Exhaust: Max.HP with Min.dB - how?

[Apolan]

Hi, i'd like to know how to make an exhaust with minimal restriction in flow (in other words, an exhaust that would yield as much HP as possible) but still keeping the loudness (not sound, but dB) stock/oem (or as silent as possible). I know countless calculations would be needed to make an exceptional compromise, but what are some of the general properties of such exhaust? Engine in question is a standard 4age..

I've heard fujitsubos and they keep the noise down, but give a gain in flow/power/torque. But they are bloody expensive. So for a homegarage inventions/improvisation guy, what is the best take?

regards,saso

[Lauren]

Apolan Wrote:Hi, i'd like to know how to make an exhaust with minimal restriction in flow (in other words, an exhaust that would yield as much HP as possible) but still keeping the loudness (not sound, but dB) stock/oem (or as silent as possible). I know countless calculations would be needed to make an exceptional compromise, but what are some of the general properties of such exhaust? Engine in question is a standard 4age..

I've heard fujitsubos and they keep the noise down, but give a gain in flow/power/torque. But they are bloody expensive. So for a homegarage inventions/improvisation guy, what is the best take?

regards,saso

A big freeflowing silencer with enough packing would be the way to do it.

[oldeskewltoy]

IMHO......
The key to the Fujitsubo(besides perfect mandrel bends) is the LOOOOOOONG resonator. The resonator section of the Fujitsubo is nearly 2 feet long in the large muffler models!



I've had two of the three LegalisR's that Fujitsubo offered...
the short muffler twin pipe and the large muffler twin pipe




The shorter muffler model was just a bit too loud for my tastes(47 here so an olde fart) the current one is just perfect.... so perfect I rarely listen to tunes, prefer to listen to the sweet symphony coming from my engine/Fujitsubo

[DJexor]

oldeskewltoy Wrote:The shorter muffler model was just a bit too loud for my tastes(47 here so an olde fart) the current one is just perfect.... so perfect I rarely listen to tunes, prefer to listen to the sweet symphony coming from my engine/Fujitsubo

soundclip!

[oldeskewltoy]

DJexor Wrote:

oldeskewltoy Wrote:The shorter muffler model was just a bit too loud for my tastes(47 here so an olde fart) the current one is just perfect.... so perfect I rarely listen to tunes, prefer to listen to the sweet symphony coming from my engine/Fujitsubo

soundclip!

I have no sound clips unfortunately.... and Fujitsubo does have clips....
http://www.fujitsubo.co.jp/sound_catalog.php
but none of the AE86, or a 4AGE.....

[dAYTONA]

If you use a 2.5" pipe, with two straight through mufflers, the exhaust will flow well, and be quiet. In australia many people I know used a 'Super Turbo' muffler which had 2.5" in/oulets and with minimal restrictions makes any car quieter. Here is a link that may be usefull.

http://autospeed.drive.com.au/cms/A_0383...larArticle

[NoHachi]

Quote:The Suzuki's dyno-recorded power output was identical for both the worse-flowing (Berklee BM480) and best-flowing (Genie resonator) mufflers!

I think design is probably a key issue. Some gains to be had from mandrel bends and smooth transitions, Then use a resonance type muffler with big volume to most efficiently reduce noise. Straight through mufflers will effectively make you deaf for a 1hp gain.

[The Doctor]

dAYTONA Wrote:If you use a 2.5" pipe, with two straight through mufflers, the exhaust will flow well, and be quiet. In australia many people I know used a 'Super Turbo' muffler which had 2.5" in/oulets and with minimal restrictions makes any car quieter. Here is a link that may be usefull.

http://autospeed.drive.com.au/cms/A_0383...larArticle

i wouldn't be too sure about that

My Celica GT (with 4A-GE) has a custom 2,5" exhaust (from the point where the 2 pipes go in to 1) with 2 (of the biggest type possible to fit) straight through mufflers, made out of Simons stuff.

I can feel a slight difference compared to the stock exhaust, but it's F*CKING loud.
I need to go back to the guy who made it, to get it more quiet.

[Apolan]

Isnt a resonance muffler same as a straight-through muffler? perforated (drilled) pipe, packed with some sort of mineral/glass/sand wool, inside a bigger pipe? is this what i should be used? or some other type? Does anybody have some "diasection" pictures of various muffler types with some descriptions etc?

[NoHachi]

Nopes, the "resonance type muffler" should have read "reflection type muffler". I just didn't write that down on account of me being a moron.

Reflection mufflers have a series of baffles inside them that form a sort of rats maze. Nothing straight through about them. Truth is, straight through exhausts will have a difficult time bringing noise levels below 90dB.

Minimum number of bends, bends that are there preferably mandrel bent, single diameter front to back (no sudden jumps ANYWHERE in the system), about 2" piping. Minimum number of welds and other connections)

Flowspeeds are so low through the muffler that its restriction (if decently sized) can be neglected. Try out several types and choose the one that doesn't make you deaf in a year.