I have a 1998 SLT Durango with the 5.2L Engine. I have 180,700 miles on it. I have been looking into Mileage improvements. I have installed and uninstalled a HyperTech ECC Code changer that improves the Horsepower output. I believe it does it by fixing the ignition advance setting curve and maybe the air-to-fuel ratio at all conditions. Hyper-Tech strongly recommends installing a 160F Thermostat to help get even more horsepower out of this engine. It probably does that but I am more interested in improving the Mileage. I get about 15.2 mpg with this code change and 160F thermostat installed. I sometimes get better mileage with the Stock code installed (like 17 mpg) but it does not stay there. I suspect the ECC plays with the engine setup a lot with all of the variables involved. My question is: I read in my Dodge Service Manual for my vehicle that when you have to change (for example) the O2 sensors the ECC will wait for 40 'trips' before setting the correct engine settings for the replaced sensor. A 'trip' is defined in the Manual as a cycle where the 'engine coolent goes above 175F and then cools to below 175F'. In this case 40 trips seems to be excessive-the microcoder must be a very conservative 'nerd'.

Will the 160F thermostat affect the settings the engine will operate at and thus screw around with the mileage? The ONLY time my engine temperature gets above 160F is while parked with the A/C full on. A recent trip from Colorado to Florida had a jump in the mileage (15.2 to 17+ mpg with the stock code installed) after the engine got over 175F in a Missouri Rest Stop. Then it went back down in Florida to under 15.

Thanks for your interest. Any informatin on this computer operation would be appreciated.

Bob Cope

 

In my experience with changing several engine sensors over the course of the last three years and of course one at a time, the change is immediate. Not sure what the 40 trips are in reference to. The PCM adjusts instantly to new programming and rather quickly to other engine modifications. In most cases you see the benefits or detrimental effects within one tank of gas. In regards to the Hypertech programmer it does exactly what you describe. The look up tables for timing and air fuel ratios are revised. How do I know this? It's a long drawn out story, just trust me. I have a history with Hypertech and the Superchips tuners.

I would not install a 160 degree stat for three reasons; it's likely to set off a diagnostic trouble code for failure of the coolant to reach operating temp, it will likely reduce your gas mileage not increase it and it will increase the amount of emissions at the tail pipe. If you are not prone to detonation (which a lower temp stat will help reduce) then you're better off staying with the stock t-stat (195 degrees) or at least a 180 stat. The vast majority of Dodge performance enthusiasts run the 180 with great results.

Just my thoughts.

 

Thanks for your input AJ. I have loaded the Stock code back into the ECC and plan to put my Hyper
Tech II on eBay when I return to Colorado next weekend. I am an Inventor of sorts and have tried to increase fuel economy with some very wierd mechanical ideas. This is a lucrative market (energy) but it is very hard to squeeze blood out of a turnip. Using my Durango as one of my MPG baselines to evaluate whether an idea would work was difficult because the MPG changed around a lot. I blamed the ECC.

I will put a 180F Thermostat in when I get back. Thanks again.

Bob Cope