I thought this would best fit in this catagory instead of my build log. I have been trying to quiet my Locost down. In that effort, last year I purchased a pair of
Harley Davidson Touring muflers. I recently purchased a sound meter for some testing. This last week, I went about fabricating a splitter to run the 2 mufflers in parallel. I thought that the flow would be a problem when used with my rotary engine.
Since today was Father's Day, SWMBO volunteered to be my test engineer. So here are the results of a day's worth of fabrication and a few hours of comparison testing. All cockpit measurements were taken in the center of the car, about head level and slightly forward of our heads so we could read the meter. Note that this is an eBay meter that cost ~12 bucks, so absolute levels may not be exact. However realtive numbers should be, well, relative.
Attachment:
dBA.JPG
What I can see is that the Touring mufflers may be slightly quieter as measured from the street. However, internal to the cockpit, they are definitly louder. The difference in cockpit numbers are probably due to the different exhaust directions. The original muffler is directed low and away from the car. The
Harley mufflers, due to their preconfigured condition, were pointed toward the rear fenders, slightly outward. My passenger/test engineer definitely noticed a difference in heat rolling into the car, much favoring the original setup. Heat conducted into the cockpit from the chassis rails were more noticable too with the
Harley mufflers. She also noticed the
Harley mufflers were louder to her.
I during the drive testing, I measured road noise by pushing in the clutch and coasting at idle ~45 MPH. Those readings were around 90dBA. That is road, tire and wind noise.
Just to check what would happen if I used just one muffler, while idling in the garage, I blocked the end or the lower muffler. There was no measurable noise difference. I then blocked the upper muffler, and there was an immediate 5dB reduction in noise. From that short test, I think that one of my mufflers are shot. If all other testing was positive, I would source another touring muffler and retest. I expect it would be quieter still, maybe by ~3dB. But I don't expect any heat difference. And we can't have any of that! Due to the passenger heat, the cockpit noise problem and the issues with redirecting the exhaust on the
Harley mufflers, I don't think I'll continue any more tests. I don't care to spend another 50 bucks to get more mufflers for further testing just for you blokes.
For comparative testing, I measured 15 random cars driving back and forth in the same setup as my 30MPH drive-by test. They measured from 61.6 to 77.6dBA and averaged 65.3dBA. Most of the noise was primarily tire noise by my estimate. My Locost averaged 85dBA! I guarantee that was exhaust noise.
Ask questions, comment away or take this test data and build on it. Your choice.
Happy driving.....
Attachment:
perforated original.JPG
Attachment:
rear original.JPG
Attachment:
rear harley.JPG
Attachment:
harley splitter.JPG
_________________
Chuck.
“Any suspension will work if you don’t let it.” - Colin Chapman
Visit my ongoing MGB Rustoration log:
over HEREOr my Wankel powered Locost log :
over HEREAnd don't forget my Cushman Truckster resto Locostusa.com/forums/viewtopic.php?f=36&t=17766