Air Filter Silencer from Walker

A Quieter Ride

We install a new High Performance Air Filter Silencer from Walker Engineering and use our sound meter to check the results.

Not long ago, Power & Motoryacht’s publisher Arnie Hammerman purchased a new 26-foot trailerable cruiser with a single 177-horsepower Yanmar 4BY3-180 diesel belowdecks. Being a family man, with a couple of sons and a wife who all enthusiastically agree that lower sound levels onboard are better than higher, he simultaneously ordered a High Performance Air Filter Silencer for his Yanmar from the folks at Walker Engineering, the idea being to upgrade the factory-specified air filter on the Yanmar for a quieter, more family-friendly ride.

air filter removal
First we removed both the factory-fit air filter and the crank-case breather hose.

“Wanna help me install it on Friday?” he asked, zeroing in on the last day of my most recent tour of the lovely Pacific Northwest.

Ever hot in the heels for comparison-type tests that may prove useful to readers, I shot back an alternative proposal. Why not run the new boat in the calmest water we could find around Hammerman’s home in Everett, Washington, collect sound data at various rpm, both before we’d installed the new Walker Silencer and after, and then report on our findings in the magazine. “We can even shoot some photographs while we hook the little jewel up,” I added, “and give the article a how-to slant.”

Air filter barbed fitting pops into the Silencer.
The barbed fitting pops quite easily into the Silencer.

Hammerman liked the idea. So we subsequently spent a wholly enjoyable Friday afternoon sea-trialing his new Walker Silencer onboard his new boat, although I need to append a caveat here concerning sea conditions, methodology, and our test equipment. For starters, the nearby waters of Possession Sound were only fairly calm (thanks to choppy, bow-slapping 2-footers briskly pushed along by 15-knot winds), so there was a good bit of extraneous noise to be heard onboard, particularly during the up-sea runs. And while we attempted to partially negate this state of affairs by recording (and averaging in) sound levels going down-sea as well, in a roughly reciprocal direction, it’s still the case that our data was recorded under distinctly real-world, as opposed to strictly scientific, conditions.

Attaching the breather hose
We attach the breather hose then tighten its clamp.

And then too, the Radio Shack sound meter we used to take our readings at the helm of Hammerman’s boat is a rudimentary tool, at least by comparison with super-sensitive, super-precise instruments that cost thousands of dollars. More to the point, based upon the findings of such instruments, Walker claims sound-level reductions between 2 and 18 decibels for some of its many, engine-specific Walker Silencers, depending upon the individual configuration of each unit used, the brand and type of engine it’s used upon, and a complex array of boat-construction and other design parameters. The claim, Walker adds, is bolstered by the fact that numerous engine manufacturers currently offer Walker Silencers as factory-installed options.

Tightening the main hose clamp for the Silencer.
And finally, with the breather hose secure, we tighten the main hose clamp for the Silencer.

The results of our testing were quite informative. While our device reduced sound levels by approximately 1 decibel (recorded on the A scale) at our lowest three data points, it cut sound levels by 2 decibels at 2000 rpm and continued to do so all the way up to 3500 rpm. Only at top end was there a negligible effect. 

These findings, I’d say, jibe with the fact that turbo whine on the 4BY3-180 kicks in at about 2200 RPM, according to Yanmar, and continues on up from there. Turbo whine, after all, is something the Walker Silencer is designed to address, at least in part. And I’d also say the findings jibe with the fact that the 4BY3-180 is an undeniably quiet engine as-is, so any gains in quietude from a sound-attenuating upgrade are likely to prove less significant than they might on a noisier engine.

Walker Silencer Test Results

factory air filter
Walker Silencer
800 73 72 -1
1000 65 64 -1
1500 69 68 -1
2000 71 69 -2
2500 74 72 -2
3000 80 78 -2
3500 82 80 -2
3800 82 82 0

The Walker High Performance Air Filter Silencer works, according to Walker’s vice president of sales and marketing Michael DeLillo, by balancing three separate factors—the appropriate amount of air flow through the unit; just the right type of sound-attenuating material inside; and finally, a geometry or shape that reduces or blocks certain frequencies, especially the whiny ones that seriously annoy human beings. “And remember,” DeLillo adds, “While we mostly sell silencers for engines with turbos these days, we also offer units for older, naturally aspirated engines as well.”

Now for the how-to slant I mentioned earlier. The entire job of installing our Walker Silencer took Hammerman and I about 30 minutes with little more than a single, slot-type screwdriver and a couple of stout hearts for tools. We began by loosening the stainless-steel hose clamp that secured the factory-installed air filter in place and then pulling the filter away from the circular flange on the after end of the turbo. Next we pried the crank-case breather hose loose from the side of the air filter, removed the plastic, splicer-type barbed fitting from the end of the breather hose (after removing another, smaller stainless-steel hose clamp), and squeezed one end of the splicer-type barbed fitting back into the hole in the side of the new Walker Silencer. The final step was the easiest of the lot. We merely pushed the entire Walker Silencer (now with the barbed fitting sticking out of its side) onto the circular turbo flange and tightened the large stainless-steel clamp we’d loosened earlier. Then we pushed the breather hose back onto the barbed fitting and tightened its stainless-steel hose clamp. 

My conclusion after all was said and done? While at first glance the benefits of adding a Walker Silencer to a relatively small, 26-foot test platform may seem a tad slight, a longer view paints a different picture. Given that the device reduces noise levels on an already rather quiet engine, it’s quite reasonable to expect greater things on noisier ones. And considering that our Walker High Performance Air Filter Silencer retails for approximately $250, a pittance considering the total cost of a freshly minted diesel-powered cruiser these days, I’d say it makes good sense to upgrade, particularly where friends and family are concerned.

This article originally appeared in the June 2014 issue of Power & Motoryacht magazine.

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