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2.0L vs 2.5l - Engine Burble


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This is my first post here and need a bit of advice.


I have always had 2.0L Impreza's over the years but recently purchased a 2.5L PPP one and have noticed how much quieter it is. It has the usual Prodrive back box I have had on my previous cars and I took out all the cats and silencer boxes and replaced them with straight through system but it has not gave me the same engine burble I had from my previous 2.0L PPP. As of yet I have not replaced the manifold as I am not sure what is the correct type to go for and if it would even make a difference.


Can anyone advise me on how to increase the burble noise from the 2.5 or what should I try next. And even dose anyone know why the 2.5 is quieter?


Your help would be appreciated.


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I do know that some jdm newage scoobs have equal length exhaust manifolds (which means you loose the burble) but I couldn't tell you what excat year's had them .

One of the newage owners might know though .

If that is the case and yours has got equal length exhaust manifold you can fit a unequal manifold to get burble back in your life

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Thanks mate. I will have to start investigating my car now. It has a burble but not what I am used to with the 2litre engine. Like I had a 2 litre beside my car the other day with same prodrive system as mine and mine just did not have the same note. I put it down to the 2.5 being quieter

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Don't think there's a great deal of difference between 2ltr & 2.5 as the 2ltr heads will fit on the 2.5 short block .

also people use the 2.5 crank in a 2ltr block to increase the displacement to get a 2.1 (stroker) engine .

I've never heard a 2.5 running myself so there might be a audible difference , but I have heard a newage jdm sti with equal length headers and it sounded like a straight line 4 engine

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i have  a Mate who works on a rolling road ,tuning all sorts of high performance cars he says.

The burble is caused by the early cars having what is called an off set turbo ,which means the 

inlet manifolds are of a different length.

Once the turbo gets up to pressure ,it eliminates the difference in pressure and the burble goes away

and is replaced with yet another wonderful sound.

which is why i will keep my 2.0 Bug eye

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