Now that I've installed my Alta intake, I notice the sound of the 'blow off' a lot more - and also, on hard acceleration I hear a similar sound. Does anyone know if the factory solenoid regulates boost on acceleration by releasing pressure as well or is that the sound of the turbo sucking air? I'm just curious about the sounds that the car makes.

 

It's normal to hear the turbo spooling up and sucking air past the compressor wheel. That sound is... well.... best described as sounding like air travelling through a pipe The factory ECU limits boost to 0.8 bar (approx. 12psi) so you might hear the diverter valve open slighly although its very difficult to hear with the exhaust noise.

 

If you are talking about the "noise maker", I wonder the same thing. I bought a noise maker delete, but have yet to install it. According to DOS, it does not do anything, but make a sporty sound.

 

welcome to the lively sound of an open air intake on a turbo car!

You should hear a loud hiss when you are accelerating hard which is air rushing in through the foam filter and a loud whoosh is you engage the clutch to shift which is the turbo diffusing boost pressure back through the intake. You couldn't hear it before due to the closed intake box design and thick paper panel filter soaking up the sound.

I removed the noise generator and the engine still sounds the same to me. The sound I thought it was making is still there. Supposedly since it feeds off of boost pressure on the cold side boost tube by removing it and plugging the hole you are retaining that pressure but it won't really have a noticeable effect to sound or performance.