delete front o2s
Typically the cars run a little richer if everything else is tuned properly. The Open Loop commanded A/F is typically slightly richer than the 14.7 A/F that is always commanded during closed loop.
Actually, the AFR will be whatever the PCM calculates it to be based on the MAF, VE, IFR, and whatever fueling tables it takes into consideration. Assuming those are tuned correctly, the car will behave 'kind of' like a carb'd application in the sense that you set it and go. There's no learning or feedback for the PCM to use to make corrections. However, the difference is the PCM is still calculating some things off of changing conditions (manifold vacuum, intake temps, coolant temps, etc.). So, it will be more forgiving to changes in weather than a carb'd application.
But, DO NOT make the mistake of assuming that just because the PCM commands a certain AFR, the car will actually produce that AFR. The tables have to be dialed in appropriately for that to happen. To anyone who runs OL full time, I highly recommend hooking up a WBO2 so you can monitor your AFR. It will vary from day to day.
But, DO NOT make the mistake of assuming that just because the PCM commands a certain AFR, the car will actually produce that AFR. The tables have to be dialed in appropriately for that to happen. To anyone who runs OL full time, I highly recommend hooking up a WBO2 so you can monitor your AFR. It will vary from day to day.
Originally Posted by SSpdDmon
To anyone who runs OL full time, I highly recommend hooking up a WBO2 so you can monitor your AFR. It will vary from day to day.
Additionally, I bump alot of cars to OL for tuning. The A/F stays very consistent.
Well, my experience has shown other results. Not saying I'm right and you're wrong - just trying to explain myself.
Take for example my drive into work this morning. The WB showed AFR's of 14.0~14.2 cruising and 12.4~12.6 at WOT. Last weekend, it was 14.8~15.0 and 12.8~13.0 and I did't change a thing to my OLMAF tune since then. What did change was the weather. 0.4 AFR points may not be much for concern in that situation. But if it was 0.4 points in the other direction, you better be damn sure I'd want to know. That was the case when I bought the car too. It had an 'professional' open loop tune in it and I found WOT at 13.50's when I first hooked up the WB. That was fixed in a hurry.
My experience aside, if the PCM was so consistent in fueling calculations, why would it require fuel trims???
Because of things like temperature, barometric pressure, relative humidity, etc. that all play a role in the fueling requirements are changing, fueling will be somewhat inconsistent. They will always change unless you drive your car in a controlled, isolated environment. There's no getting around it.
Take for example my drive into work this morning. The WB showed AFR's of 14.0~14.2 cruising and 12.4~12.6 at WOT. Last weekend, it was 14.8~15.0 and 12.8~13.0 and I did't change a thing to my OLMAF tune since then. What did change was the weather. 0.4 AFR points may not be much for concern in that situation. But if it was 0.4 points in the other direction, you better be damn sure I'd want to know. That was the case when I bought the car too. It had an 'professional' open loop tune in it and I found WOT at 13.50's when I first hooked up the WB. That was fixed in a hurry.
My experience aside, if the PCM was so consistent in fueling calculations, why would it require fuel trims???
Because of things like temperature, barometric pressure, relative humidity, etc. that all play a role in the fueling requirements are changing, fueling will be somewhat inconsistent. They will always change unless you drive your car in a controlled, isolated environment. There's no getting around it.
0.2 A/F points is a very small number and well within the 'noise' of even a factory tuned Closed Loop car. I don't think that showing a tune being different by 0.2 A/F shows that something significant has changed. You can get that kind of difference by turning your A/C on and off.
I think you have a good point regarding the LTerms, and I'm not going to argue that ambient conditions will skew the tune. However, it is much much smaller than often claimed.
For the original poster...... Removing the O2 sensors on your buddies car is not going to make a hoot of a difference. The O2 sensors are not used during WOT and if it is a drag only car then the only place the car is going to have a different a/f ratio is in the staging lanes.
I think you have a good point regarding the LTerms, and I'm not going to argue that ambient conditions will skew the tune. However, it is much much smaller than often claimed.
For the original poster...... Removing the O2 sensors on your buddies car is not going to make a hoot of a difference. The O2 sensors are not used during WOT and if it is a drag only car then the only place the car is going to have a different a/f ratio is in the staging lanes.
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Originally Posted by NoGo
For the original poster...... Removing the O2 sensors on your buddies car is not going to make a hoot of a difference. The O2 sensors are not used during WOT and if it is a drag only car then the only place the car is going to have a different a/f ratio is in the staging lanes.
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Originally Posted by SSpdDmon
Well, my experience has shown other results. Not saying I'm right and you're wrong - just trying to explain myself.
Take for example my drive into work this morning. The WB showed AFR's of 14.0~14.2 cruising and 12.4~12.6 at WOT. Last weekend, it was 14.8~15.0 and 12.8~13.0 and I did't change a thing to my OLMAF tune since then. What did change was the weather. 0.4 AFR points may not be much for concern in that situation. But if it was 0.4 points in the other direction, you better be damn sure I'd want to know. That was the case when I bought the car too. It had an 'professional' open loop tune in it and I found WOT at 13.50's when I first hooked up the WB. That was fixed in a hurry.
My experience aside, if the PCM was so consistent in fueling calculations, why would it require fuel trims???
Because of things like temperature, barometric pressure, relative humidity, etc. that all play a role in the fueling requirements are changing, fueling will be somewhat inconsistent. They will always change unless you drive your car in a controlled, isolated environment. There's no getting around it.
Take for example my drive into work this morning. The WB showed AFR's of 14.0~14.2 cruising and 12.4~12.6 at WOT. Last weekend, it was 14.8~15.0 and 12.8~13.0 and I did't change a thing to my OLMAF tune since then. What did change was the weather. 0.4 AFR points may not be much for concern in that situation. But if it was 0.4 points in the other direction, you better be damn sure I'd want to know. That was the case when I bought the car too. It had an 'professional' open loop tune in it and I found WOT at 13.50's when I first hooked up the WB. That was fixed in a hurry.
My experience aside, if the PCM was so consistent in fueling calculations, why would it require fuel trims???
Because of things like temperature, barometric pressure, relative humidity, etc. that all play a role in the fueling requirements are changing, fueling will be somewhat inconsistent. They will always change unless you drive your car in a controlled, isolated environment. There's no getting around it.
Originally Posted by Shallow Bary
That's not entirely true. If the car has positive fuel trims prior to WOT, they will be added in addition to the PE table. This usually causes rich and inconsistent WOT AFR's.