trackslut

Yes yes yes I know this thread is missing teh turboz, but just bare with me if you can...

I have Goodwins 2.5 mid pipe with a cat and resonator. The axle back I built using a 2.5 inch 24x5x11 or something HUUGE magnaflow. The exhaust is quiet DB wise, pretty lacking on tone as well. But it drones like nothing Ive ever heard before. That inside your brain rattling resonating punching babies drone... Horrible... Anyways, My theroy here is that I'm not flowing enough to actually muffle the exhuast, its just kinda boucing around in there. Above 4k the drone goes away and something resombling sound emits from the rear of the car. Under that I want to kill myself. Now Ive had FM 2.25 rear section, Goodwins RS3 rear section, Dynomax VT for above 4.0L engines, and a 2 different dynomax super turbo mufflers on there. All of those vary from too loud, to too droney, and in the case of the VT, to rattley.

So WTF people? Any ideas? Thoughful inputs? Sympathy?

Oh yes yes.. I know.. Just put a turbo on there and it will get rid of that. Well I dont have the time/money/ambition/space right now for that so that's not fully an option.

Miater

Is the exhaust touching somewhere alone the line?

trackslut

Nope. i thought of that. But checked, and its not rubbing. Its not the soild mount exhaust noise, did that once, never again. Its just crazy amounts of low hertz drone.

nitrodann

how big is the resonator? stock headers? also 2.5 is far far too big.

Dann

trackslut

Stock header. Resonator is the one that comes on the RS3 exhaust. I think its only 8 inches tho. Cant be very big. yeah yeah.. too big. Thats what everyone said. I said Ill show them! FM has a dyno showing 2.5 really isnt that bad of an idea for NA cars however... But I take that with a grain of salt. It ended up being that it was avaiable, decently priced, and will work with a mild turbo set-up.

Do you guys think that a reduction in case size, say an 18 inch case instead of an 24 inch case might help drone with an increase in exhaust sound?

nitrodann

get a bigger hotdog.

Dann

Miater

What makes you say 2.5" is way too big?

fmowry

iTrader: (8)

Have you sounddeadened the trunk with Dynomat or similar? It helps.

trackslut

Currently running two moving blankets for soundet. Haven't had the chance to run through the car yet. Its on the list for winter projects since I need new carpet anyways.

I think I'm going to hack up the mid pipe, put in a 14x5 round magnaflow. Then V-band to the giant one. Then for track days I can swap rear sections out to a straight pipe with minimal bends. Sounds great on paper. But i'm just hoping the round with take car of that under 3k drone.

Leafy

iTrader: (1)

either a 14" long resonator, Or running a side branch resonator calibrated to remove the drone at the RPM you're experiencing it at. Google size branch resonator and it'll give you the math you need if you want to go that route.

trackslut

Well I checked that out. Started to do some maths, and then my head hurt. Ordered a 14x4 2.5 inch magnaflow. Ordered V-bands so I could toss on a straight rear section so I can be annoying when I want to.

Oh, and yes, pic's and vid's will follow for the three of you guys that care.

hustler

iTrader: (6)

( ͡° ͜ʖ ͡°)

Sean

iTrader: (12)

Had similar problem with my car when it was close to stock. I went thru about 8 different designs before I got it right. I did work at a place that made custom exhaust at the time so it was east to do. Long story short is like they said above new resonator but I also ended up adding a 2.5" schoenfeld muffler insert after the cat and before the resonator as well as a vortex cone after the resonator and before the muffler all that finally killed the resonance to make it manageable.

miata2fast

iTrader: (2)

I am a little suprised you are running a stock header. Is there a reason?

If you add a header, you will change the length of the straight section of pipe, which could have an affect on the drone characteristics. I said could, others may know if this is in fact the case.

However, I think you should consider installing the header of your choice before tackling sound issues. I really think it will alter how you tackle the problem.

trackslut

Car is an 01, so the stock header really isn't that bad. Main reason is that im a broke *** ****** ******. So yeah.. I'd love to have an RB header on there. But no monies.

From my experience they tend to deepen up the exhaust and make it louder. And thats exactly what I don't want.

Sean, I was looking at the Flowmaster DBX series muffler's since they have that "cone" design for the internals of the muffler. But I'm just not a fan of the sound, and they are 2x the price of a magnaflow. And its a Flowmaster... I'd never be able to tell anyone the brand of the muffler... Ick..

I wish Corsa would make a system for us. The one on my truck is amazing!

Sean

iTrader: (12)

The cone is great for disrupting the sound waves same thing the schofeild does. When I did the exhaust recently on my 2j I had a summit 3" resonator and a schofeild muffler to try out. The schofeild even though it is smaller and has no packing works better. Just needs to interrupt the sound wave and you will be good to go.

trackslut

Well if the system I'm planning still doesn't work, I'll pick up a cone and toss it in before the tip or something. I've seen them on summit pretty cheap before.