Stock Xr6T - Why Do You Need Mufflers On A Turbo?

[CBXRT]

Exhaust systems make interesting reading.......after the last few days research, it is quite amazing how there are so many wildly different points of view. I also found this with the centre muffler removal too - in my opinion, it sounds 100% better, not even close? I would have done it from day one but for the alarming negativity on some threads.

Recently my exhaust note changed considerably - I am told it is most likely that my standard rear muffler might be struggling, and that maybe some of the cat has disintegrated and blocked the system and/or exhaust. So rather than replace it, I was advised to just also remove it, keep the stock cat in its current condition, and have resonators put in each 2.25 pipe. Power is not my aim with the exhaust change, my car goes plenty fast enough for me, its just the sound - I want it deep and angry under acceleration, and rumble a little at idle. I'm yet to hear any aftermarket XR6T exhaust that has really "wowed" me like when you hear a healthy XR8 or Clubsport roar past......

My advice of straight through with just resonators was from people who really should know - they either fit exhausts every day, or prepare racing cars. WRX/Skylines/Supras regularly only have resonators apparently, as the turbo automatically makes them quieter than NA - I was told this is safe to do for turbo motors hate back-pressure is they already have enough in the turbo....have no idea if this is the true, but it sounds Ok to me!

The question I can't answer then is why do people pay good money for cat-back systems for their otherwise stock cars (distinct from modified XRTs that require larger diametres etc etc) that apparently do very little other than change the note, sometimes even for the worse? Am I missing something here?

Its obviously illegal if you remove the cat, but when sound/emissions are the (reasonably minor) legality issues, the guys said that most XRTs with whatever brand sports exhaust most probably wouldn't pass the tests either - so again, why do it?

Anyway, looking forward to seeing how she sounds/goes once its done. My advice may be wrong of course. There has been some really positive feedback on here about doing it (but it is rarely discussed?), which is at least a good sign. At the very least, hopefully I can help other guys in my position.

Cheers.

[dule]

Sound & emissions are minor fines but if you remove the cat all together it's a big fine, well in my books at least $10000 here in NSW.

Keep in mind that if you remove or considerably reduce back pressure in these cars you need a re tune as it will run lean otherwise and a major kaboom is likely.

[CBXRT]

Dule, thanks for the reply. that's interesting - the blokes I spoke to said that since all changes are after the Cat then backpressure wouldn't change, and hence wouldn't need a tune? (if I had the cat high flowed then yes, for sure!).

Not saying you are wrong mate (no one knows anything about XRTs down here - all I get is "well, in my experience with WRXs..." ha ha) Its just another example of the differing views which led to my post - and no, I certainly don't want a "major kaboom" - I just want a rough/angry note with no issues....

ps: Sound and emissions apply similar in Tas - but going by the worked V8s that almost split the eardrums down here in Tas, it shouldn't be a major issue....

[Worm]

Remove cat = overboost and blown engine... Need a retune...

6 Turbos are just that... They don't have the lumpy idle like a v8, so they'll never sound like one... If you put in lumpier cams you will get more noise etc at idle... But it's not worth it!

[01txr]

You want it to be as smooth as possible as the sintered iron oil pump gears

Will probably smash themselves to pieces.

You want deep sound fit a 3.5 - 4 system on it.

Or illegally dump it at the diff.

But whatever you intend doing will more then likely require a retune weather keeping

The factory cat or not.

The center muffler on these cars are the biggest restriction so even just removing it

Will affect boost and AFR (air Fuel Ratio).

Just live with the characteristics of the turbo 6 silent but deadly not like a all noise no go gen 3 v8.

If you still want go risk smashing the oil pump gears you could have your car tuned with the

VCT locked so it gives you the lumpy idle.

[CBXRT]

Worm, appreciate the advice and I completely agree with you - but I'm not touching the cat so that doesn't apply to me. Understand it will never be a V8, or sound like one. Its just that the 6T sounds, in my opinion, pretty average - hence why I am trying something different using 6T/T Skylines/Supras as the template.

01TXR - have never heard of the sintered oil pump gears. So will ask the question though, and thanks for that advice.

Got the car yesterday and it sounds brilliant, really deep and purposeful, including at idle - even the exhaust guys thought it sounded awesome, and they tried to talk me out of it thinking an aftermarket exhaust is a safer option - its not anywhere near as loud as a worked V8. It also looks completely stock as the twin resonators go straight into the standard exhaust tip - so its kept its sleeper appeal.

I am having the car fully checked/tuned early next week. Might have to change it back to just to a regular/aftermarket exhaust system if it is danegrous to drive, but so far so good - no engine lights, no up-front issues.

Cheers.

[YOB POM]

If you only went cat back you wont need a tune.

If you want a V8 rumble you need a flat plane crank and discreet exhaust manifolds with the right firing order.

John.

[Rudiger]

If you have a broken toaster you don't take it to a bait and takle shop to be fixed. My point? Talk to people who KNOW our cars and dont just try to sell you their stuff. Many exhaust places will fit it and tell you all is good and the thing runs like a dog because they have no idea you may have to get it tuned.

These engines NEED to breath...simple.

Different people WILL have different opinions, but the only person you need to listen to is yourself. A mate of mine has removed his middle muffler. Certainly sounds better. He likes it so whats the issue? I'm not 100% keen on the note but he is happy.

I have a full 4" Nizpro system and I couldn't be happier. I honestly dont like chopping and changing and making up an exhaust just out of bits. My view is you get a proper one for OUR cars and that meets all criteria.

Hot Dogs are old stuff in my opinion. A CAT is necessary for emiission regulations.

But at the end of the day YOU have to be the one that is happy with the note and the performance.

[Brendan XR6-T]

Jeezuz this fellas gettin stomped on..

Personally I went the bigger cat (tuned) and centre muf gone and I think it sounds gr8 for what I payed.

But yeah as others have said the 4" might b ok too but they start to sound a little like a truck IMO.

[tonyv]

how can a centre muffler be a restriction and affect air fuel ratio's if it hardly gives u any more power?