With all the conversation about tuners. What is the difference between closed and open loop?

Also, why do some tuners eliminate the o2 sensors?
I would think they would aide in tuning. Example the fuelpak does not eliminate the o2 sensors but the fuel Moto micro and PC's do?

Not trying to start a fuelpak vs whatever thread, just trying to understand.

 

Try this:

http://www.thirdgen.org/open-loop-closed-loop

not a fan of efi on a 2-cylindar engine....

 

Hi,

There's a thread in the sportster section call "Open or Closed LOOP?"

Which has some great reading, type that in google and it will come up, very good explanation in it of things

Yeah a lot of the discussion will get down to lean/hot, tuner no tuner, xieds, nothing, bike runs fine

People call 14.7/1 lean but it's the perfect combustion ratio when all gas burnt, there's no dispute for performance a tuner is required

I and plenty others are still waiting for the pistons to go thru the motor
Thanks
Mirrmu

 

O2 sensor eliminators turn off the ecu's ability to tune your engine for different fuel, afr, or altitude and even ambient tempurature so that the tuner you buy can do it's work which you pay for.
Open loop is when you run wide open throttle which only occurs for a few seconds in most cases. Face it how long would you be willing to hold your throttle wide open on an air cooled V-twin? So most maps fine tune your calibration to about 4600 rpm and the rest is filled in logically. 95% of your riding is in the 2500 to 4500 range in most cases.

 

Good information.

I couldn't seem to figure out how it would work without the o2 sensors.

 

It won't. And it's better to tune with a tuner like the PowerVision where you still use them.

 

In general, "open loop" means that the oxygen sensors aren't being used as one of the inputs. Any engine will operate in open loop when cold, until the oxygen sensors get warm enough to put out a reliable signal.

Some of the tuners work in open loop all the time, because they put the fuel-air mix richer than what normal oxygen sensors can measure.

"Wideband" sensors will measure a much wider range, and allow even an engine which is tuned pretty rich to operate in closed loop almost all the time. Some of the newer and more expensive tuners work with these wideband oxygen sensors.

 

Open Loop is like running a carburetor. The computer uses predetermined maps to add fuel and timing, kind of like jetting a carburetor.

Closed Loop is when the computer takes the input from the oxygen sensors and the map/maf (not sure which Harleys have) and uses that info, to adjust fuel and timing.

Also, you have long and short term fuel trimming which I don't believe is possible without oxygen sensors.