im not really sure if i can post this topic in this section but im gonna try it any way.

i've got a d16z6 turbo currently on a open loop tune.

im curious if it would be better to run a close loop tune to smooth out partial throttles and and cruising around fuel tables. to achieve a better MPG. im already seeing 38-46 highway. but i was curious if it would hurt or improve to switch to a closed loop?

if this is posted in the wrong section i apologize.

any impute is appreciated

 

i tuned partial throttle, and all ends and loads open loop. got very good gas mileage.. then i drove on closed loop for a week and my mileage decreased.. when the ecu sprays more fuel into the motor it goes TOO rich, and i couldn't find any way to adjust that

 

Some people have good luck running closed loop but the adjustments for short term and long term compensation are tricky and the tune needs to be close to spot on for the adjustments to not get to crazy and run the engine rich. I've always tuned customers and my own cars open loop and left them that way, never had problems and tunes always stayed spot on. only issues were when tuned in summr they had to come back for minor cold start adjustments when i lived in new england and i did that free of charge.

If your tune is on the money and the vehicle runs good in all weather conditions, dont bother with closed loop IMO

 

^^ word, plus if your motor lasts from cold weather to warm. you can compensate correctly for the IAT readings and precentages. and You'll be spot on the the year after.

I couldn't ever get the long term and short term adjustment to do what i wanted in closed loop so i just cruise in open

 

Open.

 

Open, spend the time to tune the fuel in partial throttle. Closed loop loves to cause problems.

 

According to many full time tuners closed loop is the safe rout. I agree lots of trouble, I run close and my cel come on below 60deg, very anoying wants to run open below those temps and looks for O2 heater signal.

 

i doubt you'll see the same gas mileage with closed loop enabled. at light throttle mid 15afrs are fine, a narrowband sensor can't compute that.

 

Very interesting. I've never heard of people running open loop all the time. I've always been of the mentality tune open loop and then run closed loop.

Closed loop smooths out the little imperfections you have and by looking at your long and short term fuel trims you can see certain trends and correct those in the tune. It seems like you loose out on that driving in open loop only.

Also what about extreme temp differences? For example summers here in KC will be in the 90s with a couple days hitting the 100 mark where as winters will drop below freezing and some mornings below 0 when it's really cold out. Is open loop really going to work in that different conditions?

I noticed above someone pointed out running in open loop they can run mid 15s AFR but you should be able to set a target AFR for closed loop, you can in Hondata. Further more you can set the tune that it can only deviate from your values by X %. You could set it to something small like 3% so it'll try and correct minor issues but it'll never pull your tune out more than x% at any point.
As for narrow band, I don't even use one. My wideband O2 sensor is all the car uses.

Good thread, keep the info coming.

 

as long as your IAT corrections are right, yes.

 

having the same issue. the car is erratic in closed loop. on cold start in open loop it runs perfect, when it's warm and switches over you never quite know if it will idle right. sometimes it does, sometimes it doesn't. car is done in crome pro and runs great everywhere else. debating on if i should go back and change over to open loop. the idle is the real problem. part throttle driving and whatnot are spot on. it's just the damn idle. it hunts and is a bit rough in closed loop. sometimes it dips to 500rpm, sometimes it stays at 800. has died a couple of times.

 

IAC duty cycle and a few other settings on that screen (sorry been a few months) fixed my idle. It was doing the same thing where it was unpredictable, dip real low and even die at times. I'm using a Hondata S300 though so idle options may be completely different.

 

Open loop, ive been on open loop for 6 years. you will have to fine tune the corrections as the weather changes but thats it. every time i tried closed loop it completely killed my tune reguardless of the perameters i would set in the software so i said screw it

 

I've been doing a lot of reading up on tuning lately. Specifically I got Don Lasota's manual and video.

http://www.lasotaracing.com/MOSCTTuningGuide.html

It's geared towards Ford's mass air systems but overall the basic tuning concepts are universal and one thing he points out is if the car runs great in open loop and you switch to closed loop and it goes to crap first thing to check are your factory O2 sensors and wiring.

After I thought about it for a while it makes sense. You've tuned in open loop to have your car running spot on and then if in closed loop the O2 sensors are providing incorrect readings your tune is going to try and adjust and accommodate for that and throw things off and make it run like crap.

At least something for you to check out.

 

Im a fan of closed loop. Assuming youre running the wideband full time you just need to adjust the closed loop target to be the same AFR that you run now. Obviously you dont want to rely on closed loop to fix a bad tune. The big advantage for me was the fine corrections it can make automatically. I found that I was constantly chasing the weather in my fuel map.

 

My open loop tune gets adjusted for season changes but its not that big of a deal since im constantly tinkering with it anyway. Runs great and gets good gas mileage so I dont see the need to change.