Member Since: 22 Oct 2008
Location: Here and there
Posts: 1645
Whoosh on deaccelerating
Hi all , anyone else getting this whooshing noise on deaccelerating ?
Mines a 55 reg but have driven newer ones and nothing heard. Dealer has looked at fault but cannot find where its from but say all others driven around the same age seem to do it but the newer ones dont.
Any ideas would be welcome.Thanks
27th Oct 2008 9:01 pm
Gareth Site Moderator
Member Since: 07 Dec 2004
Location: Bramhall
Posts: 26705
Mine does it, and always has. 112k miles now. I think its the egr valves opening as you release the throttle.
It cant be a turbo wastegate, as diesels dont have wastegates. Although I suppose it could be the variable vanes in the turbo moving. My money is on the egr's working.
28th Oct 2008 12:59 am
evo8
Member Since: 29 Jan 2008
Location: Zalesie
Posts: 289
Can it be the recirc valve (known also as blow-off valve)?2013 D4 TDV6 S; Baltic Blue; IID Tool BT
2007 D3 TDV6 SE, Auto; club Faultmate MSV2
29th Oct 2008 10:26 am
davesimmons
Member Since: 11 Feb 2006
Location: Alberta
Posts: 733
mine makes a noise when I throttle off at around 30-40 mph....... I think it has always done it, but now that the warranty is soon to run out I'm looking for some reasurance from the great masses Welcome to the Global Warming Corner.
29th Oct 2008 10:44 am
Ocsid
Member Since: 29 Nov 2005
Location: Hampshire
Posts: 255
Gareth wrote:
Mine does it, and always has. 112k miles now. I think its the egr valves opening as you release the throttle.
It cant be a turbo wastegate, as diesels dont have wastegates.
I don't know enough about our Disco3's turbo to comment on it , I do however know that wastegates most certainly feature on some automotive diesel engines.
29th Oct 2008 11:25 am
wiggs
Member Since: 03 Sep 2006
Location: Manchester
Posts: 14368
Yep here is a JCB diesel engine ..just been made and approved for fire pumps ..it has a wastegate on it
G4 Gone ...but not forgotten
29th Oct 2008 6:42 pm
Gareth Site Moderator
Member Since: 07 Dec 2004
Location: Bramhall
Posts: 26705
I stand corrected 8)
So, in my never ending quest for knowledge, what is the difference between a wastegate and a blow-off valve
Or maybe I'm confused, and diesels dont have blow offs ............. so to speak
29th Oct 2008 10:25 pm
Tawny Owl
Member Since: 22 Oct 2008
Location: Here and there
Posts: 1645
Thanks for the replys , had the egr valves changed under warranty but hope its not the turbo cus am i right in saying the turbo isnt covered under the extended warranty ?
29th Oct 2008 10:31 pm
Wex
Member Since: 16 Apr 2007
Location: Knackeragua
Posts: 5173
Educate me , is it the same as a dumpvalve ?
29th Oct 2008 11:06 pm
Gareth Site Moderator
Member Since: 07 Dec 2004
Location: Bramhall
Posts: 26705
I think there must be a subtle difference between a blow off, and a dump. I'm sorry, but I cant elaborate and follow through on this one
29th Oct 2008 11:16 pm
AndrewW
Member Since: 06 Aug 2007
Location: Saddleworth
Posts: 2302
Gareth wrote:
I think there must be a subtle difference between a blow off, and a dump.
Colour of your underwear, after? 2006 D3 finally swapped for a 2016 D4 Graphite in Graphite grey. No mods
29th Oct 2008 11:18 pm
stapldm
Member Since: 11 Sep 2006
Location: Swine Town
Posts: 2330
OK, going to share my ignorance here
As far as I remember (it's been a while since I researched) the terms are as follows:
Wastegate. A device that prevents a Turbo from producing over-pressure. The silver actuator on the right of Wiggs second picture (Wiggs, once again we are indebted to your amazing collection of useful pictures ) is driven from the inlet manifold via a silicone pipe. As pressure increases beyond the set limit, the actuator rod drives the valve in the exhaust side of the turbo. This moves an internal part of the turbo which means that the exhaust gas can flow direct to exhaust rather than driving the vanes of the turbo. Result is reduced input power to the turbo, hence reduction in pressure/flow on the intake side.
Blow off valve/Dump valve. I seem to recall these are pretty much the same thing. I don't understand their use in diesel engines, but in petrol engines they react to the pressure surge that occurs when running at boost then suddenly slamming the butterfly closed in the carb. The excess pressure is vented to the outside world, and on certain cars sounds great. What these are not good for are ECU driven engines - the air is lost AFTER it has been measured by the Mass air sensor (which is before the Turbo to stop it being cooked), and hence the engine tends to over fuel and smoke/misfire.
This is why most retrofitted dump valves are so crap an addition to a Clio.
Bypass (also Recirc) valve. My Volvo T5 had one of these, and it's the ECU friendly equivalent of the Dump Valve. It is like a wastegate, but is on the Inlet side of the turbo. When the pressure before the butterfly plate exceeds a limit, the actuator allows air to flow direct from the inlet to the outlet of the intake side of the Turbo. The net effect of this is that the efficiency of the pump effect is dramatically dropped, and this immediately allows the pressure to be dissipated backwards down the air supply pipes without detonating the intercooler or supply pipes. Its method of control means that all air remains inside the system, hence the mass air sensor reading remains accurate. It is almost silent in operation so is of no use whatever to Clio owners.
Now onto my real ignorance of Diesel engines. I've learnt from this site that a Diesel engine doesn't have a butterfly (we'll ignore the one for the EGR for this, I'm talking throttle). As such, I can't see what immediate effect (other than stopping the engine dead) would produce enough of a pressure surge to require a dump valve in the first place. Any clues anyone?Dr. Ian Malcolm:
"Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should."
Transgenic tomato anyone?
29th Oct 2008 11:45 pm
Gareth Site Moderator
Member Since: 07 Dec 2004
Location: Bramhall
Posts: 26705
I think that is a most excellent explanation and all sounds very plausible. Especially Clio drivers who needlesly blow off!
29th Oct 2008 11:55 pm
Wex
Member Since: 16 Apr 2007
Location: Knackeragua
Posts: 5173
Quote:
Blow off valve/Dump valve. I seem to recall these are pretty much the same thing. I don't understand their use in diesel engines, but in petrol engines they react to the pressure surge that occurs when running at boost then suddenly slamming the butterfly closed in the carb. The excess pressure is vented to the outside world, and on certain cars sounds great. What these are not good for are ECU driven engines - the air is lost AFTER it has been measured by the Mass air sensor (which is before the Turbo to stop it being cooked), and hence the engine tends to over fuel and smoke/misfire.
This is why most retrofitted dump valves are so crap an addition to a Clio.
thanks Andrew
29th Oct 2008 11:58 pm
Tawny Owl
Member Since: 22 Oct 2008
Location: Here and there
Posts: 1645
You cannot post new topics in this forum You cannot reply to topics in this forum You cannot edit your posts in this forum You cannot delete your posts in this forum You cannot vote in polls in this forum
I stand corrected 8)
