Sorry for the newbie questions, but

1) what's the difference b/w open and closed loop?
2) Are stock evos open or closed?
3) Is it true that you can run closed loop with an AEM EMS only if you use an AEM wideband (uego)?

thanks for the help

 

If im correct..... closed loop is where your car's AFR will run to a specified target AFR (o2 sensor feedback), which requires a wideband (ie. uego). Open loop is where your car will run to your fuel map at all times. There will be no trimming. Someone else can chime in... I think I know how it works but cannot explain thorougly.

 

1. Open loop just runs off a certain setpoint, closed loop throws in a feedback loop from the response of the system.
2. I'm not sure exactly how Evo's work, but most cars operate on open loop during warm up, then switch to closed loop.
3. Since a closed loop requires some sort of sensor, I would imagine you need something. I doubt it has to be an AEM wideband though, but I'm not sure.

 

You can use the O2 feedback function (closedloop) with a variety of wideband O2 meters. I run a FJO wideband with AEM ems.

 

closed loop- ECU needs feedback from o2/ECT sensor to verify how much it has to correct fuel pulsewidth to bring the car to a stable stoichiometric value.

open loop- ECU reads airflow values from a MAF/MAP sensor and dependant on that, dumps/withholds fuel to maintain a specific a/f.

Car is turned on and up until the point of the car being fully warmed up, it will run in closed loop, once it reaches a preset operating temperature, it will switch over to open loop.

 

thanks guys...this was really helpful

 

c'mon guys

closed loop - the car fuels to a target A/F depending on the Primary 02 sensor
open loop - the car runs directly off the fuel maps in the ECU

i don't know about evo's but honda's switch to open loop at or near WOT

 

thats right.... closed loop is basically for initial warm-up where the ecu uses a basic air fuel calculation to determine the necessary conditions needed inorder for the car to run properly, once warmed up like dexmix said = runs on the fuel map of the vehicle

 

Actually it works the opposite this. ^ The car when cold is in open loop. After the car warms up it goes into closed loop (i.e. O2 feedback) Once a certain load/throttle position is achieved they will switch back to open loop. (reading from fuel map and not O2 sensor)

 

yeah, your right. my bad... i had my words mixed up..... you know what i meant though

 

The reason for open / closed loop is temperature dependent. A cold vehicle has a cold O2 sensor, which will not accurately output the correct voltage to the ECU from what the engine is seeing. Therefore, it runs on a base map until the O2 sensor has heated up (somewhere around 600F).