I was wondering what most of you guys thought about running open loop tunes? Do most people that have had there bike Dyno tuned run the tune in open loop?

 

Many tuners dyno a bike and run it in open loop for performance. I've had that done several times.

 

What are you trying to accomplish by running an open loop setting?

 

I'm not trying to accomplish anything. I'm mainly looking for info on the benefits or downfalls to running open loop. I'm hoping to get some detailed info. I've been told that in closed loop the Bike will make changes and end up leaning a tune out?

 

When you start a ECM controlled engine, it starts in open loop. That means it doesn't read too much into sensors. When it warms up, it goes into closed loop and stays there, the ECM is reading sensors and adjusting as necessary. There is no sense or reason to dyno in open loop... I say this in lamens terms... hopefully you get the point.

 

Remember that the O2 sensors are trying to maintain the EPA mandated 14.6:1 fuel air ratio when in closed loop with factory ECM settings. That's great for fuel economy and always on the edge of lean. A performance tuned motor often runs around 12.7 give or take depending if you are accelerating or in cruise mode. You usually gain performance but will probably loose some MPGs. Most of my pro tuned bikes average 37 to 39 mpg depending how I'm riding.

 

you actually have that backwards. closed loop is when the ecm will read the info from the sensors.

 

I think you have this backwards:
Start up is OPEN loop, ECM just runs from stored values. The O2 sensors need to warm up before they're able to take a reading (hence the heater circuit inside the sensor on cars and probably bikes as well)


Once the sensor warms up enough to read properly, the ECM switches to CLOSED loop. This means that it can fine tune the base fuel map using info from the O2 sensors. The sensors give real time info about how the engine is really running.


Most ECMs will switch to OPEN loop at WOT because you want to run a bit rich for max power and the O2 sensors can't keep up to that rate of RPM change.


My personal thought would be that it would be best to run an OPEN loop WOT fuel and timing curve as well as baseline numbers for a CLOSED loop idle and cruise map but I'm definitely not a dyno tuner so this part is a guess.

 

Well, as you can see from some of the responses, the difference between closed and open loop is poorly understood.

As to your statement...in closed loop the Bike will make changes and end up leaning a tune out...is a common misconception.

Open/closed loop is simply a switching number...at one number the system goes into closed loop and begins to use additional data to maintain certain parameters the tuner has set.

As stated above, as sensors are being used, the tables within the ECM will read that data and make necessary changes. If it reads "rich" the system will try to lean it out. If it reads "lean", the system will try to richen it up.

One can put a bike into closed loop and it can still run very rich...the opposite is true as well.

 

In closed loop your O2 sensors are giving feedback to the ECM.


http://www.rbracing-rsr.com/downloads/tts_tuning.pdf

Open this link to the TTS manual and look at page 7, 39, 40 and 41 to get a real idea what is happening.


Though I don't use TTS anymore this manual explains things in a way most of us can understand and gave me a better understanding of what the tuner is doing and why.


Good LUck