My1st Truck

iTrader: (8)

When at WOT, what happens to the computer? Like say on a Dyno. The question was asked on another board I hang out at. I just am not sure.
I thouht the stayed in closed loop at normal operating temp and at WOT didn't look at certain sensors.

Ryan K

iTrader: (11)

At WOT, the computer stops reading the O2 sensors. THe PCM relies on the MAF the most, and the PE table tells it what AFR to shoot for...

Ryan

My1st Truck

iTrader: (8)

Thanks Ryan,
So that is sort of like open loop, but the computer still stays in closed loop?
That is if all the requirments of closed loop are met?

Ryan K

iTrader: (11)

Well technically, if its not doing anything with the O2 feedback, then its in Open Loop.

WAHUSKER

iTrader: (4)

I believe Closed Loop is the normal mode & Open Loop is for WOT when it quits reading the O2s. (Open Loop in electronics means you aren't getting any feedback signal for control) And I think there is a table that says at xx% of TPS the PCM goes into Open Loop (can't find it now).

But like Ryan said, it mainly uses the MAF readings after entering Open Loop, and they are maxed out at 4k rpms on cars like Ryans (hence the Speed Density tuning without a MAF). The PCM also relies on the MAP readings (hence 2 or 3 BAR MAP sensors on cars like Ryans).

But the PCM sets things off the O2 readings WHEN IT ENTERS Open Loop, hence the importance of having someone like Ellis dial the car in while driving normally FIRST so the car doesn't take 2 seconds to recover when you mash the go pedal. WOT tuning is the easy part...or so they say!