Exhaust Backpressure School
#1
Exhaust Backpressure School
Here's a vid from DK Custom Products with Gale Banks refuting HD Owner's "back pressure is good" nonsense for M8 engines.
Just, no. Physics, people. Pulse tuning, yes (2 into 1 pipes). Reversion elimination, yes.
Apologies if someone already posted somewhere. This was 10 days ago. Received in Banks weekly newsletter tonight.
Just, no. Physics, people. Pulse tuning, yes (2 into 1 pipes). Reversion elimination, yes.
Apologies if someone already posted somewhere. This was 10 days ago. Received in Banks weekly newsletter tonight.
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luckiestiff (03-03-2024)
#2
Here's a vid from DK Custom Products with Gale Banks refuting HD Owner's "back pressure is good" nonsense for M8 engines.
Just, no. Physics, people. Pulse tuning, yes (2 into 1 pipes). Reversion elimination, yes.
https://www.youtube.com/watch?v=mZ53YO_RZ0E
Apologies if someone already posted somewhere. This was 10 days ago. Received in Banks weekly newsletter tonight.
Just, no. Physics, people. Pulse tuning, yes (2 into 1 pipes). Reversion elimination, yes.
https://www.youtube.com/watch?v=mZ53YO_RZ0E
Apologies if someone already posted somewhere. This was 10 days ago. Received in Banks weekly newsletter tonight.
Asking for a technical explanation will most often lead to amusement.
#3
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#5
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Y2K (07-03-2024)
#6
Backpressure? Not welcome. Resistance to reversion? Yes! This is a 114/475 combo with some cheezy imported exhaust system (CFR clone). No amount of tuning can fix that, but lollypops help. A new exhaust system (KW, FM, FS, etc) would help this bike immensely, but this system is the look he wants.
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Lonewolf176 (03-03-2024),
Old New Rider (03-04-2024)
#7
Trending Topics
#8
@rigidthumper
Good graph demonstrating reversion, where lollipops are a fix, hence riders get the impression the exhaust needs 'backpressure" to make torque. Ok, fine, but devices that fix reversion happen to add backpressure. Adding more backpressure in an by itself doesn't "add torque". Maybe the nuance isn't worth discussion.
I mean, top fuel drag engines have open, short, individual port pipes for a reason, right?
Good graph demonstrating reversion, where lollipops are a fix, hence riders get the impression the exhaust needs 'backpressure" to make torque. Ok, fine, but devices that fix reversion happen to add backpressure. Adding more backpressure in an by itself doesn't "add torque". Maybe the nuance isn't worth discussion.
I mean, top fuel drag engines have open, short, individual port pipes for a reason, right?
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#9
@rigidthumper
Good graph demonstrating reversion, where lollipops are a fix, hence riders get the impression the exhaust needs 'backpressure" to make torque. Ok, fine, but devices that fix reversion happen to add backpressure. Adding more backpressure in an by itself doesn't "add torque". Maybe the nuance isn't worth discussion.
I mean, top fuel drag engines have open, short, individual port pipes for a reason, right?
Good graph demonstrating reversion, where lollipops are a fix, hence riders get the impression the exhaust needs 'backpressure" to make torque. Ok, fine, but devices that fix reversion happen to add backpressure. Adding more backpressure in an by itself doesn't "add torque". Maybe the nuance isn't worth discussion.
I mean, top fuel drag engines have open, short, individual port pipes for a reason, right?
#10
For what it's worth... They posted this many years ago...
https://www.hdforums.com/forum/sport...l#post17075742
https://www.hdforums.com/forum/sport...l#post17075742
There are too many posts, with too many opinions for me to take the time to address each one individually.
...
I am not going to get in protracted conversations on the following subject, but will say this.
One of the strongest myths regarding Harley's is: They need back-pressure to run well.
This back-pressure myth is too strong for me to spend time fighting it.
Please do not take offense, nor think I am backing down from my statement if I do not respond, taking the time to engage in conversation on the subject.
I'll simply state:
Back-pressure fights AGAINST performance. Back-pressure holds back power, not unlike a 300 lb. rider will reduce acceleration more than a 150 lb. rider.
The reason some folks think that back pressure is good, is because when they put a baffle in (which creates back-pressure) the bike runs stronger. BUT, it is NOT running stronger because of the back-pressure, it is running stronger in spite of the back-pressure, because it is reducing Reversion.
It is wrongly assumed that the back-pressure that baffles create increases power. It is the reduction in reversion from baffles that increase power.
The baffle is reducing power because of the back-pressure, but it is increasing power by Reversion reduction. In most cases the power gained by reduction of reversion is More than the power lost to back pressure, so there is a net gain of more power.
But it is IN SPITE of back pressure, not because of it.
What would be best is if there could be a reduction of reversion WITHOUT an increase in back pressure.
...
...
I am not going to get in protracted conversations on the following subject, but will say this.
One of the strongest myths regarding Harley's is: They need back-pressure to run well.
This back-pressure myth is too strong for me to spend time fighting it.
Please do not take offense, nor think I am backing down from my statement if I do not respond, taking the time to engage in conversation on the subject.
I'll simply state:
Back-pressure fights AGAINST performance. Back-pressure holds back power, not unlike a 300 lb. rider will reduce acceleration more than a 150 lb. rider.
The reason some folks think that back pressure is good, is because when they put a baffle in (which creates back-pressure) the bike runs stronger. BUT, it is NOT running stronger because of the back-pressure, it is running stronger in spite of the back-pressure, because it is reducing Reversion.
It is wrongly assumed that the back-pressure that baffles create increases power. It is the reduction in reversion from baffles that increase power.
The baffle is reducing power because of the back-pressure, but it is increasing power by Reversion reduction. In most cases the power gained by reduction of reversion is More than the power lost to back pressure, so there is a net gain of more power.
But it is IN SPITE of back pressure, not because of it.
What would be best is if there could be a reduction of reversion WITHOUT an increase in back pressure.
...
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