EPA exhaust noise notice - good muffler?
- Thread starter ocyrion
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clone
self employed bum
Looking forward to the specs as I'm still um and aring over buying one
JETGSR
CAPTAIN BURRITO!
just tested mine ... 106db thats with a dumpy cat and largest cannon I can fit under the back.
it idles at 88db
I actually think the clutch rattling (twin plate) is almost as loud as the exhaust.
it idles at 88db
I actually think the clutch rattling (twin plate) is almost as loud as the exhaust.
ONPSI
10 second monster
You're as loud as mine haha
ONPSI
10 second monster
So quiet as a mouse now..well almost just gotta book it in to clear the defect now.
I'm currently running an active exhaust system which regulates my exhaust valve based on a few factors. Modes i can select are:
1. Exhaust back pressure (using a pressure sensor after the cat but before the exhaust valve). This allows me to define the desired exhaust back pressure and the computer well attempt to open/close the valve to obtain this. As you varex guys are aware, the car runs massive back pressure when the valve is closed. Quite yes but bad for gaskets and engine when giving it a little. So this system will keep it as quite as possible without sacrificing performance.
2. Tps input. The system also uses tps to open the valve. So if i suddenly floor it, the valve will fully open. It will close a few second after i close the throttle (Definable). Not instantly simply because you don't want it to close right after just in case you plan to get back on the gas again (good for cornering etc). This works with the above mode.
3. Fully open. This simply disables the controller and allows full open exhaust flow.
4. Fully closed.
Imo, the Varex is good but the electric motor will not be as reliable as a mechanical one. The valve on mine is controlled with an actuator/arm. Similar to an internal Wastegate actuator. It is vacuum controlled so it can be fully open at idle. Works on NA cars also.
The Varex twin tip is basically one input, two output. One output is baffled, the other has a valve and is straight through.
Pretty much a straight pipe when fully open.
I lost about 30kw going from a 3" side pipe to a full 3" exhaust without the cat. That's why i changed my exhaust system.
1. Exhaust back pressure (using a pressure sensor after the cat but before the exhaust valve). This allows me to define the desired exhaust back pressure and the computer well attempt to open/close the valve to obtain this. As you varex guys are aware, the car runs massive back pressure when the valve is closed. Quite yes but bad for gaskets and engine when giving it a little. So this system will keep it as quite as possible without sacrificing performance.
2. Tps input. The system also uses tps to open the valve. So if i suddenly floor it, the valve will fully open. It will close a few second after i close the throttle (Definable). Not instantly simply because you don't want it to close right after just in case you plan to get back on the gas again (good for cornering etc). This works with the above mode.
3. Fully open. This simply disables the controller and allows full open exhaust flow.
4. Fully closed.
Imo, the Varex is good but the electric motor will not be as reliable as a mechanical one. The valve on mine is controlled with an actuator/arm. Similar to an internal Wastegate actuator. It is vacuum controlled so it can be fully open at idle. Works on NA cars also.
The Varex twin tip is basically one input, two output. One output is baffled, the other has a valve and is straight through.
Pretty much a straight pipe when fully open.
I lost about 30kw going from a 3" side pipe to a full 3" exhaust without the cat. That's why i changed my exhaust system.
4piknup
master of none
Good one baz. I love that you have the back to back tests of what works and what doesn't.
So your muffler is similar to the bimodal gts Holden mufflers. I looked at these and didn't want to run a vacumn line the full length of the car, and it will need to be plumbed to either a vacumn tank or into the brake booster causing other issues if there is a leak.
I would want to change the actuator to a pressure type rather than be hunting for vacumn when there is 30psi in the manifold.
It would be cool if you could trigger from a airflow setting as air in would be relative to air out...
I missed out on a old Varex that was twin in and out and had a motor and a butterfly on each pipe. With some home brew electronics hardware I'm sure you could run either or both butterflies open or shut.
I think the newer dual in and out Varex run a baffled muffler on 1 pipe and straight through on the other. I like this system as it allows a large muffler volume with the butterfly closed, and big flow of a 3" muffler plus a open pipe as well.
Just for ease, say the baffled 3" part flows 100kw and a open pipe flows 200kw, then the twin innout will flow 300kw as it adds a second pipe rather than just changing the flow through the one pipe.
