A long chirp or whistle under boost

[dden4012]

If I lay into it in 3rd or 4th, along with the normal turbo sound, there is a noise that happens twice during the gear run. The sound is not high volume, has a soft start and end, and seem to happen after spool up and right before peak boost. Is this the waste-gate making the noise under certain conditions? A note that this doesn't really happen in ambient temps above 80* but can replicate in temps between 40* and 65*. Etune done 73* at sea level. This noise is recent though. Since 1-9-19.
This is a 2018 WRX with Cobb FF kit and etune. Everything else being stock. Under 17000 miles. Just changed the oil and no glitter. No CEL's or issues, just this new noise and concern. Anyone been down this road?

 

[Alin]

@dden4012

Alight, we need to clear up a few things first:

1) is your car properly warmed up (coolant and oil temps) BEFORE you go WOT in 3rd and 4th gears?
2) are you going WOT above 3,000 RPM?
3) is this the kit that you have? https://www.cobbtuning.com/products...stage-3-flex-fuel-power-package-sti-2015-2018
4) where is the noise coming from?

I was going to mention that an aftermarket BPV could cause a sound like that. (Happened to me in the past.) However, that kit doesn't mention a BPV, so I'm assuming yours is stock. I don't know if a turbo inlet could affect that, but I'm leaning more towards no. I just thought about question 4 just now. Does the sound come from the rear of the car or the front of the car? It could be be the fuel pump if from the rear. Based on your description, if the noise begins right after spool up and ends right before peak boost, any number of things could be the culprit. We need a bit more information. The kit doesn't mention an EBCS either, so I'm assuming that's stock as well.

Guys, do you have any ideas? Assuming stock BPV and stock EBCS, and with a bit more information from the OP, we should be able to determine what's making the sound!
@HolyCrapItsFast @Batmobile_Engage @Boogieman98 @Raven32 @Grinder34 @IGOTASTi @Doppelganger [MENTION=600]black bandit[/MENTION]

 

[dden4012]

Front driver side (j pipe side) best I can tell.
Yes @ running temps. Fully warmed up
The FF kit is just a sensor basically (WRX not STI).
https://www.cobbtuning.com/products/fuel-system/subaru-flex-fuel-ethanol-sensor-kit-wrx-2015-2019
Yes above 3k.

This is not the same car but the tone and type of sound is similar. Mine is not nearly as loud or persistent. Just couldnt find a better example.

 

[Alin]

Ah, alright. So, you have an FA20DIT then. I misread your original post. Well, I don't know shit about the new platform, but I do know the turbos are not from the IHI VF series. Well, your car does have 8 injectors and this does change parameters. So, now a few more questions...

1) did this noise occur before you installed the FF sensor kit?
2) what fuel are you currently running right now and how long have you been running it for?

I'd imagine [MENTION=9]HolyCrapItsFast[/MENTION] has the answer to this.

This has to do something with fueling then, right?

"COBB has performed internal testing in multiple geographic locations with different fuel sources in addition to compiling data from COBB retail shops, our Protuner network, and customers. Results varied significantly. Some users ran several tanks of E85 in a row without issue while some experienced serious loss of fuel pressure in as little as 1-2 tanks of fuel.We suggest monitoring fuel pressure for oscillations. After having fuel pressure issues, some users were able to flush the HPFP (high pressure fuel pump) out with low ethanol gasoline and get it to operate normally again, while others had to replace the whole pump assembly before they could safely drive the car again. After replacing the pump some users experienced repeat failures if they continued to run E85 fuel."

 

[Batmobile_Engage]

Front driver side (j pipe side) best I can tell.
Yes @ running temps. Fully warmed up
The FF kit is just a sensor basically (WRX not STI).
https://www.cobbtuning.com/products/fuel-system/subaru-flex-fuel-ethanol-sensor-kit-wrx-2015-2019
Yes above 3k.
https://youtu.be/zFHFcYpuPrk
This is not the same car but the tone and type of sound is similar. Mine is not nearly as loud or persistent. Just couldnt find a better example.

One thing you can try is this. At ~45 mph in 4th, put your foot down (but not quite WOT). Do you hear the noise?
Then, at ~75 mph in 4th, put your foot down (but not quite WOT). Do you hear the noise?

If YES and NO, then I would suspect compressor surge. In which case, nothing is likely to be wrong mechanically, but rather you are putting too much load on the engine for the rpm level.

One other thought is that it could be your intake. I kind of doubt this, but I used to be able to induce a whistle at the right throttle position in my NA Integra back in the day, due to my aftermarket SR Intake.

My expertise is with the GD chassis STi, so I need all the info on mods and such as possible, in order to come up with a better theory.

 

[dden4012]

One thing you can try is this. At ~45 mph in 4th, put your foot down (but not quite WOT). Do you hear the noise?
Then, at ~75 mph in 4th, put your foot down (but not quite WOT). Do you hear the noise?

