The_aSSet Posted December 12, 2012 Report Share Posted December 12, 2012 I've been running SD open loop for a few days now while I await my new o2 sensors and i'm kinda liking it. are there any negatives to running open loop I should be aware of? I'm not boosted, lq9 408 l92 heads, yadaa yadaa, its in my build thread. I will be running nitrous later on, probably next year, around 150-200 shot. Quote Link to comment Share on other sites More sharing options...
shadowsniper3006 Posted December 12, 2012 Report Share Posted December 12, 2012 My truck runs SD open loop all the time, has been for years now. I have not found an issue yet that would have been corrected by the o2s being on. I would think the 02s would catch bad gas and help correct but again in 2 years everything has been fine. I plan on adding a MSD IAT to the intake tube and getting rid of the MAF all together this off season. Quote Link to comment Share on other sites More sharing options...
The_aSSet Posted December 12, 2012 Author Report Share Posted December 12, 2012 How does it do with temp changes? I'm not running a maf, just have a GM iat sensor on the intake tube. Quote Link to comment Share on other sites More sharing options...
Blown 346 Posted December 12, 2012 Report Share Posted December 12, 2012 (edited) Open Loop and Closed Loop are two terms used to describe the fueling mode the computer is in. In closed loop fueling, the computer takes readings from the oxygen sensors which read +/- of 14.64 AFR (Stoich) and makes corrections for it. If your car is idling @ 13.5 AFR, the 02s can see this, and will know to pull out enough fuel to get back to stoich. In open loop, the fueling is purely based off the MAF transfer function and the open loop fuel table. This table has to be calibrated any time you make MAF changes, and changes that affect the airflow of the MAF. When a car is started, the computer is in open loop until certain criteria is met. The o2 sensors need to be heated to work properly, so this is the main reason there is a delay. After the sensors are heated up, the car goes into closed loop and the O2 sensors make their corrections. The computer will go back into open loop under a variety of conditions. Throttle Position (TP) is one way. There are parameters in the computer that determine what the TP is for Open Loop, and other things. When that TP is reached, and the car goes open loop, and richens up. Running in open loop will affect gas mileage and emissions. But if the MAF is set right it shouldnt be a problem. Edited December 12, 2012 by Blown 346 (see edit history) Quote Link to comment Share on other sites More sharing options...
The_aSSet Posted December 12, 2012 Author Report Share Posted December 12, 2012 I know all that lol but thanks. Looking for pros and cons to keep running open loop permanantly Quote Link to comment Share on other sites More sharing options...
shadowsniper3006 Posted December 12, 2012 Report Share Posted December 12, 2012 Yah.....nice copy and paste post..... Reynaldo or Kevin can correct me if I'm wrong, but the fuel that is added or subtracted for the iat is a table gm calibrated and not accessible to us. So as long as your Ve table is tuned properly the truck should run the same afr at any temp no matter if it's using the 02s or not. There is a iat adder table in hpt but I think that is for warm up not the actual added or subtracted fuel amount for every degree of change. Sent from my SAMSUNG-SGH-I747 using Tapatalk 2 Quote Link to comment Share on other sites More sharing options...
The_aSSet Posted December 12, 2012 Author Report Share Posted December 12, 2012 Alright, ill try it out and see how it does. I'm sure it'll warm up here soon. Its Texas. Quote Link to comment Share on other sites More sharing options...
Blown 346 Posted December 12, 2012 Report Share Posted December 12, 2012 (edited) yea I did copy and paste it. Whats the big deal, just trying to help the guy out. Edited December 12, 2012 by Blown 346 (see edit history) Quote Link to comment Share on other sites More sharing options...
chpspecial Posted December 13, 2012 Report Share Posted December 13, 2012 I have been running OLSD since about 2006 with no problems. Everynow and then I re-enable CLSD and my fuel trims are never out of control. One thing about E10 gas is that it is consistent from fill up to fill up. I still have to relocate my IAT sensor, but my MAF is completely gutted. There are tables accessible to us with EFILive that help with cold/hot climate control so that is not a big issue. The biggest negative is that you can not drive from one extreme altitude change to another with OLSD. However, a quick shut down and restart will usually solve most issues. I.E. if you go from a low DA to high, you might run slightly rich at the high DA, and vice-a-versa. Blown 346 your C+P failed to mention anything about the lack of a MAF Quote Link to comment Share on other sites More sharing options...
Blown 346 Posted December 13, 2012 Report Share Posted December 13, 2012 Not a internet wizard.... Quote Link to comment Share on other sites More sharing options...
The_aSSet Posted December 22, 2012 Author Report Share Posted December 22, 2012 Alright so bumping this back up. I'm having alot of trouble with temp changes. In the morning the truck will run rich, in the evening it will be lean. And it's a big difference. Also in stop and go traffic it leans out like crazy cause the iats get up to like ~115 and I have to bump up the ve table to keep it from dying. Should I just go back to MAF? Would running closed loop again help any of that? It's really annoying. Quote Link to comment Share on other sites More sharing options...
chpspecial Posted December 23, 2012 Report Share Posted December 23, 2012 Who is doing your tune, IIRC it was zippy, but it sounds like your tune needs to be dialed in better. Also use the IAT and ECT fuel/timing modifiers to control temp change, not the VE table Quote Link to comment Share on other sites More sharing options...
The_aSSet Posted December 23, 2012 Author Report Share Posted December 23, 2012 (edited) Krambo gave me a rough base tune and i'm going from there with a little help from Wheatley when he can. But I can't do the iat modifiers with hptuners correct? The table I was gonna mess with was the cylinder charge bias table but i've heard so many different things about messing with that. And I only use the ve cause in traffic I can change it in the RTT without having to stop and reflash something. I can put up my tune if that would help anything. Edited December 23, 2012 by The_aSSet (see edit history) Quote Link to comment Share on other sites More sharing options...
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