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pbp1 · 03-21-2017, 06:58 PM

Neither closed or open loop offer a performance advantage. In a properly set up and tuned Speed Density system, closed loop is just a tuning tool to help guide the building of your VE table, which is simply an airflow model of your engine.
I am not satisfied until the O2 correction is less than + or - 2%. At that point, your VE table is properly calibrated and you should be able to put it in open loop and the engine will perform the same.
The argument that one mode has a performance advantage over the other is completely invalid.
As for the durability of sensors, NTK is the best, and while the NTK sensor is an upgrade on some systems, it is STANDARD EQUIPMENT with the FAST XFI, always has been.
It is basically a personal choice, running in closed loop offers some protection in the event of injector or fuel system failure. The other side of that is if the O2 fails or if you develop a leak in your header, you are going to have a rich condition as a result. Live by the O2, Die by the O2.
As for it being a good or bad idea, two of the top 5 qualifiers in Super Stock at Indy last year were running Closed Loop (and Speed Density) including the #1 qualifier.

The purpose of closed loop IS NOT to correct for changes in air. Speed Demsity does that automatically and in Alpha-N, the tuner does that manually when needed.

The biggest issue that people experience when trying to run in closed loop is the correction overshooting, and then see-sawing up and down. There are gain controls and corrrection limits that you can use to get the "speed" of the correction dialed in for your application to prevent over/under correction. It also works better as you get your base numbers closer so it doesn't have "so far to go".

03-21-2017, 06:58 PM	#88
pbp1 Junior Member Join Date: Mar 2013 Posts: 80 Likes: 12 Liked 27 Times in 6 Posts	Re: Fuel injection? Open or Closed loop? Neither closed or open loop offer a performance advantage. In a properly set up and tuned Speed Density system, closed loop is just a tuning tool to help guide the building of your VE table, which is simply an airflow model of your engine. I am not satisfied until the O2 correction is less than + or - 2%. At that point, your VE table is properly calibrated and you should be able to put it in open loop and the engine will perform the same. The argument that one mode has a performance advantage over the other is completely invalid. As for the durability of sensors, NTK is the best, and while the NTK sensor is an upgrade on some systems, it is STANDARD EQUIPMENT with the FAST XFI, always has been. It is basically a personal choice, running in closed loop offers some protection in the event of injector or fuel system failure. The other side of that is if the O2 fails or if you develop a leak in your header, you are going to have a rich condition as a result. Live by the O2, Die by the O2. As for it being a good or bad idea, two of the top 5 qualifiers in Super Stock at Indy last year were running Closed Loop (and Speed Density) including the #1 qualifier. The purpose of closed loop IS NOT to correct for changes in air. Speed Demsity does that automatically and in Alpha-N, the tuner does that manually when needed. The biggest issue that people experience when trying to run in closed loop is the correction overshooting, and then see-sawing up and down. There are gain controls and corrrection limits that you can use to get the "speed" of the correction dialed in for your application to prevent over/under correction. It also works better as you get your base numbers closer so it doesn't have "so far to go".