Fuel Economy Decreasing

[toms89]

I was talking about na not in your case but as related to fordandpolaris post.

Not trying to argue with you or discredit you in anyway i know you know what your talking about. Ive been out of the seen for a while so dont know a whole lot about the new stuff.

So do our trucks look at a table when in open loop and a ratio (14.7:1) when in close loop? Im a former DSMer and this is how the ecu works on them.

Also with Eclipses, AIT is a BIG factor in A/F! The timing on these is adjusted by the ecm according to the MAF reading! More air means more timing!

I wasn't really trying to argue with you either but what you stated was contrary to what I understand. It seems the dsm vs ford tuning strategies may vary significantly.

I have been studying and applying tuning for my expy for near 18 months now with sct software. I probably have 50 different variations of programs in my file and have looked at the tune for hours on end. I have read Engine Management Advanced Tuning by Greg Banish and The Ultimate Ford EFI Tuning Guide by Don LaSota as well as SCT 2010 Training Manual several times. I also frequent the SCT Pro racers tuning forum to try and learn as much as I can.

Does this make me an expert? No!! Not by any means and I learn more each day but I do feel I have a good grasp on the basics of tuning with the expy by now.

To answer your questions.

In open loop it does utilize fuel tables which are based off load and rpm then it adds in modifiers if any. IAT is not one but engine coolant temp is. Since fuel trims are directly effected by load and rpm I adjust the tables accordingly to get the desired air/fuel ratio. So as I get into boost the load goes up and it looks up the desired lambda based on that area of the table. Open loop is commanded based on load and/or throttle position.

Ford does use the O2 sensors to maintain stoich in closed loop and constantly toggles fuel trims and stores in short term trims then eventually long term. This allows for minor differences between like motors and wear. Stoich for gasoline is 14.64 as ford defines it. The rest of the world... 14.7 Its in closed loop probably 95% of the time.

Timing tables are set up by load and rpm as well then some if any modifiers. Load is directly related to the mass of the air entering the motor. Also the higher the load the less timing. But then one of the modifiers is the IAT and it can add or subtract timing based on it.

 

[rburch]

I wasn't really trying to argue with you either but what you stated was contrary to what I understand. It seems the dsm vs ford tuning strategies may vary significantly.

I have been studying and applying tuning for my expy for near 18 months now with sct software. I probably have 50 different variations of programs in my file and have looked at the tune for hours on end. I have read Engine Management Advanced Tuning by Greg Banish and The Ultimate Ford EFI Tuning Guide by Don LaSota as well as SCT 2010 Training Manual several times. I also frequent the SCT Pro racers tuning forum to try and learn as much as I can.

Does this make me an expert? No!! Not by any means and I learn more each day but I do feel I have a good grasp on the basics of tuning with the expy by now.

To answer your questions.

In open loop it does utilize fuel tables which are based off load and rpm then it adds in modifiers if any. IAT is not one but engine coolant temp is. Since fuel trims are directly effected by load and rpm I adjust the tables accordingly to get the desired air/fuel ratio. So as I get into boost the load goes up and it looks up the desired lambda based on that area of the table. Open loop is commanded based on load and/or throttle position.

Ford does use the O2 sensors to maintain stoich in closed loop and constantly toggles fuel trims and stores in short term trims then eventually long term. This allows for minor differences between like motors and wear. Stoich for gasoline is 14.64 as ford defines it. The rest of the world... 14.7 Its in closed loop probably 95% of the time.

Timing tables are set up by load and rpm as well then some if any modifiers. Load is directly related to the mass of the air entering the motor. Also the higher the load the less timing. But then one of the modifiers is the IAT and it can add or subtract timing based on it.

I was just trying to point out that i was just asking questions and sharing info. I know how easy it is to interpret the wrong context when on forums, Just tryin to be respectful! lol!

I read this before you edited it earlier but had to run so, its basically a blended MAF system meaning it uses Maf and SD but minus the MAP. In the DSM world people usually pick one or the other with most picking SD for better drive ability and easier tuning and less restriction. Tuning and timing tables are also set up by load and rpm but also are affected by airflow. This is where safc (super airflow converter) comes in! When you install larger injectors they basically have bigger holes in the end, so if you open them for the same amount of time as the stockers, you squirt out more fuel. Of course, the ECU doesn’t know that the injectors are flowing more, so it keeps opening them for the same amount of time. Therefore, in order to get back to the A/F ratios that you want, you need to reduce the pulsewidth of the injector for each set of conditions.


The way a SAFC does this is by reducing the amount of air mass the ECU thinks it is seeing. If the ECU thinks it is seeing less air, then it will shorten the pulsewidth. Since it’s not really seeing less air (the SAFC intercepts the airflow signal and reduces it), you get the same amount of air, plus a shorter pulsewidth, plus a larger injector, and the end result puts the A/F ratio back where it should be.

One of the main side effects of changing the airflow with a SAFC, is the profound effect it has on timing. The timing map in the ECU is set up as such: the ECU looks at the engine speed and the airflow (actually the airflow per rev, but we wont go there right now), and then finds the point on the timing map. The timing map is just set up like a spreadsheet, with the columns representing either engine speed or airflow, and the rows representing the other. The tendency of the timing map is that lower airflow (less load on the motor) gets more timing advance. This is for a couple reasons, but generally lower load means less heat and less cylinder pressure, which means you can use more timing advance to get the mixture to combust at the correct point. The effect this has is that if you reduce the amount of airflow that the ECU sees, it will move down on the timing map, and you will get more advance.

Here the 02 sensors and AIT are the modifiers keeping the engine from too rich or lean.

 

[FordandPolaris]

So I tried to replace the O2 sensors in my truck, and failed miserably. I tried everything I could think of to get those suckers out. I had the special tool, all sorts of extensions, and some heat to boot, didnt budge. However, I noticed as I disconnected the sensor on the driver side that it was quite easy, as if it didnt get fully clipped in when I had some exhaust work done a couple summers ago by a shop. So I clipped it back in all the way and drove the hour and a half back to school. Getting 13 mpg's all the way! Still not good, but it is much better than the 9 mpg's I was averaging on the way home. So I guess for now it seems to be just that the sensor had come unplugged. I still have to figure out a way to remove them but in the meantime, it seems to be back to driveable conditions. I was pulling 5-6 mpg's through town these last few weeks, which I could not believe was even possible. I thought there was a leak in the system for sure...

 

[FordandPolaris]

Okay so it appears that my fuel economy woes are not over after all. I am back to trying to remove the oxygen sensors. Does anyone have any recommendations as to how to get those to unseize? I struggled with the drivers side for most of last Sunday and I don't think it ever felt like it would budge. I am unsure how to proceed other than bringing it into a shop. I am going to call my exhaust guy tomorrow and see what his recommendations are as well. Thanks in advance.

 

[buildingdoc]

maybe a good set of leather gloves... and get the truck up to operating temp. The heat may expand it enough to get it loose. I heated mine up with my torch and rosebud tip but careful enough to not melt anything in the area. they also have an O2 sensor wrench that slips over the disconnected wires. Oxygen Sensor Wrench with Flex Head Auto Tool for Some Ford Etc | eBay

 

[rburch]

FordandPolaris, If heat didnt work soak it with PB blaster for a couple of days and try reheating it.

 

[BANGEREXPO76]

O2's