Tips to make exhaust around the 92-95 db mark

[anastasios]

Hi all,

Will be taking my 71 to Marulan on the 21st.

It has a stock bluetop with pod filter and exhaust.

Exhaust wise i have 4-1 extractors, one resonator then one high flow muffler. I have a flange before the diff so i can get a quieter muffler/silencer on there without major hassles.

What are your experiences? Will a stainless muffler be quieter than a mild steel? What would be least restrictive on performance? Extra high flow muffler in middle or quieter rear muffler with silencer?

these are the rules of Marulan:

Test 1: Maintain 5000 rpm for five seconds. Requires a reading of less than 92db when measured 5m directly in line with the exhaust tail pipe.
Test 2: From the same position, return the engine to idle rpm then flatten the accelerator to 5000 rpm for a reading of less than 95db.

[Matt]

http://www.ae86drivingclub.com.au/forums/showthread.php/72544

Link in there has a silencer link on ebay which isn't too restrictive , screws onto the tailpipe.

Center muffler and rear muffler generally works well.

[sundee]

Test 2 is BS... how can that be controlled?
50 rpm could put it over the limit.

Stainless has a tinnier sound.
mild steel you get a bit more beef

Id say if you had a good hi flow muffler...
make sure its of decent size and not some chinese job... japs are ace at making exhaust systems flow, sound great and quiet at the same time.
your hot dog or resonator will cut about 3db.

the positioning of the muffler also makes a difference to how affective it is.
i think from memory... the close to the engine the more affective... just confirm that though..

if you have an I phone.. you can download a DB meter app.... will give you some idea of how much noise its making once done.


You also need to ask the Weighting the DB meter is set to.... A, B or C

usually the standard is A, it give an average reading and is a fair way to measure.

[NIZLAH]

hot tip, that iphone app is fail -

I'm looking at ways to bring my exhaust level down also, can't fit anything else in the system as I made the exhaust sit nice and tight to the body, already has a 'flowmaster' resi (interesting design compared to your normal straight through type resi's) I thought it would be a lot more effective than it actually is.... at the rear I have a powerflow straight through offset muffler finished with about a foot of 3" pipe. this all on a 20v, whole system is stainless.

I can't justify the cost of those apexi ecv so I'm going to attempt to make my own from a throttle body butterfly of the right size, I think Ive got it sussed, but until I have it in front of me the brain will come up with some way of making it work..

Best bet is something similar, or the biggest muffler you can fit under/in there.. good luck

[sundee]

not sure if X force are still making those Varex mufflers..

it depends which one you have ( iphone app ) some of them are fairly accurate.. within 2 db or so

in no way am i saying its a reference, but it give you an idea.

also id stick with a 2.25" main system... any more and your just making noise with a low/mild powered NA.
rear section take it out to 3"... but only a few ft from the end

[meadan]

I found having a muffler closer to the rear made it more quiet.

But nothing beats a decent flowing baffled muffler. Or offset to offset straight through might do ok.

I have 2 offset to centre straight through mufflers and Id say I only just meet those requirements...

[Konakid]

Cat converter, one hotdog/resonator before diff, then high flow baffled rear muffler (not a cannon) my car is super quiet mainly because the exhaust tip dumps to ground 60 degrees or so.

In Odaiba for the D1 Grand Priox the cars had to be made quieter due to the public so everyone welded on exhaust tips that basically dumped paralell with the ground (90 degrees) i'd say do this with your current setup and you'll have no issues. the ground must absorb the sound waves where as with a striaght tip they are sent outwards through the air.

[anastasios]

okay well i pick up my dizzy today and will test with an app called sound meter on my sgs2

i like the dump tip idea as it is the easiest/cheapest method i have heard so far

what about unbolting my rear muffler at the flange and putting a plate in there with holes between the flange?

[meadan]

what size tip do you have on the end?

I have a 2.5" silencer I made up which just slides onto the end if you want to use it. It has holes and scotchbrite to muffle it a bit.

[Matt]

I find that hotdogs cause drone...

[timbo]

^ Yep, I also found that oversized mufflers contribute as well. I have a 2.25" system on my car; 4-1 manifold, one hotdog and a 2.25" muffler right beside the fuel tank. Over a long weekend a while ago I had to have a 2.5" muffler put on the car, the previous one developed a crack and the exhaust shop didn't have another. Those three days were seriously terrible! No matter what cruising speed, the muffler droned to the point where it was uncomfortable to drive.

[meadan]

Remember that "drone" heard inside the car is very different to what it sounds like outside.

I found that from inside, my car sounds awful at any revs, and generally sounds louder and almost unbearable. But from outside, basically sounds like any other 4 cylinder with a sports muffler.

[sundee]

Real world example here. 2 S13's . One mine , one a mates.

Same motors virtually .

His has full 4" system, cat, center muffler and rear cannon. Not sure of brand
The drone inside the cabin is stupid!

Mine has a full 3" system.
1 priece front/dump - De cat pipe - kakimoto hyper N1, which is a small resonator and a rear cannon.
And my car had more road/wind noise then droan from the exhaust.

I think the position of the mufflers would have to be positioned to target certain frequencies at there given wave lengths.
This would need to be calculated, hence why japs make epic exhaust systems.

I would suggest googling and learning about the design and makings of race exhausts.
I once read a great article that said, there is no reason why you can't make a hi velocity exhaust system quite.
I'll see if I can find it, but in the mean time punch in exhaust system design....

[dove grey 64]

interested in this, i'm running stock headers and 2" pipe, no cat,two resonators and a baffled sports muffler with center inlet/outlet and i'd say my car is just under the legal limit. would like it to be more quiet, i think a cat would bring it down to being a nice level as this setup is pretty much what james ran with a cat and it was alot quieter then my setup.
just dont want to fit a cat and find i've lost my top end power.
at one stage i had headers>muffler>resi>muffler and i lost heaps of power above 5k and it still wasnt quiet.
was planning on saving up for a fujitsubo legalis r system later down the road

[Rice86]

i have 4-1 extractors that are jasma approved into full Fujitsubo exhaust with a Titanium tipped *now im just showing off*.. a nice level of loudness in the cabin, call it a pee shooter from the outside if you must lol

EDIT - its a FGK Fujitsubo Legalis kit in mine

[timbo]

Just have someone else drive it so as to hear it?

[dove grey 64]

i have 4-1 extractors that are jasma approved into full Fujitsubo exhaust with a Titanium tipped *now im just showing off*.. a nice level of loudness in the cabin, call it a pee shooter from the outside if you must lol

EDIT - its a FGK Fujitsubo Legalis kit in mine
So jelly right now, same setup as tsuchiya I believe, people move out of the way when I drive up

[lolwat]

trd copies, 2 1/4" mild steel 2 lukey high flow mufflers, its silent at idle, and is extremely quiet any other time(for sale too)