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.
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?
Top fuel engines are designed to run at a steady speed ( around 8500). They don't need good manners over a broad range and with around 60 psi of boost, I don't think reversion is a problem.
There are too many posts, with too many opinions for me to take the time to address each one individually.
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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.
03-01-2024, 07:03 PM
Exhaust Backpressure School
