Baffles - ruining the motor
Baffles - ruining the motor
Hello friends,
I recently removed the baffles from my screamin eagle pipes on my 2004 super glide -carb.. A friend told me that i can screw up the motor because of a back pressure issue? IS THIS TRUE?
I recently removed the baffles from my screamin eagle pipes on my 2004 super glide -carb.. A friend told me that i can screw up the motor because of a back pressure issue? IS THIS TRUE?
Banned
Joined: Mar 2010
Posts: 5,403
Likes: 7
From: Southwest Florida
There is sonic reversion, exhaust scavenging, velocity, capacity, volumetric efficiency, exhaust gas pulses, etc ad nauseam. But 'back pressure'?
Not so much. The term IS used, but it's incorrect, (again) IMO.
Could it possibly 'screw up' your motor? Well, I guess so but there would have to be something else going on at the intake end. Like, running way too lean. Never a good thing.
To be clear, I'm not a fan of removing baffles and not replacing them with -- Something. Believe it or not, Harley (and probably V&H) spent a lot of time and money trying to get those pipes to flow correctly. You don't like the way they sound? Fine, replace the pipes or replace the baffles. Running the pipes with NO baffles was not intended by the original maunfacturer.
Just my two cents.
Seasoned HDF Member
Joined: Feb 2008
Posts: 23,001
Likes: 11,441
not so simple as a yes or no
To free flowing pipes lean it out, lean is not good. Adding fuel with wide open pipes may require to much fuel for most riding this also is not good.
Wide open pipes work well only on the drag strip at the top end.
No it aint going to die over night normally the damage is slow and comes over time, the reason many get away with it is they dont ride much.
Your ride you decide and good set of slipons can be had for 300-600 price to fit any budget.
Road Master
Joined: May 2007
Posts: 899
Likes: 10
I'm running 2 1/4 diameter drags. (They are actually smaller right in the header area.) But I experimented with different length baffles, several ways of fouling the baffles, and torque cones. At one point I even packed the baffles with chicken wire (really packed it in tight) and spot welded a large washer with a 3/4 hole in it to one end. But nothing I did made any difference powerband/torque wise. Although it did alter the sound. I somewhat believe all this bugaboo about back pressure and whatnot is mostly marketing designed to separate people from their money. Although I do think the length of the pipes are important. Those LAF shorty pipes are probably detrimental to your motor.
Right now I'm running six inch open baffles (with a small rod welded in crosswise) and it runs and sounds great. I shot this vid on my DroidX so the sound isn't exact but you can get an idea . . .
http://www.youtube.com/watch?v=hRI0eeEFEPI
Right now I'm running six inch open baffles (with a small rod welded in crosswise) and it runs and sounds great. I shot this vid on my DroidX so the sound isn't exact but you can get an idea . . .
http://www.youtube.com/watch?v=hRI0eeEFEPI
Last edited by NickD; Aug 12, 2010 at 08:39 AM.
Banned
Joined: Mar 2010
Posts: 5,403
Likes: 7
From: Southwest Florida
'Back Presuure'.
It's about velocity. The flow of exhaust is inversely proportionate to the square (some claim the 'cube' not the square. whatever) of the diameter of the pipe. When your exhaust leaves the exhaust port at about 300 feet per second, it immediately starts to slow down due to heat loss (and other factors) even while it's still in the smaller header pipe.
If it then flows into a wide-open muffler that's about 3 1/2" diameter it slows down by about another half or more. Unfortunately, right behind it is another exhaust pulse haulin'-**** down the exhaust trying to get out and it slams right into the previous exhaust gas/pulse and.... Well, they can't get out of each other's way.
That is what is sometimes called back pressure. It's not, but I'll play.
In any case, my brain is starting to hurt so let's just say that removing baffles and not replacing them is not good. Will it hurt the engine? I doubt it, but why do something that's not good in the first place?
It's about velocity. The flow of exhaust is inversely proportionate to the square (some claim the 'cube' not the square. whatever) of the diameter of the pipe. When your exhaust leaves the exhaust port at about 300 feet per second, it immediately starts to slow down due to heat loss (and other factors) even while it's still in the smaller header pipe.
If it then flows into a wide-open muffler that's about 3 1/2" diameter it slows down by about another half or more. Unfortunately, right behind it is another exhaust pulse haulin'-**** down the exhaust trying to get out and it slams right into the previous exhaust gas/pulse and.... Well, they can't get out of each other's way.
That is what is sometimes called back pressure. It's not, but I'll play.
In any case, my brain is starting to hurt so let's just say that removing baffles and not replacing them is not good. Will it hurt the engine? I doubt it, but why do something that's not good in the first place?
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Road Captain
Joined: Jul 2009
Posts: 718
Likes: 1
From: Downtown Chicago
https://www.hdforums.com/forum/dyna-...ffler-mod.html
Removing the stock/SE baffles and replace with Cycle Shack baffles. Not sure what your muffs look like on your '04, but they'd probably fit. A lot of other people did the same mod with great success. Louder and still the whole "back pressure" thing.
I'm doing this in the coming weeks.
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Outstanding HDF Member
Joined: May 2008
Posts: 2,166
Likes: 4
From: la
Yes The engine requires a balanced of flow and back pressure to be at it best both in how it runs and how long it holds up.
To free flowing pipes lean it out, lean is not good. Adding fuel with wide open pipes may require to much fuel for most riding this also is not good.
Wide open pipes work well only on the drag strip at the top end.
No it aint going to die over night normally the damage is slow and comes over time, the reason many get away with it is they dont ride much.
Your ride you decide and good set of slipons can be had for 300-600 price to fit any budget.
To free flowing pipes lean it out, lean is not good. Adding fuel with wide open pipes may require to much fuel for most riding this also is not good.
Wide open pipes work well only on the drag strip at the top end.
No it aint going to die over night normally the damage is slow and comes over time, the reason many get away with it is they dont ride much.
Your ride you decide and good set of slipons can be had for 300-600 price to fit any budget.
Tourer
Joined: Jun 2007
Posts: 292
Likes: 4
From: New Philadelphia, OH
Big City Thunder!
If you like the sound without baffles you may want to check out Big City Thunder Monsters. They're the closest thing to running open pipes without completely killing low and mid range power. It is a trade off for some, though. I love the sound of gearing down the bike with open pipes (almost like a jake brake on a big rig), but alas, without proper tuning the perfomance sucks.