Silencers

hi everyone,
to re-register my GTD in my country,engine is a Ford 302 , i need to silence my exhaust a bit (about 10 db) actually from 83 down to 75db
as the space to fit it is quite reduced , can somebody help me with finding the right muffler provider
any help is appreciated
Thanks
JP
 

Randy V

Admin
Lifetime Supporter
10dB is an absolutely huge reduction on an exhaust system that is already not bad at 83 dB. Which country and what are the requirements? Does the car need to be running 90kph on a dyno as they measure or ??
You can do some tuning efforts to reduce the sound of the exhaust, but it will make it run poorly and may not pass emissions.
 

Rune

Supporter
Try to find a solution with Supertrapp mufflers then you can adjust the dB, but the negative is backpressure witch the engine does not like.
 

Eddy McClements

Supporter
10dB is an absolutely huge reduction on an exhaust system that is already not bad at 83 dB. Which country and what are the requirements? Does the car need to be running 90kph on a dyno as they measure or ??
You can do some tuning efforts to reduce the sound of the exhaust, but it will make it run poorly and may not pass emissions.
Agreed...it's a log scale, so a 10Db reduction means reducing the sound to one-tenth of what it was previously, surely?
 

Mike Pass

Supporter
As that is a very low noise level I would suggest several things to get the noise level down. Use the largest silencer boxes that will fit in the space available. Do not use a "straight through" system. Use thick mild steel and avoid any flat surfaces which could resonate. Fill with the best quality noise absorbing wadding. Use a small diameter tail pipe. Do not have the final tailpipe emerging at the back of the car. Reduce the amount of gas and noise by reducing the induction system capacity. If using a 4 barrel carb block off and disconnect the secondary section. Put a reducing plate in the inlet to reduce the amount of mixture inducted and hence the power and noise production. Less power - less noise. As long as the engine can reach the revs needed that should be sufficient induction. Use noise damping pads on engine bay surfaces. Block off open areas in the engine bay with sound deadening pads particularly at the rear and underneath to reduce non exhaust noise escape.
Hope this helps
Cheers
Mike
 

Mike Pass

Supporter
The exhaust you have is an original GTD non crossover system as far as the primaries. The silencer box is big but very short because of the primary pipes extending a long way back. If you want a really good SS system there is a really nice full Simpson system (302 size) for sale on the GT40 Enthusiasts Club website. It uses a clamp system so the silencers can be quickly changed. It actually comes with a set of megaphones as well as the silencers but these may not be the thing for a low noise level but maybe try them later after you pass the test! With the ring clamp quick change set up you could quickly test different silencer setups. If I remember correctly this system uses 1 5/8" primary pipes. The silencers would be ideal for road use after you get past the test as from what I can remember they were OK for noise.
As you have a double pumper Holley it should be easy to cut off the secondary chokes and fuel and to reduce the primary diameter with a plate with smaller primary holes to reduce power and noise.
Cheers
Mike
 
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