Open or Closed LOOP ?
Open or Closed LOOP ?
Road Warrior
Joined: Oct 2012
Posts: 1,371
Likes: 46
From: In the foothills of southwestern NC - US of A
I just posted this a few minutes ago down the board a piece:
The below is about the easiest to understand explanation I have found, taken from:
http://www.baggersmag.com/tech/0906_...s/viewall.html
The below is about the easiest to understand explanation I have found, taken from:
http://www.baggersmag.com/tech/0906_...s/viewall.html
Open-Loop Systems
We already know that the factory has used two major designs of EFI systems: throttle position sensor (1995-2001) and MAP sensor (2001-up). However, there is another major difference in how an EFI system operates: open loop (fixed map) and closed loop (variable map). An open-loop system samples data from the engine sensors, which points to a given location in the ECM's configuration map. Each map location contains fuel-injector pulse width and ignition-advance data for a certain set of sensor parameters. A change in sensor inputs points to a different location in the ECM's map, resulting in different injector pulse width and ignition-advance values. All factory EFI systems through 2005 are fixed open-loop systems.
We already know that the factory has used two major designs of EFI systems: throttle position sensor (1995-2001) and MAP sensor (2001-up). However, there is another major difference in how an EFI system operates: open loop (fixed map) and closed loop (variable map). An open-loop system samples data from the engine sensors, which points to a given location in the ECM's configuration map. Each map location contains fuel-injector pulse width and ignition-advance data for a certain set of sensor parameters. A change in sensor inputs points to a different location in the ECM's map, resulting in different injector pulse width and ignition-advance values. All factory EFI systems through 2005 are fixed open-loop systems.
An open-loop system works well when an engine is in relatively stock condition and the fixed map in the ECM contains values for the range of sensor inputs. But when an engine is modified, even slightly, it flows more air and requires more fuel to maintain the precise air/fuel ratio for optimum power. In this case, an open-loop system stumbles severely because sensor values fall outside the map parameters.
Closed-Loop Systems
Beginning in 2006, some Harley EFI models shipped with a closed-loop (variable map) system, and from 2007-up, all models have closed loop. A closed-loop system uses inputs from the engine sensors to point to a relative starting point in the ECM's configuration map for fuel and ignition advance. This system also uses a narrow-band oxygen sensor (O2 sensor) plumbed into each exhaust header. The oxygen sensors monitor exhaust gases for rich and lean conditions. Once the engine is up to operating temperature, the ECM adds oxygen sensor data to the relative starting point in the configuration map to arrive at a final map location for fuel-injector pulse width and ignition advance values.
Beginning in 2006, some Harley EFI models shipped with a closed-loop (variable map) system, and from 2007-up, all models have closed loop. A closed-loop system uses inputs from the engine sensors to point to a relative starting point in the ECM's configuration map for fuel and ignition advance. This system also uses a narrow-band oxygen sensor (O2 sensor) plumbed into each exhaust header. The oxygen sensors monitor exhaust gases for rich and lean conditions. Once the engine is up to operating temperature, the ECM adds oxygen sensor data to the relative starting point in the configuration map to arrive at a final map location for fuel-injector pulse width and ignition advance values.
Since a closed-loop system provides real-time exhaust-gas monitoring, more precise fuel and ignition advance curves are achieved. But even the factory's closed-loop system has limitations. For example, the factory closed-loop system uses narrow band O2 sensors, which means that the fuel ratio can be varied only over a narrow band or range. For improved performance, some aftermarket manufacturers offer EFI systems with wide-band O2 sensors, which are better able to handle the increased range of air/fuel ratios required by highly modified engines. Zipper's ThunderMax is such a system.
=8^)
Cruiser
Joined: Jul 2007
Posts: 136
Likes: 24
From: Florida Panhandle
Problem with H-D's closed loop system (2007-up) is that it's not a fully closed loop system. If you have a race tuner and examine the maps you will see that the system only runs closed loop at part throttle/low MAP where the narrow-band O2 sensors maintain AFR between 14.1-1 and 14.9-1 depending on the closed loop bias settings. At higher throttle/loads the EFI uses fixed mapping.
Stellar HDF Member
Joined: Dec 2005
Posts: 3,302
Likes: 274
From: Milton, Delaware
This is a question I've had as well.
So, trying to understand this part:
"throttle position sensor (1995-2001) and MAP sensor (2001-up)"
"Beginning in 2006, some Harley EFI models shipped with a closed-loop (variable map) system, and from 2007-up, all models have closed loop. A closed-loop system uses inputs from the engine sensors to point to a relative starting point in the ECM's configuration map for fuel and ignition advance.
Where is the MAP sensor located on my '06 Deuce (purchased Oct 05)? I've had the exhaust off several times and there are no sensors attached anywhere.
So, trying to understand this part:
"throttle position sensor (1995-2001) and MAP sensor (2001-up)"
"Beginning in 2006, some Harley EFI models shipped with a closed-loop (variable map) system, and from 2007-up, all models have closed loop. A closed-loop system uses inputs from the engine sensors to point to a relative starting point in the ECM's configuration map for fuel and ignition advance.
Where is the MAP sensor located on my '06 Deuce (purchased Oct 05)? I've had the exhaust off several times and there are no sensors attached anywhere.
Road Master
Joined: Nov 2011
Posts: 988
Likes: 8
From: Clinton IA
This is a question I've had as well.
So, trying to understand this part:
"throttle position sensor (1995-2001) and MAP sensor (2001-up)"
"Beginning in 2006, some Harley EFI models shipped with a closed-loop (variable map) system, and from 2007-up, all models have closed loop. A closed-loop system uses inputs from the engine sensors to point to a relative starting point in the ECM's configuration map for fuel and ignition advance.
