Turbo 'winding down noise'

[slowgsr]

My friend has a srt4 neon with a s256 and a few other upgrades. sometimes when he shuts the car off, the turbo makes like a 'winding down' noise, like you can hear it after the engine stops for maybe a second or so.

no oil getting past the seals, return/feed are good, and very minimal shaft play (almost the same as when it was new) there's a very SLIGHT amount, as there is on any turbo. Spools fine, etc.

Any idea's?

 

[HIGHPSI4]

My 35R 'spools' down for about 8 sec after the engine is shut down. Some turbos do that.

 

[slowgsr]

like you can hear it inside the car? Hm.. maybe its normal?

 

[kahl23]

It's par for the course with BB turbos, but the S256 isn't ball bearing. That being said, if it just sounds like the turbo is spooling down and there aren't any grinding/metal on metal noises being made, and there's only negligible shaft play I would say don't worry too much about it.

 

[mattdev]

Is it only when he powers down, or also when the turbo us "de-spooling"? I know an exhaust leak will cause it to sound like a turbo diesel truck when letting it spool down while driving... maybe you just cant hear that happening w/ the car running.

 

[Boosted98gsx]

My 35R 'spools' down for about 8 sec after the engine is shut down. Some turbos do that.

Just 8 secs? Mines audible for a good minute after I shut off my engine.

 

[97GSTAUTO]

Fuel pump.

 

[habitatguy187]

Open exhaust usually.

 

[turboglenn]

i've heard fans sound like this as well for a few seconds after shut down. almost sounds like the turbo is "spooling down" in stages though.

As long as shaft play is good (no in out...a little side to side) and the seals aren't leaking i wouldn't worry about it.

 

[JusMX141]

My buddy's Construction company used to have an older Powerstoke service truck. We'd beat the crap out of that thing and it's still on the road to this day with almost 300k on it. We used to pull the intake just to see how long it would take for the compressor wheel to completely stop turning after shutting the truck off from wide-open throttle....I know, the worst thing you can do, right? Keep in mind the truck still runs fine. The record for the stock Garrett journal-bearing turbo is 54 seconds.

All turbos are going to make some draw through the intake after the car is shut off....larger turbos have more rotating mass, and will spin longer after the engine is turned off. One reason the sound may be more pronounced on the SRT is because of the lack of a MAS, which would quiet the sound for most DSMer's.