Author Topic: Does your JTS engine make this 'cricket' sound?  (Read 941 times)

0 Members and 1 Guest are viewing this topic.

aggie57

  • Hero Member
  • *****
  • Posts: 1529
  • AROCA Member #: 750
Does your JTS engine make this 'cricket' sound?
« on: July 31, 2021, 01:54:02 AM »
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
Alister
14 Alfa's since 1977. 
Currently 1973 GTV 2000, a couple of Mercs,  a '14 Beetle (yes, seriously......), 2020 911 C2S (manual!)
Gone......far to many to list

Ascari32

  • Full Member
  • ***
  • Posts: 176
Re: Does your JTS engine make this 'cricket' sound?
« Reply #1 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.

aggie57

  • Hero Member
  • *****
  • Posts: 1529
  • AROCA Member #: 750
Re: Does your JTS engine make this 'cricket' sound?
« Reply #2 on: August 03, 2021, 12:15:28 PM »
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.
Alister
14 Alfa's since 1977. 
Currently 1973 GTV 2000, a couple of Mercs,  a '14 Beetle (yes, seriously......), 2020 911 C2S (manual!)
Gone......far to many to list