Unfortunately the twin loop design just won't fit neatly with the limited space. I had looked into that one already. Not only does it pass the sound twice through the mufflers, the proper ones should have the sound waves re-entering the chamber 180 deg out of phase to the ones coming into the muffler for the first time. They will effectively collide with each other and cancel each other out.

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Ongoing Project: 1972 Datsun 510 S13 SR20Det. http://ozdat.com/forum/viewtopic.php?f=33&t=17898
New Daily: D22 Navara (The new workhorse)
Retired 12/2016: MY98 Subaru Impreza RX
Previous Car: Restored Green 1972 Datsun 510, Hot L18

as long as it meets legal noise limits when open it would be.

Try a aero chamber muffler. I put a small 9" long one in my Mrs ute with a cammed l67 and it sounds pretty blood stock lol. They reduce volume A LOT.

Did you notice any power decrease?
Are they straight through?

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1972 Datsun 1600, S14 SR20DET Engineered (204rwkW @ 17psi.)
viewtopic.php?t=6579
#SR20Datsun @SR20Datsun

Makes your Datto sound like a V8 lol.
https://www.youtube.com/watch?v=k67iEZZg0g0

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Richard..........http://www.youtube.com/watch?v=rqM9_Wq-TKc

Looks cool and sounds nice too but, what's a tuning tube? Is it adjustable/tuneable and how does it cancel amplitude?

I've always wondered how these work with different capacity engines with different cylinders with different revs.
I assume there is a small Helmholtz resonator somewhere in there
Helmholtz resonators work with only specific frequencies and the associated harmonics. It's just a way of absorbing the energy using the existing energy out of phase.

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1972 Datsun 1600, S14 SR20DET Engineered (204rwkW @ 17psi.)
viewtopic.php?t=6579
#SR20Datsun @SR20Datsun

That's pretty much what i want to create within a standard muffler. Calculating the size needed isn't as simple as a 1/4 wave resonator though!

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Ongoing Project: 1972 Datsun 510 S13 SR20Det. http://ozdat.com/forum/viewtopic.php?f=33&t=17898
New Daily: D22 Navara (The new workhorse)
Retired 12/2016: MY98 Subaru Impreza RX
Previous Car: Restored Green 1972 Datsun 510, Hot L18

I am running a twin 2.5" in/out Varex muffler on my XR8 ute, pity they're not legal, but it works perfectly, quiet over the whole rev range with it closed apart from a deep idle, loud as hell with it open.

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http://www.healingchambers.com.au

I have made my sr20 1600 exhaust front to back with the intention of it being as quiet as possible at lower revs or idle. It is a full 3 inch with a 24 inch hotdog down the center and the biggest muffler I could possibly fit out the back. I bought a dynomax VT from the states as the configuration I was after wasn't sold locally. The difference with these mufflers is they have a light spring loaded valve on the exit. It is the quietest modified datsun I have heard at idle but sounds like a straight through muffler at full noise. The only thing I haven't tested yet is how it effects turbo response but it's a pretty light spring so I can't see it being much.

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Mark

Good information to know.
I'm google searching the muffler as I type this!

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1972 Datsun 1600, S14 SR20DET Engineered (204rwkW @ 17psi.)
viewtopic.php?t=6579
#SR20Datsun @SR20Datsun

It can sound a little fluffy at idle due to the valve but it reminds me of a stock 1600.

If your interested enough I can chuck a clip up of it on my YouTube channel.

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Mark

I think a sound clip would be good. Very surprised that you managed to fit a 600mm long hot dog in the middle. I built one that big and it was a very tight fit. I want happy with it so i cut it back out. My exhaust is tucked up very high.

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Ongoing Project: 1972 Datsun 510 S13 SR20Det. http://ozdat.com/forum/viewtopic.php?f=33&t=17898
New Daily: D22 Navara (The new workhorse)
Retired 12/2016: MY98 Subaru Impreza RX
Previous Car: Restored Green 1972 Datsun 510, Hot L18

I have the Datsport solid gearbox crossmember with the exhaust provision which gave me a bit of extra room.

Here is the you tube link https://youtu.be/3iUsG9yzIHI

Now before anyone flames me I am well aware of how unreliable the phone db meters are but it is hard to gauge how quiet it is just with the video of it.

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Mark

I have my own gearbox cross member. But it would need to sit between the prop shaft and the floor behind the gearbox. Thanks for the vid.
Does sound quiet at idle. What's the in cabin noise like when accelerating and cruising?

_________________
Ongoing Project: 1972 Datsun 510 S13 SR20Det. http://ozdat.com/forum/viewtopic.php?f=33&t=17898
New Daily: D22 Navara (The new workhorse)
Retired 12/2016: MY98 Subaru Impreza RX
Previous Car: Restored Green 1972 Datsun 510, Hot L18