Open Loop vs Closed Loop
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Novice
Joined: Dec 2009
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Open Loop vs Closed Loop
With closed loop feedback control, the fuel injection setpoint is lean and the O2 sensors send the signal to maintain a lean condition. The type of system I would like to see is using feedforward control, alot like the power commanders and such, with a little feedback trim. Wideband O2 sensors would need to be used with an A/F ratio that can be changed. Does a system like this exist for Harleys or motorcycles anywhere? Do autos use a system like this? These feedforward systems do exist in process controls. Any thoughts or info?
Road Warrior
Joined: Apr 2009
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Currently the sensor technology does not exist for the HD application. That kills just about any of these clever ideas. You can't trust the measurement enough to do any better than what's available off the shelf. A few cars use WB O2 sensors as you describe, but in a much more controlled and predictable environment, and therefore more accurate measurements of O2. Now O2 is just an indirect method of measuring A/F anyway. What we need is a inexpensive sensor that measures A/F directly and with quick response. Nothing out there like that. So life is a compromise.
Some systems like TMax and PCV Autotune make the attempt to use WB sensors but in practice they do not produce as good result as a system that uses narrowband sensors to establish a base and then use a calibrated VE table to predict the proper open loop fuel and timing.
Pro Dyno tuners use better quality/calibrated O2 sensors to establish accurate VE/fueling tables
Oh, closed loop NB systems can easily be set plenty rich enough for cruising, its the WOT or throttle cracking regions where you need a mix richer than a NB sensor can provide feedback.
Some systems like TMax and PCV Autotune make the attempt to use WB sensors but in practice they do not produce as good result as a system that uses narrowband sensors to establish a base and then use a calibrated VE table to predict the proper open loop fuel and timing.
Pro Dyno tuners use better quality/calibrated O2 sensors to establish accurate VE/fueling tables
Oh, closed loop NB systems can easily be set plenty rich enough for cruising, its the WOT or throttle cracking regions where you need a mix richer than a NB sensor can provide feedback.
Last edited by ColdCase; May 5, 2010 at 07:42 PM.
Thread Starter
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Novice
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I guess O2 sensor technology has to evolve for a more sophisticated control scheme to take place, but I would also like to see engine temp input and ambient air temperarure mixed into the current control system to trim A/F ratio within limits. Just mapping alone is a problem when air filters get dirty or wet, or other disturbances to the perfect conditions that have to exist for mapping, but I guess it is the best we can do.
Road Warrior
Joined: Aug 2008
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From: TEXAS
Sounds like there are some people here that really do understand this, I don't. What do you guys think if this set up? http://www.nightrider.com/parts/
Road Warrior
Joined: Apr 2009
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The XiED works great for cooling a motor a bit (fattens up the mix across the board). I ran them for months. But I wanted to get rid of an annoying surge and decel pop, which the XiED did nothing for. Its worth only a few points A/F WOT but sometimes that is all you need.
Extreme HDF Member
Joined: Sep 2005
Posts: 11,615
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From: Baton Rouge, LA
Some systems like TMax and PCV Autotune make the attempt to use WB sensors but in practice they do not produce as good result as a system that uses narrowband sensors to establish a base and then use a calibrated VE table to predict the proper open loop fuel and timing.
Oh, closed loop NB systems can easily be set plenty rich enough for cruising, its the WOT or throttle cracking regions where you need a mix richer than a NB sensor can provide feedback.
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MODERATOR
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From: New England
Just about anyone can get a fueling system to dump so much gas into an engine at cruise to make those following close behind puke from the smell of an overly rich mixture...not to mention poor gas mileage too.
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Extreme HDF Member
Joined: Sep 2005
Posts: 11,615
Likes: 50
From: Baton Rouge, LA
Some systems like TMax and PCV Autotune make the attempt to use WB sensors but in practice they do not produce as good result as a system that uses narrowband sensors to establish a base and then use a calibrated VE table to predict the proper open loop fuel and timing.