Love my exhaust sound and new stereo - how to quiet engine noise?

[jeffandpamsmith]

OK, I went with the Chuck Thorley Cat Back "stealth" exhaust. Less work to install, and there are so few Smarts where I am I didn't need the look of the dual centers to stand out. I love the sound, but it is much louder...in a good way. It seems the right amount of tone and volume to impress as a custom mod (someone who knew exhausts, but not Smarts complimented the sound when I started it next to him...it doesn't sound "too much").

Having said that, there is a large increase in cabin noise with it when the top is up. I have read and talked with both custom Smart pros and forum amateurs and the consensus seems to be not to worry about road noise, but I do wonder if using a very thick material would at least help if applied on the rear deck and behind the seats. Even an inch thick wouldn't mess up the look or storage functionality of the car, but if it helped with the volume, I would try it.

I did my boat years ago with stuff over an inch thick. I wondered about using that - or any car product made for max deadening, even doubled.

On a related note I finished my sound system. Its the nicest one I've ever had...and its in a 9' car...go figure.

Alpine PDX 4.1 amp, 2 channels bridged for JL sub box, Pioneer FH 800BT dual sized head unit. Focal 165A1 components. Had some 14 ga flat monster cable left over from a project so ran all new wires with it (double wires from amp to sub). OK maybe overkill, but it was fun. The flat wires ran well under carpet. Did the install without removing the front quarter panels (just fished the wire) and came in the same grommet the factory uses on the drivers side. Crossovers velcroed to the firewall on the drivers side (plenty of room and don't have to remove the doors to adjust). Amp under pass seat, removed sub from under driver seat so lost zero space in the car.

Fabulous sound, couldn't ask for more. Sounds great at all volumes. I can crank it up to concert level and quality with the top down on the interstate.

So I do have the volume to drown out the engine, and I consider the "sweet" exhaust sound a fair trade off for less quiet in the cabin with the windows up, but my wife would be more impressed (and I have to say I would like it too) if I could achieve significant engine noise reduction with aftermarket treatment.

If I can't, that's OK, but I have achieved so many goals already, I hope this can be tweaked too.

Has anyone tried to heavily shield the engine compartment to address just the added exhaust noise?

I thought of air induction too, but that is more noise. I would probably just replace the filter per Breathless' suggestion, especially if I could somehow do the "50 cent mod" and not actually remove the baffle chamber so it didnt show (and affect warrentee). I'm not convinced that air inductions by Smart Madness or Genius will not be a warrentee issue (I have an extended warrentee).

Finally, I want to put in a good word for 4smartcar.com. I know some here have felt they were rude or uncooperative. I'm fairly anal about asking questions, and although I could tell I was pushing him at times, he talked to me many times, gave me the best prices I found on everything...some by a wide margin. When I had technical questions, he let me talk to one of the installers in the shop. He suggested the Pioneer unit (which on research from Crutchfield, local installers, and forums on getting high quality MP3 copies to play in a car, was one of best units...plus it is flat out beautiful) I just wanted to tell the forum a tale of a good experience.

Even though I nagged him with several "question calls" before I even bought anything, he put up with me. He's sort of "curt" (in fact I thought he was from Brooklyn) but his advice was dead on about everything so far.

[John_H]

You can use sound/vibration dampening to affect the resonant transfer of sound through large, flat sections of metal or plastic. That's only a portion of the heightened sound you're hearing, much of which may be transferred on other than resonant modes. To get rid of those noises, what has the most effect is pure mass.

Are you ready to add some serious poundage to the back?

I wouldn't expect a couple layers of sound/vibration dampening material to significantly affect the amount of sound transferred, given the nature of the noise. But you could try it and see where it gets you.

[smart fortimo]

Then there is this upcoming--

finally got my exhaust and cold air intake installed

[jeffandpamsmith]

OK, I did get some material and talked to the audio guys at Cascade Audio. They recommended something called VB 4. I think its the same type stuff someone on the forum is using to make a barrier commercially, but his says its 1/2 inch thick, so he's added something. They sell a precut piece big enough for the entire rear deck, down the angle in front of the engine and 4" under the seat slides. They said I should try it under the carpet, which I did. They also said the stick-on damping would add maybe 10% better results, and I had some left so I did that too. That was the hard part. It has to fill the cracks and stick tight...its a pain. The actual mat stuff was easy.

I got very good results. I cant measure, but all I know is it made the noise from the performance exhaust much more subdued when the windows are up. Its still louder than stock, but now it just sounds good, not annoying.

If I had it to do over, or if I were to advise you...I would consider the premade mat that the forum guy is making. It will cost twice as much, but would cut sound as well, I'm sure (I wouldn't have done the ""fatmat" part if I didn't already have some...just go with the "lay on" foam and vinyl mass loading layer).

I like to DIY, and enjoy taking the Smart apart and doing things, but I would have spent less overall if I'd bought his and spent a little OT at work (where it's got AC!!).

Either way, I feel it was time and money well spent, as the only mods I wanted for the car were a killer stereo, and exhaust/intake upgrades. Now the performance mods don't degrade the stereo sound.

I love my car!