OK...I need some help here. About a year ago I had a custom exhaust put on the car. I loved the way it sounded and I have never regretted getting it. However, because it is my daily driver, the reverberation is very loud on the inside of the car. Am I getting old? Does anyone have any suggestions? Getting rid of the exhaust is not an option. Driving it around town is not a problem. I have mad a few drives to Oklahoma from Kentucky and after the drive my entire insides feel like they've been massaged by one of those vibrating chairs they sell at Wal-Mart.

I would love to hear what anyone has to say.

Thanks.

Ms. Perky? Thanks for the badge.

 

^ You are welcome...I'm sure you will get some feedback here, but you can also go to the Techie forums like Under the Hood and S2000 Talk, and/or do a search on "exhaust". You'll find LOTS of stuff.

 

What? What, what you say?

Some things to consider, from one of our expert owner's: Noise induced hearing loss is dependent upon: sound level measured in dB, spectral distribution-sound energy vs. frequency, and duration of noise. Permissible levels and durations are: 90dBA-8hrs/day, 92dBA-6hrs/day,95dBA-4hrs, 97-3hrs, 100-2hrs, 105-1hr, 110-1/2 hr, 115 1/4 hr. For short exposure of about 80 dbA for 8 hrs you may experience a temporary hearing loss but with continued exposure this will become permanent with the shift starting at about 3-6KHz. Sound level meters are rated in dBA because low freq. are weighted differently than high freq. in steady state noise due to the more dramatic effect on the highs. Examples of noise: Conversation-55 dB, Rush Hour traffic -80 dB, Truck/lawnmower-100dB, jet airplane-120 dB, shotgun-140dB. Impulse noises such as guns, should not exceed 140db. Levels above this can cause pain.

 

As I have said many times, all aftermarket systems have the dreaded "drone." Here is a summary of my research, which includes both my experience and thoughts and those of others.

The factory system has a short pipe welded to the main exhaust pipe just north of the resonator. Its purpose is to cancel out certain unpleasant frequencies. I can't recall the name of the pipe, but it is a recognized device used for canceling certain frequencies. Some of the engineers on here will be able to name it and perhaps explain it better than I, but the idea is that sound waves of certain frequencies will be cancelled out by traveling down this short dead end tube. Some think this cancels the dreaded drone. I'm not sure that this has bveen confirmed either in whole or in part. That pipe was the result of significant design work at the factory.

You will also notice that the rear mufflers on the factory system have what appear to be extra exhaust tubes that exit and re-enter at the rear of each canister. This additional plumbing continues inside the canister and allows the exhaust to be passed through the muffler twice and creates a much longer route for the exhaust to take before exiting the tail pipes. Some think this design cancels the drone. Again, this was the result of extensive testing at the factory.

Others have tried to add sound canceling pipes to aftermarket exhausts to cancel the drone with only limited success. Some might say the limited success is more imagined than actual. A baffle at the end of the system (right in the tail pipe) will reduce the drone significantly, but it will also reduce power below what is delivered when using the factory system. You can make the baffle removable so that it can be inserted for long trips and then removed when you want full power.

I made my own baffle and it was the result of a number of experiments with different diameter pipes. I ended up using exhaust pipe reduction sections (like you can buy at Pep Boys) until I found the largest diameter connector that would still reduce the drone. I assume you know what I am talking about here, but in brief, the reducer is a short section of pipe that has about a two inch length at one diameter and a two inch length at a larger diameter. The reduction section is about 5 inches long and you insert it small end first into the tail pipe. The big end of the reducer should be a sliding fit inside the tail pipe. Once inserted, you will need something to hold it in. I drilled a hole in the underside of my tailpipe about 1/2 inch in from the opening. I drilled all the way through the tail pipe and through the side of the big end of the reducer. I then removed the reducer and redrilled the hole in the reducer one size bigger. I then tapped threads into my tailpipe. Then I reinserted the reducer and installed a stainless steel screw from inside the reducer using a 90 degree bent screwdriver. PM me if you need better instructions. It can be difficult to visualize.

Another member of Vintage posted his experiments with sound proofing and he claims it was a success. I have not heard this car firsthand, but the member says others in his area have now copied his method, so it may well be valid. You would have to be willing to add sound proofing to your car, which adds some weight and is difficult to remove if you want to return your car to stock. It will also reduce road noise and reduce the sound you hear from your exhaust as I understand it.

In short, there is no easy way to eliminate the drone without either adding soundproofing to your car or engaging in a lengthy and expensive reasearch project.

Good luck.

Bill

 

Here's one link where a few sound proofing ideas are discussed.

https://www.s2ki.com/forums/index.php?showt...0&#entry5263689

Personnally I discovered a large part of the cabin noise comes directly through the transmission shifter area and by sound proofing the opening under the boot it made a terrific improvement.

 

I agree soundproofing under the console really helps. I also used some behind the rear panels. That took care of some more.

I really like what you did to your console.


fltsfshr

 

Thanks everyone! I appreciate the ideas and opinions.

Ken

 

Thanks. It definitely works for me. Here's shot which shows my inverted insulated boot.