Spark advance?

[Jackpine]

Everything Longshot just said is bang on. I asked Bill for a tune that would maximize highway economy but still give me good passing performance when I needed it. As far as I'm concerned, he nailed it.

My truck, a 4x4 SCrew with a bed cap and factory tow is probably a lot heavier than yours. I get about 15.5 mpg in highway driving averaged over MANY tankfuls (I use a spreadsheet do do this). And, one factor that has a big effect is headwind. If I'm driving into a headwind at 70-75 mph, it probably cuts my mileage by at least 2 mpg.

Do try the tow tune, and don't "tinker" with it much. I think you'll like it.

One thing you CAN try though if you're trying for economy, is to change the part throttle shift and torque lock points. I reduced mine by the max for all upshifts and downshifts and gear ranges. My goal was to get the truck into the highest gear possible at the lowest speed with the torque converter locked. This has reduced the tendency of the truck to downshift so quickly on uphill grades and of course gets it into 4th gear at lower speeds. There's probably a bit of "point of no return" here, I may have reduced these too much, but I can't tell much difference between what I have and a more mild reduction. It's all about optimizing the engine load for efficiency.

This only effects part throttle acceleration. Wide open throttle is not changed.

- Jack

[tmsbandman]

Thanks both of you. I have already reduced Converter lock the max amount on 1-2, and 2-3. I had it way dow on 3-4, but I was having problems with downshifting at unusual times so I brought it back closer to center. My shift points are lowered by only 1 MPH. Maybe I'll try lowering it some more. If I do, should I keep the downshift points matched with the upshift ones?

[Longshot270]

Yes, they must be the same to avoid transmission confusion and trouble.

[tmsbandman]

Oh yeah. You told me that on another post. I was studying the graph you posted. What are the units on the axes? I would guess MPH, and RPM, but I'm not sure.

[Longshot270]

Originally Posted by tmsbandman

Oh yeah. You told me that on another post. I was studying the graph you posted. What are the units on the axes? I would guess MPH, and RPM, but I'm not sure.

The graph is actually multiple graphs overlaid upon each other. The X axis is time from the start of recording. The Y axis is just a scale where the individual graphs must be multiplied or divided by factors of 10 to match. Or in other words, just the red line is MPH with the graphed line being 10x of the true value. The green line is 1/10 of the true RPM.

[tmsbandman]

Ahh... Makes sense. Will study it some more tonight. Thanks again.

[60DRB]

MPG is all about driving habits. The headwind is an aerodynamic issue (drag) and definately makes a difference. With my 2006 4.6 4x4 SCAB 6.5' bed at about 200' MSL, I find I get the best mileage at an effective 55-60 mph (accounting for any/no headwind). About 19 mpg if traffic cooperates. Increase speed above 65 mph and mpg drops about 3-4. Add a light trailor and the road friction (extra tires) comes into play-drop 2 mpg. Sitting at lights in town traffic...is like pouring gas onto the road while idling. Makes me want to scream as mpg drops to around 9-10. Strangely (or maybe not) my truck responds best to moderate acceleration to cruise speed rather that a slow acceleration. This is using the canned 87 tow tune.

I drove a friends 2005 5.4 2wd SCAB 5.5' bed this summer at higher elevations, (2000-4800' MSL) and saw very similar results. No tuner on his truck and it felt like a wallowing pig compared to mine.

I also tried running a three consecutive tanks of no-ethanol gas as an experiment. Despite theory on energy potentials of ethanol blend vs pure gas, my actual results showed no difference whatsoever in my mpg.