Turbo flutter

bax

Torque Junkie
Points
157
Location
Mars
Car
Rexton 270xdi 2005
So i recently shared a video of my Car while offroading and people pointed out that my Turbo was making that flutter noise we all love and said that was bad for the turbo and will end its life alot sooner than it should ,they recommended installing a dump valve to solve that issue ..

What are your thoughts on the matter ? i love that Turbo flutter but if its really killing my Turbo then i guess ill have no choice ... The turbo is a Garret GT2056 with a internal Wastegate on a Diesel engine dunno if that changes anything
 
Personally, I wouldn't have thought it would do any harm on such a small turbo, I've been running my 18T for a couple of years with no recirc valve.
 
I noticed that theres no dump valve at all on my car .. while there is one for the newer model of my car (same engine) .. im guessing theres also no throttle body in my car ... ive read a little and some are saying that its pointless on a Diesel , now im confused
 
im quite lost right now , bare with me i woud like to understand .. so theres no need for a dumb valve on my Rexton yet my Turbo flutters due to high boost from the Remap which is unhealthy (according to some) for the turbo and the way to get over that is with a Dump valve which isnt present on my car ..
that alone is quite confusing but then theres another matter , the newer model of my car (Same engine , same Tranny , same turbo but with a different housing and different EGR system) comes with a Throttle body and a Dump valve ... so looking back at the statement that Diesels dont need dump valves it all becomes a mess now ...
can you help me understand just whats going on ?
 
I think what you're experiencing with your car is wastegate flutter. This occurs when using full torque and power (pedal right down).

I used to get this with my Peugeot 406 (2.2 HDi) which used a Garrett T3 fixed geometry turbocharger. All fixed geometry turbochargers have wastegates. VGTs often are without wastegates.

The remap certainly made the wastegate flutter more apparent but I am led to believe that this is harmless.

Turbo flutter is when a throttle plate is closed and the excess boost vents back through the turbo compressor. So the flutter would be heard when lifting off the accelerator pedal suddenly, rather than when accelerating. Turbo flutter is not a good thing.

Onto throttles - yes, there are diesel engines now which utilise ECU controlled throttle plates as part of the emissions management. I am not sure what the advantages are, but I would guess it's something to do with restricting airflow under low load or idle conditions in order to regulate NOx emissions. At idle a diesel engine can breathe up to 600x the amount of air needed to fully combust the fuel. So the air is throttled so that only enough goes through to fully burn the metered fuel. Less air of course means less N and O2 therefore less oxides of nitrogen emitted. Of course, the turbo is not spinning at all under idle conditions, so a DV would have no purpose here other than to quench boost if the ECU closes the throttle plate quickly during normal operation.

Some people do fit them simply for aural effect but this is artificial with a diesel engine as there can never be such a thing as excess boost.

The other reason for a throttle plate is possibly to do with engine switch off, basically starving the engine of air when you pull the key. This serves no purpose other than to subdue the propensity to run on and make 'dieselly' like sounds.

There's probably still more to this, but this is the limit of my understanding thus far.
 
Hmmm what i have is this , get the Rpm somewhere between 2.3-3 Rpm quickly then take your foot off completely , thats what when i get the flutter sound , cant hear it any other way (my car is an automatic one so theres no flutter when shifting like in a petrol car

Heres a clip that has the Flutter in it , you can hear it clearly at around 3:11-3:21 or at 4:02
 
would a picture of the turbo or the engine bay or some a vid of the acceleration and the flutter help with something ? i mean how can i help i giving you the info you need ?
 
