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Mechanics 101 Can't get it to run right? Find a trick to add HP?
From the first oil change to completely rebuilding the engine,
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Old 02-18-2012, 10:49 PM   #1
Talltec
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Question Repack and Octane

a few questions. ok i have d&d exhaust which is super loud. was told be coworkers all i have to bring the volume down is drill the rivets out and stick steal wool in the muffler and rivet it back together.

first is that right, second what kind of steal wool, third how much, forth drill out rivets on the end only, 5th should anything be removed?

part two

i read the how to's and octane was talked about by cyberpoet and it brough up something what octane should be used on a bike with stage three jets. and should we add anything to the fuel because of the ethenol?

thanks
Manny
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Old 02-18-2012, 10:54 PM   #2
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Quote:
Originally Posted by Talltec View Post
a few questions. ok i have d&d exhaust which is super loud. was told be coworkers all i have to bring the volume down is drill the rivets out and stick steal wool in the muffler and rivet it back together.

first is that right, second what kind of steal wool, third how much, forth drill out rivets on the end only, 5th should anything be removed?

part two

i read the how to's and octane was talked about by cyberpoet and it brough up something what octane should be used on a bike with stage three jets. and should we add anything to the fuel because of the ethenol?

thanks
Manny
1st question... its not as simple as just stuffing more sound deadening material in. A D&D is going to be loud regardless, thats the way they are made to be.
2nd question, just stick to 87.
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Old 02-18-2012, 11:14 PM   #3
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repacking is not done with steel wool. Not alone anyway.
You need to buy fiberglass packing for mufflers.
Some people prefer to wrap the baffle with steel wool first then the fiberglass, you can skip the steel wool completely if you wish.
Pipes need to be repacked once a year or sooner.

Most people dont and it costs them HP
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Old 02-18-2012, 11:15 PM   #4
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Might be worth repacking the can. Repack kits typically just come with the fiberglass batting, though. Pick up some #0 steel wool and unroll it. Wrap it around the baffle tube and cover it with the glass mat before stuffing the whole mess back into the sleeve. What you get with that will be as good as your D&D will get. That's why I like Yoshimura pipes.

FTR, Yoshimura has a great video how-to on repacking pipes. Same principles apply to a D&D or Vance & Hines, even.
http://www.yoshimura-rd.com/t-engine...lerRepack.aspx

Reason for the steel wool is to protect the fiberglass.

Reason for the regular repack is that it affects backpressure. If it's been too long since the last repack then you don't have enough backpressure and that effectively leans out your jetting. You'll get backfiring when you chop the throttle as well as reduced power during the transition between the pilot circuit and the mains. Repack and that goes away.
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Last edited by Wild-Bill; 02-18-2012 at 11:19 PM..
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Old 02-19-2012, 08:11 AM   #5
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Quote:
Originally Posted by Wild-Bill View Post
Might be worth repacking the can. Repack kits typically just come with the fiberglass batting, though. Pick up some #0 steel wool and unroll it. Wrap it around the baffle tube and cover it with the glass mat before stuffing the whole mess back into the sleeve. What you get with that will be as good as your D&D will get. That's why I like Yoshimura pipes.

FTR, Yoshimura has a great video how-to on repacking pipes. Same principles apply to a D&D or Vance & Hines, even.
http://www.yoshimura-rd.com/t-engine...lerRepack.aspx

Reason for the steel wool is to protect the fiberglass.

Reason for the regular repack is that it affects backpressure. If it's been too long since the last repack then you don't have enough backpressure and that effectively leans out your jetting. You'll get backfiring when you chop the throttle as well as reduced power during the transition between the pilot circuit and the mains. Repack and that goes away.
Actually thats completely backwards

It increases back pressure as the packing breaks down.
By packing the exhaust tightly it allows sound waves to be absorbed but also insulates the exhaust and keep the inner pipe hotter. Hotter gasses/air move faster then cool air.
As the packing breaks down the soundwaves start to bounce around and gasses cool as they pass through the baffle slowing down the flow increasing backpressure.
Packing the exhaust ensures that the exhaust flow is fast and unrestricted but allowing sound waves to be absorbed.

