Stock Cat Back Power Limit - R33 Gtst

[eightsixboy]

Hi all,

I'm looking at getting the quietest exhaust possible while still managing around 200rwkw or slightly over.

Every exhaust I have seen on 33's is to loud (over 87db).

As my 33 is my daily I want to keep it as quiet as possible while still gaining some benefit from having an aftermarket Dump/front pipe and a highflow cat.

I was thinking of just leaving the stock cat back portion of the exhaust but with an after market dump and highflow cat.

Would this still be highly restrictive?

My understanding is that the most restriction on these systems is the dump and cat but not so much the rest of the system.

Thanks.

[niZmO_Man]

Reason those exhausts are loud is because the mufflers don't do much muffling.

If you get a cat back made up with two fat mufflers (e.g. Magnaflow, AES which is Australian), your exhaust will be quite.

[GTSBoy]

What he said^.

It is dead trivial to get a full exhaust in 3" or even 3.5" that flows a lot and makes little noise. You want the biggest cat you can fit and afford too, not the shitty little stocker.

[Blackkers]

I agree with nizmo_man. You can have a decent flowing exhaust that isn't over the top loud by using proper mufflers.

This idea that unless it's a 3.5" straight through with a decat means it won't flow for shit is complete bullshit. You can have a 3inch exhaust from the dump to tailpipe with decent mid and rear mufflers (no cannons) and still perform well while being quiet.

I guess what you percieve to be quiet is down to personal preference. Also the stock catback is the cheapest option if that suits you; just wanted to throw in the idea that you can have a decent performing system without it being obnoxiously loud.

Having said that it would be pretty hard to pass the EPA noise test with anything bigger than the stock system I imagine, hopefully someone can weigh in here

[Ben C34]

I am making around 300rwkw and it's quiet, I think it was 86 but can't remember.

Get a decent exhaust.

Don't mesa around with the stock one.

[eightsixboy]

I guess I just don't want to spend mega bucks on a system if the stock cat back system is still good enough with an aftermarket dump/cat combo. If I was chasing 300rwkw or something then fair enough, but I think I'll be staying with the stock turbo for awhile.

[GTSBoy]

I think you're missing the point. There is no "power limit" for the stock cat-back. You can flow any amount of "power's" worth of exhaust through it you like. It's just that as you get up into bigger flows it starts to put up more of a fight and the backpressure mounts. At some point you would be silly to continue winding up the boost and doing whatever other mods to the engine to make it able to push that extra gas through the exhaust. But long before that point you would be well advised to upgrade the exhaust to something larger because it is basically free power and free boost response (compared to bigger turbos and all the other stuff you can buy to strap on to the engine). A good exhaust is not that expensive and will immediately allow the engine to make more power and boost faster even with nothing else changed. To ask if it is "good enough" for 200rwkW ignores the fact that if you leave it on and try to make 200rwkW you will need more boost and use more fuel, possibly run closer to detonation, need more conservative timing, etc, than if you were to put a bigger exhaust on it.

In reality, the correct order of modification for a turbo engine is almost always exhaust first, everything else second.

[Ben C34]

You can buy r33 cat backs for 100 bucks.

Then if it's too loud put in a decent muffler.

It's hardly any money to spend in the scheme of things.

[eightsixboy]

^ That's very true.

I wasn't arguing what's better or what was achievable, I know the stock system is restrictive and not ideal, but for all I know the stock cat back portion flows ok for a stock system and could be fine for the stock turbo boosted etc.

I'll keep an eye out for a decent second hand system, something without a canon.

[macaroni646]

I've got stock exhaust bar an aftermarket muffler welded on, making 207rwkw on 10psi

[picklesRs4]

Cat back exhast only will make it hard to get around 200kw mark, I have a full 3" turbo back xforce system on mine and noise when cruising is no problem at all even with the added drone of having a wagon.

Definitely keep an eye out for a 2nd hand system and just make sure the mufflers are in good nick so you can minimize noise but still have no problems with restriction in the exhaust.

As others said rather than screwing around trying to fine tune everything with various mods just go exhaust first to have good starting point to see what mods you need rather than going all out on a restricted exhaust.

Sorry for the essay and any typos which I am prone to with lack of proof reading