I’ve been considering doing this for ease of tuning but i’m unsure how drivability would be. i can’t really find any info about it or any other guys that do it, is it more common with the LSx crowd?
I’ve already seen what high overlap can do to closed loop operation…basically my car thinks its lean all the time and it’s damn near impossible to dial in fuel trims. so if i didn’t have fuel trims then i wouldn’t have to worry
only cars that I know of that run open loop tunes are full out drag cars.
not sure how OBDII runs, but i’ve tuned my car open loop and it ran great. Not sure how OBD II would be any different. Just give it the fuel it wants
you ran your car at open loop 24/7???
As long as the tune is spot on you won’t have any issues, and could improve drivability due to not fumbling around with fuel trims
I love the way my car responds OLSD but I don’t have the balls to run it all the time… I run CLMAF, thinking of swapping to CLSD tho
24/7
Used air fuel gauge and wideband to dial in fueling.
Cam’s overlap fooled the o2 sensor so it would idle all messed up. There was a way around that with my 89 ecm and i found a way to make it work just fine at idle in closed loop but there was a o2 timing error i couldnt track down. The car was going into closed loop too early and the o2 sensor wasnt heated up all the way.
I think i found the solution to that with the o2 ready timer tables i have but never played with it
I went to open loop and never looked back. problem is, come winter time you run richer than normal, the MAF sensor reads cooler denser air, but with the o2 sensor taken out of the equation, there is no fuel correction.
So you may need to retune.
Open loop is just like a carb. give it fuel and the only corrections will be YOUR corrections. No automated stuff.
Not sure how it works in the LSx world, but open loop is very popular among the OBD I pre-LT1 era. But there are ways to keep closed loop and a big cam as i’ve mentioned above. New codes were written to allow more adjustment of the o2 sensor values and closed loop timers. More knowledge was gained and now there are some guys with monster cams idling in closed loop no problem
For that past year or so I have run my Typhoon in open loop all the time, it is OBD I. I haven’t had any issues at all except for highway driving it will sometimes hit a rich spot, but ive pretty much worked out alot of driveability issues.
yeah i’ve got a wideband going on pretty soon. i don’t really have any closed loop drivability problems infact the car is very mild manored off idle. it’s just that long fuel trims will not dial in(without being overly rich) and any skewing being done at the point of closed to open transition will carry over.
say your LTFT is +5% when you hit the wot range, that 5% is carried over to your base AFR regardless of what it’s already set at. no narrowband = 0 fuel trims
i guess it’s possible i could just make 2 files
what program are you using, i have HPT and dont have any problems dialing in LTFT. you have to use your historgams
i can help with the tune if youd like
Your PCM carries over even NEGATIVE LTFT’s into PE?
The E40 in my LS2 GTO will ignore negative fuel trims, it only adds positive trims into PE, You will never get 0% fuel trims in Closed loop, even with a stock cam, that is what they are there for.
I get them as close to 0 as possible while keeping them on the negative side, then watch them as the weather changes to make sure they go more negative rather then go over to positive.
can you run both? i have megasquirt and i run closed loop from 1100-3800 rpm and open for the rest of the fuel map. my cam has 308 duration so i cant run closed loop at idle and running closed loop at wot is dangerous
see that is where the 3800 is very different from the LSx motors. It will carry Negative and positive into PE. the Trims are acutally based off the MAF, and all the changes to the MAF effect the Trims. My LTFT’s lock in at 0.0 every single time when i enter PE, and all the other cars that i have tuned lock in too. It takes ALOT of dialing in the MAF to achieve the trims where you want them. There are alot of factors that play a part in the trims. I can have perfect trims one day, the weather changes and they are shit the next. I have done alot of MAF tuning over and over to get them right. My crusing trims are +/- 3 and yes they do bounce around depending on TPS/MAF
If the LTFT’s lock to 0.0, then it is not carrying trims over, cause theres no way your running 0.0 LTFT’s all the time…
The trims are based off of the MAF in every car tho, because the fueling is based off of the MAF, and the front O2’s give a reading to the PCM and the PCM adjusts fueling via the trims for that MAF cell
That is what the trims and MAF is there for tho, is to adjust to the weather and altitude… If I wanted to retune my car every time I ran it at the track, I would run OLSD 
Dont you have a temp sensor too? a MAT sensor that also adjusts for the weather, mainly air temperature?
i don’t know that I’m actually gonna do it all the time, i’ll probably give it a try though, or maybe even wire up a switch on the narrowband
don’t forget, closed loop is ONLY for the cat. you switch rich and lean because the cat needs both fuel and air to operate properly.
Closed loop is for a lot more then the cat… Didn’t we just discuss Fuel Trims? lol
Is this on a naturally aspirated engine?
yeah but all the switching bullshit is strictly for the cat.
nope
Why not get a switch that can be activated on pressure to trick the ECU into open loop while under boost for ease of tuning?
i was thinking about that honestly. but first things first the wideband has to go in and i’m going to try to tune it the way it is right now, that seems to be the best option
2003 ssei I’ll let you know if i need your help, sure as fuck there’s going to be some tables i need to modify that i don’t have access to with the PT.