Blown06

iTrader: (32)

What is the difference between Open Loop SD tuning and Closed Loop SD tuning. Also are there any write ups on tuning both ways (for a beginner). I've searched but most of the stuff I find is too specific or over my head.

truckmann

iTrader: (8)

I believe the tuning is the same for both. You generally do your tuning in open loop that way the o2 sensors aren't trying to make corrections while you are making your fueling/airflow adjustments. From there you can eith leave it in OL or re-enable the o2 sensors for closed loop operation. After it is tuned properly in OL mode then the pcm shouldn't have to work as hard (do as much calculation) to keep the fueling at the commanded rates, fuel trims will be at or close to 0.

There are some good write up stickies in this section!

03sierraslt

iTrader: (22)

As truckman said plus I will add too it.. In OLSD any error that exists in the tune will show up in the AFR, there is nothing that compensates for the AFR. When you are CLSD the 02 sensors are used so that the computer can use the fuel trims to make smaller corrections to keep the AFR at or as close to commanded as possible. Now keep in mind when you go Wide open you are open loop regardless. The difference between OLSD and CLSD will only be apparent when you are not in PE mode or BE mode if you are 2Bar. Now its also not quite that simple, when you are CLSD any positive fuel trims will carry over to your Wide open fueling to make sure that you are not lean. I am currently running OLSD and have been for about 7months. I am going to switch to CLSD because of the constant weather changes around my area. When you are OLSD weather changes and everything will have a greater effect on the tune from day to day. I am not sure if any of this helps but.... That is my rant anyway.

03sierraslt

iTrader: (22)

I see you are running boost, if so I would suggest going 2BarSD if you havent already. I am much happier with the way mine responds since going SD.

thunder550

iTrader: (70)

I recently put mine back into closed loop as well. I ran open loop for a long time, and temperature and altitude affect it a lot. Closed loop is muy bueno.

03sierraslt

iTrader: (22)

Ya I am going to do that one of these days, gotta get new front 02's first

KySilverado

iTrader: (7)

I ran OLSD just to tune then went CLSD. Only caveat is that I only enabled STFT's. I still have LTFT's disabled and WOT AFR has stayed close enough in varying weather. Truck runs great.

Blown06

iTrader: (32)

I got the 2-bar OS from HPTuners, however I can't use it cause I will be hitting more than 14psi boost at the shift points once I get everything dialed in and spin it up that high. I've been waiting on the 3-bar OS now for 2 months. I got an email from them and it should be done this week. I have alot of reading to do, I know, but I can't seem to find any good step-by-step tuning guides for SD.