Multivan Turbo noise

[gregozedobe]

IIRC the turbo vanes change from "max possible boost" to "partial boost" at around 2,000rpm (to stop over-boosting and subsequent engine damage), so that might be the change in sound you are hearing. Can't say I've noticed anything like that on mine, but I do notice the 5cyl "warble" from the injectors under load at around the same engine speed.

[Silver Caravelle]

IIRC the turbo vanes change from "max possible boost" to "partial boost" at around 2,000rpm (to stop over-boosting and subsequent engine damage), so that might be the change in sound you are hearing. Can't say I've noticed anything like that on mine, but I do notice the 5cyl "warble" from the injectors under load at around the same engine speed.

Thanks for the feedback. Regards, Scott

[BobD]

I can't hear anything from my turbo still but mine is auto so I can't give it heaps at low revs. It will always change to a lower gear at 1500 revs or more depending on load. It will only stay below 2000 under very light throttle or on over run.

My main complaint after the T4 TDI is the fuel consumption. Wheras the manual T4 would get around 7.5l/100km in most conditions the T5 auto is getting around 10.5l/100km in the same day to day driving conditions. I especially miss having to fill up at 1000km instead 650km or so in the Multivan. I keep on nearly running out of juice as it goes to empty much quicker then the T4 when the fuel gauge is low. I have put in over 84l on several occasions at different garages and the tank only holds 80l. This is not the cause of the rough running though. The rough running happens when I have used about 70l and it ran fine on the times I let it get really low.

[Silver Caravelle]

Thanks Bob for the feedback. My auto Multivan has averaged 9.7L/100Km on the trip computer (no) 2 for it's 4000 km so far.

For specific trips, it tends to average about the same with a mix of city and highway driving. I have seen about 7.0l/100km at best and over 10l/100km in a head wind and city driving.

It can be up around the 35 to 40 l/ 100km until it warms up, then it settles down to the above averages.

Regards,

Scott

[BobD]

Mine says about the same on the trip computer. This is always optimistic and if you check the km vs litres you will not get such a good reading. I usally put in around 75l after about 650 to 700km and on the T4 I put in 65l for 900 plus km. Both cars also have optimistic speedos and are out by about 6kmh at 110kmh (116 on the speedo is 110 on the GPS). I'm not sure of the distance accuracy as I haven't got around to a serious check against a GPS.

The T4 had fantastic economy and made diesel a cheap way to go. The T5 makes the extra cost of diesel of marginal benefit at most. My T5 is up to 50,000km since July 2007.

[Ivo]

Finally heard my turbo spool up the other night. 6th gear at about 90km then squeeze on the accelerator and I could hear it wind up. It was fresh tarmac so no road noise.

Has anyone fitted a popoff valve like all the boy racers have on subarus etc. Not sure it would work on the bus though but would be good for a laugh!

[Silver Caravelle]

I am not sure a pop off valve works on one of these machines.

Incidentally after a good fang on Sunday, I got home only to notice the engine doing the same occasional rough running as I have mentioned before. It is only noticeable in neutral when revved at about 1500 to 2000 RPM, the turbo whooshing noise is apparent and the engine is fluttery.

I have been reading a fair bit about the EGR's and ACTIVE DPF regeneration. I have put it down to the computer kicking in the turbo to force some exhaust gas through the intake for ERG at a certain exhaust gas temperature to assist and DPF active regeneration functions. I suspect after a highway run and crawling back into the city and pulling up in the driveway, that the above was occurring to complete the DPF regeneration. After a little while, it is all back to normal again.

Apparently DPF regeneration be it active (low or no load conditions - activated by the engine computer) or passive (high load highway conditions - activated by exhaust temperature) occurs quite often.

As mentioned no fault codes were previously found by the dealer.

Does this makes sense?

Regards,

Scott

[Silver Caravelle]

This is not a bad thread on this forum regarding Active DPF regeneration and sort of explains what I have experienced, including the 'cold' regeneration cycle. I also believe a constant turbo boost pressure controlled by the ECM also plays a part in the active DPF regeneration process, hence the additional turbo noise experienced when stationary in neutral during this process.

Regards,

Scott

http://www.vwwatercooled.org.au/newf...f+regeneration

[thevwbug]

Hello Guys My Multivan 2,000 KM was suffering the same noise turbo noisey when you back off. As suggested it sounds like blow off or bearings. Picked up local VW Mechanic to go for a spin. It was in the next day apparently a leaking delaminated hose.
Going well now.

[Silver Caravelle]

Hello Guys My Multivan 2,000 KM was suffering the same noise turbo noisey when you back off. As suggested it sounds like blow off or bearings. Picked up local VW Mechanic to go for a spin. It was in the next day apparently a leaking delaminated hose.
Going well now.

Hi there,

Apparently the 'blow off' noise is normal, not withstanding any turbo hose leaks; which mine does not have.

The periodic turbo noise heard in neutral, I have concluded as part of the DPF active regeneration process, which is triggered by time and distance and driving conditions. It stops after about 15 to 20 mins of driving and will likely reoccur again in a couple of weeks.

Regards,

Scott