power differences between 2-1 pipes vs. duals
Elite HDF Member
Joined: Sep 2007
Posts: 4,541
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From: Nuevo México, Los Estados Unidos de América
...ummm some interesting answers...
Okay... an exhaust pipes have one function... to take the exhaust away from the engine... the quicker they do it, the more power you make... it's about exhaust velocity, plain and simple... higher velocity = more power.
The ideal exhaust will give you the highest possible exhaust velocity for a given RPM... to do that, you'd have to have a self-adjusting exhaust... but you can get close without one.
There are a few factors that play into the velocity, there is savaging from all the vibrating and bouncing going on, there is diameter, there are baffles... you'll notice even you sock pipes have that crossover... that's to equalize cylinder pressure... that's important. True duals don't do that.
Think about water, and how, given a certain pressure, how you would speed up or slow down the velocity... too large a pipe on a small engine will have a low-velocity... too small a pipe on a large engine will get clogged, and also have a low velocity.
What a 2>1 does is function as a collector that almost acts "self-adjusting" or it gives the a similar effect... 2-2s are not bad... but depending on diameter, length, e& they basically have a very narrow band in which they are anywhere close to ideal.
2>1s have a larger one.
Short drag pipes are fine for WOT, but won't make much power anywhere else... the exhaust velocity drops way down... that tends to be true of many 2-2 pipes, so what people do is put baffles and torque cones in... they just restrict air flow, which is antithetical to making power... these too slow down exhaust velocity... but they make the bike more "streetable" by basically de-tuning the engine to run with a clogged pipe...
It's a Harley, it's really about looks, but you will have a much nicer power-band going with a good 2>1...
Okay... an exhaust pipes have one function... to take the exhaust away from the engine... the quicker they do it, the more power you make... it's about exhaust velocity, plain and simple... higher velocity = more power.
The ideal exhaust will give you the highest possible exhaust velocity for a given RPM... to do that, you'd have to have a self-adjusting exhaust... but you can get close without one.
There are a few factors that play into the velocity, there is savaging from all the vibrating and bouncing going on, there is diameter, there are baffles... you'll notice even you sock pipes have that crossover... that's to equalize cylinder pressure... that's important. True duals don't do that.
Think about water, and how, given a certain pressure, how you would speed up or slow down the velocity... too large a pipe on a small engine will have a low-velocity... too small a pipe on a large engine will get clogged, and also have a low velocity.
What a 2>1 does is function as a collector that almost acts "self-adjusting" or it gives the a similar effect... 2-2s are not bad... but depending on diameter, length, e& they basically have a very narrow band in which they are anywhere close to ideal.
2>1s have a larger one.
Short drag pipes are fine for WOT, but won't make much power anywhere else... the exhaust velocity drops way down... that tends to be true of many 2-2 pipes, so what people do is put baffles and torque cones in... they just restrict air flow, which is antithetical to making power... these too slow down exhaust velocity... but they make the bike more "streetable" by basically de-tuning the engine to run with a clogged pipe...
It's a Harley, it's really about looks, but you will have a much nicer power-band going with a good 2>1...
6th Gear
Joined: Nov 2007
Posts: 10
Likes: 0
HP drop with duals...
Okay, just finished two "true dual" installs on identical bikes with wildly different results (both bikes were 08 Deluxes)
- first install: the samson longs (S2-431), PCIII, HD stage1, custom dyno tuned map.
- second install: V&H true duals (stock endcaps), PCIII, Ness big sucker, canned map from Fuel Moto.
Samson pros: look tougher, continuous diameter all the way back, deeper rumble, fishtails look more "nostalgic".
Samson cons: pipes blue (no issue with heat shields so its pretty much invisible), install much more complicated than the V&H due to custom seat bracket to allow the rear pipe to come left (otherwise fit fine), also access to the rear lower head bolt is "challenging".
V&H pros: no blueing whatsoever, better power, louder idle but higher pitch with std baffles,
piece cake install due to the squished rear head tube (lots of space compare to the "honeymoon fit" on the samson.
V&H cons: short pipes dont look as good, rear pipe (left) a little closer to your leg (heat).
