BPP Center Exit Exhaust too loud? Here’s a mod.

[Lgaruti]

I like the look of the BPP center exhaust but found it a bit too loud for every day driving. I measured 94db four feet back from the exhaust and 90 db in the cabin at idle. 50 mph the cabin varied between 92 – 96 db noise level (road noise + exhaust). Just too much for me.
After the mod. the cabin measured 84 – 86 db and the exhaust four feet back at idle was 92 db. It still sounds great but not overly loud.

Gas mileage and performance is yet unknown as the inserts do add some backpressure. The smart seems to have a little more bottom end and less top end over 6000 rpm.

Here’s the mod:

Purchase (2) 4” long exhaust baffles for a 2” motorcycle exhaust pipe. They are available via the internet and cycle shops.
Purchase (2) 1 ¾ id to 2”od exhaust adaptors. I got mine at AutoZone. see pic.




If you can find a baffle for a 2 1/8” pipe the adaptor is not need.


Slide the baffle into the adaptor. The baffle has a ¼” mounting hole. Mark this hole on the adaptor and drill a ¼”. Place the baffle into the adaptor and line up the mounting holes.






Insert the adaptor & baffle assembly into the exhaust tip with the mounting hole down and place a mark on the underside of the tip corresponding to the mounting hole in the adaptor. I used a bent paperclip placing one end in the adaptor hole and the other marked the drill point.






Drill a ¼” hole in the bottom of the twin tip outlet. Center punch then start with the smallest bit possible and work up to ¼”. The tip is double walled so take your time.

Re install the assembly, insert the bolt that came with the baffle and secure with lock washer and nut.

[geosynch]

Did you have the sport or touring version?

[Lgaruti]

Originally Posted by geosynch

Did you have the sport or touring version?

Sport version...

[BreathlessPerformance]

I like the mod very ingenious.

However you can always purchase the touring version instead of the sport.

Ernie

[Lgaruti]

Originally Posted by BreathlessPerformance

I like the mod very ingenious.

However you can always purchase the touring version instead of the sport.

Ernie

Ernie, How much quieter is the touring version? Larry

[SylenThunder]

I seem to recall reading somewhere that the touring version is in the 60's, but don't recall exactly. It was either that or about 60% louder than stock. IIRC

[BreathlessPerformance]

Now about 20% quieter

Ernie

[Broken Kid]

Since getting the sport version, I'll say this - the only time I thought it was a little too loud was when pulling into a church parking lot. Every other time, I think it sounds great, and everyone who hears it really likes it. No, it doesn't wake the neighbors!

[bjchism1]

Originally Posted by BreathlessPerformance

Now about 20% quieter

Ernie

Hey ernie, is there really a 20% decrease in sound? on your site it still says 12%

"Available in Sport Version or Touring ( a little quieter 12 percent)"

[geosynch]

I should be getting my touring version tomorrow. I'm a little nervous it'll be too loud, as there have been complaints about the touring version as well.

What I'd like to know is, how is the 12% (or 20%) quieter measured? Typically sound is measured in decibels, which are logarithmic. 80 db v. 90 db is 10 db quieter, which means it is 10 times quieter, not 11% (90-80)/90 taken as a percent. 3db quieter is a reduction of 50%.

A true 12% (or even 20%) reduction would be less than 1 db. One db is about the limit of most peoples ability to perceive a difference.

So, if the sport and touring versions have been measured by a db meter, I'd love to know the results.

geosynch