Deep Tone Straight Pipe Sound for
Hard Krome's 2.75" Big Straights
w/adjustable Top-end Horsepower, Low-end & Mid-range Torque.
By Tony Anzalone - GoldKnight67 (on the V-Star Forum)
2002V-Star 1100 Custom
Lets first start by admitting that the HK 2.75 Big Straights are great performers right out of the box. The thing I like most about the 2.75 pipes is the full size 1&3/4 pipe from header to baffle.
I being a bit anal in the "I can get more out of this setup", type of person, have taken a closer look.
The Baffle reduces the 1&3/4" pipe to about 1&5/8 ,plus that entire nice baffle is lined with protrusions to slow the exhaust gas flow, to give a desired degree of backpressure.
I tried like many of you, running without the baffles, but found that the exhaust tone became "tinny sounding" in that large 2&3/4 megaphone environment. I wanted Deeper & Louder, not Tinny and Louder!
I was running prior to the HKs, a set Barons Nasty Boy slip on pipes with a modified racing tune-able baffle. So I was familiar with a nice chunk of torque and almost straight pipe sound.
I also read the Dyno charts, (Below), on the simple modification at the Night Rider web article "Making Drag Pipes Work, and decided that could be incorporated in the HK 2.75 Big Straights
Easy Installation with Internal Adjustments
Just set your backpressure settings and replace your stock HK Baffles with these inserts!
Infinate Adjustment for Backpressure Torque & HP
90 Degree setting for High Lowend Torque & Backpressure
45 Degree setting for High Midrange Torque and Increased Horsepower
180 Degree setting for High Flow Topend Horsepower & Low Backpressure
90 Degree setting 45 Degree setting 180 Degree setting
Making the Adjustable Baffles:
End View Stock Baffle and 1.75 Pipe Parts Old & New
I set the Pipe in place of the baffle for fitting and Marking, ( length and drilling).
I cut screwdriver slots in the ends of the Backpressure units.
This allows you to see the exact angle while installing of the units.
Since I am anxious to test the units and do not at this moment have a welder at my disposal, nor have I found a 2&5/8" X 1&3/4" IO pipe adapter.
I decide to just shim the Pipe to center as I do some testing. I also have painted the ends of the baffles with high temperature "Black" to help them blend in.
If You like the straight pipe sound this will do it. The pipes sound Loud and Deep .
This has given a nice increase in low-end Torque at a bit less than 45 degrees of angle and also a nice gain in the torque in the mid RPM's, over the straight pipes with out a baffle.
If you find you need to be greater than 45 degrees with the thumbscrews, you may want to increase the size of the adjusting washer. (weld or screw a waser to the thumbscrew). Why? Because, even if the 45+ degrees gives the desired low-end torque, it will also multiply the turbulence as the higher RPM's build, causing extreme turbulence that will hinder the Top end power.
I believe a larger 1' or .75" diameter washer that would give the desired torque at a much lower angle, (45 degrees or less), will cause less turbulence at higher RPM ranges, or a cleaner smoother backpressure. Allowing both Torque at the low to mid range & still allow Horsepower to build at the higher ranges.
*Prior to installing the "DBAK" I used the 1" wasers. After installation of the "DBAK" a big increase of intake air & gas increased overall flow. I found that the engine is running better with just the original thumbscrews set at a bit less than 45 degrees.
**As a final thought to rid the pipe of any tinny sounds, like you would get if you tap a tool on the pipe and it rings. I rapped a 5" wide layer of high temperture insulation and tie wired it around the pipe to deaden any tinny reverbs. (You could also use some baffle rap).
Materials & Cost = $14.00 & 3 hours Labor
2 - 1/4" 20 x 1&1/2" Zink Plated Backpressure units, (Thumbscrews)
2- 1/4" 20 Zink Plated Nuts
2- 1/4" Zink Plated washers
2- 1/4" Zink Plated loc washers
2- 1/4" 20 x 1" Stainless Steel Allen Cap Screws
6 -1/4" 20 Stainless Steel Nuts
2- 1/4" Stainless Steel washers
2 - 1&3/4" od x 20" Tailpipe assemblys
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