Have a few Questions

[GlockBoss]

Thank you very much for your quick and in depth response I REALLY appreciate it.

2. Summing up my driving habits in detail is tough because it can change so often. Any given day will bring city driving, non-traffic(high speed) highway, or heavy traffic(slow) highway. Any increase in overall economy throughout general driving conditions would be great with me, if that's possible.

3. That's great that the canned tunes can be kept because I occasionally tow and don't find it happens enough to get a custom tune. The canned tow one should do just fine when its needed.

4. I currently rarely run 91 octane in my truck. I remember reading that these trucks would barely see a performance gain by running 91 octane without a performance tune of some sort. I would run 91 octane if i would be truly getting the performance advantages out of it.

5. Pod coloring be fixed as the slate grey should be just fine my interior is grey. Just wanted to make sure of my options and didn't have to specify when ordering.

6. As for the mods done to the truck I completely understand where you are coming from!

a. The Throttle Body Spacer was a gift so I figured I would use it. I never personally bought one based on having the same idea as you, that they don't help. The funny thing is and surprise to me is that I have actually seen an increase in MPG's since installing it. So I guess it cant hurt!

b. I will look into the Gotts Mod, as I have seen it mentioned before. I am so pleased with my current CAI as I have had issue as of yet! I will keep my fingers crossed!

c. The big tires and rims are definitely the culprit to the poor fuel economy right now. Once those were put on is when things changed. Since then is also when I noticed the transmission shifting a bit different. I hoping that the tunes will improve the shifting as well. I have not put to much thought into re-gearing but that is always another option!

Thanks again!

[Jackpine]

You're actually the second person here who's said the TB spacer helped economy. Working on the principle that, "If it ain't broke...", I'd just leave it in place. And, if you're happy with the CAI, same goes for that. Some people really feel they help, and, who am I to disagree? I think the Gotts Mod helped me, but again, it's just my opinion based on many tanks of gas before and after the mod.

As far as the tires go - when you're in the 32" diameter bracket as OEM, every 2" bigger is going to be a 6% hit in performance (or a 6% increase in engine load, depending on how you want to look at it.) I would guess you've lost about 10% with your tire/wheel combination. The only thing that's going to really recover this is new gearing. A tune will help some, but it will continue to help with new gears too. The changes you noticed are due to the "load" seen in ordinary shifting. Part throttle shifts are based on vehicle speed (which is now wrong due to the big feet) and engine load (actually throttle position, but it indirectly equates to engine load). The load is 10% higher and the speed is probably 10% higher than is being reported to the PCM. I'd be confused, and I think the PCM is too.

I kind of look at it this way: "If you're willing to spend the money for the new feet, you really ought to spend something on the gearing too."

If you always put 91 octane in the tank, you definitely want a custom tune for that.

- Jack

[Longshot270]

If you are focusing mainly on economy, tow tunes have a tendency to get better fuel economy. They may also be beneficial in the type of driving you do. They are designed to get tires turning and keep them turning. My tow based tune gets better mileage than my performance tune because of that. It is also better behaved in crowded city driving because it isn't as jumpy due to a less aggressive throttle map. With the tow based tune my truck is actually the same speed as everyone else, just with more grunt power. The only problem is it does not have the same get up 'n go as the performance tunes until you are at upper highway speeds. If you dont usually use 91, that might be worth considering.

[PhqChevys]

Originally Posted by Longshot270

If you are focusing mainly on economy, tow tunes have a tendency to get better fuel economy. They may also be beneficial in the type of driving you do. They are designed to get tires turning and keep them turning. My tow based tune gets better mileage than my performance tune because of that. It is also better behaved in crowded city driving because it isn't as jumpy due to a less aggressive throttle map. With the tow based tune my truck is actually the same speed as everyone else, just with more grunt power. The only problem is it does not have the same get up 'n go as the performance tunes until you are at upper highway speeds. If you dont usually use 91, that might be worth considering.

Funny... my truck is exactly opposite of yours. My truck get's around 15-16 mpg in 87 performance tune and around 13-14 mpg in 87 tow tune. I asked Bill about this and he said that with the tow tune the A/F ratio is much richer to keep the cylinders cooler while under the heavy load of towing... makes since to me...

[Longshot270]

Yep, goes to show that every truck is different.

The trend is usually better mileage from a tow tune when you have a low axle ratio, bigger tires, lifts and such. There is also a throttle input difference for me as well. My tow tune has a throttle response more lethargic than stock because I had intended to use it for driving off road where I dont want a sensitive pedal. That basically gives me a smarter foot for fuel economy when on the street. It isn't as much fun as my performance tune but I'm not having to visit the gas station as much.