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1979 450SL UK spec
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1,435 Posts
Discussion Starter #1
I noticed that the exhaust sounded better/quieter when I did this when I was measuring the CO and adjusting the AFR.



So today I tried making a passive exhaust valve.

Needs to fit this size tightly.



First find an old washer that is close to size. To make the body of the valve.



Made up a mandrel for the washer with an old bolt.



Washer cut down to size.



Then bored out.



Then slotted to give a spring hold inside the exhaust.



Next on to the flap part of the valve.



Then identify a suitable hinge.



The two parts welded to the hinge.





Tapped into place.



Then a splash of paint.



...and a quick video, I haven't been for a drive yet as its a bit wet out. Measurements on my phone sound meter app showed a 4dB sound level reduction over no valve.

 

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Outstanding Contributor , Bob's Your Uncle!
-----'83 280 SL----- 5 speed....The PIG
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29,507 Posts
You are crazy.
This pretty much confirms it.
Or you need to get a job.
 

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Premium Member
1983 380 SL
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2,822 Posts
How did you figure that a cloths pin spring had just the right tension?
And kindly ship that lathe to my house when your done with it. Years ago I threw out my 9 inch South Bend Lathe because it was taking up too much room in my shop. I've been kicking myself ever since.
 

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'79 450SL, '04 CLK200 convertible; former A124, W210, A209.
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1,860 Posts
That's brilliant Jim, I mean MacGyver doesn't come close to you! 👍👌😁 How does she sound when you give her some revs?
 

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1979 450SL UK spec
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1,435 Posts
Discussion Starter #5
Don't know yet, its raining again today, I may get out later. As for the spring, I tried a few different pegs till I got one the "felt" right. I also ordered up some stainless steel wire wool and plan to pack one of the tail pipes to see how that sounds.

I wish I had a pipe bender so that I could try more setups more easily as I have a spare exhaust for the xk8, it would be interesting to experiment with bits of it on the 107.

2633439
 

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'79 450SL, '04 CLK200 convertible; former A124, W210, A209.
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1,860 Posts
Jim, I think you're aching from projectitis (I feel its onset too) and now that the R107 project has reached its conclusion I think we both need to move on and find another toy to spend time with.... Me thinks 124 or 126, either body will do. 🤔
 

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1979 450SL UK spec
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1,435 Posts
Discussion Starter #7
Kim wants me to build a camper van but the garage is just not big enough.

Anyway, I got the car out today but didn't get off the drive, as soon as I gave it a bit of throttle, the flap started to rattle against the exhaust pipe and make an even worse noise, so I pulled it out and went on to experiment 2.

I had ordered up a few meters of 3 inch wide stainless steel wool (see how I like to mix metric and imperial).



I bunched it up and pushed about 2 feet into one of the exhaust tubes which are about 30cm long (and perforated in the box) using a piece of hose, it had just the right curve.



I am delighted with the result, the loud drone has gone, and overall sound level dropped about 3dB so half the energy level. I think this cheap back box was just poorly designed and was amplifying the sound rather than attenuating it.



There was no point trying to record the sound as the AGC in the camera negates the point.

I took it out for a blast on the motorway at WOT up to 70mph and the wool did not budge at all, I will monitor on an ongoing basis to ensure it doesn't move.

I call that a big success and a much better result than putting in the expensive middle box.
 

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Premium Member
1983 380 SL
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2,822 Posts
Not for nuttin but when we were kids we used to take steel wool and tie it to a wire, then put the steel wool into a fire and then spin it around by the string and watch the sparks fly like fireworks.
I don't know if SS steel wool has the same properties but you might want to check it out before leaving it in your tailpipe too long.

 

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'79 450SL, '04 CLK200 convertible; former A124, W210, A209.
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1,860 Posts
Brilliant Jim, you are persistent :D

Jyuma, that's pretty awesome - I'll have to remember that next time we have a bon fire :D
 

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Premium Member
1983 380 SL
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2,822 Posts
Brilliant Jim, you are persistent :D

Jyuma, that's pretty awesome - I'll have to remember that next time we have a bon fire :D
FYI... you don't need a fire. A 9 volt battery scraped across the steel wool will ignite it. Just start spinning right after you touch the battery to the steel wool and that's all it will take.
 

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1986 560SL with M120 V12 Engine, 1988 560SL Stock
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10,196 Posts
Not for nuttin but when we were kids we used to take steel wool and tie it to a wire, then put the steel wool into a fire and then spin it around by the string and watch the sparks fly like fireworks.
I don't know if SS steel wool has the same properties but you might want to check it out before leaving it in your tailpipe too long.

Did that many times. Also set many bushes on fire when the steel wool flew off.
 

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'79 450SL, '04 CLK200 convertible; former A124, W210, A209.
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1,860 Posts
Thanks guys, that's a pretty good trick - I'll be a hero in the eyes of my 4 year old :D
 

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w108 & w107
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144 Posts
This was my solution to the previous owner putting on what he thought was a sports muffler, resulting in the wrist sounding 500 I've ever heard.
1.6mm galvanised steel mesh (painted flat black), cut into a cone, then fill exhaust end with steel wool before inserting the cones...last photo without flash shows they're not really visible from the outside. Just need an exhaust top with a lip to make sure the cone springs into place
 

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'79 450SL, '04 CLK200 convertible; former A124, W210, A209.
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1,860 Posts
Nice one Matthew - it looks like the exhaust itself was custom rather than just a replica?
 

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w108 & w107
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144 Posts
Nice one Matthew - it looks like the exhaust itself was custom rather than just a replica?
Yes - the rear section has the muffler replaced with 2x hotdogs, and although much better with the wool packed cones I installed, it sounds shit in my opinion (well compared to my W108 280SE 3.5 anyway). I'll either replace it with a replica original muffler, or I'd prefer to have something that looks original but actually sounds good, but unless I can hear another one and get that replicated exactly, it's not worth the risk. But it's not high on the list of priorities at the moment.
 
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