exhaust question
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Road Warrior
Joined: Jun 2012
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From: Orange, VA,
exhaust question
I just bought my first big twin, a 99 EG Standard, it has V&H slip ons, I noticed the rear cylinder exhaust pipe splits and goes to both sides. The front cylinder pipe goes down the right side with the rear cylinder pipe going into it, it seems that you have 1 1/2 cylinder exhaust in one pipe and 1/2 a cylinder in the other, why? Is a true dual exhaust better and does it sound better?
Thanks?
Thanks?
Extreme HDF Member
Joined: Sep 2010
Posts: 14,744
Likes: 402
From: Phoenix '53, '88, '09 Big Twins
yes, flow is probably 65%/ 35%.
the connected exhaust tract is a cheap, easy way to get better efficiency from BOTH cylinders ( this effect is called scavenging) and it is why if you crawl under your car, you will see that the exhaust tracts for both banks of a v8 are connected to each other, usually via an "x" pipe.
this scavenging is more noticeable at lower rpms, where we need power to get that barge moving from a light, or pulling power up and hill or through the twisties.
a true dual system does not have this advantage.
The stock header system easily supports power up over 100 hp and it's large volume is an advantage for power
sound better ?- that's up to the guy opening his wallet and what he determines is "better sound".
( "wait but p51 mustangs and dragsters have short exhaust systems and the pipes are not connected"
yes but in both of those cases the motor run at a high rpms ALL the time. prop planes use propeller pitch to control the power, and drag cars use clutch slip as well as gears.- you notice that drag cars have trouble just holding an idle speed as the entire motor is designed to make power above 4000 rpms
Our bikes spend most of their lives below 3000 rpms.)
Mike
the connected exhaust tract is a cheap, easy way to get better efficiency from BOTH cylinders ( this effect is called scavenging) and it is why if you crawl under your car, you will see that the exhaust tracts for both banks of a v8 are connected to each other, usually via an "x" pipe.
this scavenging is more noticeable at lower rpms, where we need power to get that barge moving from a light, or pulling power up and hill or through the twisties.
a true dual system does not have this advantage.
The stock header system easily supports power up over 100 hp and it's large volume is an advantage for power
sound better ?- that's up to the guy opening his wallet and what he determines is "better sound".
( "wait but p51 mustangs and dragsters have short exhaust systems and the pipes are not connected"
yes but in both of those cases the motor run at a high rpms ALL the time. prop planes use propeller pitch to control the power, and drag cars use clutch slip as well as gears.- you notice that drag cars have trouble just holding an idle speed as the entire motor is designed to make power above 4000 rpms
Our bikes spend most of their lives below 3000 rpms.)
Mike
Last edited by mkguitar; Jun 24, 2012 at 01:52 PM.
Thread Starter
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Road Warrior
Joined: Jun 2012
Posts: 1,672
Likes: 17
From: Orange, VA,
Thanks, I have a x Busch car that i race in the SCCA, I do have a crossover tube on the exhaust system, just never have seen a system like on my new to me Harley. What sound difference is there between the stock and the true dual exhaust?
Extreme HDF Member
Joined: Sep 2010
Posts: 14,744
Likes: 402
From: Phoenix '53, '88, '09 Big Twins
well, true duals are 1 pipe per cylinder- no crossover.
and the stock has the crossover.
I think at low/moderate rpms the exiting gasses from the front cylinder will pull the rear exhaust out the right side- once pressure builds up in the rt side, then I think more of those gasses will go left.
BTW the "Y" pipe right at the rear cylinder can crack IF the header system is wracked when putting on new mufflers- this is a quick easy weld job. and common
you understand scavenging from the scca car.
alot of riders do not understand that motor design is a whole pile of compromises, and that piling everything up in a planned way can get power where we want it.
yes straight pipes make better HP at 6000 roms, ( and decrease power at 2500 rpms) but who evers rides their bike at that motor speed
we could match the fuel delivery, intake, headwork cams and other factors to make a 6000 rpm motor- but we are stuck with a pushrod valvetrain that won't reliably work at that speed and at some point the valves will smack the pistons.
also the length of our stroke gives very high piston speeds which are not good for high revs
the valvetrain is one of the reasons overhead cam motors can rev higher.
