I've got a 2020 Porsche 911, yeah I know it's not an Alfa. I've got one of them too! But why I'm posting here about it is that it makes this weird sound just above idle that sounds like crickets, not the 11-man version but the sort you find in the garden. I'll post a video below of it.
It seems that many but not all 911's of this model make this noise and the latest suggestion is that it's the high-pressure fuel pumps (there are 2 on the car). So then I thought, well Alfa JTS engines also have HP fuel systems so hence my question.
Here is the short video, you can hear it as I lift the revs off idle.
https://youtu.be/lSKX23yq-jU
Could it be that when you lift-off, the fuel is dramatically cut and essentially the engine is winding down on an extremely lean - almost pure air intake - such that it is almost what you get when a waste gate opens and dumps air into the exhaust manifold, with Turbo-ed petrol engines.
A video of a 3.2 JTS with C.B. cams on the Webb sounds very "hissy" on lift off. I can only think it is due to the dramatic change in the AFR as the ECU winds back the fuel in response to the driver lifting.
Quote from: Ascari32 on August 03, 2021, 05:45:41 AM
Could it be that when you lift-off, the fuel is dramatically cut and essentially the engine is winding down on an extremely lean - almost pure air intake - such that it is almost what you get when a waste gate opens and dumps air into the exhaust manifold, with Turbo-ed petrol engines.
A video of a 3.2 JTS with C.B. cams on the Webb sounds very "hissy" on lift off. I can only think it is due to the dramatic change in the AFR as the ECU winds back the fuel in response to the driver lifting.
Thanks, that's certainly worth looking into. It does sound like some sort of air leak or similar to me. I've bought a mechanics stethoscope, for some active investigation.