Specs:
stock LS on ten psi DD
S300

ok so I got my car sreet tuned and I got to looking at the parameters and noticed the tuner left it open loop, it was my understanding that the best thing for a street car is to run closed loop, because of varying conditions.

So I put it in closed loop and tried it out, srt term was adding up to 40% and 02 voltage was only reading .1 volt and it seemed to be running a little worse than in open loop. so what should I do? give me some advice please.

 

Talk to your tuner as it sounds like something was not done correctly. You'll need to verify your AF readings with a wideband.

 

talked to him. this is what he says.

1 they run better in open loop, the stock narrowband o2 sensor is not accurate and it tends to mess up with hondata.

2 his suggestion was to get a wideband and use that o2 for the input into the ecu

he just sounds like a somewhat ammature tuner that doesnt really know how to tune using the stock o2 sensor... am I right?

he also said ten psi is pushing the limits of 91 octane on a stock LS...

please gimme ur input

 

You cannot proeprly tune with only a narrowband O2 sensor. Tuning must be done with a wideband. When tuned correctly it will run perfectly in closed loop.

 

If a car is properly tuned there is no need for closed loop. Shouldn't ect and iat corrections make the difference for weather. I haven't run with a narrowband for many years. I just got 36mpg on the highway @80mph in my boosted sohc. Right now I'm getting my map as close to perfect and then going to try my wideband narrowband sim and compare mpg's. I'm sure it debateable but I have ran this way for years and no problems and good mpg. How are your afr's?

 

It will only run perfectly in closed loop if the narrowband O2 sensor is actually good and working properly.

I would suggest just getting a wideband in there then you know exactly what is going on.

 

you can get as good if not better mpg in open loop operation and still have the engine running on the safe side.

 

im not talking about tuning, of course tuning was done with a wideband.. duh.. My tuner said that u should not run a narrowband 02 sensor AT ALL, not even for the normal 02 input into the ecu for DDing in closed loop.

and I dont have a wideband hooked up right now so I cant tell you my AFR's, but it was just tuned so im sure its good, im just trying to see what the norm is for boosted cars running closed or open for DD, I thought its was norm to run closed because of all the variations a DD sees, hot, cold, wet, dry, ect. My first setup was ran closed loop on s200 and it ran great for 50000 miles. but i guess if its fine to run open loop than ok... it just doesnt seem ideal.

 

bump, any more input?

 

That is absoultely incorrect. Your narrow band is only going to fine tune your partial throttle areas. You can observe that in loaded situations (in boost) it does not rely on the stock narrowband oxygen sensor, usually around 600 mb if i remember correctly. (user defined value)

You should absoultely use a narrowband O2, if your sensor is functioning properly, if your wiring is correct, and if your tuners partial throttle tables are close, the only thing that will happen after that is a cleaner burning engine, and better MPG.

sander

 

thats exactly what I thought, thank you, idk why everyone is saying open loop is fine. sure its "fine" but it not how the car is supposed to run. I think my tuner is just incompetent and inexperienced and doesnt know how to tune closed loop.

 

open loop is fine. ive only run open loop in my cars. im not 100% but if its tuned for fuel economy at 0 inches maybe a little boost; closed loop will try to get that 14.7 correct? which in reality is a little worse mpg. if your tuner tuned leaned it out a little on partial throttle to get better mpg, then like i said youll get worse as closed loop will try to correct it to 14.7. my tuner tunes a little leaner so itll get better at cruising and partial. then again, im on e85.

 

when in open loop. for cruising and in vacuume you can lean the engine out as long as you retard the timing maps appropriately. you can achieve good gas mileage this way,