Mike
and the stock has the crossover.
I think at low/moderate rpms the exiting gasses from the front cylinder will pull the rear exhaust out the right side- once pressure builds up in the rt side, then I think more of those gasses will go left.
BTW the "Y" pipe right at the rear cylinder can crack IF the header system is wracked when putting on new mufflers- this is a quick easy weld job. and common
you understand scavenging from the scca car.
alot of riders do not understand that motor design is a whole pile of compromises, and that piling everything up in a planned way can get power where we want it.
yes straight pipes make better HP at 6000 roms, ( and decrease power at 2500 rpms) but who evers rides their bike at that motor speed
we could match the fuel delivery, intake, headwork cams and other factors to make a 6000 rpm motor- but we are stuck with a pushrod valvetrain that won't reliably work at that speed and at some point the valves will smack the pistons.
also the length of our stroke gives very high piston speeds which are not good for high revs
the valvetrain is one of the reasons overhead cam motors can rev higher.
Mike
Last edited by mkguitar; Jun 24, 2012 at 02:54 PM.
Thread Starter
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Road Warrior
Joined: Jun 2012
Posts: 1,672
Likes: 17
From: Orange, VA,
I am concerned about performance with my race car, my new to me 99 FLTH I just want to run and sound nice, am a easy cruiser and do my speeding and aggressive driving on the race track lol. Just am curious what the sound difference is, if any between the stock and true duals exhaust.
Extreme HDF Member
Joined: Sep 2010
Posts: 14,744
Likes: 402
From: Phoenix '53, '88, '09 Big Twins
you should get to a bike event and hear other bikes and see what you like.
BTW IMHO the "real" harley sound went away with 8:1 comp ratio'd hemi headed, manually advanced point ignitions systems with a waste spark.
I keep threatening to sell cd's of my panhead idling at 650 rpms to the guys with monster stereos.
Mike
BTW IMHO the "real" harley sound went away with 8:1 comp ratio'd hemi headed, manually advanced point ignitions systems with a waste spark.
I keep threatening to sell cd's of my panhead idling at 650 rpms to the guys with monster stereos.
Mike
Thread Starter
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Road Warrior
Joined: Jun 2012
Posts: 1,672
Likes: 17
From: Orange, VA,
The sound I guess I am trying to get is the blah blah blah when getting on the gas, I feel mine is more mixed because of the crossover tube and the cylinders mixing, maybe it will sound better with each pipe isolated to their own cylinder. I love the bike, is all i could afford and want to create it and make it sound and look to they way i want, have had metrics in the past, this by far has opened a whole new world to me.
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Extreme HDF Member
Joined: Sep 2010
Posts: 14,744
Likes: 402
From: Phoenix '53, '88, '09 Big Twins
if you are mr DIY- some have converted stock headers with a freeze plug.
cheap and easy.
I think fullsac even sells a kit
I'm not always easy- i am cheep.
Mike
cheap and easy.
I think fullsac even sells a kit
I'm not always easy- i am cheep.
Mike
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Thread Starter
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Road Warrior
Joined: Jun 2012
Posts: 1,672
Likes: 17
From: Orange, VA,
I can weld and have a shop in my garage, just never had a big twin, had a couple of sportsters and just traded my 1100 V star in on this 99 FLHT that is in great shape.
When i pulled the baffles out of the V&H slipons they had half a license plate wraped around the baffles lol, I took them off and put fibreglass back in them, sound good, I guess I can buy the V&H head pipes and put the slip ons back on, the head pipes are $300.
When i pulled the baffles out of the V&H slipons they had half a license plate wraped around the baffles lol, I took them off and put fibreglass back in them, sound good, I guess I can buy the V&H head pipes and put the slip ons back on, the head pipes are $300.
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