Quick question regarding turbo dump noise

This question will probably make me look silly, and given it's my first post... However I am looking to buy a Supra and I drove one recently and noticed this characteristic about it; and wanted to ask on here. I've searched a little and found some worrying info and not so worrying info which has ultimately confused me.

When I drove this Supra it made nice boost and you could feel the toque. When I let off the throttle under boost, or changed gear instead of hearing a tishhhhh sound I heard a sound which I can only describe as SHOOO SHOoo shoo shoo. (say that fast and breath out quickly and you can get the idea )

My question is, is this "compressor surge" or "wastegate chatter" ? I've heard this on other vehicles to, usually non standard ones, from memory.

Also, I assume someone has played around with it to do this.. the Toyota standard one is recirculating, correct? How should this sound, is there even an audiable noise? It looked as though the standard airbox had been removed and a K&N cone filter fitted instead.

Welcome

More than likely just wastegate chatter.

not comperssor surge but compressor stall , you maybe right and someone has removed the stock bov and blanked the fitting, so now the compressed air has to go back through the turbo as it is no longer being suck in the engine and there is little resistance on the turbine side of the turbo, so then the compressor stalls (stops) to let the air passed making the shooo noise

Thanks Mellonman, this doesn't sound good to me! Using your info I'll take a look to see whats been done. I keep getting confused / mixed up regarding wastegate use and dumping the turbo pressure on the inlet side.

So what is likely happening is the pressurised air cannot enter the engine when the throttle is lifted / butterfly closed. The turbo keeps producing boost, which then this air tries to leave back through the turbo the wrong way?

yep thats pritty much it, there are lots of talk about this! some like it some hate it some say it causes damage some say bov are just fitted to stop the noise by the manufacturer,

when dbb single turbo apliction is involved you get this more as the bov can not react quick enough to release the preasure of the free spinning turbo

Hmm..

What's dbb? (sorry, I'm a noob)

dual ball bearing, this is a turbo that spins for about 30 seconds after the engine has been shut off , meaning fast spooling due to its ease of movement from the exhaust gas

stock if i remember correctly are thrust bearings and well dont spin that freely really

turbos have come a long way,

do you know if the supra you drove was stock? being twin turbo?

have a look at this vid is that the noise?

http://www.youtube.com/watch?v=rMOhqa_vmBQ

or was it something like that? higher pitched

I get some BOV noise on my TT BPU. Its stock but with a cone K&N air filter.

'Wastegate chatter' doesn't exist. It's compressor stall as mentioned above.

I have run my 700 bhp Supra with no bov for the last 5 years... And my turbo is still there. I think its a nicer sound than a bov anyway, sounds meaner. Dont worry about it...

I have run my 700 bhp Supra with no bov for the last 5 years... And my turbo is still there. I think its a nicer sound than a bov anyway, sounds meaner. Dont worry about it...

Tbh, depending on inlet post turbo piping size/volume, having a dump valve blow all the pressure completely between gear changes in an effort to preserve turbo speed isn't ideal, given the volume of air needed to be compressed in a large inter cooler/pipe work to bring back boost pressure it's more beneficial to set the bov lower or not at all so the residual boost is retained (to some extent) at the cost of a little compressor stalling,slowing

You can tune the bov position and spring pressure to either amplify the pressure bounce dump wave, or tune it out completely

My system with a forge bov, 3" ic and piping, t67 turbo with the bov set fairly soft and near the turbo outlet, I get a pronounced "pshh sho sho sho sho" noise, just dumps a little but not completely , if I set it to completely dump, I get a big "pshhhhhhhh" and a slight increase in boost build up time

Every systems acoustic length and flow differs, position and size of bov have a huge effect also

personally my decision to run a bov or not depends on the volume between turbo and butterfly

If its a huge volume then no

If its a smaller more normal volume then yes

The debait begings

Meanwhile, I love the attempts at phonetically describing various dump valve noises!

Also:

'Wastegate chatter' doesn't exist. It's compressor stall as mentioned above.

Well said.

Pshhhhhh

Cho chooo choooo

Shoooo shoo shooooo

All of these are good

Grrrrrrrrr

Meaw

Squeak squeak

Mooo

Is bad and means you've selected "animal sounds" on your bov

I should have known I'd get wronged for putting "Wastegate Chatter". You are correct, it is Compressor Stall, but sometimes its just easier to call it what moast do, to avoid the elongated explanations

'Wastegate chatter' doesn't exist. It's compressor stall as mentioned above.

Im glad someone said it.

My single makes this exact noise with my BOV shut off which caused quite a debate with someone I knew, he thought my wastegates were s*** and said it was down to the rubber diaphram in the wastegate being too flimsy which vibrates open and shut when you let off causing an irregular boost pattern

Im glad someone said it.

 

My single makes this exact noise with my BOV shut off which caused quite a debate with someone I knew, he thought my wastegates were s*** and said it was down to the rubber diaphram in the wastegate being too flimsy which vibrates open and shut when you let off causing an irregular boost pattern

Iiiiiiiiiiinteresting...