I will be looking at going for a 3.5" system (maybe 4") into a twin 3" in and out Varex. And trying to use the factory ecu boost control to trigger the Varex into full noise. (using a ebc to control the wastegate).
So your muffler is similar to the bimodal gts Holden mufflers. I looked at these and didn't want to run a vacumn line the full length of the car, and it will need to be plumbed to either a vacumn tank or into the brake booster causing other issues if there is a leak.
I would want to change the actuator to a pressure type rather than be hunting for vacumn when there is 30psi in the manifold.
It would be cool if you could trigger from a airflow setting as air in would be relative to air out...
I missed out on a old Varex that was twin in and out and had a motor and a butterfly on each pipe. With some home brew electronics hardware I'm sure you could run either or both butterflies open or shut.
I think the newer dual in and out Varex run a baffled muffler on 1 pipe and straight through on the other. I like this system as it allows a large muffler volume with the butterfly closed, and big flow of a 3" muffler plus a open pipe as well.
Just for ease, say the baffled 3" part flows 100kw and a open pipe flows 200kw, then the twin innout will flow 300kw as it adds a second pipe rather than just changing the flow through the one pipe.
I will be looking at going for a 3.5" system (maybe 4") into a twin 3" in and out Varex. And trying to use the factory ecu boost control to trigger the Varex into full noise. (using a ebc to control the wastegate).
Jack,
I am running a one way valve right after the intake manifold which then connects to the hose to the actuator. The long length of the hose acts as a vacum tank so to speak.
Rule of thumb from my experience and other cars I've seen on the dyno is:
3" exhaust is good for under 300kw.
3.5" exhaust is required for 300kw plus.
A simply way to test is to connect a boost gauge to your exhaust system before your muffler and measure the pressure on full boost.
You'll also see alot of XR6T make easy 300kw at the wheels on a 3" system.
Anything above needs a bigger system.
I've seen stock XR6T's make 250 easy just on a flash and boost.
My first hand experience.
330kw with an exhaust that vented under the steering rack (3" turbo to valve).
No other change except exhaust - 270kw with a full 3" exhaust with a hi flowing metal cat (Magic CAT) and varex twin tip muffler (3" in, 3" out dual).
Removed cat and replaced with straight pipe - 300kw.
Upped the boost from 24psi to 30psi - 330kw.
All on the same day. Same dyno.
I'm now on a 4" exhaust and am finding it difficult to reduce the volume of the exhaust even with the valve simply due to the size of the pipe (echo).
I think in order to obtain a quiter exhaust, I'll need something to absorb the vibration or harmonics. Maybe a high temp dampening rubber at the front of the exhaust somewhere. Although it does sound good, it would be hard to hide from the po po.
I am running a one way valve right after the intake manifold which then connects to the hose to the actuator. The long length of the hose acts as a vacum tank so to speak.
Rule of thumb from my experience and other cars I've seen on the dyno is:
3" exhaust is good for under 300kw.
3.5" exhaust is required for 300kw plus.
A simply way to test is to connect a boost gauge to your exhaust system before your muffler and measure the pressure on full boost.
You'll also see alot of XR6T make easy 300kw at the wheels on a 3" system.
Anything above needs a bigger system.
I've seen stock XR6T's make 250 easy just on a flash and boost.
My first hand experience.
330kw with an exhaust that vented under the steering rack (3" turbo to valve).
No other change except exhaust - 270kw with a full 3" exhaust with a hi flowing metal cat (Magic CAT) and varex twin tip muffler (3" in, 3" out dual).
Removed cat and replaced with straight pipe - 300kw.
Upped the boost from 24psi to 30psi - 330kw.
All on the same day. Same dyno.
I'm now on a 4" exhaust and am finding it difficult to reduce the volume of the exhaust even with the valve simply due to the size of the pipe (echo).
I think in order to obtain a quiter exhaust, I'll need something to absorb the vibration or harmonics. Maybe a high temp dampening rubber at the front of the exhaust somewhere. Although it does sound good, it would be hard to hide from the po po.
