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Paint and BodyworkDynanometer RunsVTX ModificationsBaffle Experiments

I am one that likes the sound of the Vance and Hines Big Shots, however, I don’t particularly enjoy causing too much commotion in the neighborhood or in other residential areas.  For me, the standard Big Shots baffles (not to mention, no baffles) are just too loud.  Additionally, I think the timbre has a tinny component to the note.  I have been looking for a deeper, richer sound that is also quieter.  However, I do not want to give up the safety aspect of being heard by other motorists.   I ordered and installed the quiet baffles for the Big Shots.  The dyno results showed that the quiet baffles yielded about 5% less top-end horsepower than with no baffles.

I like what the quiet baffles provided: quieter and better sound quality as described above, however, after about 5 months there were four things that made me want to “tinker” with this a bit more.

1)     I could not take an A/F ratio reading with the Quiet baffles installed during dyno.

a.      My first dyno results were obtained without baffles and I want to do more pulls with the baffles installed.

)     The Fiberglass was starting to deteriorate.

3)     I wanted to see if I could get an even better exhaust tone than the basic quiet baffle.

4)     I wanted to see if I could increase the flow (horsepower) without increasing the noise pressure.

What follows is an experiment I did:

Baffle Concept

 

The concept is to start with a V&H Quiet Baffle and Modify it slightly to help take out some of the mid-range out of the sound.

Quiet Baffles

 

Started with the Vance and Hines Quiet Baffle and unwrapped the fiberglass wrap.  The fiberglass wrap was still doing its job, however, it got bunched up making baffle removal in one of the pipes quite difficult.

Drilled End Cap

 

Drilled ˝” hole to increase flow through baffle and to allow A/F sensor tube access up the pipe for measurements during dynamometer pulls.

Baffle Concept

 

Materials needed:

Purchased a 25 ft. roll of 3” x 1/8” Ceramic wrapping material from McMaster.  This stuff will outlast the fiberglass stuff.

http://www.mcmaster.com/asp/enter.asp?partnum=
87575K89&pagenum=3257

Baffle Concept

 

Cut the ceramic material into single wrap sheets.

Made the cones out of 16 ga. Sheet metal. 

Cut them into shapes like this.  Formed the cones with hammer and vise.

Took some 18 ga. perforated sheet metal and formed cones out of these for the inserts.

 

Baffle Concept

 

Welded the assembled cones on the end of the quiet baffles

Baffle Concept

 

Re Dyno’d with the cones installed

SAE horsepower/torque at 5500 RPM was 97/107ft.lb

Horsepower improved by 2-5 horses in the range from 2000-3000 RPMs under WOT.