My car came with a huge 4"-5" melon launcher when I first bought my car. Needless to say it was loud. The first day I could, I drove up to Tim's Custom Exhaust in Anoka to get a different muffler welded on. It was quieter, but it still droned. After doing some research a lot of domestic guys have had a lot of luck with Helmholtz resonators. G8, camaro, and some mopar guys swear by it. Most oem mufflers have a Helmholtz chamber built into the exhaust to help with drone. When an aftermarket exhaust is used in place, you lose that chamber. The basic principal behind the Helmholtz chamber is similar to noise canceling headphones. You find the frequency at which you want to tune out the sound and create an equal, but opposite wave to cancel the incoming one. This will, in theory, reduce the amount of sound you hear. Last night I downloaded a suit of sound analysis software and found the loudest drone happened between 3-3.5k rpm with a frequency of 90-100hz From the above internets, I get a chamber length of around 34.74in tuned for 95hz I would consider this a low estimate since the speed of sound increases depending on the temperature. The max length of the pipe could be as long as 62 inches (for a exhaust temp of 900F) So two questions. 1. Does anyone have a more accurate number for the temperature of our exhaust gasses 2. Does anyone want to help me cut/weld something together FOR SCIENCE!
Up to 62 inched? Pretty sure mid pipe isn't even that long. You on the north side of the cities? Could be the exhaust you have.
Yeah and I am sure my exhaust temps dont get up to 900F either. And yes I am sure its because of the exhaust I have + the fact that I own a wagon.
About 1600f at the header (usually tuned for this) slightly less at the downpipe (based off gauge readings), and usually about half that at the muffler after a hard run (based on a hobbiest grade ir temp gun). A lower tech solution some wagon/hatch owners do is sound deadening in the exhaust tunnel and/or hatch floor.
@Tash - I have two resonators. Not sure on exact size. I have 3" piping all the way through. And im down in savage remember?! @idget. Thanks for the numbers man. So lets say 750F after a hard run. Maybe half that for normal operating temps? After reading a g35 forum member who did this. He used exhaust temps closer to 300f at the tip. I am assuming that being a turbo car we might be running a bit higher. Sound deadening might be low tech, but its high $$ compared to welding a pipe to an exhaust. If you plan on doing it correctly. MLV + dynamatt material + foam for the ultimate solution. Work smarter not harder From the temps of 300F-500F and frequencies from 90hz-100hz I calculated a length from 40" to 50". Id have to take a look under the car to see how much space I got, but one could make some sort of variable length chamber with pipes and clamps to tune it based on what frequency you need to tune out. A 10" difference is kind of extreme though so I would maybe try to work with a 5" variable pipe for the "final" version. (if this ever comes to fruition)
That's what I thought, what made you go all the way up to Tim's? This seems like a lot to get rid of some drone, is it really that bad in the wagon vs sedan? Quieter exhaust maybe less drone. Q300, spt and such
Seems like a lot of work when it could be as simple as different mufflers/resonators. Vibrants are nice.
ARK uses a dual Helmholtz resonator setup on most of their designs: http://www.arkperformance.com/ProductDetails.asp?ProductCode=SM1301-0110G
I went to Tim's based off a friends recommendation.. and yes the drone is really bad in a wagon from my experience. Yeah.. it could be as simple as another muffler / resonator setup, but I like to tinker, and if it works... (and thats a big if) it could be a breakthrough for the subie community just like it has been for the G8/Camaro. If it doesn't work I can at least die knowing I tried And its really not "a lot". Look at the picture xluben posted.. Its just a capped piped welded onto a regular exhaust. I still have my melon launcher from when I bought the car. I can modify that as my alpha build. If it works I cam implement it on my current one!
Well, I'm interesting in finding out how it turns out! EDIT: But 5 feet long seems like a bit much, lol. Even 3 feet long seems like a lot...
yeah... I hear ya. Hopefully it will take closer to the 3ft range Here is a pic of someone doing it to a camaro. Hopefully I can find enough room back there to wrap this baby around.
That's exactly what a stock subaru resonator is (except covered with a heat shield and further upstream). I've only opened up a few but iirc GC impreza < GC Forester < GD sti < GD wrx in terms of length. Might be easier picking one of those midpipes up and rotating the flanges. That's what I did on my h6 rs swap anyway. I was looking at building one for my car but given the distance between the turbo and the rear bumper (18" or so), an x-pipe or crossover would be more efficient. A lot of the v8 guys do this as well (not really an option on your car though). As far as sound deadening goes, Ted (Gridlocked) is really cheap. Do people even buy dynamat brand stuff anymore? Does it come free with $200 monster cables?
True that on all points Sheen. Thing is I dont think subaru has any stock 3" piping Also I said dynamat material.. I know there are cheaper and better alternatives.. its just the most well known. Thanks for the suggestion though, I just pm'ed gridlocked!
I'm not saying you should do it, but as an option, an oem midpipe would be an easy and cheap fix. You can buy reducers for cheap at most autoparts stores and most exhaust shops will be able to expand pipe for you. Take a look at my 3.3rs thread to see how Nate (tstrboy) took the eg33 ypipe (1.5ish") and connected it to a wrx midpipe (quite a bit larger... 2.25"?). It shouldn't be very noticeable of a retriction if your muffler is baffleless and you're in the 300whp range.
