Silencer Advice

Russ Noble

GT40s Supporter
Lifetime Supporter
Further to Jac Macs post, here is the muffler I am using, that I built in consultation with him.

Salient points are that it retains the tuned tailpipe length before dumping into the muffler. The cross sectional area the gas has to pass through between the baffles is greater than the tailpipe area. The muffler is seperated down the middle as two self contained units, but would probably be even quieter if both tailpipes dumped into the whole thing as a common chamber. It contains no sound deadening packing. I guess a picture is worth a thousand words.

Although I have not done back to back dyno testing with and without the muffler, I am confident that I am not taking a power hit with it. Disadvantages are weight (28kg) and size, but I feel the superior power I'm sure this gives me over most other setups more than compensates. To give an idea of scale, tailpipes and muffler outlets are 3" diameter, primaries 2" and the muffler is 6" deep.

Trackside observers cannot believe how quiet the car is. That is the first comment, usually followed by equal disbelief about how much grunt it has got. Guys who have watched the video Leon posted of the first start up have made the same comments about quietness. The lap times I am doing put me firmly in the top three in my class, so I think I have achieved my goals with regard to the muffler......
 

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Russ - that looks good. Of course, Jac Mac's advice is on-the-money. Co-incidently, that internal design is exactly like one of the commercially available mufflers but they are single units,and that unit is supposed to be efficient and quiet.
As for the original thread question, if you're looking for the cheap way out, Patriot makes some disc inserts,centrally rod mounted, for less than $20 and they should be available from Summit or Jegs. A.J.
 
As for the original thread question, if you're looking for the cheap way out, Patriot makes some disc inserts,centrally rod mounted, for less than $20 and they should be available from Summit or Jegs. A.J.

Here's a photo of the Patriot insert with a 3" outside diameter, 11 inches long.

737-H3844.jpg


Available from Jegs for $14.99. Such a deal!

Patriot Exhaust H3844 Patriot Exhaust Muffler Inserts

If the inside diameter of your pipe is less than 3 inches, you can probably trim this one to fit. Alternately, you could copy this design and fabricate one yourself.

My 427 Cobra had standard Cobra side pipes, which were made with a simple glasspack muffler. The exhaust system consisted of headers with 2-inch primary pipes, going into a 3.5 inch collector, but then the ID of the glasspack muffler was only 2 inches!!! It was loud but cost over 100 horsepower on an engine dyno!!! I had the mufflers replaced with Lobak mufflers, which use a similar spiral core. They are just about as loud (which is to say, VERY loud) but flow substantially better.

I would guess that using these Patriot spiral cores (or something similar) in your tailpipe downstream of your existing mufflers would do the job for you.
 

Malcolm

Supporter
Stephen

Think twice about using pop rivets for the fixing of your repacking plates. I tried that and after a short period they failed due to the high heat cycles. I also tried self tapping screws and they also failed, I can only guess they vibrated out. I ended up using rivnuts and brass bolts (M6) with spring washers. No problems since I used this method although I tend to carry spares for track days.
 
Malcom

Thanks for your advice. Unfortunately I read it after I have repacked the silencers and used pop rivets ! I will keep an eye on things, and at the first sign of any problem, will go doen the rivnut route. The good news is that with the silencers now repacked, on tick over we are reading 82 dB. Cadwell here I come :heart:

I do realise this is not permanent, as the packing material will gradually come out of the exhaust. I will test at a greater rpm shortly, but hopefully we will be all right for the track.

Stephen
 

Malcolm

Supporter
Malcom

Thanks for your advice. Unfortunately I read it after I have repacked the silencers and used pop rivets ! I will keep an eye on things, and at the first sign of any problem, will go doen the rivnut route. The good news is that with the silencers now repacked, on tick over we are reading 82 dB. Cadwell here I come :heart:

I do realise this is not permanent, as the packing material will gradually come out of the exhaust. I will test at a greater rpm shortly, but hopefully we will be all right for the track.

Stephen

Stephen

If your exhaust is repackable, then consider exhaust wadding a consumable! If you use higher RPM then you will need to repack more often than if you don't. Again I normally carry a sq metre or two of wadding as a spare on track days in case I fail testing so can add more as needed. Have fun at Cadwell.
 
was curious how the system sounded and found 2 video's of wich I believe is fitted with that muffler without padding.

[ame=http://www.youtube.com/watch?v=foPp7PoWVww]Russ GT40 startup - YouTube[/ame]

and round 2

[ame=http://www.youtube.com/watch?v=JrritijI5FM]Russ GT40 Start Up No2 - YouTube[/ame]

wonder how much db this is for track-days measurements
 
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