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The Conception of Mufflers with Exceptional Amplitude for M-8 Touring

The Conception of Mufflers with Exceptional Amplitude for M-8 Touring

Posted by Wiley Moody on Oct 4, 2021

M-8 Harley-Davidson

I’m sure the first thing you noticed about your new M-8 Harley-Davidson touring model is that the exhaust is very quiet. Many would say too quiet for a motorcycle that has been setting the standard of what an iconic engine sounds like. Of course, this is done by design by the manufacturer. All motor vehicle companies are bound by federal law and leave it up to the customer to make their vehicle non-compliant with federal emission and sound standards. This keeps the manufacturer out of trouble, or in H-D's case, getting into trouble again.

If you have previously owned a Harley-Davidson touring model, it was easy to achieve the throaty Harley growl and roar on a Twin-Cam or an Evo. But the Milwaukee-Eight inherently has a different tone altogether due to the head and valve configuration (4 exhaust valves vs 2 exhaust valves of the Twin Cam).

Plus, the sound you want is a little harder to achieve because of the catalytic converter in the stock header. It chokes off performance and sound, not to mention adding extreme heat to the passenger’s leg. But because of Harley-Davidson’s warranty procedures, it leaves you with little choice but to keep the stock header until the warranty has expired.

Touring BaffleTouring Baffle

In the meantime, what can be done to get better sound? A few manufacturers have designed baffles in their mufflers to give you the most you can get from the stock headers. The solution to get a better sound from the M-8 is much louder baffles than in previous systems. The bigger the baffles inside the muffler bodies, the more of the sound will reach your ears.

There is a trade off. The golden rule for Harley-Davidson has always been, "The better it sounds, the worse it runs." Let me explain.

Loud mufflers have less backpressure that some the “quieter” or more baffled mufflers. I put quieter in quotes because you can still get pretty loud mufflers that offer decent back pressure. If you’re looking for performance, the loudest mufflers probably won’t do it. 

The Milwaukee-Eight uses the back-pressure in the exhaust system to actually help move the exhaust through the engine quickly and to help prevent reverberation, or a shockwave moving back up through the pipes cancelling out big chunks of your torque curve. The M8 seems much more sensitive to changes in back-pressure than its predecessors.

After installing aftermarket slip on mufflers, you will notice a big change in sound, but not much in performance. That’s because you’re only opening up the end of the exhaust that delivers the volume and not adding any more fuel or air that makes the power. If you install a high flow air clearer kit, you will have to have the engine flash tuned by a Harley dealer to stay in warranty and to enrichen up your air fuel mixture your your engine doesn't run too hot, or too lean.

M-8 Touring Volume Chart

Today’s uber loud muffler systems exist because of the stock header you’re forced to use until the warranty has expired. Some manufacturers offer different size baffles as an option if the uber loud is too much for you or your passengers ears. When your warranty is over, the sky's the limit. You'll be able to decide on what fuel management would be best for your bike and also head pipes to gain performance and lose the heat of the cat. 

For example, TAB Performance offers their loudest Zombie baffles for the ultimate in volume, but also offers a 2.5” louvered baffle and 1.75” quiet baffle that you can select at check out. Not to be outdone, Penn Steel Works Rebellion slip on mufflers arrive with all three baffles in the box for you to custom tailor your sound and power as you see fit. 

Call 570-992-1113 if you have any questions about getting a set of aftermarket slip on mufflers for your Harley-Davidson.

Shop all 2017-2021 Harley-Davidson Touring aftermarket slip on mufflers here.