My supercharged MX5 makes a cool hissing noise when I...

[Howard-]

... Turn off the engine. For about 2 seconds after you turn the key off, it'll make a hissing noise that disappears over those 2-3 seconds. Is this normal? Something to do with vacuum around all the supercharger/inlet pipes/tracts?

I quite like it.. But only if it's normal


Would a vacuum leak be apparent when driving? The only noise like that I hear when giving it some welly is induction noise really. And it's not what I'd call down on power. And it's only there very quietly when you open the bonnet as the engine's idling.


Ta


I can get a video at some point if people are confused

[iguana]

Mines the same, so hope its normal

[MX-5 Lazza]

It is normal and it's not only with an SC. My old Mk1 with JR CAI also did it

[Howard-]

OK I hadn't heard it before the SC was fitted

What is it?

[snotrag]

Yup, mine (NA) does it with a big fat cone filter on. Its just the Vacuum causing it.

If you stand with the bonnet open and rev it from idle it makes an almighty induction noise. no wonder its so bloody noisy on the motorway. Tempted to try a standard airbox to be honest.

[Howard-]

Fair enough! Must be that the standard airbox hides the noise then! I like it

[b4bby]

Yep, its normal.

Ive one sc'd and a few (dont ask!) normally aspirated ones.

All have the same hissing noise when turning the car off.

[The Tea Boy]

mine makes a hissing noise if ive had the aircon turned on!