Product Review

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 retain performance.

The Issue:

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 rail, Gibson 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 performance

The inlet on the new Gibson Quiet Tip can either have a 3" slip-on or a 4 way collector.

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 tips.

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 level preference.

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

Testing:

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: