baffle removal...bad?
#11
08-07-2009 | 06:46 AM
#12
08-07-2009 | 12:20 PM
Advanced
Joined: Jul 2009
Posts: 70
Likes: 1
There will absolutely be issues!!!! The bike needs back pressure to run correctly. Without it you will have decel pop and the bike will be running extremely lean. Highly do not recommend doing this. Even though you are "cheap" it is well worth the $$$ to get a set of after market mufflers and have the bike dyno tuned. You'll get sound and performance. imo
#13
08-09-2009 | 01:17 AM
Cruiser
Joined: Jun 2009
Posts: 172
Likes: 2
Removing Baffles
When you remove the baffles from the exhaust you create an untuned condition in the exhaust system. Open drag pipes are mostly untuned exhaust pipes, the length dictated by style rather than function. Any untuned exhaust pipe can cause an engine to exhibit lean and rich conditions but at different engine speeds and throttle openings. Drag pipes, and some other open pipes, can allow an engine to make more WOT top end power, but you might not see that power increase until the engine speed exceeds 5,000 rpm. Below that it can be a crap shoot, and mostly crap.
Backpressure doesn't allow an engine to make power and Harley engines don't "need" backpressure to run right. Exhaust backpressure can only cost power due to pumping losses as the piston has to push against any backpressure in the exhaust to empty out exhaust gases from the cylinder. The engine needs SOMETHING but it isn't backpressure. In virtually every test ever conducted on an engine, backpressure caused a net loss of engine power. What the engine needs is consistent intake and exhaust flow, and a consistently appropriate air/fuel ratio. When you remove the baffles from the exhaust pipes you are changing the pressure drop points. The point and size of the pressure drop determine how the exhaust pressure waves (not backpressure) exit the exhaust pipe. A plain, straight pipe has no control, and the pressure waves hit the atmosphere like a high speed handball hitting a wall. There will be one or more reflected waves that will return back up the exhaust pipe. One is a reflected pressure wave and the other is a reflected sonic shock wave that moves at the speed of sound, and loses very little energy when it is reflected from the open end of the pipe. If those reflected waves reach the exhaust valve before it closes, they can push exhaust gases back into the cylinder. This dilutes the intake charge, and you lose power. If the sonic shock wave arrives at the exhaust valve while the intake valve is open during overlap, the shock wave, moving at something like 1500 feet per second, can actually make it all the way through the cylinder and into the intake manifold, and can blow the intake charge right out of the intake manifold. Less intake charge means less power. These shock waves raise holy hell with both the density and the air/fuel ratio of the intake charge in that cylinder. Depending on pipe length AND DIAMETER, this may cause the engine to run super lean or super rich depending on throttle opening and load. Larger diameter pipes make a bad situation worse. Exhaust backpressure won't fix any of this.
Some engines don't run too bad with open pipes. It depends on the individual engine, and factory tolerances can shift cam timing by several degrees from one engine to another. What works on one engine may not work on an "identical" engine.
Baffles reduce sound levels by breaking up the pressure waves and shock waves. Some baffles break up the high frequency waves while leaving the low frequency waves.
But no baffles at all leaves you with a crap shoot over a wide rpm range.
Backpressure doesn't allow an engine to make power and Harley engines don't "need" backpressure to run right. Exhaust backpressure can only cost power due to pumping losses as the piston has to push against any backpressure in the exhaust to empty out exhaust gases from the cylinder. The engine needs SOMETHING but it isn't backpressure. In virtually every test ever conducted on an engine, backpressure caused a net loss of engine power. What the engine needs is consistent intake and exhaust flow, and a consistently appropriate air/fuel ratio. When you remove the baffles from the exhaust pipes you are changing the pressure drop points. The point and size of the pressure drop determine how the exhaust pressure waves (not backpressure) exit the exhaust pipe. A plain, straight pipe has no control, and the pressure waves hit the atmosphere like a high speed handball hitting a wall. There will be one or more reflected waves that will return back up the exhaust pipe. One is a reflected pressure wave and the other is a reflected sonic shock wave that moves at the speed of sound, and loses very little energy when it is reflected from the open end of the pipe. If those reflected waves reach the exhaust valve before it closes, they can push exhaust gases back into the cylinder. This dilutes the intake charge, and you lose power. If the sonic shock wave arrives at the exhaust valve while the intake valve is open during overlap, the shock wave, moving at something like 1500 feet per second, can actually make it all the way through the cylinder and into the intake manifold, and can blow the intake charge right out of the intake manifold. Less intake charge means less power. These shock waves raise holy hell with both the density and the air/fuel ratio of the intake charge in that cylinder. Depending on pipe length AND DIAMETER, this may cause the engine to run super lean or super rich depending on throttle opening and load. Larger diameter pipes make a bad situation worse. Exhaust backpressure won't fix any of this.
Some engines don't run too bad with open pipes. It depends on the individual engine, and factory tolerances can shift cam timing by several degrees from one engine to another. What works on one engine may not work on an "identical" engine.
Baffles reduce sound levels by breaking up the pressure waves and shock waves. Some baffles break up the high frequency waves while leaving the low frequency waves.
But no baffles at all leaves you with a crap shoot over a wide rpm range.
#14
08-10-2009 | 08:49 PM
Cruiser
Joined: Aug 2006
Posts: 133
Likes: 0
From: sa tx
When you remove the baffles from the exhaust you create an untuned condition in the exhaust system. Open drag pipes are mostly untuned exhaust pipes, the length dictated by style rather than function. Any untuned exhaust pipe can cause an engine to exhibit lean and rich conditions but at different engine speeds and throttle openings. Drag pipes, and some other open pipes, can allow an engine to make more WOT top end power, but you might not see that power increase until the engine speed exceeds 5,000 rpm. Below that it can be a crap shoot, and mostly crap.
Backpressure doesn't allow an engine to make power and Harley engines don't "need" backpressure to run right. Exhaust backpressure can only cost power due to pumping losses as the piston has to push against any backpressure in the exhaust to empty out exhaust gases from the cylinder. The engine needs SOMETHING but it isn't backpressure. In virtually every test ever conducted on an engine, backpressure caused a net loss of engine power. What the engine needs is consistent intake and exhaust flow, and a consistently appropriate air/fuel ratio. When you remove the baffles from the exhaust pipes you are changing the pressure drop points. The point and size of the pressure drop determine how the exhaust pressure waves (not backpressure) exit the exhaust pipe. A plain, straight pipe has no control, and the pressure waves hit the atmosphere like a high speed handball hitting a wall. There will be one or more reflected waves that will return back up the exhaust pipe. One is a reflected pressure wave and the other is a reflected sonic shock wave that moves at the speed of sound, and loses very little energy when it is reflected from the open end of the pipe. If those reflected waves reach the exhaust valve before it closes, they can push exhaust gases back into the cylinder. This dilutes the intake charge, and you lose power. If the sonic shock wave arrives at the exhaust valve while the intake valve is open during overlap, the shock wave, moving at something like 1500 feet per second, can actually make it all the way through the cylinder and into the intake manifold, and can blow the intake charge right out of the intake manifold. Less intake charge means less power. These shock waves raise holy hell with both the density and the air/fuel ratio of the intake charge in that cylinder. Depending on pipe length AND DIAMETER, this may cause the engine to run super lean or super rich depending on throttle opening and load. Larger diameter pipes make a bad situation worse. Exhaust backpressure won't fix any of this.
Some engines don't run too bad with open pipes. It depends on the individual engine, and factory tolerances can shift cam timing by several degrees from one engine to another. What works on one engine may not work on an "identical" engine.
Baffles reduce sound levels by breaking up the pressure waves and shock waves. Some baffles break up the high frequency waves while leaving the low frequency waves.
But no baffles at all leaves you with a crap shoot over a wide rpm range.
Backpressure doesn't allow an engine to make power and Harley engines don't "need" backpressure to run right. Exhaust backpressure can only cost power due to pumping losses as the piston has to push against any backpressure in the exhaust to empty out exhaust gases from the cylinder. The engine needs SOMETHING but it isn't backpressure. In virtually every test ever conducted on an engine, backpressure caused a net loss of engine power. What the engine needs is consistent intake and exhaust flow, and a consistently appropriate air/fuel ratio. When you remove the baffles from the exhaust pipes you are changing the pressure drop points. The point and size of the pressure drop determine how the exhaust pressure waves (not backpressure) exit the exhaust pipe. A plain, straight pipe has no control, and the pressure waves hit the atmosphere like a high speed handball hitting a wall. There will be one or more reflected waves that will return back up the exhaust pipe. One is a reflected pressure wave and the other is a reflected sonic shock wave that moves at the speed of sound, and loses very little energy when it is reflected from the open end of the pipe. If those reflected waves reach the exhaust valve before it closes, they can push exhaust gases back into the cylinder. This dilutes the intake charge, and you lose power. If the sonic shock wave arrives at the exhaust valve while the intake valve is open during overlap, the shock wave, moving at something like 1500 feet per second, can actually make it all the way through the cylinder and into the intake manifold, and can blow the intake charge right out of the intake manifold. Less intake charge means less power. These shock waves raise holy hell with both the density and the air/fuel ratio of the intake charge in that cylinder. Depending on pipe length AND DIAMETER, this may cause the engine to run super lean or super rich depending on throttle opening and load. Larger diameter pipes make a bad situation worse. Exhaust backpressure won't fix any of this.
