These are some mods Ive use to fix my gutless gas guzzling dakota 3.7. It is a 6 speed and ran terrible below 2000 RPMs and never got over 18MPG before the mods. I had tried a chip and K&N intake but they only helped high RPM not where I needed it. This will probably work for the automatics and v8s too.

I also tried to get the ECM Reprogrammed, but the programmer was not compatible with my ecu so I was stuck with stock.

The first thing I did was try adding an EFIE to the O2 sensors. This made it run leaner but didn't help power or gas mileage. My normal altitude is 6000 feet and I realized after a trip to sea level that the MAP sensor was retarding the timming even more when I go down in elevation.

So I got a cheap EBAY ELM usb OBD scanner and it could tell me real time ignition advanvce and other tunning parameters. Then I started to try Pots and resistors on the MAP wires to see what I could make the timing do.

I took a picture of the resistors I ended up with. The best combo was a 3.9k between the ecu signal wire and the sensor output and a 20k (2 -10ks) between the ecu signal wire and ground. There are other people using a 50k potentiometer, but I found better results using independant resistors. I found that the resistor to ground affected the sensor more at low pressure readings (idle and low load) and the resistor to the sensor affected more at WOT and high load.

The timming I ended up with is at times 12-15 degrees more advanced than stock at low RPMs. It would not only advance the timming but it would force the ECU to run less fuel because it thinks it is at a higher altidue than it really is. This cause me to have to turn up the EFIE really high so it wouldn't throw a (system to lean) code. So I had to use the EFIE to make the ECU happy but it is allowing the motor to run %20 leaner than the factory program. It turns out the pipe is now total clean all the time (it used to be BLACK) No codes ever pop up. I get 24 MPG at 65-70 MPH average. It has twice the torque at the point when you let the clutch out. I can actually spin the tires now. It will ping very briefly below 1000 RPMS if you let the clutch out to hard but the Knocks sensors keep it from pinging the rest of the time. I run 85 octane here.

Ive run it this way up to 11000 feet and down to 4000'. It might be too aggressive for a sea level mod but could be a good starting point for big MPG gains.

 

I am not sure all of that sank in... So basically you manually advanced your timing using resistors on the MAF? I am blown away that you see close to 6mpg increase, and would love to replicate that result.

 

That's incredible, good work man. I am most interested in the EFIE, how's that work? I, for instance, will be running a Hemi in my truck and one thing I am concerned with is the possible codes that might be thrown due to the different readings from the O2s.

 

FYI: We don't have mass air flow sensors. Our intake volume is calculated with a combination of a Intake Air Temp sensor and a MAP sensor.

 

Gotcha, so educate me further on what 'EFIE' is.... Electronic Fuel Injection Something?

 

wtf..how to do on a v8?

 

all i heard was BLAH BLAH BLAH 6mpg increase......come do it to mine.....lol

 

I am throwing down the B.S. flag here. If that 24 MPG reading was from your USB tool you got off of eBay, its worthless with all the modifications you made to the MAP. The computer is getting false readings, and it wasn't that accurate before with true readings.

Until I see some actual miles divided by actual gallons math here, not picking up the B.S. flag. Even then, it'd have to be pretty convincing. Not to mention the computer will eventually learn around the faulty MAP sensor readings by utilizing the other sensors it has available.

 

I don't think EFIE's are a good idea. Most engines are designed to run at stoichiometric(14.7:1 afr).

Adding voltage to your O2 signal tricks your pcm into thinking its running rich(<14.7:1). The pcm then leans the mixture untill the modded O2 sensors indicate a "good" reading. Less fuel injected into the cylinder = better economy.

The problem is is the extremly high temps created in a lean mixture. You can burn a valve, it can knock and ping untill a valve break. Which the PCM cuts out timing and therefore power. Overheat and warp or melt a piston.


The fuel when injected also acts as a coolant inside the chamber. That's the reason forced induction guys run their engines extra rich(~12.5:1, depending on application). It seems like a good idea but our engines aren't designed for it.

 

This is the EFIE I am using.

http://www.fuelsaver-mpg.com/digital...d-digital-efie

I have it set at 2.55v trigger on the front o2s. The engine stops running at 2.52 because its too lean and throws a code. It is VERY close to the edge.
This setting without the timing mods did not even run....

Wingman is right about the bad side effects of running too lean. I am aware of them and pay close attention while tuning. The EFIE has been on the truck for 50k miles. The settings work as they are for me I purposely did not post this until I was sure of my gains because so much data on the internet is very questionalble. The Knock sensors work well and retard the timing ALOT if they have too. If not I would have burnt a valve long ago.

My truck is an 06 2wd 3.7 with a 6 speed manual and the MPG was checked over many tanks of fuel. Long Wyoming highway trips "miles/gallons" method. If there is a headwind involved milage drops to 22 a 65-70mph. Which is what the factory says it should get anyway.

My truck does NOT have a mass airflow sensor, I think the HEMI's do but not the 3.7. It is also the old style throttle cable motor, not drive by wire.

I was always thinking something had to be wrong with my truck before, but it might be that the factory just really screwed the pooch on the programming. Or they used the same program for the Manual tranny as they use for the automatic. Before the mods my truck always ran good above 3000RPM. And anytime you stomp on it with an auto it should downshift to keep the motor revving. But my truck runs below 2000RPM in overdrive at 65MPH. So before the mods i could never use 6th unless I was going down hill.

This all could be done with an ECU programer, but I did not have that option.

Also if you get an ebay USB scantool they will allow you to reset a code if you screw up while tuning. Do a search for ELM OBD. The ECU was really picky about the o2 sensors before the timing changes and a half a turn on the EFIE would set a code. After the timing changes the Motor runs so much cleaner, that the o2 readings are always closer to being correct and the EFIE settings can vary alot and not throw a code.

The ECU is a dynamic learning computer. It uses the o2 sensors to learn the best amount of fuel to spray and then it stores that info into whats called a "Long Term Fuel Trim". You can view the LTFT on the OBD scantool. On our ECU's The LTFT can only adjust for + or - 30% before it throws a code. Mine is running the LTFT's at close to 0 most of the time unless it is under a high RPM load then it adds 10-15% more fuel. But the info it is using to create the LTFT is from the o2/EFIE and is is under my control so even though it is adjusting itself , I control the ultimate fuel to air ratio it tries to achieve.