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Comment by amelius | Hacker News Reader

Isn't there a legal limit on the amount of dB(A) produced by any vehicle?

(Sweden situation). There's recurring inspections of any vehicle, binannually or something maybe for motorcycles. The HD people I know/knew, would change back to the stock pipes for inspection, because the loud ones were not legal to use. Then just change back again.

Or they just add/remove the DB killer (removing a small plug vs dismantling the exhaust)

With Euro4 and later exhausts this is no longer possible. Db killers need to be not removable, so you need to replace the whole slip-on.

Had a friend who put an Akrapovic on his MT-07 - DB killer is welded but once you drill through a small part on the weld you can remove it/put it back easily and the drill hole is covered by carbon shield so unless they disassemble the shield to check (and my friend had it like this for 5 years before selling IIRC) it was just pull out - put it back in for technical

Just curious, do these changes affect power output in either direction?

Generally, well designed bikes assume a certain pressure in the exhaust pipe and use it as a way to compute the internal combustion cycle timings, since it affects the movement of air and how long it stays and how fast it is likely to move on. So changing the pipes without doing anything indeed affects performance. That’s why most pipe changes usually also come with a reflash of the bike’s ECU so that the onboard computer can know new pipe’s air resistance parameters.

yes this is exactly what people do with modified cars too

I would love to see statistics on how many tickets are issued per year for these violations. I suspect zero.

USA long-time motorcycle owner here: agree. I believe there have been laws on the books for many years regarding noise limits, but they are (effectively) NEVER enforced. No-muffler-at-all ("straight-pipe") exhausts on V-twin (EX: Harley Davidson and its countless clones) are de facto standard (and for reasons unclear to me are accepted).

Also, aftermarket exhaust systems for motorcycles (99.9% of these being much louder than stock/OEM) are a huge business: I'd guesstimate that 50% of motorcycles sold in the USA soon (< 1 year old) end up running aftermarket exhaust systems; it's a standard first modification done by almost all enthusiast owners.

> it's a standard first modification done by almost all enthusiast owners.

Since laws are unenforced, it's also possible for dealers to upsell louder exhausts without even needing to visit a 3rd party shop.

About the same as for leaf blowers.

Anecdotally I've heard that they are mostly used as a way to stop riced out Japanese cars.

Not ppl on motorcycles. As someone who has run straight pipes across two major cities never had an issue. A bunch of motorcyclists don't even have licenses lol.

Several beach towns in my area have enacted local ordinances and have handed out citations for excessive exhaust noise.

Such laws are almost never enforced in the US.

The EPA prohibits modifying exhausts on motorcycles to exceed some decibel limit (80 something IIRC?), and this is stamped into the muffler on my motorcycle.

Yes, and many aftermarket sets say "not for road use". Harley Davidson was fined for installing them on too many daily drivers. https://www.reuters.com/article/us-usa-harley-davidson-lawsu...

(Switzerland here)

Yes, but they're surprisingly recent, so most vehicles are grandfathered into "may still make a shitload of noise" levels.

Yes. Look up passby noise.

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