If YES and NO, then I would suspect compressor surge. In which case, nothing is likely to be wrong mechanically, but rather you are putting too much load on the engine for the rpm level.

One other thought is that it could be your intake. I kind of doubt this, but I used to be able to induce a whistle at the right throttle position in my NA Integra back in the day, due to my aftermarket SR Intake.

My expertise is with the GD chassis STi, so I need all the info on mods and such as possible, in order to come up with a better theory.

Yes from a 45mph roll on in 4th gear but only one instance of the sound with a "not quite WOT" input, so there is a threshold that has to be reached to hear it twice.
Maybe from 75mph in 4th, but the onset of good boost is much faster, spending less time in the whistle zone conditions.

I would be suspecting a boost leak by the drivers side of the intercooler but I'm still hung up about the influence of cooler outside temperature. In 80* + temps i never heard this whistle noise. But i should double check this because I really don't want to have to talk the tuner into doing anything yet, he is suspecting a mechanical issue. I would much rather fix a minor boost leak. But the temperature is the only variable that has changed since the e tune.
Since it only happens when the outside temp drops, I think it has something to do with temp comps in the tune. Fuel pressure, LT and ST trims, look good, hits boost no problem. No obvious issues just this new temperature biased noise.

 

[Batmobile_Engage]

Do you have a Cobb AP or some other means of data logging? A boost leak could be noticeable in a log, as well as a handful of other potential issues. I still have a slight suspicion that you are hearing some compressor surge...nothing damaging per se, just something that is pretty common with the factory turbo due to it's small size. At heavy throttle input at lower rpms, the turbo is producing more flow than the engine can consume. So pressure waves are reflected back into the compressor which can cause that noise. Not saying I'm 100% sure that is the issue though...just a theory.

Do you have a boost gauge you can monitor?

 

[Batmobile_Engage]

Compressor Surge examples...

https://youtu.be/N7ok3AmTSyk

https://www.youtube.com/watch?v=pKddHah07yw

Sometimes the "sh-sh-sh-sh-sh" sound can take on more of a high-pitched tone due to other factors such as an aftermarket intake.

(I apologize if you are already aware of all this. I can never be sure what knowledge level we're all at, here on the forums.)

 

[dden4012]

This is my clip. Got three chirps now. Stock intake and filter.

 

[Batmobile_Engage]

From the video, the sound seems to be completely different than what I expected. Am I right in saying it sounds a little like blowing over the neck of a glass bottle? It almost sounds like a high-frequency, metal-on-metal vibration that is reverberating into the cabin. It reminds me a little bit of when I had a turbo go bad years ago. But it sounds even more like a slightly loose heat shield or like my aluminum skid plate, when my header used to vibrate against it at certain rpms/engine loads.

I'm very hesistant to suggest turbo bearing failure, car sounds are just so hard to diagnose on the internet.

Is this your first turbocharged car?

 

[dden4012]

From the video, the sound seems to be completely different than what I expected. Am I right in saying it sounds a little like blowing over the neck of a glass bottle? It almost sounds like a high-frequency, metal-on-metal vibration that is reverberating into the cabin. It reminds me a little bit of when I had a turbo go bad years ago. But it sounds even more like a slightly loose heat shield or like my aluminum skid plate, when my header used to vibrate against it at certain rpms/engine loads.

I'm very hesistant to suggest turbo bearing failure, car sounds are just so hard to diagnose on the internet.

Is this your first turbocharged car?

Yes first turbo charged car.
It is more like when your trying to whistle and it doesnt go right kinda.
I have breeze clamps fot the intake tract, I will be doing those this weekend. I should check for exhaust leaks while I'm under there.

 

[Batmobile_Engage]

Another thing to check... have someone rev the engine while you are looking around under the hood. If you don't notice the same noise in this case, then we at least know that there has to be a load on the engine for the sound to manifest. Which, while pretty basic, at least helps us understand the issue a bit more.

 

[dden4012]

Another thing to check... have someone rev the engine while you are looking around under the hood. If you don't notice the same noise in this case, then we at least know that there has to be a load on the engine for the sound to manifest. Which, while pretty basic, at least helps us understand the issue a bit more.

There has to be a load on the engine. The video is with the car running an E60 blend. I'm at an E17 blend now and it seems to have somewhat subsided or at least require more load to get the whistle. Not as loud either.

 

[Batmobile_Engage]

Good to know. Thanks :tup:

Man, this is a weird one. Do you have a stock or upgraded fuel pump?

 

[Batmobile_Engage]

Can you datalog fuel pressure for us?

