Strange RPM-dependent “grrr / rotating” noise (1,000–3,000 RPM) after hybrid turbo installation – Any ideas?
Hi everyone,
I’m from Japan, so I apologize if my English isn’t perfect.
I’m looking for advice about a strange noise on my 2019 Golf GTI MK7.5 DSG (EA888 Gen 3).
The car has:
Mamba hybrid turbo (IS20 compressor / IS38 turbine)
RacingLine intercooler
RacingLine catch can
Stage 2 ECU tune
Symptoms
A “grrr / rotating / fluttering” noise appears between 1,000 and 3,000 RPM.
The sound follows engine RPM exactly (gets faster as RPM increases and slower as RPM drops).
It is most noticeable when revving the engine in Park or Neutral.
In Drive with the brake applied, the noise is much less noticeable.
It is heard much more clearly inside the cabin, especially around the driver’s footwell/accelerator area.
I can also feel a slight vibration through the floor when the noise occurs.
What I’ve already checked
Removed the accessory belt → No change
Disconnected the Soundaktor → No change
Turbo actuator output test with VCDS → No abnormal noise
Wastegate adaptation completed successfully
Boost pressure is normal
No white smoke
Engine runs normally with full power
The noise started after the hybrid turbo installation. Since then, I’ve reinstalled and cleaned most of the turbo-related pipes myself because the original installation quality was poor.
At first I suspected the wastegate, but since the noise also occurs during free revving (with almost no boost), I’m no longer sure that’s the cause.
I’m wondering if it could be:
Turbo mounting bracket
Downpipe contact
Exhaust vibration
Fuel line resonance
Pipe or bracket touching the firewall
Something else related to the turbo installation
Has anyone experienced a similar RPM-dependent rotating/fluttering noise after installing a hybrid turbo or working around the turbo area?
I’ve attached a video. Please turn up the volume and listen around 1,000–3,000 RPM.
Any ideas would be greatly appreciated.
Thank you very much!