Wow, you lost me after "So in the name of science..." lol i didn't know we had to be rocket scientists to work on exhausts!

 

I need a drawing. Words taste like pickles today.

 

FrenicX

The exhaust dumps out the side behind the rear wheel.

 

You don't have to be Rocket Scientists, but it's cheaper!

You can come up with all kinds of ideas, mock up some stuff, try again, and keep going till it works, or you can put pencil to paper and come up with one or two ideas that "should" work and try them.

Guys that do it all the time will have good ideas before they start the trial and error stuff. Duffers like me will put the science to work before they pull out the tubing bender.

 

The dynamics of exhaust systems have been largely ignored by most people. The average driver either settled for whatever came from the dealership, muffler shop, or did a custom job for sound only. By just piecing the system together, you can run into consequences like this buzzing/drone as well as power loss - especially in a V8.

The term "tuning" as applied to exhaust systems isn't new, but it's not well understood - essentially, it's the methodology used to build the exhaust in such a way that it can scavenge the exhaust gases from each cylinder in time for a clean mix of fuel/air going in. There are quite a few "easy to digest" write-ups that can be found on the internet.

Although my background in engineering isn't in this particular field, mechanics has always been a hobby of mine & I did experiment with exhaust systems quite a bit a few years ago - mostly with header fabrication. I have worked a bit with the rpm dependent buzzing/droning aspects and although I find the article that DM_kota is referencing to be interesting, I have found that varying some of the other variables to be effective as well. A break in the pipe length (using a piece of flex pipe), change of pipe diameter, repositioning of the muffler, etc. This is done to change the potential resonant frequency to which the pipe will respond (sort of like a tuning fork).

 

Here you go pickles


This isn't my field either, but most of the time, the suggestions I find on the internets are just slapped together, or the comglomeration of 2 or 3 different opinions. I try to make my own and put them all together for everyone to see. I find that I sleep better at night knowing some guy is in his garage later than he should be due to some "engineer on the internets" giving him and idea.

the other variables of change (pipe bends and diamaters and such) I have thought about, and for me, this one seems the most do-able. I am an engineer, so this kind of stuff is fun to me, especially when it works.

I got the pipe yesterday at a midas, I told them what I needed and they said the paperwork to write the labor and pipe up was more than the cost of the material. He told me just to refer some buisness his way and we will call it even. ( o I guess I will bring my struts in when come time to swap the springs) I got 3 feet of 2.5" pipe, same as my exhaust.

so hopefully I can chop into it sometime soon. I will keep you posted

 

[quote=Alfons;2707450]
Although my background in engineering isn't in this particular field,[quote]

Engineering is a problem-solving method! Most of us (especially old-skule) can take formula A from fluid dynamics and apply it to create formula B for mechanical impact . . . .

I might not be efficient (work wise) at electrical and mechanical engineering, but when I get a report from one of those guys, I can understand it and talk to my clients in a way that makes sense to them.

 

Since you're cutting into your pipe anyway, why not just try inserting a very short piece of flex pipe into the spot you'd be inserting your other pipe and see if your resonance is still there? By doing this, you should have altered the frequency to which the pipe responds and might save you a bunch of work.

 

Hey DM

Here is a link u may want to check out

http://forums.corral.net/forums/gene...tely-gone.html

 

So I have been working on the pipe, a little slower than one would hope just because of my busy schedule. I took the pipe that I had bent and took a grinder and notched it to match the pipe that I would weld it to.

I started thinking some more about the length of the pipe, and went back and tried some more numbers for the speed of sound in teh exhaust. I plugged in 200 and got 1260 ft/s and plugged in 400 and got 1430 ft/s. This would have quite the effect on my resonator length (difference of 9 inches)

I then tried to figure the max length I would need and the min length I would need based on my max and min temp w/ the freq of the drone. I also downloaded another app to see if I could get a more specific reading on the drone.

200° 300° 400°
(v)s 1260 1345 1430
Hz
110 34.4 36.7 39.0
115 32.9 35.1 37.3
120 31.5 33.7 35.8
130 29.1 31.0 33
140 27 28.8 30.6

I came to 29.1" and 37.3" long

I had also read somewhere that you could just measure the length of your tailpipe from muffler to tip and divide it by 2 and that would be a good starting point.

My exhaust measured 67 inches long; so half would be 33.5 So that will be my starting point and I will adjust from there.

I went to Advance and bought 2 - 2-1/2" exhaust sleeves for being able to make varying lengths or my pipe. I cut the resonator 6" short of the min length. Then welded my "sleeve" on it with the other part of the pipe so I could adjust length

After enough trial and error hopefully I will find the length that will cancel it out. Its warm this week so I will see if i can get it done and get some pictures up.