This is something that I've been wondering about for a while, but never really got a good explanation anywhere else...

Why is it that some turbo's are louder than others?

Is it simply the size? The bigger it is, the louder it is?

I've heard it has something to do with the style of the wastegate...
Any truth behind this?

I want to make it a point to mention that I am NOT talking about the BOV.
I know most people always want to know how to make thier BOV sound louder, but this isn't what I'm talking about at all.

Here is a video clip of a single turbo Supra which has one of the nicest sounding turbo's I've ever heard.
What would make the spool so loud like that?

http://supra.sysadmin-racing.com/videos/temp/cruise.wmv

I've done quite a bit of research and have read Maximum Boost numerous times and own a Subaru Sti, so I know a little bit about how turbo's work, but I just have never understood why some are so much louder than others.

I am talking about the sound of the turbo spooling to be exact.

 

BB (ball bearing) turbo's are unique in sound, and louder.

A lot has to do with the shape of the compressor blades.

14b/t25/lots of t3's have straight finned, identical blades. They are boring and not very loud.

 

also the turbos are probably the size of ur head!

 

hahaha

I wouldn't doubt it.

It's wierd because even some small ones are just really loud.
I've noticed with my Sti that you can't even really hear it at all with the windows even down a little

 

a lot of it has to do with the exhaust and filter set up. i have straight 3" exhaust with no cat/resonator/muffler and no filter on my turbo at all and the turbo whistles louder than a damn mack truck.

 

You would figure the exhaust would drown it out, that's strange...

Maybe it has something to do with the filter then, because most of the time a wide open exhaust would make it harder to hear the turbo (or anything else for that matter)

 

i have a dinky t25 with an open dp, but you can hear this little ****** whistle from almost a block away at wot!!! (no joke)

 

There are about 3 things you can do to make the turbo you have louder.

- hard metal intake

- open inlet on teh turbo (no intake pipe or filter)

- straight through exhaust (no cat/straight through muffler)

 

So it must be because of the plastic intake (stock).
It probably makes it real quiet.

What do you guys use to put over the turbo inlet?
I've seen some people use something that almost looks like a regular screen door material...

 

the open exhaust makes it louder b/c the turbine wheel is right at the beginning of the dp, so if there are no restrictions, the exhaust acts as a megaphone sort of and amplifies the sound of the turbine wheel spinning, that paired up with as little as possible restriction on the intake allows the comp. wheel to be heard more also. you'll hear the turbo whistling even when it's not spooling in vacuum because the wheels are still spinning even when you're not building boost.