thorne Posted April 25, 2007 Report Share Posted April 25, 2007 I've been learning allot along the way but I don't understand how the car in open loop calculates the AFR. in openloop the 02 sensor is ignored, But in my cars current OTS tune it has target afrs as does every other tune I've looked at. How does the car know if its hitting that number? or how does it even know what to put in to it. I'm postive the MAF sensor matters because it tells it atleast how much air is going in. Quote Link to comment Share on other sites More sharing options...
Guest Removed Posted April 25, 2007 Report Share Posted April 25, 2007 it depends on the system you are working with.in closed loop the 02 is ignored(if i remember right) cause it does matter in open loop. or vise verse you have a lot too learn grass hooper. Quote Link to comment Share on other sites More sharing options...
Guest Removed Posted April 25, 2007 Report Share Posted April 25, 2007 go pull off a big vacuum hose and watchs what happens(something like the booster hose). watch what happens(o2 should respond fast), that is lean. its not just looking at one thing, its looking at least 40 inputs. at like 3000 times a sec.(for newer stuff, it verys per car maker) Quote Link to comment Share on other sites More sharing options...
RUTAN TA1647545492 Posted April 25, 2007 Report Share Posted April 25, 2007 The PCM will calculate the airflow from the TPS,MAF and/or MAP and reference them to the VE table to calculate for fuel. Quote Link to comment Share on other sites More sharing options...
thorne Posted April 25, 2007 Author Report Share Posted April 25, 2007 The PCM will calculate the airflow from the TPS,MAF and/or MAP and reference them to the VE table to calculate for fuel. Thats what I was wondering. ROB I already know what lean looksl ike on my car..... It did it on the dyno, We had to abort a run with my 13.6 AFR. but my car thought it was at 11.5 the entire time. Quote Link to comment Share on other sites More sharing options...
Guest Removed Posted April 25, 2007 Report Share Posted April 25, 2007 Thats what I was wondering. ROB I already know what lean looksl ike on my car..... It did it on the dyno, We had to abort a run with my 13.6 AFR. but my car thought it was at 11.5 the entire time. its a easy test too see how fast the o2s respond. Quote Link to comment Share on other sites More sharing options...
BIG SHAFE Posted April 25, 2007 Report Share Posted April 25, 2007 Open loop traditionally, the ECM looks up values in a table that are set (long term trims still apply in most cases I think). Then that value is changed by multipliers like intake air temp, coolant temp, cold start, map, EGR, etc. In closed loop, the ECM looks up values for a target AFR, then uses feedback from the O2's to match the desired AFR, a la short term trims. While still using the same multipliers from before but I think they have less effect than in open loop. Obviously this can very from engine to engine and manuf. to manuf., but this basically how it works. I dont know anything on Suby's but I do know in depth on the LT1 (my car) and and most of LSX stuff. I'm sure someone who does a bunch of tuning can tell you more (Bill Wright, RUTAN TA). EDIT: I see RUTAN TA posted while I was typing. Quote Link to comment Share on other sites More sharing options...
thorne Posted April 25, 2007 Author Report Share Posted April 25, 2007 Yeah , My understanding was the 02 was not used at WOT. I'm just tryin to prepare as much as i can to see if my OXY is is going to be right. Quote Link to comment Share on other sites More sharing options...
BIG SHAFE Posted April 25, 2007 Report Share Posted April 25, 2007 Yeah , My understanding was the 02 was not used at WOT. I'm just tryin to prepare as much as i can to see if my OXY is is going to be right. Right, although I think trims can still be applied to WOT though. Quote Link to comment Share on other sites More sharing options...
thorne Posted April 25, 2007 Author Report Share Posted April 25, 2007 ok So the Amount of fuel to add is pretty much assertained from the MAF/TPS then. There for my maf being screwed up could have most likely been my lean issue. thats what i was trying to figure out, Quote Link to comment Share on other sites More sharing options...
BIG SHAFE Posted April 25, 2007 Report Share Posted April 25, 2007 ok So the Amount of fuel to add is pretty much assertained from the MAF/TPS then. There for my maf being screwed up could have most likely been my lean issue. thats what i was trying to figure out, I would lean towards MAP/TPS for WOT. Only reason I say that is because for LT1's and LSx's the WOT table is based on a MAP and TPS. I would assume it would be similiar, but could be different. You really need a data log of regular driving and a few WOT runs to really say whats going on. If your trims are ok then maybe look at the MAF, but if they are out of whack maybe you have some type of intake/exhaust leak? Quote Link to comment Share on other sites More sharing options...
thorne Posted April 25, 2007 Author Report Share Posted April 25, 2007 If you would not mind taking a peak a tmy logs I can upload them. There just CSV they open in excel. I've got allot of data capped so far and I've been capping everyday on the way home. since the day I was knocking really bad my car has atleast puts ome timing back in and stuff. Quote Link to comment Share on other sites More sharing options...
thorne Posted April 25, 2007 Author Report Share Posted April 25, 2007 I just finished a safer tune. I took the base tune I was using (Written by someone else) I took the 5000-6800 Range and richened it up by target afr of .15, Not much but If I'm close on WB saturday then I can adjust it with this. I'm also testing with a diffrent MAF friday.(Just loggin) Any suggestions on loggable WBs? I'm going to buy one right quick. Quote Link to comment Share on other sites More sharing options...
Guest WizardBlack Posted April 27, 2007 Report Share Posted April 27, 2007 Assuming this is a WRX (most things apply elsewhere)... closed loop: It takes all engine sensors (RPM, MAF, TPS, CLT, IAT, BOOST, KNOCK) and looks up the resultant fuel and timing. This is altered by long term corrections stored in memory and then sent out. The resultant O2 level is checked and fuel is adjusted to attempt to hit the target A/F ratio. If a particular rpm/load area is consitently needing adjustment, then it changes the long term memory for that spot to try to get a "head start" next time. Similarly, the knock sensor is also used to provide long term memory adjustments for timing. open loop: Same exact thing as before but O2's are not used to correct fuel in real time. Knock sensors are still used, though. Subaru's have a tendency to go overboard on corrections if you go too far once; then you have to put it through several pulls (with the problem fixed) before it will back out of the extra corrections. WRX's like about 11.8:1 on boost. Tweak your timing to gain the extra power from there. hope that helps Mark Quote Link to comment Share on other sites More sharing options...
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