No more drone!

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gtxdude

gtxdude

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Took 65 Dart in last week to take Flowmaster 40's off and replace with Magnaflow's to get rid of drone. First off the Magnaflow's sound great, very mellow but nice when you stand on it. Trouble was I still had a drone but now at 40 to 50 in the 2000 to 2300 rpm range, we're in town so there's alot of driving around that range. Went back to shop and they put a j-pipe (sort of) on exhaust at back of system. Not enough room behind mufflers so he went behind gas tank and tucked pipes up high. Well it sounds great!!! I couldn't believe it and kept waiting for drone to come back on test drive. I was kind of sceptical at first but now a believer in j-pipes. Car sounds great and my ear drums are no longer vibrating at certain rpm's. It's a 318 mild build so nothing crazy but couldn't get rid of drone till now.
IMG_20170711_131222753_HDR.jpg
 
Are those cross pipes connected to each other (flow wise)? I guess they let the exhaust flow under the car to some degree?? Otherwise it looks pretty cool if it solves the problem.

Treblig
 
Pipes are individual for each side. and capped. I guess that allows the sound waves to go down pipe hit cap and when it bounces back it neutralize's sound waves. All I know is that it works.
 
That is known as a Helmholtz Resonator and work very well when done correctly.
 
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just out of curiosity .... how did the helmholtz effect the tone of the exhaust from outside the car?
Quieter ? ......No Difference?
 
I've never seen that done that way on a car before, but they do work extremely well if done right.

Buell motorcycles used them extensively on intakes and exhausts, and if you've ever wondered what that dead end pipe was on a late model oem intake......helmholtz resonator.

How long are those?

Thank you for sharing!
 
Have seen articles and pics of those the all claim they work well.

Can you see them from behind the car?
 
jos51700 said:
I've never seen that done that way on a car before, but they do work extremely well if done right.

Buell motorcycles used them extensively on intakes and exhausts, and if you've ever wondered what that dead end pipe was on a late model oem intake......helmholtz resonator.

How long are those?

Thank you for sharing!
Click to expand...
2" pipe 20" long. They have a formula they use depending on what your rpm is when drone is the worst. He showed it to me, but it was all Greek to me.
 
abodyjoe said:
Have seen articles and pics of those the all claim they work well.

Can you see them from behind the car?
Click to expand...
Can't see from behind car unless you get down to look. It looks like back of gas tank unless you look really close.
 
They use them on modern intakes. People always ask about them when I show them the engine bay.
 
gtxdude said:
2" pipe 20" long. They have a formula they use depending on what your rpm is when drone is the worst. He showed it to me, but it was all Greek to me.
Click to expand...

Be a neat formula to have. Snap a pic and post it when you go back to tell him how much you like it.

That's a clean install, I'll say that.
 
Do you know of a wee site/page that has the math and science of this stuff?
 
It works better to measure the drone frequency instead of trying to calculated it or experiment on tube length since is can be different. Mine was 125hz and another guy posted was 105hz. The thread gtxduded posted has information on the phone app to use to measure DB verses frequency and a web site to calculate tube length. I see the website isn't valid anymore.
 
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