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Learning how to build Lotus Seven replicas...together!
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 Post subject: Re: Quieter exhaust
PostPosted: September 3, 2017, 9:02 am 
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Joined: September 22, 2005, 8:12 am
Posts: 1505
Location: 4AGE in S.E. Michigan
Larry
Both of the spring type exhaust hangers and heat shield where made at WMC, "Whitt Motor Co.
A lot of GP bikes used springs for hanger, so I just copied the concept.
The only trick: the front hanger W/ the heim joint has rubber around the center of bolt and top/bottom where it passes thru the aluminum bracket. Other wise the bolt rattles against the bracket.
The add on muffler was an E-bay find. Only 12 or 13 bucks and it really mellowed out the sound.
I wanted to package the exhaust under the fender, but it just would not fit. I end up with 3.5" of ground clearance as it passes under the frame. Same the my engine sump guard.
Dave W


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 Post subject: Re: Quieter exhaust
PostPosted: September 7, 2017, 7:58 pm 
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Joined: August 27, 2005, 1:04 am
Posts: 1348
Location: Kamloops, BC, Canada
rx7locost wrote:
FYI, A few years back, I measured the road/wind noise at 45 MPH with a noise meter. I pushed in the clutch, and let the engine idle. The noise measured 90-93dBA at the driver's ears. (exhaust on passenger side) Hearing protectors are required above 90dBA fr the workplace and in some cases, as low as 85dBA. I know from experience that driving above 45 MPH will add significantly to that level as does a crosswind.

I always wore hearing protection on the highway ( in my outboard ear so I could still hear my passengers and traffic around me) and also carried a spare pair for any passengers. It was even louder on the exhaust side of the car.

I've never measured the wind or exhaust noise of my car, but I know it's loud. I have old school glass pack mufflers and turnouts in front of the rear fenders, and the exhaust actually isn't all that loud just cruising around town if you're careful with the throttle. On the highway I can't even hear the exhaust over the wind noise. Combined with my lack of windshield, I normally where a full face helmet if in going to spend any amount of time over 50mph. I think in going to start getting my kids to wear ear muffs when they ride in the car, as they're getting tall enough to be closer to the airflow now, and are starting to go for longer rides than just around the block.
Kristian

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