones which are very Loud and do it every gear change.