Some engines don't run too bad with open pipes. It depends on the individual engine, and factory tolerances can shift cam timing by several degrees from one engine to another. What works on one engine may not work on an "identical" engine.
Baffles reduce sound levels by breaking up the pressure waves and shock waves. Some baffles break up the high frequency waves while leaving the low frequency waves.
But no baffles at all leaves you with a crap shoot over a wide rpm range.
#15
08-10-2009 | 09:36 PM
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#16
03-09-2010 | 11:17 AM
Advanced
Joined: Jan 2010
Posts: 57
Likes: 0
From: Las Vegas, NV
Back pressure
When you remove the baffles from the exhaust you create an untuned condition in the exhaust system. Open drag pipes are mostly untuned exhaust pipes, the length dictated by style rather than function. Any untuned exhaust pipe can cause an engine to exhibit lean and rich conditions but at different engine speeds and throttle openings. Drag pipes, and some other open pipes, can allow an engine to make more WOT top end power, but you might not see that power increase until the engine speed exceeds 5,000 rpm. Below that it can be a crap shoot, and mostly crap.
Backpressure doesn't allow an engine to make power and Harley engines don't "need" backpressure to run right. Exhaust backpressure can only cost power due to pumping losses as the piston has to push against any backpressure in the exhaust to empty out exhaust gases from the cylinder. The engine needs SOMETHING but it isn't backpressure. In virtually every test ever conducted on an engine, backpressure caused a net loss of engine power. What the engine needs is consistent intake and exhaust flow, and a consistently appropriate air/fuel ratio. When you remove the baffles from the exhaust pipes you are changing the pressure drop points. The point and size of the pressure drop determine how the exhaust pressure waves (not backpressure) exit the exhaust pipe. A plain, straight pipe has no control, and the pressure waves hit the atmosphere like a high speed handball hitting a wall. There will be one or more reflected waves that will return back up the exhaust pipe. One is a reflected pressure wave and the other is a reflected sonic shock wave that moves at the speed of sound, and loses very little energy when it is reflected from the open end of the pipe. If those reflected waves reach the exhaust valve before it closes, they can push exhaust gases back into the cylinder. This dilutes the intake charge, and you lose power. If the sonic shock wave arrives at the exhaust valve while the intake valve is open during overlap, the shock wave, moving at something like 1500 feet per second, can actually make it all the way through the cylinder and into the intake manifold, and can blow the intake charge right out of the intake manifold. Less intake charge means less power. These shock waves raise holy hell with both the density and the air/fuel ratio of the intake charge in that cylinder. Depending on pipe length AND DIAMETER, this may cause the engine to run super lean or super rich depending on throttle opening and load. Larger diameter pipes make a bad situation worse. Exhaust backpressure won't fix any of this.
Some engines don't run too bad with open pipes. It depends on the individual engine, and factory tolerances can shift cam timing by several degrees from one engine to another. What works on one engine may not work on an "identical" engine.
Baffles reduce sound levels by breaking up the pressure waves and shock waves. Some baffles break up the high frequency waves while leaving the low frequency waves.
But no baffles at all leaves you with a crap shoot over a wide rpm range.
