Tuning for Fuel Economy

[m396 #00-011]

Lets start a discussion on parameters inside the PCM to tune for economy over performance.

 

I for one, am willing to sacrifice performance a few weeks for fuel economy. I'm not looking forward to a little planned trip this weekend.

[zippy]

playing with the timing is one of the most imporant factors i've found in getting more milage out of your truck. most only go in and change their timing at wide open and that's it. keeping the converter locked in more is another big deal. i've also been playing with that lean cruise a bit. pulling the screen on the maf sure proved that leaning the engine out some pick's up some milage. it's nothing i'd recomend though. there are better ways to get milage ouf ot it. i've considered telling the pcm to try to run at a 15:1 afr instead of 14.7:1. i just haven't tried it in anything yet.

 

not only in tuning though is lighter. going with a roll pan takes alot of weight off the rear as does removing the spare tire. a 265/75/16 on a steel rim is heavy and takes more gas to move as does the entire rear bumper assembly. having a slight rake to the truck gives a bit more aerodynamic effect as does having a nice toneau cover on it. i've found that the closer you have your v.e. tables to correct the less often it will run rich. this i've found from running the wideband for the last 1000 or so miles. keep your idle low and bump your idle timing a bit if you're running good fuel and a cooler thermostat. this will use less fuel when you're idling which can be alot in around town driving or construction zones. if you play with speeds alot, you'll find that the SS seems to have a big fall off around 76-78mph and up. from around there the milage just takes a big crap and you milght as well just pour the fuel on the ground. we found this to be true in a friends stock 03' as well as matt's. more so in matt's truck with the bigger engine. for the guys with a radix or other supcharger, stay out of boost at all costs. you don't run a 2bar map and even at low boost you're fueling it for max boost. anytime you get into power enrichment you just about can't put the fuel back in quick enough. this is often around 40% of throttle or more on anything boosted. boost makes killer power, boost sucks major fuel. much of your normal driving would involve more than 40% throttle, don't do it if you want milage. power enrichment is just as it says. it sprays fuel like no other to make sure you aren't detonating under boost.

[TBSS]

Zippy's right about the speed, it's RPM related. The 4.10's are killer. I was seeing 19 MPG highway when I had 3.73's, now I see 17 MPG. All-around mileage is down from 16 to 13-14. Only difference was changing gears, which changed the RPM's at which I drive. Before I could cruise at 1900-2000 RPM's or so....now it seems I'm at 2200-2300 all the time.

 

I know this isn't the topic of the thread (sorry....I'm going with the overall theme of gaining mileage rather than just via PCM), but besides the obvious mods like CAI, e-fans, weight reduction, etc., the best thing you can do besides getting into the computer is drive at (or below) 65 MPH. And watch everyone pass you.

[wkdivr]

That's entirely true. On a trip out to the west coast recently, I noticed decent mileage while cruising at 65-70, but get out in Oklahoma, New Mex, etc. where the speed limits are 75, you HAVE to go at least 80 to not be a traffic hazzard. The mileage goes to s---, then!!