Lost Torque

[doctorgski]

As most of you that have changed to after market exhaust systems have noticed, they do sound better. But, you do loose some mid range torque. That torque you need at about 65 mph, and go to pass in 5th w/o a down shift. In the April 2008 issue of ROADBIKE there is a good article on "The old bolt trick".Â*I have Cobra Complete Duel Slash Cuts, and noted from the start a loss in the torque from the stock set-up.Â* Well about a month ago I did the bolt trick and I can say it did give back some of that lost grind. I did not have the bike on a dyno prior to or after the operation of the exhaust, but in the ol' butt I can feel it.Â* All you do is drill a 1/4 inch hole thru your exhaust, as close to the baffles as you can get, and put a 1/4 inch bolt thru the hole with a double nut... you don't want to loose a bolt at 70mph! Now after reading "The air intake mod" by Blowndodge, I did that too. As you can see, I'm not afraid to drill !!!Â* I have found this to help with some of the pinging on real hot days. I run a power commander, but like to keep it on the conservative side due to bad fuel mileage, and it would ping on real hot days if I would grind it out a bit.Â* I too used 3/16 inch holes, and 14 in each row. I use a K&N oil filter so I wonder if I could just drill the rest of the way around for even more cool air, or would the small crossover tube not pass that much air anyway?Â* ??? Just food for thought. ????

Before you go drilling your hands numb, I'd try this:
Just flip that lid upside down, screw it on, and go ride. Yeah I know it'll look like hell, but sacrifices must be made in the interest of science!

OK, did it run better? If so, then more air would help, so keep drilling.

If not, then you are at that point of diminishing returns (well past it actually) where additional effort will avail you nothing.

[dogdoc]

this drilling a 1/4 inch hole thur your exhaust(where exactly Im not sure) sounds like it might ruin the chrome? cause rusting? whats a bolt do for you really?? just pondering.

This is an old trick for drag pipes. sometimes people use eyebolts or bolts with washers welded to the heads also.

Anyhow, it splits up the exhaust stream and makes it crash back into itself, which causes some back pressure and quiets the pipes somewhat.

[ringadingh]

I rode my bike last season with the V&H baffles removed for a few minutes, there was a noticeable drop in torque,(and lots of noise) it runs much better with the baffles installed.

[dkdixie]

Originally Posted by caddmannq

This is an old trick for drag pipes. sometimes people use eyebolts or bolts with washers welded to the heads also.

Anyhow, it splits up the exhaust stream and makes it crash back into itself, which causes some back pressure and quiets the pipes somewhat.

There's an item called Thunder Monsters (www.bigcitythunder.com) which are basically as CQ described except they are installed in a short tube with a washer in the center. Like an aperature front sight on a target rifle.

They do produce a great sound. Installed them on my Harley, about two inches in the header pipe before the slip on muffler. With baffles removed on Screaming Eagle pipes, made for a real low rumble sound.

Plan to try on my V&H pipes but just haven't got around to it yet.

[doctorgski]

Originally Posted by Doc (Lonewolf)

this drilling a 1/4 inch hole thur your exhaust(where exactly Im not sure) sounds like it might ruin the chrome? cause rusting? whats a bolt do for you really?? just pondering.

[doctorgski]

I drilled a hole so that the bolt was about a inch out from the baffel (looking from the exhaust tip ). From what I read, this bolt will disrupt "reversion waves". As for the rust, I will have to let you know.

[flightdoc]

I read that same article. What I took away is when the exiting exhaust hits the bolt it acts similar to what a wing does. The bolt causes the exhaust to accelerate around it thus allowing a more free flowing exhaust. my 2 cents

vin

[bobzinger]

We used to put an eyebolt in the exhaust stream on unbaffled pipes. It gave a little back pressure.
I think anything other than straight thru pipes have enough back pressure.

[tomk]

Originally Posted by bobzinger

We used to put an eyebolt in the exhaust stream on unbaffled pipes. It gave a little back pressure.
I think anything other than straight thru pipes have enough back pressure.

I think that you're right. We used to build buggys and baja bugs with small diameter exhaust (for torquier engines). The drag cars had larger diameter pipes for high rpm hp with almost no torque.

[rlfaubion]

Originally Posted by "dk dixie"

There's an item called Thunder Monsters (www.bigcitythunder.com) which are basically as CQ described except they are installed in a short tube with a washer in the center. Like an aperature front sight on a target rifle.

They do produce a great sound. Installed them on my Harley, about two inches in the header pipe before the slip on muffler. With baffles removed on Screaming Eagle pipes, made for a real low rumble sound.

Plan to try on my V&H pipes but just haven't got around to it yet.

I ran Big City Thunder baffles in my V&N on the Classic. Worked well, sounded excellent! You'll be happy with them.

[macmac]

Sometimes a drop of clear fingernail polish in a drilled hole in chrome will prevent rusting.. Drilling thru chrome cuts thru the layers of what ever the chrome is based on, and so leaves jagged edges open to the atmosphere. I can't say how hot nail polish can get though and still seal.

[dkdixie]

Valdez.....did you remove the V&H baffles?