# Pls help - It's just too loud



## Cactussed (Aug 5, 2010)

Chaps

Have bought an R33 GTR. Currently has some aftermarket downpipes, de-cat, looks like a 3.5-4in straight through system then a straight muffler with 5in tip. So pretty much no silencing whatsoever.

It's really doing my head in.

I presume putting a cat back in and switching to a 3.5in system with two inline mufflers will go a fair way towards making the car usable day to day? At the moment, either the fuzz or (more likely) the other half are going to kill me.

Andrew


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## markM3 (Jan 7, 2008)

Ask a trader if you can get a silencer to replace the decat.

cheers,


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## GTR_chris (Jan 25, 2010)

Yeh jap speed do a silencer that replaces a de-cat section AIRK it's £100???


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## Cactussed (Aug 5, 2010)

Has anyone fitted a decent variable exhaust?


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## damodeane (Dec 23, 2010)

dosent apexi do a silencer that you just fit to the back box


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## Cactussed (Aug 5, 2010)

They do a few.


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## mattysupra (Oct 31, 2008)

I have the same issue with my car. it is just to loud! 

I changed the whole exhaust for another system (nismo) and it was alot quieter. Perfect in fact. BUT it really zapped the power away from the car. For instance i was hitting around 99% injector duty on the MFD Display but with teh new exhaust it would never get to 90% injector duty. Basically a 10% loss. 


Next refitted the old exhaust (HKS) and tried a silenced decat. This helped alot but is still way to loud. For instance im getting 102db on tickover and 106 db i think it was at 4000rpm. ( i was getting 122db before inside the car, cant remember what the outside noise but think it was 112db @ 4000rpm) 

I then fitted a apexi exhaust valve (manual valve operated by a handle inside the car). This only reduced the noise by 2db and also you cant drive the car with it fully closed apart from moving the car out the garage and to the end of the road etc at low revs. However! I think if i fitted the apexi valve closer to the back box i will get much better results. But i need to chop my exhaust and weld flanges on to install the apexi valve further back.


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## matty32 (Dec 18, 2005)

you cant really have it both ways

go for a HKS Hi Power muffler, but you will notice the power drop

replacing the decat with a hiflow cat (hks or MINES) will also help but is very costly


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## Cactussed (Aug 5, 2010)

Yeah, I know its always a tradeoff however its not usable right now IMHO. I've ordered a japspeed cat replacement muffler and will give that a shot. 

I think I might try a generic 3.5in system as well (if the extra muffler is no good) or a slightly smaller rear silencer and see if they help. Both should flow sufficiently for up to 500bhp.

Its not a massive power car anyway right now. 

Oh, and very intersting re: the valve. My 355 runs a bypass arrangement (they all do) and that's reasonable at idle and normal driving (133.1db at WOT is another story). Thinking perhaps a 2 stage system controlled by boost pressure is what's needed here also...


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## matty32 (Dec 18, 2005)

it may help if you posted up a pic of the rear of the 33, to show people what muffler is on it

depends what you mean by "loud"


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## Cactussed (Aug 5, 2010)

I don't have a DB meter at home but I'm guessing well over 100DB on startup, maybe 98 on idle and a fair bit louder driving around. Very deep and bassy as well which adds to the problem.


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## matty32 (Dec 18, 2005)

Post a pic & we can tell you the db


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## Cactussed (Aug 5, 2010)

Well, I spent some time under the car this weekend. Full coolant and engine flush and new fluids. 


The exhaust is 3.5in system with a decat and single muffler at the end which has a 5in tip. Daft looking if you ask me. 

I pulled the decat off and shoved on a japspeed silencer which seems to have made some difference. I expect the next step will be to swap the end muffler for something slightly smaller that actually lowers the noise. 

The issue now seems to be more with boominess inside the car than horrendous noise outside. I'll see how the new muffler performs once it cokes up a little but I think a slightly quieter muffler will see me right.

Anyone want to swap their 3.5in in / 4in out muffler for a 5in one?


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## Mikeydinho (Jan 30, 2009)

post a pic and ill let you know


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## murano3 (Mar 23, 2005)

I've got the HKS Silent ... quiet on idle - only loud on acceleration - then quiet again when you are at a steady speed. No idea how much it would reduce your power compared to the current set up but would certainly recommend it.


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## TREG (May 20, 2004)

murano3 said:


> I've got the HKS Silent ... quiet on idle - only loud on acceleration - then quiet again when you are at a steady speed. No idea how much it would reduce your power compared to the current set up but would certainly recommend it.



As above.

Idle 78db
2000 rpm 85db
4000 rpm 92db

Car is a Gtr 33 with a Hks Silient Hi power fitted- 528bhp no cats. If your bhp is higher the readings above will be higher 
__________________


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## Cactussed (Aug 5, 2010)

Is the rear HKS muffler a straight through design? (I presume so).


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## murano3 (Mar 23, 2005)

Bolts straight onto the Decat if that helps


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## Cactussed (Aug 5, 2010)

Also, does it have a small in-line muffler? about half way down?


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## Cris (Sep 17, 2007)

If it's any help this is what my HKS system looked like. The left hand pipe sits between the backbox and the cat/decat.










With the valve closed mine is very quiet, open it's pretty quiet.


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## Cactussed (Aug 5, 2010)

Ah, OK. 
So it has the inline muffler which is probably what makes all the difference....


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## Cris (Sep 17, 2007)

Should have said mine is an EVR. I can't remember if it comes under the Silent Power or Hi Power bracket. None the less with the middle box and the backbox it's quite quiet even with the EVR valve open.


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## Cactussed (Aug 5, 2010)

OK. I guess I need to keep my eyes peeled for a centre section with the muffler in or a muffler that I can have put in...


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## Cris (Sep 17, 2007)

You could go somewhere that makes custom exhausts and get them to splice in a silencer box and retain your current backbox.

My brother used a Powerflow fitter and is very happy with the result. Was very cheap all considered.


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