I understand that open loop happens when you are WOT and at startup, but what is this? Does it mean that its just dumping as much fuel as possible? At WOT(What TPS voltage? Mine only goes up to 3.999 then it doesn't transmit any voltage after that) ? Closed loop is like when its not floored all the way and its still taking sensor readings. Anyone care to elaborate on this?

~Ryan

Hmm..... closed loop. Well, like the term implies, it's closed like a circle. So... say you're at half throttle, the car injects some amount of fuel, then it reads the info from the o2 sensor. From that info, it'll go back and adjust the amount of fuel injected. So it goes in a circle, closed loop. You tell it how fast you want to go (throttle position), it reads the MAF, injects the gas, checks the A/F ratio, then adjusts the amount of gas to get the A/F where it is suppose to be.

Now in open loop, it's like a straight line. It never goes back and makes adjustments. So when you floor it, it goes to open loop and just dumps in how ever much gas the fuel maps are preprogrammed for. Doesn't check the o2 and therefore doesn't make any adjustments and therefore is not a closed loop system.

Or something like that..... :)

Khiem

Thats some good info, thanks. I have a few more questions though..What conditions would make it go into open loop? Does anyone know at what voltage does the TPS tell it that its floored? The reason I ask my TPS wouldn't show past 3.999 volts(at WOT) so I adjusted the screw on the part where the throttle cable hooks to so it wouldnt go over 3.998 volts, since I didn't know what would happen if it wasn't sending any voltage back...

~Ryan

Originally posted by spdracerUT
Hmm..... closed loop. Well, like the term implies, it's closed like a circle. So... say you're at half throttle, the car injects some amount of fuel, then it reads the info from the o2 sensor. From that info, it'll go back and adjust the amount of fuel injected. So it goes in a circle, closed loop. You tell it how fast you want to go (throttle position), it reads the MAF, injects the gas, checks the A/F ratio, then adjusts the amount of gas to get the A/F where it is suppose to be.

Now in open loop, it's like a straight line. It never goes back and makes adjustments. So when you floor it, it goes to open loop and just dumps in how ever much gas the fuel maps are preprogrammed for. Doesn't check the o2 and therefore doesn't make any adjustments and therefore is not a closed loop system.

Or something like that..... :)

Khiem

Very well put. And this is a good thing because it allows for the use of SAFC without fight back from the ECU in open loop. And can also tune down injector flow at idle if useing 370cc/min on 259cc/min computer. Ahh the beauty of it for $320.

Closed loop mode means that the ECU will compare the measured air/fuel ratio to the target air/fuel ratio and automatically increase or decrease fuel delivery accordingly. In open loop mode, the ECU will still use the oxygen sensor to read air/fuel ratios, but will not adjust fuel delivery as in closed loop mode.

Originally posted by SENTRASER
Thats some good info, thanks. I have a few more questions though..What conditions would make it go into open loop? Does anyone know at what voltage does the TPS tell it that its floored? The reason I ask my TPS wouldn't show past 3.999 volts(at WOT) so I adjusted the screw on the part where the throttle cable hooks to so it wouldnt go over 3.998 volts, since I didn't know what would happen if it wasn't sending any voltage back...

~Ryan


3.5 to 4.0 volts is considered wide open throttle on most cars.