What is this sound? Loss of acceleration power

[cornflakes2]

It's been an issue for a long time but the past week it's gotten much worse.
I have very low power acceleration from standstill like at a redlight. When I step on
the gas the car doesn't accelerate smoothly or as much as I'd expect and I can hear
this loud whoosing sound when I roll down the windows. Please take a listen here:

https://youtu.be/qWvDtsycFIE


I have a long history of issues with this car that still hasn't been resolved.
I've taken it to 3 diff. mechanics and each of them say no vacuum or air leak
even though I swear it sounds and feels like a leak somewhere.

I hope the sound in the video helps. It's getting dangerously close to not being
safe to drive now because I have no acceleration power. I can get up to speed
if I drive slowly and build my speed up eventually but instant power isn't there anymore.

[The Wookie]

Could be a boost hose collapsing under vacuum maybe?

[cornflakes2]

The Wookie said:

Could be a boost hose collapsing under vacuum maybe?

Thanks for the reply but I don't understand what that means. Can you elaborate what this means?
Vacuum is when I let off the accelerator correct? My issue is when I am stepping on the accelerator and I hear
this rush of air or whoosh sound at the same time, while my turbo gauge reads about 0.5 bar (very high for such low
speed acceleration only pushing 2000 rpm and driving 60 km/h).

I did fail my emissions test so do you think this issue has to do with a clogged catalytic converter?

[Pastie Bloater]

cornflakes2 said:

Thanks for the reply but I don't understand what that means. Can you elaborate what this means?
Vacuum is when I let off the accelerator correct? My issue is when I am stepping on the accelerator and I hear
this rush of air or whoosh sound at the same time, while my turbo gauge reads about 0.5 bar (very high for such low
speed acceleration only pushing 2000 rpm and driving 60 km/h).

I did fail my emissions test so do you think this issue has to do with a clogged catalytic converter?

It won't be 'clogged' as such (clogged with what?) but it could have broken up inside and essentially blocked the exhaust.
That would kill your power stone dead.
There could also be another exhaust blockage say you hit a speed bump and flattened the exhaust (just for example).

[The Wookie]

cornflakes2 said:

Thanks for the reply but I don't understand what that means. Can you elaborate what this means?
Vacuum is when I let off the accelerator correct? My issue is when I am stepping on the accelerator and I hear
this rush of air or whoosh sound at the same time, while my turbo gauge reads about 0.5 bar (very high for such low
speed acceleration only pushing 2000 rpm and driving 60 km/h).

I did fail my emissions test so do you think this issue has to do with a clogged catalytic converter?

No what I’ve experienced before is a boost hose which folds in on itself when you lift off the throttle (and there’s a brief vacuum in the inlet system), then stays collapsed until the engine is turned off and it relaxes again giving the impression nothing is wrong

In the case of that car it produced a whooshing sound and a lack of power, although after several miles it did eventually it did also throw an engine management light .

Could be a clogged cat or exhaust somewhere also, but it would have to be epically clogged to really slow the car down that much

[cornflakes2]

The Wookie said:

No what I’ve experienced before is a boost hose which folds in on itself when you lift off the throttle (and there’s a brief vacuum in the inlet system), then stays collapsed until the engine is turned off and it relaxes again giving the impression nothing is wrong

In the case of that car it produced a whooshing sound and a lack of power, although after several miles it did eventually it did also throw an engine management light .

Could be a clogged cat or exhaust somewhere also, but it would have to be epically clogged to really slow the car down that much

Thanks for explaining. Unfortunately, mine never throws an engine light. Hmm, I have gone over quite a lot of speed bumps and my car is lowered but visual inspection I don't see any flattened parts of the exhaust.

The thing is, it's not so bad when up to speed. It's mainly an issue only from 0-60 km/h driving light acceleration of 2000 rpms no higher. The boost goes all the way up to 0.5 bar and the car doesn't get up to 60 km/h like it should. It just sort of climbs very slowly to 60 even though my throttle is opened to about 80-99 from the idle reading of 13-16....meaning, throttle is opened quite a bit but car isn't accelerating faster. It's just driving slowly picking up speed until I get to about 80+ I can drive no problem up to 160 km/h or faster if I wanted but mostly acceleration power is lost at low speeds.

