I do the sme thing with my motorcycle. I have a pot that I can advance the timing up to 10 degrees below 3500RPMs. It's carburetor and works off the cold choke sensor. Helps with MPG. I don't know about 6MPG but the science is sound.

 

Eric,

Here's my problem: you are basing all of your values on the ECU's data...not actual. At no point have you mentioned wideband O2 ratios, or any numerical timing values. You mentioned the "front O2 sensors", but they are not widebands....and you are at 2.XX volts, when narrow bands read from ~0 to ~1.00 volts. At no point have you mentioned when the ECU goes from closed loop to open loop (a necessity when triggering front O2 sensors as a calculation of timing and fuel trims). Where are the live time values? Timing, fuel, O2 voltage, Lambda (if you are a real stud muffin with tuning), rpm, speed, coolant temp, etc. You should probably consider posting some data logs of your findings with this mysterious increase in low rpm power. Since you haven't (I don't want to jump the gun), but do you even have any? Or, have you used any form of logging to make your adjustments?

So, are you aware that Hypertech makes a Max Energy tune for the 3.7L? According to their dyno data, on 87oct fuel they saw a 24whp/24torque peak gain on a chassis dyno...most of it in the top end.

http://www.hypertech.com/Performance...ishi_52501.pdf

This is most likely due to keeping the tune conservative (still), so that that the engine can live. I would be hard pressed to say that they missed 6 mpg by advancing the timing down low and compensating with fuel. The idea of aggressive tuning is to get as much as you can with out an immediate failure. Based on your data (or lack there of) my initial thought is that you are on the edge of what is considered by most to be "safe".

 

There are NO wide band o2 sensors on the 3.7 The front ones are the only ones that really matter for tuning, the rear ones are only there to throw a code if the cat isn't working.

The 2.55 v is the reading on the EFIE. Not the actual o2 voltage. It sounds odd because apperently dodge uses a 3v signal on the ground reference, so the zero volt base line on the efie is actually 3 volts. It means the efie is adding .45 volts to the real o2 reading.

The live timing values are available on the OBD scan tool except the actual injector fuel pulse width. The obd scan tool I have does not log anything, I have to watch it while I drive. (or have the wife drive)

I don't need any top end power. its a truck. It needs low rpm torque.
My 4 cyl colorado had more torque than this pig. I should have never bought it. But I am happy with it now.

It is right on the edge but that seems to make it run the best. If I ever go down to sea level again I will probably turn the EFIE down a bit to be safe. It may be that this only works at high elevation.....

I had a Jet chip on it before and it was only effective at high RPM.

I just looked at the hypertech link. I think they are thinking the same way the dodge engineers were thinking. BIG peak numbers to impress the media. The dyno curve doesn't even show anything below 3200 RPMs. How many miles per gallon can it get driving your truck around above 3200 RPM's all day? My cruise RPM is below 2000 at 65MPH.

I think the Intake is tuned to max high rpm power as well but there is nothing I can do about that.

I remember seeing the dyno chart on a chevy colorado 2.8 4cyl and the torque peak was 1700 RPMs. It towed my camper better than the dodge 3.7.

It might not be possible to accurately Dyno an automatic below 3000 RPM because it will either down shift and rev or the torque converter will be multiplying the torque and giving a much larger HP reading than it really has at low RPM.