You could try, I'm no expert with hands on stuff but let's have a look and see if we can guess what's going on. Is it a new symptom? What you're video shows does indeed sound like turbo flutter. Do you know if the turbo is a VGT type? Possibly the vanes are sticking??
 
its not a VGT , and its not exactly new ive had the flutter ever since the first Remap which was maybe 4 years ago , its alot louder and easier to trigger now that i have the Open pod instead of the simple drop in k&n filter , i cant trigger the flutter when the car is in neutral the more the stress on the wheels the easier it is to trigger the flutter (uphill , sand , towing etc ) . ... now sure if this has anything to do with the matter but the turbo currently runs 1.74 Bars of boost or so says the guy that remapped my car
 
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okay so heres a vid of the Flutter and how i can do it

and here are some pictures of the turbo and the engine




 
It's certainly a strange problem. I will have a serious think about it. I can't see how a diesel engine (which has no throttle) can force air back through the compressor. Presumably EGR etc is all working correctly?
 
The Egr is Deleted both through the ECU and physically blocked from the EGR valve side and the Exhaust manifold side ..
the Mods on the car are mainly a slightly bigger Intercooler made entirely of aluminum , bigger aluminum intercooler pipes , Bigger downpipe , Open pod filter and an aluminum pipe connecting the Open pod to the turbo and a Thinner silicon Vacuum hose for the Vacuum modulators and the Turbo actuator
 
I think your just hearing the normal turbo operation, it's just amplified because of the intake pipe and cone filter.
 
I think your just hearing the normal turbo operation, it's just amplified because of the intake pipe and cone filter.

I am thinking the same thing. I always now when my cone filter needs to come off and given a clean as my flutter noise all but disappears, but after a generous cleaning and then a thorough drying out, the turbo starts chirping away again quite loudly.
 
Well as far as MapTun is concerned yes it does Paul. They will comfortably remap Saab cars with the manufacturers own air intake setup, but for particularly high powered versions produced they prefer to use a particular K&N twin cone filter. Yes it is ruddy expensive as filters go mine is about £130, but I would much rather pay the extra for a setup that has no restrictions to the tuning criteria than to hold the thing back which sort of defeats the object of having a high power producing engine.
 
Regarding the cone filter , there really was no change on the performance for my car , But i should mention that it has no heat shield and sucks hot air from the engine bay , however an issue i had with both stock filter and K&N drop in filter is that once you really stress the engine you can hear some loud noise as if the airfilter box starts rattling but i was told thats not the filter box but some component in the engine that does that due to air restriction ... so my diesel needed more airflow which is why im using the cone filter ... its temporary for now , im wating for a cold air intake i ordered on Ebay , not sure how it will go but im hoping it would be better considering that it only costs 100$ compared to some of the serious cold air intake systems out there ..

someone i know with the same car as mine and almost the same mods said that on the dyno the cone filter granted him 15Hp .. i really didnt feel any gain on mine , but perhaps 15hp shouldnt make that much of a difference to begin with on a Diesel ? (165hp stock ,~220hp remapped)
 
^^ Understood about the cone filter, BUT, if you don't get the ECU remapped to allow for the twin cone filter which is what I did not do when I was green and new to all this, then the damn thing actually brought up an engine check light in my car. Once it was remapped and thus taking into account the volume of air that the ECU can now recognise from the TCF instead of seeing it as fault (A Saab thing maybe) the car flew after this and no more ECL.
 
yes without the remap not only will there be a drop in performance but it can also trigger a check engine light and cause the car to go limp
 
Good point , sadly i wont know until i get the part , theres no doubt that it will be getting less air that the Cone can , but the cone has no limits until you put a heatshield on it , the cold air intake is pretty much a cone filter inside a carbon housing with a 3inch pipe that connects it to somewhere near the grill of the car , giving it access to cold air , i tried to get the biggest housing i can fit there to make sure the filter is getting as much air as possible .. the reason im not too concerned is because the engine is just a 2.7 liter one so its not a massive engine like the ones ull find on the Ram/Silverado/F350 , its almost as big as the stock filter housing (which also had a small pipe that connected it to the grill of the car for cold air ) , so compared to the stock filter this cold air intake should provide colder air due to it being from carbon (not that the original plastic one was getting that hot ) and should allow better air flow at possibly higher volumes ... if the stock filter was equal to the Cone then this cold air intake (in theory) should be superior to both
 

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