Whay Kray said about the fuel is correct. If you bike runs better on higher octane then you have jetting issues. The higher the flashpoint of the fuel (octane) the harder it is to ignite the fuel. Run an EGT gauge and you will clearly see that the higher octane runs colder/richer as the engine is unable to burn the fuel completely or as effieciently. This means its actually costing you power and mpg. The leaner you run the engine the more power it will produce, too hean and you get overheating and engine damage.
so why does it feel smoother running higher octane? Simple its not producing as much power and its correcting the jetting in the lean flat spots but overly rich everywhere else. All it does is carbon up the engine and cause premature ring/cylinder wear.

Last edited by hardlydangerous; 02-19-2012 at 08:24 AM..
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Old 02-19-2012, 06:42 AM   #6
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Your probably better off considering a different can, or an insert if you really want to make a change in the noise level. Repacking won't do much to drop the level of sound on the D&D even if it does need to be done as mentioned.

D&D is generally considred to be the loudest can out there for the most part, so... :sm102.

As for the octane... the only reason one would need to change the octane for these bikes is if they greatly increased compression. With out engine work, and only doing carb/exhuast mods... you should always stick with and tune for 87 octane.

If your bike "runs better/sounds better" with a higher octane, then fix your bike... it's not properly set up and is running lean. The change in octane doesn't fix the issue, it just hides it.

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Old 02-19-2012, 07:49 AM   #7
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my question is, why do you want a quieter bike?? lol besides a small preformance boost, isnt that one of the main reasons we all get an after market exhaust?
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Old 02-19-2012, 01:25 PM   #8
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Quote:
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my question is, why do you want a quieter bike?? lol besides a small preformance boost, isnt that one of the main reasons we all get an after market exhaust?
1.) You want a quieter bike because you arent an attention craving Harley douche...

2.) The "small performance boost" is imperceptible unless you're also throwing on header, readjusting your jetting, adding ignition advance etc all at the same time. It's a Katana, not a gsxr,
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I love how the most ignorant people I have met are the ones that fling the word "ignorant" around like it's an insult, or poo. Maybe they think it means poo
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but personaly I dont see a point in a 1000 you can get the same power from a properly tuned 600 with less weight and better handeling.
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Old 02-19-2012, 08:19 AM   #9
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There's loud and then there's loud. There's a lot of reasons for not going too loud. There's the po-ing off the neighbors thing, the whole encouraging laws prohibiting any aftermarket exhaust at all thing, and so on... Oh, and there's always that whole hearing loss thing but who really cares about that?

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Originally Posted by hardlydangerous View Post
Actually thats completely backwards...
Hmm... Exactly the opposite of what I've always "known" but the physics sounds right. No denying that when the can needs re-packing the bike runs like the jetting's too lean. But how do you explain that when you install a free-flow exhaust (as opposed to a stock-style pipe) you need to richen the mixture?

Last edited by Wild-Bill; 02-19-2012 at 08:19 AM.. Reason: Automerged Doublepost
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Old 02-19-2012, 08:48 AM   #10
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Because a strait thru, free flowing pipe flows more gases then a stock pipe. A new exhaust is packed tight and flow is increased as the gases have no place to go but strait out.

As the packing breaks down it starts to restrict the flow more and more because gases are being absorbed thru the baffle. These gases have to come back thru the baffle to get out the pipe. this cools the gases and slows the flow

The baffles job is to absorb sound waves only,

if you took all the packing out completely and ran an empty can with the baffle. It will have far more back pressure then an can tightly packed forcing the gasses out the pipe rather then bouncing around inside the can.

Do you know how a two stroke pipe works?
the expansion chamber on a 2 stroke works much like a supercharger. soundwaves bounce off the end of the pipe forcing unburnt mixture back into the combustion chamber to be re-burnt. By adjusting the length and shape of the pipe you control the sound waves and how they affect the power.

Its much the same with a 4 stroke except they use actual valves to control the mixture coming in and out. But the sound waves still work the same way. If your exhaust gases are being slowed down and redirected in the exhaust your increasing the back pressure.

FWIW I used to work for MBRP building custom exhaustm back when their shop was located on #518 in Emsdale.
Oh and now you know why I run a Hindle ss pipe. (wink)
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