How to keep a car in open loop

Modifying cars is a great hobby to have. It’s even better if you can do the work yourself. From tuning to racing the more you can adjust your car the better.

If you have a custom tune on your car you may be wondering how to keep a car in an open loop. You can do this by unplugging the O2 sensors. This will force the ecu to use the preset instructions. These are usually based off the throttle and where the revs are.

What is an open loop for car tuning?

An open loop for car tuning is when the oxygen sensor isn’t being used to affect the way the engine is running. Typically in a closed loop the oxygen sensor sends data back to the ECU to change the fuel trim. This feedback tells the computer whether to add more fuel or use less fuel.

When the system is running on an open loop the engine runs based strictly on the parameters the tuner has set. These settings are usually related to the revolutions of the engine and the throttle position. In an open loop the parameters aren’t dynamically updated.

How to keep your car in an open loop?

By unplugging your O2 sensors you will effectively be driving with an open loop. Without the O2 sensor sending data the car won’t know whether it’s running lean or rich. This can lead to a rich condisition which can foul plugs and negatively affect our gas mileage.

On the other hand, if the engine is running lean it can lead to some combustion problems. You’re likely to get some knock. While if you know what you’re doing running a car in an open loop might be ok just know that it can damage your engine if not done correctly.

Open loop vs Closed loop

An open loop is when the engine is running on pre set parameters. It isn’t affected by the oxygen sensors. To run correctly the correct air/fuel ratio has to be manually set. Closed loop on the other hand is where the engine can dynamically change the air-fuel ratio. The oxygen sensors can play a part in determining if it needs more or less fuel.

Setting Closed loop without unplugging the o@ sensors

Another way to get an open loop condition is to sent the parameters so high that they will never be met. That means setting a fuel condition that in normal instances the engine would never reach. This would effectively be open loop tuning.