Designing a quiet (ish) yet free-flowing exhaust

[smitty]

Hey boys and girls,

With the advent of a new police station opening just up the road from me, the Frankston TMU seems to have moved in, and there's an awful lot of highway cars patrolling my area preying on all the rich bogans in their V8s or fully sik skylines.

This troubles me, so seeing as the most obvious reason to pull me over is the loud-arse exhaust system, I need to quieten it down. Step one is obviously changed the muffler to something a little more discreet, but AFAIK that can only do so much, and it's not like you can try-before-you-buy with this shit (this is my third exhaust so far, not been happy with any of them) so I'm a bit hesitant to go buy whatever crap the local exhaust guy tries to sell me.

What sort of stuff should I be looking at? What else can I do apart from changing the muffler?

It's a 3" mild steel setup with a varex cannon fitted, and a resonator somewhere along the line. No drone, fairly quiet inside but outside it definitely is not.

 

[Black_Ice]

If you have the varex should'nt you be sweet?

Are you looking at modifying your current exhaust to be quitier or you wanna get another quiter exhaust put in?

 

[naughtika]

you need to replace your muffler with chambered rather than straight through.. this should minimize the noise..

 

[unclepaulie]

Lots of resonators
Maybe a triple flow mid muffler
Varex on the back will be ok.

Also, reducing from 3" to 2.5" after the dif will drop the dB a bit too...but obviously it'll cost you a kW or two.

One thing to consider is a jasma branded Japanese muffler. That's their street legal classification. Most fujitsubo's are jasma approved. They're quiet on idle/low throttle but scream on boost

 

[smitty]

I want to get rid of the varex, the sound from it is not what I'm after. Plus I'm over the look of cannons, I'd rather a single or twin tip oval muffler.

I did consider importing a jasma exhaust but to keep costs down I'd rather modify the existing one, eg new muffler and as you said, adding resonators etc.

On that note, there are a lot of brands of mufflers out there, none of which I know anything about, quality or sound-wise. Im after something growley, but definitely not tinny or droney.

 

[mfbamba]

I have a Tanabe Jasma branded muffler and I agree with Paul.

 

[jet150]

I have a KAKIMOTO Jasma exhaust and it's bloody loud. I think like Paulie said lots of resonators min 2-3.

 

[Black_Ice]

Ask Mchieff..he has a fujitsubo (I think) and I have heard it once..not too loud and had a deep nice growl on idle...liked it alot...I had a custom exhaust with a varex..very convenient as you can turn it on and off..but when on it was pretty loud...

 

[fieldy107]

I have a 3" oval chambered muffler I took off because I found it to quiet, can have that for $20+ postage if you want, can take photos if your interested. Surprised its still loud with varex.

 

[Scottie]

Just get a Fujitsubo muffler and get some good resonators..

 

[unclepaulie]

The difference between my oval and my fujitsubo is huge, but my oval looks stock and my fujitsubo is huge and chrome

Most Nissan guys flog good jap mufflers off cheap (cause they want dori pipes) best bet would be to grab a r33 cutback or similar and cut te muffler and resonators off and use them.

 

[lathiat]

You can get varexes in oval variety and they are amazingly good and quietening the exhaust down.

probably in quiet style though they flow less well than a well designed big muffler. due to the big center section for straight through.

 

[jungle]

Its a funny old thing exhausts. My 3 litre GTR is the quietest car i own ( ASX not included) from softest to loudest is GTR SIl80 Leggy!. The GTR exhaust is 3.5 inch, cat, resonator, muffler with 4.5 tip. I can barely hear it on the highway at 100. When i get up it though it really starts to scream. The Leggy on the other hand is the opposite. 100 i can hear it no problems but it gets hard to hear when up it. The Leggy has 3 inch, cat, 2 resonators and fujitsobosomething but Jasma muffler.
I would have thought the varex would do the job for you?

 

[smitty]

The Varex i have is insanely loud from outside the car, not so much from inside. To me, the sound of my exhaust system just doesnt suit the car. It sounds meaty, beasty, burbles like no tomorrow on deceleration, but just too loud. I had the girl take it round the block a couple of times while I was standing on the driveway listening. Sounded like some 1000hp fire-breathing track monster was approaching, then a sport sedan rolled around the corner instead. Just doesnt suit.

And when I turn it down, say for a 100kph freeway trip or for avoiding mr plod, it is quiet (quieter than stock by far) but my lovely 550-600 k/tank economy drops to about 350. At half volume it sounds like a forced fart.

Let's not forget the illegality of the varex either. Not that Im too fussed about following the letter of the law in regards to some mods, but the TMU around here are fairly clever, and a car rolling past with a 4" cannon but not making a sound is sure to raise suspicions eventually.

And Trent, in answer to your question, in quiet mode it's forcing the exhaust through a hole not much bigger than 1". I'd imagine that all that gas trying to squeeze through such a small hole would generate too much back pressure and cause all kinds of bad ju-ju.

 

[BuzzPuppy]

You've heard what Loki's got with the Fujitsubo JASMA setup (cat-back stainless steel, oval chambered muffler) on the way home from the meet.

Doesn't quite line up with the Super's rear skirt opening (*heh* the "Quagmire" part of me still laughs quietly at that line, giggity...).

 

[unclepaulie]

quick ebay search:

http://www.ebay.com.au/itm/HKS-SUPE...=AU_Car_Parts_Accessories&hash=item256b85e7c2

http://www.ebay.com.au/itm/Nissan-S...=AU_Car_Parts_Accessories&hash=item3370d4fafe

http://www.ebay.com.au/itm/JDM-NISS...=AU_Car_Parts_Accessories&hash=item33701c3fff

surely nissansilvia or SAU would have a lot more

 

[mookers]

I really like the muffler I got from Ivan, but I don't know if he'd be interested in making any more. So many people said they wanted something like it, but when he put the offer out, nobody actually came forward to buy one

 

[pu-11-me]

I have a silencer for the HKS Super Dragger.... Quiter than stock with it in.

 

[Guest]

 

[Guest]

This is going to sound super dodgy haha but I know on me and my mates Dirtbikes when we would get done for being too loud or when there were a lot of cops out in the sticks chasing the riders we would get a net like type mesh bag (kind of like an onion bag) and stuff it with some stretched out cheap steel wool and push it into the exhaust.It worked absolute wonders and made it very quiet.I have seen on two separate occasions people get noise defects cleared by doing this.(Ripley's believe it or not can verify this lol)
Don't get me wrong I'm not suggesting anyone does this and I realise its not a real solution OR even a good idea at all I just thought it was something funny to share. Sorry to get a bit off topic.

On a more serious note I am looking at getting a decent turbo back system for my Legnum before I start tuning it but I don't want to deafen my kids. Hopefully I can discover something on this thread, and if I discover something first ill let you know.