Where is the MAP sensor located on my '06 Deuce (purchased Oct 05)? I've had the exhaust off several times and there are no sensors attached anywhere.
So, trying to understand this part:
"throttle position sensor (1995-2001) and MAP sensor (2001-up)"
"Beginning in 2006, some Harley EFI models shipped with a closed-loop (variable map) system, and from 2007-up, all models have closed loop. A closed-loop system uses inputs from the engine sensors to point to a relative starting point in the ECM's configuration map for fuel and ignition advance.
Where is the MAP sensor located on my '06 Deuce (purchased Oct 05)? I've had the exhaust off several times and there are no sensors attached anywhere.
Stellar HDF Member
Joined: Aug 2009
Posts: 3,212
Likes: 212
MAP = Manifold Absolute Pressure. It's going to be in your manifold behind the throttle plate. It reads high vacuum (low pressure) when the plate is closed and reads low vacuum (high pressure) when the plate is open. The ECU then runs those values through an algorithm along with other sensors to calculate the mass of air entering the cylinder, which it then matches to a specific mass of fuel via injector pulse width.
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Road Warrior
Joined: Oct 2012
Posts: 1,371
Likes: 46
From: In the foothills of southwestern NC - US of A
But a tuner utilizes a calibrated MAP developed ON A DYNO to change the original factory MAP so that the ECM contains the proper data parameters for optimized performance and peak efficiency, by adjusting the air/fuel ratios during acceleration/deceleration/constant RPM, and the engine's timing to coincide with these ever changing conditions.
As such there's no comparison between the two entities, and if you wish to call an exhaust + intake + XiED's a "Stage 1 upgrade" you're not really being honest with yourself.
=8^)
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Outstanding HDF Member
Joined: Dec 2010
Posts: 2,036
Likes: 8
From: Temecula, CA
To the OP. There is a simple definition for closed and open loop.
You know, I had an explination drawn up but I see this information be asked enough, in various forms, that I went one better (and hopefully in a way that will save me from writing so much). So, The differences between open and closed loop:
Sidebar:
Not to make a huge debate out of this...but it will devolve into that I'm sure...that's assuming they create a calibrated fuel map (not to be confused with a MAP sensor) on a Dyno. Most folks who do a stage one upgrade will purchase a tuner and used the canned map for thier modifications that comes with it. As such, the accuracy of that tune probably isn't that far off than what Xieds achieve.
Also, one could argue that a Dyno tune isn't a real world tune since a Dyno has a number of set parameters. Multiple scans of the ECMs performance over real world conditions and then a calibrated fuel map derrived from the data from those scans is probably a more accurate map than one derived from a dyno session.
Even with a full dyno session or real world scan tune the difference between a "properly" tuned bike and an Xied tuned bike is going to be marginal and probably not noticable. To say a bike with exhaust, intake and Xieds really doesn't have a stage 1 on it comes across as sounding more eliteist and defensive than rational and accurate. And before someone accuses me of just defending my Xied purchase, I run a PowerVision with the Autotune Pro module and have both Narrow and Wide band O2s installed in the exhaust at the same time. HUGE overkill for Stage 1 upgrades but I have no reason to defend Xieds other than most people tend to rabidly defend or staunchly attack their use.
But I highly digress.
You know, I had an explination drawn up but I see this information be asked enough, in various forms, that I went one better (and hopefully in a way that will save me from writing so much). So, The differences between open and closed loop:
Sidebar:
An enrichened air/fuel ratio will of course decrease a lean condition aiding in acceleration and will provide cooler cylinder and exhaust temps.
But a tuner utilizes a calibrated MAP developed ON A DYNO to change the original factory MAP so that the ECM contains the proper data parameters for optimized performance and peak efficiency, by adjusting the air/fuel ratios during acceleration/deceleration/constant RPM, and the engine's timing to coincide with these ever changing conditions.
As such there's no comparison between the two entities, and if you wish to call an exhaust + intake + XiED's a "Stage 1 upgrade" you're not really being honest with yourself.
=8^)
But a tuner utilizes a calibrated MAP developed ON A DYNO to change the original factory MAP so that the ECM contains the proper data parameters for optimized performance and peak efficiency, by adjusting the air/fuel ratios during acceleration/deceleration/constant RPM, and the engine's timing to coincide with these ever changing conditions.
As such there's no comparison between the two entities, and if you wish to call an exhaust + intake + XiED's a "Stage 1 upgrade" you're not really being honest with yourself.
=8^)
Also, one could argue that a Dyno tune isn't a real world tune since a Dyno has a number of set parameters. Multiple scans of the ECMs performance over real world conditions and then a calibrated fuel map derrived from the data from those scans is probably a more accurate map than one derived from a dyno session.
Even with a full dyno session or real world scan tune the difference between a "properly" tuned bike and an Xied tuned bike is going to be marginal and probably not noticable. To say a bike with exhaust, intake and Xieds really doesn't have a stage 1 on it comes across as sounding more eliteist and defensive than rational and accurate. And before someone accuses me of just defending my Xied purchase, I run a PowerVision with the Autotune Pro module and have both Narrow and Wide band O2s installed in the exhaust at the same time. HUGE overkill for Stage 1 upgrades but I have no reason to defend Xieds other than most people tend to rabidly defend or staunchly attack their use.
But I highly digress.
Last edited by Robotech; Feb 5, 2013 at 07:17 PM.