Regearing?

[Shdwdrgn]

Yeah I thought you had 35's... but really? With that setup, I can't imagine ever thinking that MPG would figure in to the build.

[HARDTRAILZ]

Why not? I built something that can wheel or commute in the winter. Something that can handle decent trails in multiple states and not kill the wallet getting from adventure to adventure. I did not build a rock crawler or a mud bogger that does not need MPG.

I spent some good effort to balance the truck overall and fuel mileage was a definite factor. I had the sub-10 mpg rig... hell I still do and it has been parked for years in a good portion due to that flaw in its build.

[Shdwdrgn]

I guess in my mind I assumed that once you get past a certain point, there's really nothing you can do about MPG. You get the parts that do the job, and the MPG is what it is.

[HARDTRAILZ]

There is a trade-off for everything, but it is possible to fully build out the stock style suspension and keep good MPG with the right parts and gearing and watching weight and aerodynamic stuff. I dont get my stock 20+ but I have 35s and 15+. Pretty happy with that combo. SAS and 40+ inch tires would likely be hard to get decent mpg, but I imagine with proper gearing you can still stay above 10, but that is alot more weight and wind resistance at that kinda stance.

[Shdwdrgn]

What we need are forcefields. Something to shape how the air flows around the back of our vehicles so it's not a giant vacuum. At least then we'd see some decent highway mileage.

[Grimor]

4.10 and 35's are effectively the same ratio as stock and 3.42 highway isn't too bad

[HARDTRAILZ]

My calculations came to about 3.55 for my effective ratio.

[Trail X]

I can't seem to get better than about 14.5 mpg now with the 33s and 4.56s. I used to be able to get 18 with 32s and 3.42s. I think I need 35s.

[v7guy]

5.13s and 37s are effectively stock with 4.10s


that gearing calculator and chart is wonderful

[Shdwdrgn]

@Trail X -- I'm surprised you even got 18 with 32/3.42. That combination has to put a huge load on the drivetrain. Last time I actually took a road trip I think I got around 19 with my 30.6/4.10. I so rarely burn through a tank of gas on the highway that its hard to get a reading. However for my typical driving to work and around town I'm typically in the low 16's in the Summer and mid-15's in the Winter.

Sometimes I do miss the mileage from the stock setup. When I was on the highway, I could push close to 450 miles on a tank. These days I never reach 300 (but again, I'm rarely on the highway now).

[Edit] I just checked the numbers, you're only running about 60rpm higher than me at the 65mph mark, so I wonder what else is eating into your mileage? I know I saw a hit going to M+S tires and I bet yours are more aggressive, but still?

@v7Guy -- thanks, that's exactly why I set it up, so I could compare with what I already had and have some clue what affect the new gears would have. I was sweating bullets trying to figure out if I really wanted to go to 4.10s, but the numbers made more sense to me and showed that it wouldn't be as big of change as I thought.

[HARDTRAILZ]

http://www.4lo.com/calc/geartire.php

[MKETrailblazer]

I get 11 with my 32's… but I also have the 3.42 gears I believe

[Trail X]

@Trail X -- I'm surprised you even got 18 with 32/3.42. That combination has to put a huge load on the drivetrain. Last time I actually took a road trip I think I got around 19 with my 30.6/4.10. I so rarely burn through a tank of gas on the highway that its hard to get a reading. However for my typical driving to work and around town I'm typically in the low 16's in the Summer and mid-15's in the Winter.
...
[Edit] I just checked the numbers, you're only running about 60rpm higher than me at the 65mph mark, so I wonder what else is eating into your mileage? I know I saw a hit going to M+S tires and I bet yours are more aggressive, but still?

It did put a large load on the engine at that RPM, but that is why it gave good fuel mileage. IC engines perform more efficiently when run with minimal intake vacuum (ie, wide open throttle). I had a good system for minimizing intake vacuum by watching the scangauge intake pressure reading. The intake has around a 0.9 psi pressure drop, so for me, the ambient pressure is 14.9ish, so if I can set the throttle to achieve 14.0psi, I'm running at essentially peak efficiency. Since I am now running a higher rpm at speed, where I'm creating more power, if I set my throttle to 14.0psi, I would go too fast. So therefore my efficiency took a big hit (unless I want to accellerate and then coast, accelerate then coast, etc).

Plus, yeah, I think these tires don't help anything. Their rolling resistance seems awful.

[Shdwdrgn]

I had a good system for minimizing intake vacuum by watching the scangauge intake pressure reading. The intake has around a 0.9 psi pressure drop, so for me, the ambient pressure is 14.9ish, so if I can set the throttle to achieve 14.0psi, I'm running at essentially peak efficiency.

And I thought *I* was the geek.

[tsmith1156]

Man I must need a tune up bad cause I'm pretty sure I'm at luke 16 or 17 mpg highway and I'm running stock with highway terrain tires

[Shdwdrgn]

Did you clean your throttle-body? Refill the blinker fluid? Grease your muffler bearings?

[tsmith1156]

Haha no, I really do need a tune up but don't have money for it right now.

[Trail X]

I'm not sure you can really perform a "tune-up" on electronic ignition fuel injected cars. Its not like the points need adjustment or the carburetor needs tuning anymore. If you're paying a mechanic to 'tune up' a TB, you're getting scammed.

[HARDTRAILZ]

I am about to do a tune-up.

Plugs
Clean air filter
Clean throttle body
May do fuel pump n filter

Not same as traditional but still a tune-up.

[Trail X]

"Tune-up" implies tuning of something. You're not tuning or adjusting anything. You're cleaning and replacing parts.