Really n00b turbo / dump question...

[RedRummy]

Hi,

I\'ve been looking into buying a Skyline or an Rx7...

A question that\'s been bothering me recently, but I don\'t now much about turbo technicalities or dump valves etc...

Most Skyline (and other turbo\'ed cars) give off a loud hiss when you lift off - the dump valve \'dumping\' right?

But looking at the MRC London Tunnel run vids and other RX7 vids I\'ve seen, most RX7\'s seem to give off a kind of chirping sound, or purring sound, and not a hiss like other turbos..

what gives?

Is it just a special kind of dump valve, or what?

You can here the chrip i mean here: at about 07min35secs to 07min45secs
http://video.google.co.uk/videoplay?docid=-2049615832735105543&q=tunnel+run

[ScuttleRX]

Hi Red Rummy

The sound varies on what dump valve you use, my rx7 has the hiss sound your talking about (apexi), whereas my friend with a supra has the chirpy one (HKS  one I think he has).

[prince_of_tokyo]

the chirpy noise is the waste gate chatter let off by your wastegate actuator...get it on my fd3 with a blitz super sound...

[MillSpeed]

Sounds like compressor surge, anyone know who\'s RX7 that is and if it\'s a single?

[Frankie]

That\'s Laeeq\'s car with smallish single turbo.

[RedRummy]

ok, cheers guys

[ScuttleRX]

Sorry I replied to your post without listening to the sound clip, was talking about a totally different chirp

Some dump valves are more chirpy than other, my apexi was adjustable until the adjusting thingy broke, but like Prince says thats wastegate chatter

[MillSpeed]

There\'s no such thing as \'wastegate chatter\'. That chirrupy noise is in fact compressed air passing back through the compressor housing of the turbo due to the closed throttle plates. Found a pic of Laeeq\'s engine bay and there was no dump valve, which would explain the compressor surge.

[ScuttleRX]

Fair enough, that sounds always been described to me as wastegate chatter so thought thats what it was, definately not a dump valve which is what I basically meant.

Does an external wastegate make a similar noise as well then? phrase has gotta have come from somewhere

[MillSpeed]

Yeah, I\'ve seen the term used quite often (usually in reference to compressor surge), not sure where it\'s come from. Sometimes you\'ll get compressor surge even when there\'s a dump valve fitted, so perhaps that\'s why people blame the wastegate. Can\'t think of a reason why a wastegate would ever \'chatter\' on the overrun.

[Ricco_04]

You can still get the flutter from the surge with a DV if the spring in the DV is too tight (high boost applications)  Then when you boost small ammounts the DV cant open thus you get the flutter. :cool

[RedRummy]

ok, guys, thanks...

I like the chirpy noise and would much prefer it than the hissing of normal turbos....

Just wondered if it was a specific kind of turbo / dump valve... sounds like its more complicated that that tho  :rolleyes:


:3gears-lh

[Ricco_04]

How about the HKS SSQV - what do they sound / preform like on an FD?

[prince_of_tokyo]

but laeeqs car does have a blow-off valve...the chirp is the the wate gate opening allowing instant boost release leading to the chatter...

[prince_of_tokyo]

personally i h8 of the hks on a sequential set-up...