When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
I currently have a GT3 exhaust bolted to a 964 with no cats but I'm hoping this forum will have more experience with this muffler. The muffler is bolted to the "open" port openings on the muffler. The "closed" port openings have a panel cover bolted on the outside. I'm getting drone in the 2.5K-3.3K rpm range. Would rebolting the exhaust to the "closed" port openings eliminate the drone? The car has no sound insulation so I'm not concerned about a softer exhaust note (would be welcome since I'd like to DD the car).
Not sure anyone will be able to give you an answer for sure. However, on the GT3, the side mufflers are what kills the drone. This is why the center muffler delete is so popular because the center muffler just brings the sound down a bit. I've tried side deletes and center muffler and found it to be very boomy in the same range you describe. Wish I had a better answer for ya. Good luck!
OP, when you say you have a GT3 exhaust bolted to your 964 (of which I have both of these cars, so I am familiar), I am not clear how you could have all three of the GT3 mufflers bolted to your 964 (both sides + center).
Maybe you could further describe the actual setup you have on the 964. Pictures from underneath would help too.
OP, when you say you have a GT3 exhaust bolted to your 964 (of which I have both of these cars, so I am familiar), I am not clear how you could have all three of the GT3 mufflers bolted to your 964 (both sides + center).
Maybe you could further describe the actual setup you have on the 964. Pictures from underneath would help too.
just the gt3 center muff is bolted in. The two side mufflers are not installed (no room)
Ahh,... so essentially that is a similar setup to the original oem 964 center muffler design.
Then the answer to your question is yes. If you switch to the "muffled" port on that center muffler, then it would indeed quiet the car down, and it would most likely reduce the drone you are experiencing.
I have both of these cars (964 & GT3). They are side by side in my garage, so I have experience with both exhaust setups.
You may have to fabricate a turn, in order to switch to the upper port.
You want the upper entry (red-to-blue-to-black) gas flow to quiet things down ....
With the loud muffler setting I'm registering about 80 db at idle in the cabin (no sound insulation but some rear trim). No cats. Headers connecting to center muffler on loud setting. I'm going to add some HJS 200-300 cell cats and switch to the quieter center muffler port. My goal is to get down into the mid 50 bd range at idle without adding insulation or additional exhaust mods.
What's your cabin sound level like in the 964 on the quiet setting?
On my 964 Turbo I do not have anything like your setup. I use a GHL system that has one side muffler (in the rear haunches behind passenger rear tire). No cats, not even behind my wastegate on the drivers side. So when I go WOT & in overboost, the wastegate dumps the excess & it gets quite loud. But when I'm not up in the 7 lb boost range, its got a nice muffled growl.
The GHL muffler is not super loud like a Rarly8 muffler, but it's fine for my wife & I. I've never done a sound check with a decibel reader, so I have no idea what the numbers are there.
My wife & I do like it loud though,... so I have often thought of going to a more aggressive exhaust setup (but would still want to keep the heat exchangers around the headers for heat in the cabin). We use the car year round,... and of course if we really want something loud, we jump in the GT3.
I’ve added the cats and they’ve eliminated the drone. I also added vaccum valves to divert exhaust to either soft or loud gt3 center muffler ports. Issue: there is no difference in the sound level between soft and loud. The valves are working - I can see them move from one setting to the next. I purchased the Gt3 muffler used. It has no signs of damage or repairs. Anything that could be wrong with it?
I’ve checked inside the GT3 muffler with an endoscope and confirmed that the valve is opening and closing completely. A decibel meter detects no difference in the sound level between low and high flow settings and I can’t hear a difference. Any advice about how to quiet it down?
03-07-2022, 06:53 PM
Exhaust Noise
