Can anyone please explain some of this stuff to me .. as it may pertain to a 88 TII. I was reading a S-AFC FAQ. and it talked about setting low throttle mode to 0% and let the ECU learn the fuel curve from the O2 sensor before making adjustments. ??? It said somting about that puting the ECU into closed loop mode.. or somthing like this. Now this was a general FAQ, so I am not sure how much of this info pertains to RX7's .. thats kinda what I'm asking. What is closed & open loop mode.. how do they differ, do are ECU's "learn" things? ... how can I turn my S-AFC off entirely .. withiut unwiring it? ...

Please explain .. im confused to all hell now.

Thanks alot,
Robert

 

as for open and closed loop mode.

Open loop. This is when the engine runs with out useing its sensors, like the O2 sensor. It runs in open loop when cold at startup because some things dont work untill warm(O2 sensor!). When running in open loop. You engine runs inefficiently and has less power. Its also hard to pass emissions tests in open loop. basically, when running in open loop, you engine is running "dumb" its just running off of a pre-determined script not really useing any of the functions of the computer. Just like a carbureted engine. This is also your engines "limp mode".

Closed loop is when the engine is warm and useing all its functions and sensors. Making it the efficient, powerful engine that it is.

Does our ECU learn stuff. I dont think so, our cars are to old for that. I think cars (at least affordable ones) started comming with ECUs that could learn in the mid 90's some one correct me if im wrong. I just seem to recall commerical ad's saying this at that time.

 

as far is i understand it, closed loop is what ecu enters after the car is warmed up, basicly it has to do with fuel econ.

here, i just found this, i haven't read it yet but it seems promseing

http://hondata.com/techclosed.html

 

The engine doesn't get more "powerful" being in closed loop; the ECU doesn't even use the sensors when you floor the pedal. If it was using sensors, such as the O2, you would run lean, your O2 sensor would read it, along with your Apex seal flying out before your ECU would adjust. Open loop is just for good gas mileage.

 

I can never remember which is which LOL.. but with an A/F gauge you can easily see it. when it goes back and forth really quick. it's reading off the 02 sensor. trying to keep it at 14.7:1 for best gas millage and emmisions. this happens at part thortle, under 3800rpm.


the other one (open or closed, whichever the top one iesn't) is when you give it more gas, or go above 3800. it uses the AFM, boost sensor, and TPS, to match what it has programed into the ecu, the A/F gauge will stay steady on one light.

 

Closed loop is the gas saver mode, it occurs at like 1/3 throttle or less. Scott's post is close to my understanding of it, except my A/F gauge would read a closed loop status at above 3800, I think it's dependent upon throttle position and engine load. Open loop is when the ECU uses preset maps. As to your original question, I'm not familiar with the SAFC, so I can't help ya. Sorry.

Steve

P.S. Last I checked, our ECUs WERE capable of learning different settings. Do a search on resetting the ECU by disconnecting the battery and depressing the brake pedal(or something like that).

EDIT: Check that P.S. I know that's true for 89+ ECUs, 86-88, I'm not so sure...

 

Right on .. thx for the info fellas. It's making more sense now.

Anyone know how to totally disable the S-AFC.. if you set Low T. position to 0% will that do it?

Also .. anyone know if the 88 ECU's "learn" things? I have read how other cars ECU's even start to adjust to your typical driving sytle .. thats freakin sweet! Does a Halthech "learn"??

 

no it won't learn it's sorta learning in closed loop, when it goes back and forth. but if it's too rich, sometimes it won't even go into it. when I had my AFC tuned on the low settings. basicly the guy was just trying to get it into closed loop, instead of running rich in open. by leaning it out on the low settings, the ecu will put it into closed loop. if you go too far. it'll come back outa closed loop, and run too lean. a basic A/F gauge would be used for this. for the high settings. a wide band is really needed.

as for the settings. what they do is, when you set low to say 30%, and high to 80 %. and say lean out the low to -8 and the high to -4. that just means that anything under 30% throttle is -8, anything over 80 is -4, and everything in between is an avg. for ex. at 55% (half way between 30 and 80) throttle it would be at -6

however the 87-88 gets trickier.. cause it only has the narrow range TPS that maxes out at 30% throttle. so what people do is set the low to 98, and high to 99%. so basicly what you are doing is making everything under 30% thotrol the low setting. and everything over 30% the high setting.

if all the adjusting settings are at 0 (the rpm + or - ones). then it's basicly off, as it's not doing anything but taking readings.