My bike came with some aftermarket mufflers, I think they are cycle shack, but I'm not sure. I don't think they have their baffles in them because they are insanely loud, I drive through a parking lot and I set off car alarms everywhere. I am wondering if I'm losing some backpressure due to this. I want to try out some stock pipes to see the difference.

I found some stock pipes for sale but they are off of a 2006, is there any difference in the mufflers between 2000 and 2006 (I know they changed the frame ect in 2004) Any help would be helpful.

 

I have the stock mufflers off my 2003 883C. I'd sell them to you if you'd like. The back muffler has a scratch (about the size of a nickel) and they have about 2700 miles on them. Let me know.

 

The need for backpressure is a myth.

Power=Highest exhaust velocity. If they are slipons and have the stock headers, you are fine for back-pressure, all back-pressure will do for you is slow exhaust velocity. What you need to do, if you are worried, is get on a dyno and make sure your A/F is good, and if it's not, get it tuned.

Back-pressure is good for one thing: sound control. If that's important to you, go for it, but you will loose power.

 

You want at least some back pressure. Your valves will thank you

 

True -But only if you spend all your time at the drag strip keeping the revs above ~4500 RPM.

A lack of adequate back pressure will tank your torque in the low-mid RPM range which is where most people spend their time riding on the street. There is no debate here, it's been proven time and time again on a Dyno.

 

Not true, it's just easier to tune the top end... also drag-pipes and the like can create all kinds of nasty reverbs that eat-power through the scavaging effect.

Here's a good article: http://www.rbracing-rsr.com/exhausttech.htm

Backpressure Physics

We are going to state this very clearly...Backpressure does not increase horsepower. Period.

An often heard statement from the well-informed is "You need a bit of backpressure for an exhaust to work". Usually this comes from someone who is not a tuner or someone who is faced with a situation where he does not have the tools or means to adjust things. Anything you do in the exhaust will change the flows, the pressures, or velocities somewhat. The correct scenario is that the exhaust has to be properly designed and then you optimize the jetting, ecu data inputs, camshafts, port dimensions, valve sizes and the like. The exhaust has to be designed for the intended use.

This all dates from the early 1980's when Supertrapp invented a muffler designed for dirtbikes to trap potential sparks, or burning, carbonized, bits, so it could have US Forrestry Approval for off-road use. The "trapp" tells what the intended purpose was. If you wanted a Harley to barely work you had to stick a couple of pounds, or about 23-25 of these discs in the end of your exhaust. Of course this didn't really work, which is why they ended up putting a hole up the middle anyway. You don't tune an exhaust.

Your engine has 15 psi (1 Bar) of atmospheric pressure sitting at the inlet and another 15 psi lurking at the end of the tailpipe. The inlet stroke creates a pressure differential and the atmosphere goes rushing inward. The exhaust valve opens and there is a pressure rise in the tube followed by a strong vacuum signal as the gases head down the pipe. Note that we said "vacuum signal."

Pressure differentials can be seen in the exhaust of a jet engine. We have a high pressure pulse coming out our exhaust system but it's just not visible as in the photo above.

The pattern of evenly spaced rings sometimes visible in the exhaust of jet engine is typically referred to as shock diamonds or Mach disks. The phenomenon occurs anytime a flow exits a nozzle at supersonic speeds and at a pressure that is different than that of the external atmosphere. Most of us are probably used to seeing shock diamonds occur near sea level during the takeoff of an aircraft, like in the above photo of the SR-71 Blackbird.

Logical extremes are often used to illustrate a point. For those who argue that backpressure can be a help they might say, from an extreme position, "Let's throw away the exhaust system so we have no backpressure at all". They would then conclude that the motor would run like crap and we would agree completely. The only problem is that they haven't gotten rid of backpressure, they simply have introduced 15 psi at the exhaust port and have given up any inertia, gas speeds or vacuum signals that exist in a primary tube.

The vacuum signal or low pressure that follows an exhaust event can be used to help scavenge the cylinder during overlap when both exhaust and inlet valves are open. Conversely, during this overlap period, the increase in backpressure can cause these burnt gases to re-enter the combustion chamber and contaminate the inlet charge. Result...loss of power.

The proper way to look at exhausts is to view them as a way to maintain the highest velocity that will not impede flow. As velocity increases the pressure drops and the engine can become more efficient. We have all the variables of length, diameter, rpm, collector size, internal shapes and the reflective waves that all this causes. There is no "one answer".

For those of you who disagree because of anecdotal evidence we would agree with you also. Altering an exhaust's flow can correct someting else like mixure or spark timing. In the end, if you have to throw it off a cliff to win, do it. Only results count and if increasing backpressure helps your situation then do it.

As a final thought...Gale Banks doesn't make money selling increased backpressure exhaust systems. Think about it. That picture above is a dedicated exhaust backpressure gauge. We use them.

 

I worked on cars for years but this Harley is my compromise with my wife between having a cool ride and getting decent fuel economy, I know if you drop exhaust backpressure you lose fuel economy. In my 88 Camaro I raced in autocross, I switched out to a bigger free flowing exhaust and I lost a bit of low end gained top end, and lost 3 or 4 MPG. Trying this is just one of many things I am trying. I am going to:1. Do an oil change (_any reccomendation on oil and filter?)2. change plugs and wires (any reccomendations here?)3. check the jets to make sure they didn't put bigger ones in. if they did Ill save em for later if I want more power.Id be happy to hear any other suggestions too. I just want a perfect running bike before I start tinkering.

 

Yes... more air+more fuel = more power

...you can see in that equation you are obviously consuming more fuel... if you leave the stock a/c with all it's housing and plug up those pipes, you can run the engine correctly tuned using very little fuel with a loss in power.

 

Awesome, thank you very much.. So, back to my question, Will 2006 stock mufflers fit on my 2000? These are very cheap, in perfect condition, and local, so no shipping.