This is straight from Cobb (in regards to the flex fuel kit):

Fuel System Considerations
As with other DIT platforms i.e. VW, BMW, Mazda, the fuel pumps in Subaru DIT vehicles are not designed for ethanol use beyond 10-15%. That said, ethanol levels between 15-30% are generally well tolerated. Those comfortable with mild risk can run ~E30 and enjoy improved knock resistance, charge air cooling, and a mild improvement in engine power potential. While you can't get E30 at the pump, pumping a combination of E0/E10 gas and E85 in an appropriate ratio will allow blending of a near E30 mixture in your tank.
On DIT platforms not set up for flex fuel from the factory, at greater than 30% concentration, ethanol has caused oscillating fuel pressure first, progressing to loss of fuel pressure, high pressure fuel pump damage, even making the vehicle inoperable in some cases. Sudden loss of fuel pressure can cause sudden loss of acceleration, stalling, which can reduce braking performance and steering control. Long story short, while the power potential is very attractive, use of high ethanol content fuel is at your own risk.

COBB has performed internal testing in multiple geographic locations with different fuel sources in addition to compiling data from COBB retail shops, our Protuner network, and customers. Results varied significantly. Some users ran several tanks of E85 in a row without issue while some experienced serious loss of fuel pressure in as little as 1-2 tanks of fuel.
We suggest monitoring fuel pressure for oscillations. After having fuel pressure issues, some users were able to flush the HPFP (high pressure fuel pump) out with low ethanol gasoline and get it to operate normally again, while others had to replace the whole pump assembly before they could safely drive the car again. After replacing the pump some users experienced repeat failures if they continued to run E85 fuel.

 

[dden4012]

Can you datalog fuel pressure for us?

This is straight from Cobb (in regards to the flex fuel kit):

Fuel System Considerations
As with other DIT platforms i.e. VW, BMW, Mazda, the fuel pumps in Subaru DIT vehicles are not designed for ethanol use beyond 10-15%. That said, ethanol levels between 15-30% are generally well tolerated. Those comfortable with mild risk can run ~E30 and enjoy improved knock resistance, charge air cooling, and a mild improvement in engine power potential. While you can't get E30 at the pump, pumping a combination of E0/E10 gas and E85 in an appropriate ratio will allow blending of a near E30 mixture in your tank.
On DIT platforms not set up for flex fuel from the factory, at greater than 30% concentration, ethanol has caused oscillating fuel pressure first, progressing to loss of fuel pressure, high pressure fuel pump damage, even making the vehicle inoperable in some cases. Sudden loss of fuel pressure can cause sudden loss of acceleration, stalling, which can reduce braking performance and steering control. Long story short, while the power potential is very attractive, use of high ethanol content fuel is at your own risk.

COBB has performed internal testing in multiple geographic locations with different fuel sources in addition to compiling data from COBB retail shops, our Protuner network, and customers. Results varied significantly. Some users ran several tanks of E85 in a row without issue while some experienced serious loss of fuel pressure in as little as 1-2 tanks of fuel.
We suggest monitoring fuel pressure for oscillations. After having fuel pressure issues, some users were able to flush the HPFP (high pressure fuel pump) out with low ethanol gasoline and get it to operate normally again, while others had to replace the whole pump assembly before they could safely drive the car again. After replacing the pump some users experienced repeat failures if they continued to run E85 fuel.

If your wondering if any part on the car is stock, yes. FF kit and AP are the only mods.
Fuel pressure is solid. I had a log from the video run but in my haste i forgot to select RPM...give me a list of what you would like to see in a data log and I will get one. This kinda sucks being my first turbocharged car, first season change with it (going from 100* down to 45*, first time running ethanol, first time tuning an ecu, and a weird noise that isn't a common tell. Well at least this experience will go on record for the next guy/gal.

Log: https://datazap.me/u/gantz/log-1547769765?log=0&data=3-14-22-23&zoom=5800-5895

 

[Batmobile_Engage]

^^^ [MENTION=9]HolyCrapItsFast[/MENTION]

 

[HolyCrapItsFast]

when it does this, does the power surge in response to the noise or is it consistent through out a run?

 

[dden4012]

I would say it runs consistently throughout the gear run. No sag or surge in power. Another odd thing is the RPM marks that the noise occurs during, the sweep through 4k and 5k RPM. This is a very consistent variable.

I changed the clamps to breeze clamps and snugged the turbo housing couple clamp gently. Went for a test drive and thought all was well, no more noise. After some moderate beatings, no noise, I decided to go add some ethanol. Ended up at E57. Got into some boost and sure enough, at the same rpm spots, a much fainter shorter noise of same tone. So i kinda fixed it lol.

 

[dden4012]

Could this be the hpfp whining about ethanol? I haven't read anything about a noise in relation to this cam driven pump. Its definitely coming from the front drivers side and quite possibly from up top. I'm sure the hoses are on correctly and tight with breeze clamps. TMIC wasnt cracked or coated in oil. None of the intake pieces had an oil residue. As far as the way it drives, its beast for stock trim. I know there is an ethanol approved HPFP for a pretty penny but I cannot for the life of me find it, it was a HPFP and DI injectors package.