Backpressure doesn't allow an engine to make power and Harley engines don't "need" backpressure to run right. Exhaust backpressure can only cost power due to pumping losses as the piston has to push against any backpressure in the exhaust to empty out exhaust gases from the cylinder. The engine needs SOMETHING but it isn't backpressure. In virtually every test ever conducted on an engine, backpressure caused a net loss of engine power. What the engine needs is consistent intake and exhaust flow, and a consistently appropriate air/fuel ratio. When you remove the baffles from the exhaust pipes you are changing the pressure drop points. The point and size of the pressure drop determine how the exhaust pressure waves (not backpressure) exit the exhaust pipe. A plain, straight pipe has no control, and the pressure waves hit the atmosphere like a high speed handball hitting a wall. There will be one or more reflected waves that will return back up the exhaust pipe. One is a reflected pressure wave and the other is a reflected sonic shock wave that moves at the speed of sound, and loses very little energy when it is reflected from the open end of the pipe. If those reflected waves reach the exhaust valve before it closes, they can push exhaust gases back into the cylinder. This dilutes the intake charge, and you lose power. If the sonic shock wave arrives at the exhaust valve while the intake valve is open during overlap, the shock wave, moving at something like 1500 feet per second, can actually make it all the way through the cylinder and into the intake manifold, and can blow the intake charge right out of the intake manifold. Less intake charge means less power. These shock waves raise holy hell with both the density and the air/fuel ratio of the intake charge in that cylinder. Depending on pipe length AND DIAMETER, this may cause the engine to run super lean or super rich depending on throttle opening and load. Larger diameter pipes make a bad situation worse. Exhaust backpressure won't fix any of this.
Some engines don't run too bad with open pipes. It depends on the individual engine, and factory tolerances can shift cam timing by several degrees from one engine to another. What works on one engine may not work on an "identical" engine.
Baffles reduce sound levels by breaking up the pressure waves and shock waves. Some baffles break up the high frequency waves while leaving the low frequency waves.
But no baffles at all leaves you with a crap shoot over a wide rpm range.
Thanks for all of the great info!
#17
04-11-2010 | 07:44 PM
Novice
Joined: Aug 2009
Posts: 18
Likes: 0
From: Jax, FL
When I took the mufflers off my bike and I was just running the stock exhaust pipes, the bike was freaking ridiculous. I do have a PCV on the bike. Constant blue flames out the exhaust, ridiculous acceleration. The bike ran awesome whenever I twisted that throttle, but whenever you let out of it, it would backfire which I liked. I think my setup is running very rich, especially with the constant blue flame coming out the exhaust. I put the mufflers back on the bike because I was told I would burn up my exhaust valves with the short pipes and no baffles. Since I have had the mufflers back on I have had no problems but the performance is not the same. I want to go back, because the sounds and performance were just ridiculous.
What could I do to run short drag pipes? I saw somewhere somebody saying to drill a hole through the end of the exhaust and to install a bolt which would give you some back pressure, who knows. I want to run drag pipes, but I dont want to burn my motor up. I do have access to a dyno, but this guy works with cars, not bikes. Thanks.
What could I do to run short drag pipes? I saw somewhere somebody saying to drill a hole through the end of the exhaust and to install a bolt which would give you some back pressure, who knows. I want to run drag pipes, but I dont want to burn my motor up. I do have access to a dyno, but this guy works with cars, not bikes. Thanks.
#18
09-21-2010 | 02:51 AM
Novice
Joined: Sep 2010
Posts: 15
Likes: 0
When you remove the baffles from the exhaust you create an untuned condition in the exhaust system. Open drag pipes are mostly untuned exhaust pipes, the length dictated by style rather than function.
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But no baffles at all leaves you with a crap shoot over a wide rpm range.
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But no baffles at all leaves you with a crap shoot over a wide rpm range.
Thanks for the info...
I bought my bike 2nd hand with 2-1-2 exhaust (Dyna Fat Bob 2009). The previous owner had cored the baffles.
I'm not really a fan of the noise.
Someone told me that the stock baffle (un-cored that is) will give me better performance than the cored baffle... is that true?
I also test driven the Fat Bob demo bike in the dealer (before I bought my bike) and I remember very wekk that it was much less rumbley and shakey. Is that because of the cored baffle or because the engine has 5000 miles on it, as some say?
Is there any tuning that can be done to the engine to reduce the rumbling? Maybe change the sparkplugs?
I've done my standard services at 1000 and 5000 Miles, not sure if sparks are part of these.
Thanks
#19
09-21-2010 | 09:20 AM
Elite HDF Member
Joined: May 2009
Posts: 4,904
Likes: 8
From: Streetsboro, Oh
#20
09-21-2010 | 02:02 PM
Is there a certain way to remove the standard mufflers because I have removed the heat shields, loosened the clamps that hold the joint together and removed the bolts from the collector box but the mufflers are so tight on the down pipes that they will hardly move and I am afraid that with all the pulling and tugging, it will damage the header pipes where they bolt on to the barrels.Do you think I will have to remove the complete pipes or is there an easier way without disturbing the header pipes and sensors that are attached to them?