Accelerator sound

[Gatrhyde]

2023 Bronco Sport Outer Banks with 10K miles makes a strange medium-high pitched blowing/whirring like sound when I let off the the accelerator. It’s especially bad when going up an incline. Happens in all GOAT modes. No check engine lights.
Anyone else have this happen? I do t want to waste an entire day at the dealership if it’s “just what that engine does”. Ya know?

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[Nam3]

It's your turbo!

 

[Gatrhyde]

Is it normal? It’s annoying, lol

 

[Mark S.]

2023 Bronco Sport Outer Banks with 10K miles makes a strange medium-high pitched blowing/whirring like sound when I let off the the accelerator. It’s especially bad when going up an incline. Happens in all GOAT modes. No check engine lights.
Anyone else have this happen? I do t want to waste an entire day at the dealership if it’s “just what that engine does”. Ya know?

There is a device installed on the engine called a recirculation valve. It opens when the throttle plate closes to route air that's been pressurized by the turbo back into the intake tract ahead of the turbocharger. It's meant to prevent pressurized air trapped between the closing throttle plate and the compressor from pushing back on the compressor blades and slowing spinning turbocharger. Normally you don't hear anything when that valve opens. It may be that the duct that transfers pressurized air back to the intake has developed a leak, allowing that pressurized air to vent to the atmosphere. Some people install "blow-off valves" on their cars to replace the recirc valve, because they like the sound it makes. Search for "blow off valve sound" on YouTube to hear what it sounds like.

 

[Gatrhyde]

Thank you!

 

[Gatrhyde]

I watched the videos, it sounds just like that. Do you think I should take it to the dealership?

 

[jkeaton]

No. It’s fine.

 

[Mark S.]

I watched the videos, it sounds just like that. Do you think I should take it to the dealership?

Generally speaking, the sound should not be as loud as compared with a blow-off valve, where the pressurized air is vented to atmosphere. One of the primary reasons for using a recirc valve instead of a blow-off valve is to limit the sound heard in the cabin. That's not to say the sound is completely inaudible. Some people have more sensitive hearing than others, especially at certain frequencies. If what you're hearing is relatively quiet compared to the videos it may be that you have really good ears!

As to whether you take to the dealer or not, that's your call. If you're not experiencing any driveability issues--lack of acceleration, hesitation, etc.--then I don't believe you risk any engine damage driving it the way it is. Even if there is a leak in the conduit between the recirc valve and the intake tract it won't hurt anything--the pressurized air is simply going to atmosphere instead of back into the intake. But if you want to make sure everything is working as designed, the only way is to take it to your dealership and have it inspected.

One thing you might try: Go test drive another Bronco Sport like yours. Make sure it has the same engine. If it makes the same noises then you just have sensitive hearing!

EDIT: It IS possible that the valve is malfunctioning in a way that doesn't permit the pressurized air to escape. If that's the case then you might hear a sort of "chuffing" noise--this is called turbo flutter. It results from the pressurized air pushing back on the compressor blades. The chuffing is the compressor blades "chopping" through the pressurized air pushing against them. This is abnormal; you shouldn't hear a noise like that. If that's what you're hearing then you should take the car back to the dealership sooner rather than later. I don't believe it will damage anything in the short term, but you are placing greater stress on the turbocharger which will result in increased wear.

 

[Gatrhyde]

You have been very helpful, thank you

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