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Godders

Unlocking the rumble on a hawk

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My wrx hawk is totally standard except a cosworth panel filter and a remap which I am perfectly happy with, except for the lack of boxer rumble in the cabin. I know the 2.5’s are almost silent compared to the 2.0’s but what would I need to change as a minimum to get a whiff of rumble in the cabin whilst cruising? Would a de-res centre section on a standard back do it? Or should I look at adding a prodrive back box to a de-res? I’m really trying to avoid noisy exhausts and get a good amount of rumble in the cabin with not much more noise out the back end (bit of an oxy moron I know) any ideas gents? 

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Not sure where you got the impression the 2.5 is quieter than the 2.0 because that's not true?

Its all about the exhaust system on both. Need to have some of the cats removed and you'll find a big difference 😉

Back box would be a good start, but you wont increase cabin noise without external going up as well

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Its a bit extreme but you could remove all the sound deadening material but that means taking your interior apart, seats, carpet out etc. That will make the cabin noisier - that authentic race rally feel?

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On 12/3/2018 at 10:45 AM, Tidgy said:

Not sure where you got the impression the 2.5 is quieter than the 2.0 because that's not true?

Its all about the exhaust system on both. Need to have some of the cats removed and you'll find a big difference 😉

Back box would be a good start, but you wont increase cabin noise without external going up as well

There’s a stock bugeye wrx at my work and when it’s crawling around the burble is more pronounced, it might just be me but the 2.5 seems a lot quieter and refined. I only get a whiff of the boxer if I hang on to 1st. 

Was kinda hoping a de res centre pipe would do the trick but i’ll keep my eye out for a prodrive back box and work backwards if needed 👍🏻

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i suspect its exhaust related, plenty of burble from a 2.5.

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It might be the unequal vs equal length manifold. 

around 2006 2007 Subaru went to an equal length manifold (the bug definitely has an unequal length fitted), not too sure but I wonder if this also coincided with going from 2.0l to 2.5l - it may be that giving the more distinctive rumble you are looking for??

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When I got my WRX it was bog standard and had zero burble. Changing the back box was enough to unleash the burble, then over time the rest of the exhaust was changed until it was stupid loud.

I would start with a cat back system, saves messing around with cats and see how you like it.

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5 hours ago, Jay762 said:

It might be the unequal vs equal length manifold. 

around 2006 2007 Subaru went to an equal length manifold (the bug definitely has an unequal length fitted), not too sure but I wonder if this also coincided with going from 2.0l to 2.5l - it may be that giving the more distinctive rumble you are looking for??

Ah I see, thanks that makes total sense now 👍🏻

 

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The hawk has the same manfold design as a bug, both unequal, its nothing to do with that.

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On 12/5/2018 at 8:38 AM, Tidgy said:

The hawk has the same manfold design as a bug, both unequal, its nothing to do with that.

even though engine capacity is the same?? If that is the case then loosing the middle resonator and the prodrive back box will give you the rumble you are looking for 

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49 minutes ago, Jay762 said:

even though engine capacity is the same?? If that is the case then loosing the middle resonator and the prodrive back box will give you the rumble you are looking for 

yes matey. both unequal length. (assuming not import which are 2.0 twin scroll equal length just to throw another confusing thing into the mix lol)

Change happened at hatch when twin AVCS came in. (hawk is just single AVCS), the heads are the different.

Alot of the blocks/heads are interchangeable, My type r was a 2.5 block out of a hatch with the stock classic v5 heads bolted to it (bearing in mind were talking actual engine heads that bolt to the short block, not exhaust manifold which gets renamed 'headers' just to clarify to anyone reading). Other changes did happen at blob to hawk, drive by wire being a notable one.

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