4piknup
master of none
Baz,
So if we say a 3" pipe is fine on 300kw. A 3" pipe is 7.06" square. So delivers 42.5kw/square inch
A 3.5" pipe is 9.62" square so will handle 409kw.
A 4" pipe is 12.55" square so will handle 534kw.
Just a rough estimate.
Old hot rodders used to run 300- 500mm of copper pipe in their exhaust to soften the note.
But I've never heard it
So if we say a 3" pipe is fine on 300kw. A 3" pipe is 7.06" square. So delivers 42.5kw/square inch
A 3.5" pipe is 9.62" square so will handle 409kw.
A 4" pipe is 12.55" square so will handle 534kw.
Just a rough estimate.
Old hot rodders used to run 300- 500mm of copper pipe in their exhaust to soften the note.
But I've never heard it
ONPSI
10 second monster
LOL Jack no need to make it sound so technical 
Baz: Bigger exhaust will always be louder, You can try to shut it up but then again you're only restricting it aren't you. I've got 3 baffle plates in mine at the moment to get it under, Lucky I have V-band as it has made what could have been a pain in the arse matching flanges an easy job with a hole saw I have sound deadening in my boot so internally my car is pretty quiet until you hear it from behind or hear me coming down the road.
Baz: Bigger exhaust will always be louder, You can try to shut it up but then again you're only restricting it aren't you. I've got 3 baffle plates in mine at the moment to get it under, Lucky I have V-band as it has made what could have been a pain in the arse matching flanges an easy job with a hole saw
I have sound deadening in my boot so internally my car is pretty quiet until you hear it from behind or hear me coming down the road.
khubner1
Moderator
baz you may need to add sections of pipe 4.5' round further up to cause the gasses to slow all the will be is a 10 - 20cm peice of larger pipe bofre returning to 4" and continuing to the muffler.
Rockabilly
Well-Known Member
Got away with my dumby tail pipe this morning during a random breath test.
I was asked when am I getting the hole in my exhaust fixed ? Hole I asked,
what do you mean ? No exhaust is coming out your tail pipe he said. You must
have a huge hole in your exhaust sir. Without laughing, I told him the twin
exhaust pipe next to the old original tail pipe is the new muffler that the
exhaust shop fitted, because my old muffler was too loud. Oh he said, I'll
have another look & can you rev it a bit so I can hear how loud your new
muffler is. Ok sir, you're right to go. It looks fine & sounds ok. Had a good
laugh up the road a bit. I knew an osifer would bust me one day, but telling
me I had a huge leak cracked me up ;-)
Cheers !
I was asked when am I getting the hole in my exhaust fixed ? Hole I asked,
what do you mean ? No exhaust is coming out your tail pipe he said. You must
have a huge hole in your exhaust sir. Without laughing, I told him the twin
exhaust pipe next to the old original tail pipe is the new muffler that the
exhaust shop fitted, because my old muffler was too loud. Oh he said, I'll
have another look & can you rev it a bit so I can hear how loud your new
muffler is. Ok sir, you're right to go. It looks fine & sounds ok. Had a good
laugh up the road a bit. I knew an osifer would bust me one day, but telling
me I had a huge leak cracked me up ;-)
Cheers !
4piknup
master of none
Only cause you are such a gentleman.
Random breathe tests are a farce. The Police use that 'excuse' as a means to get people in modified cars to pull over so they can go over them, without being accused of 'targeting' or 'discriminating' against modified cars.
evo-gsr
Well-Known Member
Agreed on that one Rob.
khubner1
Moderator
I wounded if there is a way to argue that the purpose of the stop was for a random breath test and that the officer was only able to issue said test.
Eg disco disco
Good evening sir/madam we stopped you today for a random breath test as a result we require you to provide a sample of your breath.
You come ok now we are going to conduct a vehicle inspection
Officer you state the purpose of the stop was for a random breath test I have complied and would like to be on my way now.
You would probably be stopped again very quickly for a vehcle check if it worked though
Eg disco disco
Good evening sir/madam we stopped you today for a random breath test as a result we require you to provide a sample of your breath.
You come ok now we are going to conduct a vehicle inspection
Officer you state the purpose of the stop was for a random breath test I have complied and would like to be on my way now.
You would probably be stopped again very quickly for a vehcle check if it worked though
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