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Dyno mufflers

General engine tech -- Drag Racing to Circle Track

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SupStk
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Dyno mufflers

Post by SupStk » Sat Jun 20, 2020 3:39 pm

I'm relocating my dyno to a new building next to the shop. I've done several searches trying to learn what what I should be looking at for mufflers. Previously used class 7 truck/ heavy equipment mufflers that have 5" inlet and outlets. They were "okay" but still a little more noise than I'd like. The existing mufflers lasted 5 years before rusting out so would like something with more life expectancy.

Looking for suggestions that hopefully won't break the bank.
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Re: Dyno mufflers

Post by nhrastocker » Sat Jun 20, 2020 7:23 pm

I recommend hospital/industrial class generator mufflers.
Low restriction, great sound reduction and attenuation.

https://www.nettinc.com/products/engine ... -silencers

https://dynesystems.com/wp-content/uplo ... st-Kit.pdf

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Re: Dyno mufflers

Post by RCJ » Sun Jun 21, 2020 8:49 am

Building dyno exhaust also. I going to build a termination box inside the building with flex tube to attach to headers. Being in a rural area, the outside mufflers will the the simplest thing I can find. I have built mufflers before and the quietest was a heavy gauge pipe drilled full of holes running the entire length on entry. The exit was was a second pipe full of holes running entire length. The casing was 10 gauge.

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Re: Dyno mufflers

Post by R.Brown » Sun Jun 21, 2020 9:08 am

A pair of Nelson 41180F is what I have used. 8" in/out.

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Re: Dyno mufflers

Post by SupStk » Sun Jun 21, 2020 3:08 pm

RCJ wrote:
Sun Jun 21, 2020 8:49 am
Building dyno exhaust also. I going to build a termination box inside the building with flex tube to attach to headers. Being in a rural area, the outside mufflers will the the simplest thing I can find. I have built mufflers before and the quietest was a heavy gauge pipe drilled full of holes running the entire length on entry. The exit was was a second pipe full of holes running entire length. The casing was 10 gauge.
I'm curious about your fabricated mufflers.

What was the inlet and exit pipe diameters? How long was the muffler? What size and number of holes you used?
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Re: Dyno mufflers

Post by gunt » Sun Jun 21, 2020 4:16 pm

Made this up haven’t tried it yet it’s outside after the fan I have another one done , read about the idea here somewhere , it’s facing down and room to add another 1 on also I can fill each tyres with a different material , if needed
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Re: Dyno mufflers

Post by shoedoos » Mon Jun 22, 2020 8:35 pm


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Re: Dyno mufflers

Post by RCJ » Tue Jun 23, 2020 8:21 am

Several years back a friend and I came up with some 6'' diameter pipe. we decided to try and make mufflers for our trucks. We used 2 1/2 pipe and only extended it a couple inches in to the 6'' tube. We built H pipes and the entire exhaust system. Everybody was surprised how good it sounded ,it was not as loud as we wanted.
Anther friend had a 428 FE in a truck ,he built his muffler by extending the 2 1/2 pipe the entire length of the muffle (24'') and capping the ends and drilling 3/8 holes in the pipes. He used an h pipe also.That mufflers was very quiet.
You would have to build everything larger for the high hp motors on the dyno. After building a few mufflers, in seems the added volume helps quieten things down as much as the packing. That's why I'm going to build a termination box as close to the header and I have seen some dyno shops where the exhaust had to effect the tune on the motor.
If you did build a termination box and had the room, I would bet adding a pipe from one box to the other would quiet things some.

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Re: Dyno mufflers

Post by ptuomov » Tue Jun 23, 2020 9:10 am

Why not fill the “terminator box” with sound absorptive material and a high porosity perforated pipe?

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Re: Dyno mufflers

Post by n2omike » Tue Jun 23, 2020 11:50 am

Saw where a guy built a box about the size of a small dumpster outside of his building. He lined it with insulation, put a big exit or two on it, and called it 'good'.

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Re: Dyno mufflers

Post by CamKing » Tue Jun 23, 2020 12:11 pm

Don't use mufflers. Build a baffling system around the dyno room.
There use to be an NHRA Pro-Stock team down the street from me.
The dyno room had a large ducting system to baffle the exhaust noise. The exhaust went into a duct that was big enough for a few people to stand in. It went up, and then over the dyno room, and then exited out of the roof. It was extremely quiet.
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Re: Dyno mufflers

Post by dynoflo » Wed Jun 24, 2020 3:31 pm

i run 4 inch flex into 5 in and out truck mufflers from NAPA into a car storage insulated 24x36 garage. it has 2 exhaust fans in ceiling. jere stahl gave me the idea when i was setting up dyno. i have never had a complaint and i live by police station and municipal building.

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Re: Dyno mufflers

Post by SupStk » Wed Jun 24, 2020 4:05 pm

dynoflo wrote:
Wed Jun 24, 2020 3:31 pm
i run 4 inch flex into 5 in and out truck mufflers from NAPA into a car storage insulated 24x36 garage. it has 2 exhaust fans in ceiling. jere stahl gave me the idea when i was setting up dyno. i have never had a complaint and i live by police station and municipal building.
Your suggestion got me to thinking about a block enclosure with maybe prestressed concrete panels for the roof.
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Re: Dyno mufflers

Post by Dave Koehler » Wed Jun 24, 2020 5:39 pm

Read an article years ago about the late Earl Gaerte's shop. At that time it was in town.
He opted to blow out to and into an underground baffled system.
Reportedly it was stupid quiet.
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Re: Dyno mufflers

Post by Circlotron » Thu Jun 25, 2020 9:32 am

If I was making something for myself I would have a pair of termination boxes made from a pair of 100 litre propane cylinders, then lead the pipes outside to a (possibly) underground concrete septic tank, then to a large straight-through absorption muffler with the exit pipe finishing as high as reasonably possible above ground. Ground level pipes seem to propagate low frequencies better than if they are high up. Some sculptured sound absorbent foam rubber on the walls and ceiling and some old carpet on at least part of the floor would definitely help too. I have seen guys in garage bands put mattresses against the wall.

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