I have bought a Monster 937 with decat + SC Project S1- it's really loud. Need advice on quieting it down without messing up the bike
Okay, I know I'm probably the odd one out here - most people post asking how to make their bike louder, and here I am asking the opposite. Feels a bit backwards but hear me out 😅
I have picked up a used Monster 937 recently and I'm loving the bike, but the exhaust setup is making my life difficult. Previous owner ran:
- SC Project S1 slip-on (db killer removed)
- Decat
- Custom map done on a dyno to suit the decat
It's extremely loud. Not "fun loud" - more like "I'm going to lose my license / scare every neighbor I have that germans came back (i live in Poland)" loud. I want to bring the volume down but I'm trying to figure out the smartest way without spending a fortune or making the bike run badly.
If it weren't for the custom map, I'd just slap a cat back on and run it with the db killer and call it a day. But I'm worried about how the map will behave with changes.
I spoke to the tuner who originally did the map and he said the map will be fine with a cat installed too, in his words "it's not a huge difference, I'd estimate around 5% more fuel." Wanted to get a sanity check from people who've actually done this.
Options I'm weighing:
- Easiest / cheapest - Just reinstall the db killer. I have it. Problem is I don't think it'll drop the volume as much as I'd like. Was thinking about adding some sound-dampening wrap around the db killer to take a bit more edge off. Anyone tried this? Is it safe in my case and does it actually drop down the volume noticeably?
- Middle ground - Put the cat back in and keep the current map. Tuner says it'll just run ~5% rich. Will I notice this in real world riding? Throttle response, fueling at low rpm, fuel economy, anything I should watch for? Could it trigger any fault codes or damage bike in the long run?
- Most expensive "proper" fix - Cat back in + return to the dyno for a fresh map tuned to the new setup. Mainly because the 937 is known for that low-rpm jerkiness and I don't really want to go back to the original map.
Has anyone here gone through something similar? Which route should I take, and is the "rich by 5%" thing really nothing to worry about long-term? Cheers.