Summary: with the V&H combo, power is much better than stock (samson is also better but the V&H kicks ...). For looks go with Samson (otherwise I'd choose V&H... very hard to be disappointed with this install)...
Hope it helps,
Ralph-
- first install: the samson longs (S2-431), PCIII, HD stage1, custom dyno tuned map.
- second install: V&H true duals (stock endcaps), PCIII, Ness big sucker, canned map from Fuel Moto.
Samson pros: look tougher, continuous diameter all the way back, deeper rumble, fishtails look more "nostalgic".
Samson cons: pipes blue (no issue with heat shields so its pretty much invisible), install much more complicated than the V&H due to custom seat bracket to allow the rear pipe to come left (otherwise fit fine), also access to the rear lower head bolt is "challenging".
V&H pros: no blueing whatsoever, better power, louder idle but higher pitch with std baffles,
piece cake install due to the squished rear head tube (lots of space compare to the "honeymoon fit" on the samson.
V&H cons: short pipes dont look as good, rear pipe (left) a little closer to your leg (heat).
Summary: with the V&H combo, power is much better than stock (samson is also better but the V&H kicks ...). For looks go with Samson (otherwise I'd choose V&H... very hard to be disappointed with this install)...
Hope it helps,
Ralph-
Banned
Joined: Jul 2006
Posts: 643
Likes: 0
...ummm some interesting answers...
Okay... an exhaust pipes have one function... to take the exhaust away from the engine... the quicker they do it, the more power you make... it's about exhaust velocity, plain and simple... higher velocity = more power.
The ideal exhaust will give you the highest possible exhaust velocity for a given RPM... to do that, you'd have to have a self-adjusting exhaust... but you can get close without one.
There are a few factors that play into the velocity, there is savaging from all the vibrating and bouncing going on, there is diameter, there are baffles... you'll notice even you sock pipes have that crossover... that's to equalize cylinder pressure... that's important. True duals don't do that.
Think about water, and how, given a certain pressure, how you would speed up or slow down the velocity... too large a pipe on a small engine will have a low-velocity... too small a pipe on a large engine will get clogged, and also have a low velocity.
What a 2>1 does is function as a collector that almost acts "self-adjusting" or it gives the a similar effect... 2-2s are not bad... but depending on diameter, length, e& they basically have a very narrow band in which they are anywhere close to ideal.
2>1s have a larger one.
Short drag pipes are fine for WOT, but won't make much power anywhere else... the exhaust velocity drops way down... that tends to be true of many 2-2 pipes, so what people do is put baffles and torque cones in... they just restrict air flow, which is antithetical to making power... these too slow down exhaust velocity... but they make the bike more "streetable" by basically de-tuning the engine to run with a clogged pipe...
It's a Harley, it's really about looks, but you will have a much nicer power-band going with a good 2>1...
Okay... an exhaust pipes have one function... to take the exhaust away from the engine... the quicker they do it, the more power you make... it's about exhaust velocity, plain and simple... higher velocity = more power.
The ideal exhaust will give you the highest possible exhaust velocity for a given RPM... to do that, you'd have to have a self-adjusting exhaust... but you can get close without one.
There are a few factors that play into the velocity, there is savaging from all the vibrating and bouncing going on, there is diameter, there are baffles... you'll notice even you sock pipes have that crossover... that's to equalize cylinder pressure... that's important. True duals don't do that.
Think about water, and how, given a certain pressure, how you would speed up or slow down the velocity... too large a pipe on a small engine will have a low-velocity... too small a pipe on a large engine will get clogged, and also have a low velocity.
What a 2>1 does is function as a collector that almost acts "self-adjusting" or it gives the a similar effect... 2-2s are not bad... but depending on diameter, length, e& they basically have a very narrow band in which they are anywhere close to ideal.
2>1s have a larger one.
Short drag pipes are fine for WOT, but won't make much power anywhere else... the exhaust velocity drops way down... that tends to be true of many 2-2 pipes, so what people do is put baffles and torque cones in... they just restrict air flow, which is antithetical to making power... these too slow down exhaust velocity... but they make the bike more "streetable" by basically de-tuning the engine to run with a clogged pipe...
It's a Harley, it's really about looks, but you will have a much nicer power-band going with a good 2>1...
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