Can a 600 HP LS2 sand car meet
a 96 decibel sound limit?
Most folks tend to think that more noise equals more
power. We are going to test that theory, and see if we can reduce noise and
Off-Highway Vehicle Noise Emissions is an issue that
will soon affect not just motorcycles and ATVs at a few select locations, but
will also include sand rails. Noise emission laws are on the books in most
states, and enforcement is ramping up. Closures and restrictions on OHV use is
sweeping the nation, and excessive noise is often cited as the reason.
Every area that you ride in will most likely have a different
restriction. For example, Sand Lake Recreation Area in Oregon limits your
allowable decibels to 97. But at the Oregon Dunes Recreational Area, the limit
is 93 decibels. Sound has been a huge issue at the Oregon
Dunes National Recreation Area. If you exceed the limit, you could get
a citation. More importantly, sound violations could lead to more closures. The
riding area on the west is bordered by the Pacific Ocean, on the east US 101.
Between the highway and the sand and on the other side of the highway are
homes and communities. It only takes one excessively loud OHV to give all
users a bad name and increase the pressure on the Forest Service to close more
sand to motorized recreation.
In California's noise standard for off-highway motor vehicles
was 101 decibels, one of the most excessive in the nation. AB 2274 reduced the
level to 96 decibels, consistent with the federal standard for manufacturers.
In Michigan, the limit is 94 decibel at the Silver Lake Dunes.
Like it or not, noise restrictions are here to stay.
Since V8 engines have become so popular, and can be quite
loud, we are going to focus our attention on GM LSx engines. There are several
options available now to reduce the amount of noise produced.
Noise Reducing Options:
In general, longer exhausts systems with bigger mufflers are
going to be the quietest. But when it comes to exhaust for sand cars, the
biggest problem is lack of space.
Rear-engine bolt-on: If you have a rear-engine LSx sand
Performance Exhaust has introduced a bolt-on header and tip that shows some
promise. In their tests, a LS2 achieved 95 decibel. The 5" tip will be available separately if you are building your own exhaust.
Gibson's New Quiet Tip - Designed to reduce noise emissions and increase
The inlet on the new Gibson Quiet Tip can either have a 3" slip-on or a 4
Doug Thorley Headers has slip in Quiet Module Inserts that have a OD of 2
15/16". We will be testing a set of these connected to our Camco
Rear-engine custom exhaust: If you are willing to spend
a bit more, a custom exhaust can be built to match your chassis and sound
Dual in/out muffler like the one from Magnaflow shown below
offer a fairly tight package with generally lower noise levels.
Custom LSx exhaust from Scotty's Muffler - Dual in/out
Gibson Performance Exhaust also has a universal muffler that can be configured
with single or dual inlet and outlet.
Mid-engine custom exhaust: Mid-engine setups have
a bit of advantage over the more common rear-engine because of space. With the
engine farther forward, there is more opportunity to have a longer exhaust.
Some results also show that a two-into-one exhaust will increase performance,
while also lowering noise levels.
Custom LSx mid-engine exhaust - two into one
The official way of testing DB limits is defined by “SAE
J1287”. To do it the approved way as set forth by the Society of Automotive
Engineers, you need a sound level meter and calibrator, a sound level meter
windscreen, a tachometer, and a tape measure.
At the Oregon Dunes for example, the decibel meter is held 20
inches away from the exhaust output, and at a 45 degree angle.
Mid-Engine Video Clips with Sound:
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