Subaru turbo and wastegate
Discussion
Right im no good for things of a mechanical nature. I have 2 Imprezas one of which is tuned and i love the dump valve noise but with my other one a standard P1 I would prefer it to make the nicer chattering noise which im led to believe is a wastegate? external wastegate? I dont know, guess some of you guys do, wondering if anyones knows about this as I have never seen a scooby running one its always just dump valves. failing that what is it that makes squeaky whistle noise on the rallycars, I met a guy whose scoob did this and he said it was not dump valve or wastegate just air going back through the turbo if so how the hell did it make that noise and so loud? what work is involved in fitting a different noisy wastegate? cheers guys
The cool whistling noise is the anti-lag system. Basically that is done by mapping, when the driver lifts of the throttle the ignition timing is altered (retarded). Then there is a constant air supply allowed into the engine (butterfly stays partly open or air injector) which allows the now richer air/fuel mixture to get into the combustion chamber. Due to the delayed spark when it starts to burn the exhaust valve is starting to open, this explosion keeps the turbo spinning whilst off the throttle.
The wastegate simply regulates the amount of boost, it only allows a certain amount of exhaust gas to hit the turbine. Most cars have an internal wastegate as standard and if you want to increase the boost you could go to an external wastegate which can sound better.
Hope this helps a bit.
The wastegate simply regulates the amount of boost, it only allows a certain amount of exhaust gas to hit the turbine. Most cars have an internal wastegate as standard and if you want to increase the boost you could go to an external wastegate which can sound better.
Hope this helps a bit.
To get the noise you refer to Will you will need to clamp the vacuum line (or cut and block the two loose ends)going to your dump valve (to stop it operating) and fit a cone filter such as a K&N. This will produce compressor surge (air rushing back out past compressor blades when the throttle shuts), some people claim it will damge the turbo over time, some swear blind it has no effect at all on turbo life.1
The chattering sound is as the previous post said. When the throttle is shut off the air hits it and reverses direction and is forced back through the turbine trying to stall it, hence the noise is the air being "chopped up" by the blades. In reality the dump valve is supposed to be as close to the throttle body as possibly so when this happens it is vented to the atmosphere not back into the system. On the subject of it being no good for the turbo, trying to stall a turbine at 100k+ rpm is not good for the blades lifespan.
If the dump valve is situated properly the chirping would be from an external wastegate as it bypasses the excess boost to the atmosphere, but i doubtyour impreza will have one unless it is heavily modified.
If the dump valve is situated properly the chirping would be from an external wastegate as it bypasses the excess boost to the atmosphere, but i doubtyour impreza will have one unless it is heavily modified.
eliot said:
The cool whistling noise is the anti-lag system. .
I thought anti lag was the loud banging and popping - introduced by the technique you described above.
It does pop and bang on cars such as Escorts, Evos etc. But on Subarus it tends to just chirp. Its the movement of air, induced by the anti lag, that causes the chirping I beleive. Imprezas only tend to pop and bang when you rev them with the anti lag on whilst sitting still
you also get some lovely big flames!David H said:
To get the noise you refer to Will you will need to clamp the vacuum line (or cut and block the two loose ends)going to your dump valve (to stop it operating)
Doing that will simply cause the dump valve to leak when on boost.
If you want the chirping/fluttering noise, you need to remove the dump valve completely, and plug any holes where it used to be.
The IHI range of turbos arent as robust as the earlier Mitsi's, but on an otherwise standard car, it wont have an effect on reliability.
It may however muck things up, as the airflow meter wont have a clue whats going on, when air suddenly tries to go backwards through it.
well iwould recomend you get a 2.5ltr block and then fit a tubluar turbo manifold with an external waestgate and a GT35R turbo. then you will need forged internals, a HUGE fromnt mounted intercooler, water injection, uprated fuel system (maybe including a race fuel set up to), a MoTec M800 ecu to run eveything, an elctronic boost controller so you can up it when you want and a ,load of other little bit an bobs that make it all work! 
then you want ahve to worry about the noise the thing is making! you will just be interested in how fast it is lol
Sorry Chris.
then you want ahve to worry about the noise the thing is making! you will just be interested in how fast it is lol
Sorry Chris.
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