great thread

 

OK, so I used sqrt(gamma * R/M * T), where gamma is the adiabatic index, R is the molar gas constant, M is the mean molar mass of the gas mixture in kg, and T is the temperature of the exhaust gasses toward the end of the exhaust in kelvin (I used 400 degrees F, which is 477.6 kelvin).

This is sqrt(1.3147 * 8.31451/0.027925 * 477.5944) = 432.379 m/s for the speed of sound at the end of the exhaust. Anything I missed? This seems to be working better in the calculations.

 

The only way to know is to try it.

 

I'll probably be trying this next weekend

 

Please keep us updated on your progress.

I have a custom dual 3" exhaust and there is a ton of drone. I've been looking into making a pair of helmholtz resonators for it as well.

 

Will do. I had originally planned on doing it this week, but unfortunately I'm having trouble getting one of the nuts off on my ART pipes (it's stripped). Took it to a shop on Monday and they wanted to replace my entire header. I still think I can get it off with enough work, so that will be the first thing I have to get done.

 

Awesome, thanks!!

 

I don't understand a single thing in this thread

Moral of the story....pay Tony the $$$ and he'll do the thinking for you

 

How did you measure the exact frequency of your drone? Did you have access to an o-scope with a mic or were you able to do it another way?

 

I just used my iPhone. I took some recordings and emailed the files to myself, then used Audacity on my computer to find the loudest frequencies. There's also an iPhone app you can use to view it in realtime called SignalScope Pro, but I found that a little harder since I have to be driving while using it

You could probably also bring your laptop in your car and used that too, if you have a mic for it.

 

The Shockwave TDX2 is an awesome exhaust for sure, but I have a sedan and the options for it are very limited. Most of the sedan exhausts don't even sound as good as the stock coupe one. So for me, custom was the way to go. Plus, once I am able to get this working properly, I'll be able to apply it to any cars I have in the future for a drone-free experience

 

Sub'd for results

 

Just an update:

Still don't have the stripped nut off. I've bought a few different wrenches and sockets from Sears to try and get it off, with no luck so far. If it was one of the other 2 holes with a stripped nut and not the one with the stud it would be much easier. There's very little room to work with.

And I'm changing out my valve covers right now since they're leaking pretty bad, but once this is done I can work on the nut again.

My buddy who helped me build the exhaust has a turbo SpecV Sentra, so we'll probably do this for his car first. He wants an electric cut-out on his car, so the plan is to put it at the end of the resonator so he will have no drone with it closed, and he can still open it up when he wants it loud

 

I'm going to do the same thing with mine. LOL

We started on mine but have not put them on the car yet.

 

Nice! Did you do quarter-wave or helmholtz resonators? You gotta post up some pics.

I still don't have the stripped nut off my header stud This is really driving me crazy. Probably going to try and borrow a sawzall and try to chop it off.

Also, what frequency was your worst drone at?