S-afc Ii ......

[Ho0ked]

So I followed the instructions I got from another thread in tuning here.
My S-AFC II LOW settings look like this
1000rpm -3%
1600rpm -5%
2400rpm -8%
3200rpm -18%
3800rpm -18% ----->
7600rpm -18%

Used to have -30% from 1600rpm------->7600rpm LOW settings.

Doesn't really feel any diferent /shrug
Car is eating even more gas then before

HIGH settings are -34% across the board. logger shows timing climbing smooth from 6-26
O2 shows .98 solid.

Am I doing something wrong ? I know im going to use more gas but qtr tank per 60 miles ? WTF

 

[spyderturbo007]

What do your fuel trims look like with those settings? How old is your O2 sensor?

60 miles in a 1/4 of a tank isn't really that bad. That would be 240 miles/tank, and if your car is anything like mine you will really only be putting in 10 gallons. Do you know what your actual gas mileage is?

Gas mileage also depends on how you drive the car. If you are out there making 3rd gear pulls back to back, you are going to be sucking down some fuel.

Also, you shouldn't be using anymore gas than normal, even with the larger injectors if they are compensated for correctly with the SAFC-II.

Just to clairify my last statement:

You need to know how a SAFC-II works in order to understand what you are doing. If you already know, then you can skip this part, but it might help someone else down the road.

The SAFC-II is an airflow converter. That means that it intercepts the airflow signal before it reaches the ECU and alters that signal based on whatever the correction factors are. The airflow is then passed along to the ECU so it can perform it's fuel calculations. When the ECU receives this molested airflow value, it uses that, along with various other sensor feedback to calculate the amout of time to open the injectors (IPW).

Now remember, we are dealing with larger injectors. The ECU has no idea, nor does it care, what injectors you are running. It assumes that you are running the stock 450's and has no way of directly measuring how much fuel it has just injected. The larger injectors will inject more gas in a given unit of time than the stock 450's will. This causes the O2 sensor to report a rich condition and the ECU attempts to drop the amount of fuel injected. It continues reducing fuel flow until it either maxes out the fuel trims, or it reaches it's target AFR (14.7:1).

The problem is that the ECU will run out of pre-programed adjustment before it compensates for the larger injectors. This is why we use the SAFC to molest the airflow. When the ECU "sees" less air, it will automatically lower the IDC thereby injecting less fuel. This corrects for the increased flow of larger injectors, and keeps the FT's in line.

So, if your FT's are around 0, then you are normally fine. There are other factors that can screw up your FT's. For example, a bad water temperature sensor will report an incorrect low temperature to the ECU. If I remember correctly it's somewhere around -15 degrees. This will keep the ECU in what is called "limp mode". At this point you will not see the FT's changing and the ECU will be dumping in an abnormally high volume of fuel because it thinks the car is still cold. Limp mode is a safety feature built into the ECU in case of a major sensor failure. For example, if the MAS dies, the ECU will default on it's pre-programed fuel tables. They are only there to get you home, are very rich and extremely conservitave with timing. But that is just one example.

Also, one last thing.......The above statements are for idle and cruise only, not WOT.

Ok, I'm done, my fingers hurt!

 

[Ho0ked]

What do your fuel trims look like with those settings? How old is your O2 sensor?

60 miles in a 1/4 of a tank isn't really that bad. That would be 240 miles/tank, and if your car is anything like mine you will really only be putting in 10 gallons. Do you know what your actual gas mileage is?

Gas mileage also depends on how you drive the car. If you are out there making 3rd gear pulls back to back, you are going to be sucking down some fuel.

Also, you shouldn't be using anymore gas than normal, even with the larger injectors if they are compensated for correctly with the SAFC-II.

Just to clairify my last statement:

You need to know how a SAFC-II works in order to understand what you are doing. If you already know, then you can skip this part, but it might help someone else down the road.

The SAFC-II is an airflow converter. That means that it intercepts the airflow signal before it reaches the ECU and alters that signal based on whatever the correction factors are. The airflow is then passed along to the ECU so it can perform it's fuel calculations. When the ECU receives this molested airflow value, it uses that, along with various other sensor feedback to calculate the amout of time to open the injectors (IPW).

Now remember, we are dealing with larger injectors. The ECU has no idea, nor does it care, what injectors you are running. It assumes that you are running the stock 450's and has no way of directly measuring how much fuel it has just injected. The larger injectors will inject more gas in a given unit of time than the stock 450's will. This causes the O2 sensor to report a rich condition and the ECU attempts to drop the amount of fuel injected. It continues reducing fuel flow until it either maxes out the fuel trims, or it reaches it's target AFR (14.7:1).

The problem is that the ECU will run out of pre-programed adjustment before it compensates for the larger injectors. This is why we use the SAFC to molest the airflow. When the ECU "sees" less air, it will automatically lower the IDC thereby injecting less fuel. This corrects for the increased flow of larger injectors, and keeps the FT's in line.

So, if your FT's are around 0, then you are normally fine. There are other factors that can screw up your FT's. For example, a bad water temperature sensor will report an incorrect low temperature to the ECU. If I remember correctly it's somewhere around -15 degrees. This will keep the ECU in what is called "limp mode". At this point you will not see the FT's changing and the ECU will be dumping in an abnormally high volume of fuel because it thinks the car is still cold. Limp mode is a safety feature built into the ECU in case of a major sensor failure. For example, if the MAS dies, the ECU will default on it's pre-programed fuel tables. They are only there to get you home, are very rich and extremely conservitave with timing. But that is just one example.

Also, one last thing.......The above statements are for idle and cruise only, not WOT.

Ok, I'm done, my fingers hurt!

My Fuel trims bounce from no more then 3 to 0 to -3 in each rpm point from 1000-3000 after this point I carried the last value across to 7600rpm. I couldn't get them to stay exactly at 0 except for 1000-1600 set points.

Brand new bosch O2 sensor installed last saturday reading normal on my logger

Don;t know my actually mileage but it sure went down ALOT from before my turbo swap, I was well over 300 miles to the tank before the swap /shrug the price of power I'll live with that I reckon, but those low settings seem correct ? or close atleast ?

Thanks fr the info very good stuff

 

[spyderturbo007]

You FT's are fine. They don't have to be perfect, so I would let them where they are.

Also, are you sure that you aren't driving the car a lot harder now that you have a bigger turbo

Just remember that a larger turbo will flow more air than a smaller turbo (obviously ), so at WOT you will be using more gas in the same period of time. So even if you aren't pushing the car at WOT more than you were before, you will still be using more gas.