Quiet 3" System Is There Such A Thing

[zebra]

Yep

Hooker claim it as a gas velocity increasing thing

Prob works ok on an atmo engine

[TiTAN]

My soarer is loud as f**k with its 3.5" system

Has a big hooker aerochamber at the back and a custom mid muffler (its small cause f**k all room with a 3.5" pipe)

What mufflers are you guys using on the quieter systems?

4" dump, 3.5" cat, 3.5" mid muffler, 3.5" massive 18x12x6 rear muffler.

Both just off the shelf straight through glass packs from an exhaust shop, did a little shy of 400kw just fine on a 35r years ago, dyno sheets somewhere in the rb30 threads I believe.

[-S-]

Apexi ecv ?

[Ben C34]

Apexi ecv ?

Why?

[-S-]

He said he wanted quiet?

[Kinks]

Low frequency components (~120Hz) seem to be the main frequencies transmitted into the cabin and the source of exhaust drone. An uninterrupted exhaust diameter from front to back (think 3" straight through) seems to be prone to resonances around low frequencies. The only way to break up the low frequency resonance is to make the length of the constant 3" section shorter. The way of doing this is by changing the exhaust diameter in the middle with a full size centre muffler. This is why basically every quiet exhaust has a full size centre muffler. A hotdog resonator in the middle won't do much, they are too small to change the pipe tuning.

I had a Fujitsubo catback in my R33 and it had full size centre and rear mufflers, very quiet system. I'm about to buy something very similar for my R34.

[mattie4270]

Checkout AES website and on facebook

[-S-]

I have a straight cat that has a perforated pipe inside. Supposed to quiet it done by messing the sound waves. .. but i don't know ...

[discopotato03]

Mine is 3.5 to the back of the cat and 3 through two large strait through mufflers to atmosphere .

One thing you can do is to put a "soft" part in the system to isolate engine vibration from the exhaust system . Most of you would have seen those spring loaded carbon ring and cup joints many transverse front wheel drive cars have . Because the across car engine rocks back and forth under acceleration (torque reaction) the exhaust can't be rigid or it'll act as a tie bar .

This clever joint allows engine movement whilst staying sealed , it also isolates to a degree engine noise and vibration .

Big diameter tube is very rigid and tents to transmit lots of vibration and noise into your cabin . I got my one off exhaust fitted with one of these spring loaded cup joints behind the cat and roughly where the gearbox exhaust hanger is . That way the front of the exhaust system is supported the length of the rigid engine and gearbox but allows movement south of there .

A bit of mucking around but it does work .

A .

[XGTRX]

Mine is 3.5 to the back of the cat and 3 through two large strait through mufflers to atmosphere .

One thing you can do is to put a "soft" part in the system to isolate engine vibration from the exhaust system . Most of you would have seen those spring loaded carbon ring and cup joints many transverse front wheel drive cars have . Because the across car engine rocks back and forth under acceleration (torque reaction) the exhaust can't be rigid or it'll act as a tie bar .

This clever joint allows engine movement whilst staying sealed , it also isolates to a degree engine noise and vibration .

Big diameter tube is very rigid and tents to transmit lots of vibration and noise into your cabin . I got my one off exhaust fitted with one of these spring loaded cup joints behind the cat and roughly where the gearbox exhaust hanger is . That way the front of the exhaust system is supported the length of the rigid engine and gearbox but allows movement south of there .

A bit of mucking around but it does work .

A .

Is it the same as a normal flex joint?

[Scott Black]

Nope. He means literally a dome shaped mating flange

[Scott Black]

[Ben C34]

Heaps of rwd cars use them.

[discopotato03]

Noise reduction is more important than ever with the laws being the way they are , which is why standard cars now sound like vacuum cleaners .

That "soft joint" also takes a lot of load off your turbine housings bolts/studs and very likely the manifold itself .

A .

[Ben C34]

I always thought that those joints were just easier for manufacture and assembly.

[niZmO_Man]

Rigid front pipe breaks dump pipe gaskets.

True story.

[discopotato03]

No they are actually better things than the bellows type ones with the braided wire outer covering . The braided ones don't like really high temps and the word on the street is that they expand inwards creating flow restrictions .

With the spring loaded "cup" joints the only things that can fail are the carbon ring or the two bolts and springs but I've never seen the fasteners or springs give up . The other thing is that they are really simple to take apart and the usually the only consumable part is that carbon ring - which if in fair condition goes straight back in .

I had to insist the exhaust place that made my system fit one but it was well worth it . Truck exhausts sometimes use these kind of joints so big bore parts shouldn't be hard to get . Some better exhaust places may even have the press dies to make them .

The obnoxious hum/buzz/drone in aftermarket exhausts is often the exhaust pipe and mufflers vibrating/resonating particularly if the engines torque reaction is being restricted by 3 or 4 metres of big bore tube . The engine and gearbox mounts are there to dampen engine/trans NVH , but hang a long rigid tube off something solid like a manifold and or a turbo and you can expect noise and vibration issues .

My old Subaru RX Turbo had a 3" dump pipe and 2 1/2" behind the middle muffler , think 1800cc flat four with small port prehistoric heads and a little GT2554R turbocharger . In legal rally trim (Grp A cams/pistons/computer/exhaust) these engines put out a great snappin 190 hp at the flywheel .

Really that exhaust was too big for what I was doing but with straight through mufflers and one of these joints in the factory position it was NOT noisy - at all .

I'm not saying that these joints are a magic bullet but together with big can area straight through mufflers (no baffles) you can have an exhaust that doesn't wake the dead or irritate your cars passengers .

A .

[AngryRB]

How much can the "cup" joints flex/move ? Wondering if they could be used to help line up segments of the exhaust ( making home made exhaust here.. lol )

Anyone used this style flexi joint part?

Edited June 25, 2016 by AngryRB

[steve200b]

Yep. Last 31/2in exhaust I used one of those from Aeroflow. Looks neat.