[cornflakes2]

Pastie Bloater said:

It won't be 'clogged' as such (clogged with what?) but it could have broken up inside and essentially blocked the exhaust.
That would kill your power stone dead.
There could also be another exhaust blockage say you hit a speed bump and flattened the exhaust (just for example).

Yes, I am not sure what it be clogged with but since I can smell fuel burning from my exhaust when standing at the back, it indicates that there's burnt/unburnt fuel getting to the exhaust system and it's burning up inside there which is why you get the gasoline smell from the exhaust. All that burnt fuel in the exhaust system probably gets caught in the cat or maybe even mufflers which is causing this build up of restriction over the past 3 years? It's progressively getting worse (the acceleration and engine start up in cold weather where it dies unless I give it lots of gas for 1 minute and keep it alive to warm up enough before I drive).

[E-bmw]

It won't be clogged/blocked etc unless you have MAJOR combustion issues, it just isn't possible.

You need to get it somewhere competent to get checked over by someone who knows what they are doing.

Where are you? I would imagine there would be someone that someone on here knows is up to the task.

[cornflakes2]

E-bmw said:

It won't be clogged/blocked etc unless you have MAJOR combustion issues, it just isn't possible.

You need to get it somewhere competent to get checked over by someone who knows what they are doing.

Where are you? I would imagine there would be someone that someone on here knows is up to the task.

Thanks for the reply. It seems like there's always been some unburnt (or burnt?) fuel in the exhaust system. Could that be what clogs up a cat very quickly if fuel is burning up in the exhaust/cat?

Unfortunately I am an english speaking worker in Korea and I don't speak the language fluently. There are a few mechanics I've talked to who tried to help me out but in the end after 3.5 years nobody has really been able to solve my issue. They just don't seem to know or have the tools to run basics tests. It's so weird. I don't get it. It might be because it's a tuned car so they don't want to touch it. The only place I can take it to is the original tuning shop that did this car in 2015 under the previous owner. The problem is none of them speak english and I'd basically be handing my car over to them leaving it there for 3-4 days and they can't communicate anything to me well except tell me the bad news after it's done and I'd have no choice but to just believe them. I wanted to try and prepare myself to get familiarized with what could be the most likely issues causing this but it looks like I'm running of options. I've been asking for years on tons of forums and appreciate the tips but the advice is all over the place and basically just says to me it could be "ANYTHING" lol.

I was hoping that video clip with the sound would really help someone to recognize what that airy whooshing noise is and where it's coming from. It's really clear in the video. I think I need to just increase the volume again and point out when I am accelerating and when I am off the pedal so that the viewer can be prepared to hear the difference and ignore the rumbling sound of my APR downpipe exhaust system which seems to throw people off as all they hear. They have to block that part out and just listen for the WIND/AIR noise that comes ONLY when I depress the accelerator and disappears when I let off the accelarator.

[csd19]

Boost leak somewhere possibly? How about your diverter valve, has this been changed to an aftermarket one or is it still stock, this may have split the diaphragm and is leaking boost.

Is there a chance the previous tuner has VCDS and is able to log requested boost vs actual boost during a road test?

[cornflakes2]

csd19 said:

Boost leak somewhere possibly? How about your diverter valve, has this been changed to an aftermarket one or is it still stock, this may have split the diaphragm and is leaking boost.

Is there a chance the previous tuner has VCDS and is able to log requested boost vs actual boost during a road test?

The DV was an aftermarket one made by Forge. We replaced that one last year to a brand new stock DV. It didn't really make any difference.
I kept telling diff. mechanics that I think there is a leak somewhere but every single one said there is no leak. I don't get it. I've never seen anyone do any testing on it other than one place that was spraying the joints/hoses in the engine bay to see if idling stumbles and he didn't find anything.

I'm confused about leaking boost. If it was a leaking boost, wouldn't my boost gauge needle show low boost or none at all? The problem I have is the opposite. I have too much boost showing up on my gauge but no actual power in the car...it just stumbles and hesitates to pick up any acceleration speed to 60 km/h but the boost is at 0.5 bar (7-8 psi). It's really become almost undriveable now because it's dangerous not to have acceleration power when I have tons of cars behind me waiting for me to go.