Db killer out = less low end power?

[bob795]

Hi guys,

Hopefully it's the right forum to post.

I just bought and installed Leo Vince One evo II carbon slip-ons. I removed the db killer to try the sound without it and see if I like the sound. I rode it this morning to the office, and found out that it was LOUD. Much louder than I expected.

But there's another thing that I notice. I noticed that I lost low end power. I mean I ride this bike for quite some time now, and have gotten used to it. But this morning I noticed something was different, it felt like I had to rev to higher rpm to get to a speed which previously I could get to at lower rpm.

Is it real ... or is it just my imagination, which is caused by the fact that the bike is louder so naturally it feels like it revs higher than before?

[Dirty Duc]

The real answer: Your ear is tuned to a specific level of noise and equates that to a specific speed.  You changed the noise level, and now have to adjust your ear to the perceived RPM (it's really the same, just noisier).

That said, there might actually be less low end power available.  This is hard to quantify without scientific dyno results.  Scientific in this case means, same dyno, same operator, same equations for adjustment.

[J5]

quite possible

without the db killers in the exhaust could be more free flowing and this may
cause your bike to run lean and less power

[Raux]

buy earplugs. re-assess

[brad black]

some of the dyno runs i did with my 600 showed more power at the very bottom end with std mufflers, and you could feel it too when getting off the line.

same with my 750, more power under 3,500rpm with std mufflers all else as was.  hard to tell on the air/fuel, as with the std mufflers you tend to get a lagging signal at the mufler exit.  last two graphs of this report (right at the bottom) http://www.bikeboy.org/brads750m.html

[SpikeC]

 The exhaust has no effect on the rpm/speed. Removing the restriction of the Db killers will reduce low end torque, but the rpm at speed is set by the gearing.

[bob795]

Thank you very much guys.

I decided to put the db killer back in because it set off cars alarms  

Last night, when I started the bike in the parking lot at the office, the sound set off a couple of cars alarm. It's quite embarrassing for me. I park my bike at the basement parking lot which is parking lot for cars, instead of at the motorcycle lot outside. Last night when I left at 8 pm, there were not many cars left so only two got their alarms set off ... had there been more cars I guess it would've been really interesting

Brad black, I enjoy reading your site   brings back memories of my sportster days when I did many dyno runs to get my sportster run as good as possible  

[Raux]

try a straight 2 into 2 with no db killer 
they heard me about 5km away in the valley 

[ccm900]

Give it a week or 2. I just did the same thing but went the other way around, onto pipes WITH db's. I though I lost a bit of power too. After a few weeks it feels normal again. Probably my ears just adjusting

[Howie]

Assuming you are still running the O₂ sensor I doubt your low RPM small throttle opening performance is affected.