Running Closed loop
Yes, but I don't have his book in front of me, and I'm sure someone more knowledgable will school me. But it's my understanding that closed loop runs cooler because the ECM hunts and can attain the proper AFR. In open loop it cannot.
Seasoned HDF Member
Joined: Jul 2007
Posts: 6,336
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From: SW Minnesota
I think too you have that backwards. The proper AFR in closed loop is the EPA mandated AFR...which is lean and hot.
Road Warrior
Joined: Aug 2010
Posts: 1,268
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From: Detroit, the asshole of America
The A/F ratio isn't "epa mandated", exactly. It's where the emissions tradeoff output is lowest, and happens to be near 14.6:1 (the stoichiometric air/fuel ratio for gasoline), +/- a tiny margin to bias the ratio for optimum tailpipe emissions. Leaner than stoich, NOx goes up, richer than stoich, hydrocarbons go up. For the most part, closed loop is required for this as it's usually switching around a target air/fuel or equivalence ratio, as catalysts work best when they're constantly storing and releasing.
Cold starts are open loop, and above a specific throttle position and engine speed the bike is open loop as well. It is also run in open loop, richer than stoich for peak power and to protect components. Even the stock bikes run rich to make power at WOT.
Problem is, air cooled engines get some form of cooling from running rich. So, when the new bikes are running where they're supposed to for efficient combustion, the engine runs warmer as a byproduct. They don't run as cool as they used to, but are also several orders of magnitude cleaner, and as long as oil temps aren't too high, engines last longer running warm vs. cold. Everything is a tradeoff.
Cold starts are open loop, and above a specific throttle position and engine speed the bike is open loop as well. It is also run in open loop, richer than stoich for peak power and to protect components. Even the stock bikes run rich to make power at WOT.
Problem is, air cooled engines get some form of cooling from running rich. So, when the new bikes are running where they're supposed to for efficient combustion, the engine runs warmer as a byproduct. They don't run as cool as they used to, but are also several orders of magnitude cleaner, and as long as oil temps aren't too high, engines last longer running warm vs. cold. Everything is a tradeoff.
Seasoned HDF Member
Joined: Dec 2007
Posts: 8,341
Likes: 713
i stand corected emision output is epa regulated ,harley chose to meet the epa regs by running lean.14.7-1 is considered by most too lean for an aircooled motor.
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