3" mild steel exhaust with resonated test pipe and oval, straight-through Magnaflow muffler.
Hit 92.0dB from 50' away. Meter was sitting on the ground, FWIW.

Okay, probably a dumb idea, but I figured I'd ask here to see what other folks thought about it. How about putting a layer of Flex Seal (liquid) in the cabin? I think if applied in the front/rear footwell areas, it would help to reduce cabin noise and not be to bad to remove if it didn't work. Has anyone else thought about this?

I'd suggest selling the Evo and buying a BMW.

is this while revving at a standstill? I've never done this test. also, what is a straight-through muffler? is it built into the overall 3" diameter?

you'd probably be better off using dynamat... I don't know how much flex seal will do for nvh, I think it's just for leaks.

getting my resonator installed tomorrow. fingers crossed for decent results. honestly I'm expecting improvement but idk how much will be captured in a raw decibel reading vs overall decreased vibration along certain rpms.

Straight through mufflers = you can look through one end to the other. No chambers, no bends, etc. Least restriction but most noise.
I tested @ full tilt, 7kRPM in 3rd gear. It's the most load/noise I could get out of the car.

ahh, got it.

Okay, I finally got under the car, and man this vibrant piece is big. It's going to be a way tougher fit than I thoguht due to how closely the exhaust runs to the driveshaft. There's only one spot that's going to work, and I think angled at that. It is going to have to go slightly in front (actually, behind - hard to tell cuz that exhaust is different than mine) of where the resonator in the picture above is shown, I believe. Will be easier to tell when the car's on a lift.

if the piece doesn't work, i'll get the bottle style version to weld on instead

welder's looking... we're not sure if we can fit it, but fingers crossed... I think it's just gonna get too close to the driveshaft and body though.

unfortunately as I was worried about, the vibrant ultraquiet will not fit.

going with the 1795, which is a bottle shaped resonator. 18" long, with a diameter of 4". I lose some volume compared to the oval, but hopefully I get a satisfactory result out of it.

not too much quieter... doubt anything will show up on a db reader. it's smoothed out the tone and certainly quieter in some spots but overall nothing crazy. this setup is as quiet as i can get now without swapping out the cat for a mid muffler, which i am not willing to do

Thank you for sharing your results. Also, I believe the high flow cat will make a car quieter than a straight flow through mid muffler. So dont bother thinking “what if” .

Right now my current loud setup is :

Downpipe > Magnaflow 4” Diameter Center Muffler > Buschur SD Rear

I’m convinced that we cannot make a exactly as OEM quiet straightflow through setup. Only way to achieve that is by introducing restrictions in the exhaust stream. Obviously to make power we need to remove restrictions. So adding a bunch of straight through mufflers will quiet it down a pretty good amount for WOT standards but I’m going to have to add something in the mix for exact OEM quietness during non boost acceleration.

My plan for making it quiet as OEM:

Downpipe > Milspec 100 Cell > Magnaflow 4” muffler > Inline Boost Actuated Valve > Buschur SD Rear .

I’m going to drill a hole(s) on the plate of the boost actuated valve to allow the engine to breath because its not going to be a cutout but rather inline with the exhaust. Like the one MAPeroformance sells. But MAP’s item is electric motor activated and I some what prefer it to be Boost actuated so its all instantaneous .



After I do the above, I'm going to town on the interior of the car. I’m going to put foam, rubber mats and some sort of soundproof cotton padding all under the carpet.

I’m also doing a little research if i should paint the floor and trunk with either Rhino Liner and or with Underbody Rubberized Paint/coating . Your experience and opinions are welcome. I’m trying to stay away from Dynomat or Second skin stick on stuff.

By the way, what sound deadening mats do the OEM use that are stuck and hardened on the chassis floor ? I would really like to get some of that if they are not pricey .

I'm hesitant to go the actuated route, just because. I had my car out at autocross and someone commented that it seened barely louder than stock, so I guess that's good enough for me. I'm dailying a prius & a corolla, and my other race car is a stock Mini, so that may be skewing my experience a bit.

I have had the carpets off, there's little to no sound deadening. maybe a few rubberized mat looking things a few other bits, but otherwise nothing. I'm not willing to add weight to the car but the previous-previous owner def put dynamat in the trunk. it has been hell removing it, but most of it is off and not much impact on sound from there as far as I can tell.

Im running the tanabe medallion touring exhaust ---recently had to replace it with new, I cut out the resonator and put in the vibrant untraquiet at a slight angle. Doesn't hang down low--then Im not lowered that much on worx springs. Had it welded in, very quiet under 4k in any gear and you can whisper at 3k in the car and hear fine---exactly what I was after...at 4500rpm its letting you know its alive and well. No drive shaft issues or rattles.

got a pic of the setup under the car?