Author Topic: dB Killers  (Read 1712 times)

0 Members and 1 Guest are viewing this topic.

Offline rogracer

  • Training Wheels
  • *
  • Posts: 76
  • AREA: Southeast Area
  • COG#: 11346
  • Membership Level: Active
dB Killers
« on: May 18, 2014, 02:18:46 pm »
Seems like lots of exhausts are coming with dB killers (butt plugs) now....my Delk and Vince had them. Id say they both had a modest effect on sound level...and the design of both are very similar. Visually, though, both would appear to provide a massive restriction in flow. Im curious if anyone has seen a dyno comparison with and without these dB killers in place.

Offline Gypsy JR

  • American Gypsy
  • I Need a Life
  • ******
  • Posts: 6697
  • Living the Gypsy Life
  • AREA: Southeast Area
  • COG#: 9279
  • Membership Level: Active
Re: dB Killers
« Reply #1 on: May 18, 2014, 09:57:04 pm »
Yeah, thanks to the CARB law in California, all exhaust makers who ship into California are required to restrict dB under CARB limits.
----------------------------------------------------------------------------------
2017 Forest River Flagstaff Super-V 27VRL travel trailer
Where are you? [insert random forest name]

Offline rogracer

  • Training Wheels
  • *
  • Posts: 76
  • AREA: Southeast Area
  • COG#: 11346
  • Membership Level: Active
Re: dB Killers
« Reply #2 on: May 22, 2014, 07:23:20 pm »
So I measured the dB butt plug on my Delkevic and it has an OD of 1.2 inches. The outlet of the exhaust has an ID of 1.9 inches. If you do the math, that means the plug is restricting 40% of the cross sectional area of the exhaust outlet.  :-\

Offline Gypsy JR

  • American Gypsy
  • I Need a Life
  • ******
  • Posts: 6697
  • Living the Gypsy Life
  • AREA: Southeast Area
  • COG#: 9279
  • Membership Level: Active
Re: dB Killers
« Reply #3 on: May 23, 2014, 12:18:44 pm »
So I measured the dB butt plug on my Delkevic and it has an OD of 1.2 inches. The outlet of the exhaust has an ID of 1.9 inches. If you do the math, that means the plug is restricting 40% of the cross sectional area of the exhaust outlet.  :-\

Which doesn't necessarily tell you anything about actual flow changes.  :beerchug:
----------------------------------------------------------------------------------
2017 Forest River Flagstaff Super-V 27VRL travel trailer
Where are you? [insert random forest name]

Offline Texas

  • Tricycle
  • Posts: 10
  • AREA: South Central Area
  • Membership Level: Forum Subscriber
Re: dB Killers
« Reply #4 on: May 23, 2014, 01:33:27 pm »
Actually when you install the plug it redirects air into baffles to cancel sound waves. It would be nice to know the difference in flow.

Offline rogracer

  • Training Wheels
  • *
  • Posts: 76
  • AREA: Southeast Area
  • COG#: 11346
  • Membership Level: Active
Re: dB Killers
« Reply #5 on: May 23, 2014, 11:53:54 pm »
^hence why I was asking about dyno results. 40% blockage is not an insignificant number. It may even benefit low end torque...but I bet ya it is costing something in terms of high end horsepower.

Offline ghostrider990

  • Crotch Rocket
  • ****
  • Posts: 1076
  • AREA: Southeast Area
  • COG#: 12649
  • Membership Level: Active
Re: dB Killers
« Reply #6 on: May 24, 2014, 03:23:52 am »
I have db inserts on my Akra Racing system on my Aprilia.
I've seen dyno charts with and without on similar systems, and there IS a decrease in power
output when they are inserted, but it's not relative to outlet restriction size.

more along the lines of a 3-5% reduction in certain areas of the powerband.

I ride with mine in regularly.  The butt dyno CAN tell the difference, but it's minute.

I am looking for a dual system currently that has the option for db inserts...I will likely USE them regularly
as well.

gr
My Horns have Horns.

Offline rogracer

  • Training Wheels
  • *
  • Posts: 76
  • AREA: Southeast Area
  • COG#: 11346
  • Membership Level: Active
Re: dB Killers
« Reply #7 on: May 24, 2014, 02:19:44 pm »
That sounds pretty believable.  It kind of suggests that the stock exhaust may make more power than aftermarket with the dB killer. Wonder if thats true.

Offline fartymarty

  • Crotch Rocket
  • ****
  • Posts: 1003
  • AREA: South Central Area
  • COG#: 9712
  • Membership Level: Asst. Area Director
Re: dB Killers
« Reply #8 on: May 24, 2014, 03:43:45 pm »
That sounds pretty believable.  It kind of suggests that the stock exhaust may make more power than aftermarket with the dB killer. Wonder if thats true.

Those of us that love the quiet of the stock tater tosser tell ourselves that it is true. We quietly (pun intended) disbelieve anyone that tries to prove otherwise with their "flawed* data" dyno or otherwise.  :D

* if it's noisy, then it's flawed.  :)

Offline stevewfl

  • Iron Butt
  • *****
  • Posts: 4155
  • COG# 9334
  • AREA: Southeast Area
  • COG#: 9334
  • Membership Level: Active
Re: dB Killers
« Reply #9 on: May 28, 2014, 05:18:05 pm »
One thing to note is a huge weight savings can be found with the aftermarket stuff. Between just losing the bazooka and switching to a lithium bat, the bike sheds significantly
KiPass!