Carlanga

I had some questions about our close/open loop and fuel trims system and stumble upon this. It helped me understand key points that have been mistakenly posted wrong around here.

http://www.autoshop101.com/forms/h44.pdf

This is just some, there are a lot more systems to see at that website. Best of all, Toyota based training series.

Ace83

iTrader: (6)

nice link

Carlanga

I was having some hesitation issues right before full boost, didn't think much of it 'till I realized that it was happening in close loop instead of open. Hopefully is just the map and not the sensor dirty or something (look at note in link). Might have to take a look at the changes I made a while back to the O2 map. Also when cold in open loop idle the car will go up and down in rpms, not much but enough to check what's going on in my fuel map. Didn't know that short term fuel trims only work in close loop.

Ace83

iTrader: (6)

yes LTFT/STFT all in closed loop. your idle is surging? check your vac reading if its going up and down too, it could be it.. or a rough fuel map at idle

SoccerBoy_AP

So our cars run off of a closed loop system, constantly adjusting based off of the exhaust output. What kind of car/setup would be able to safely run open loop?

Not that I want to, because my assumption would be that you would have to program the ECU to the correct fuel measurement for each 250 or 500rpm gain... yes?

Ace83

iTrader: (6)

our car runs closed and open loop depending on situation.. most of the time our car is in close loop to keep afrs dead on despite changes in operating conditions.. our car goes on open loop on heavy throttle/wot, deceleration and cold start up

gwopsta

my car stays in constant open loop, runs like a champ!!! a lil rich but whatever

m6ar2cel6oTC

Stays on how? Disconnected o2 sensor?



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gwopsta

yep, only afr reading is from my uego. no fighting with the ecu, no switch over stumbles,

been riding like this for a while now in changing fl temps and crazy humidity. my afrs normally read around 13.5-14.5, i love the way my car feels

flip that ecu lol

Carlanga

hum, I forgot I did that with Chris to his car. Unpluged the O2 and drove while he tuned it. Got to do that with mine as well to see how my fuel map is going.

gwopsta

i do have a blow thru maf setup tho

Carlanga

no he does not, nor do I. Only reason I was going to try it was to get the map in check and mirror the 02 map, then hook up the o2 and see how close it is.

Unrelated question, how long does the ecu stays in OPEN Loop when the car is first cold started?

johnhawkins

iTrader: (1)

I beleive until it reachs normal operating temp on the coolant thermostat. I believe Open Loop 1 is cold start, Open Loop 2 is WOT pretty much and then Open Loop 3 is when you disconnect the primary o2 sensor which makes it run at 10AFR consistent so pretty much you can disconnect the primary o2 sensor and just simply subtract fuel. I believe this is what I remember but its been a while.

johnhawkins

iTrader: (1)

Also, I think I like the idea of the Open Loop 3 method because if for some reason your tune poops out, it will run off the 10AFR and keep the engine safe until its fixed.