Accurate MPG calculations

[97BlackBetty]

Will thats not true. All of the Maritime Academys in the US teach celestial navigation. But im an engine cadet so I just turn wrenches. I however cannot celestial navigate, but I can pull out my charts and using a compass a watch and a speedometer, plot my location. Its a little harder when your sailing and having to figure in current and wind but I can still be pretty close.

 

[Rarasranger]

I have some idea how to navigate celestially because one of my major projects is the reverse problem. Calculating true headings to fly an aircraft to keep the azimuth of a given celestial object (star, planet, or the Moon) constant. It's an airborne telescope with very little lateral motion. Not that I've ever used an astrolabe.

See why I love these forums? Where else can you say "Hey guys what kind of mileage you gettin?" and end up learning about calculus, trig, gps errors and inadequacies, and celestial bodies movements?

Where I ask you... Where?

 

[rboyer]

A couple of problems with that. First of all you have a certain refresh rate all depending on what kind chipset your GPS has. If the refresh rate is 1hz then that means it's giving you coordinates one time per second. Now lets say you're driving down the interstate and it starts to veer off to the left a little bit in it's placement and then all of a sudden puts you back on track with the right coordinates. Now if you're travelling at 65mph and your refresh rate is 1hz then it will refresh every 95 feet. Picture three refreshes in a row here, the first one shows you on track, the second one shows you 10 feet off to the side, and the third one shows you back on track again. It will come up as a curve if you drew it out on a map and just that ten foot curve will throw you off by several feet if not way more over the course of a 190 foot stretch. Now imagine that happening several times over a several hundred mile trip. The hard part is that calculating something like this and comparing it to coordinates on a map would be far too complex for any of these little palm pilot style gps units out there.

 

[Yettoblaster]

Gee, I didn't realize you needed a GPS to calculate mileage. I'd say using your wife's car as a control you're data's prolly pretty good.

I used to get 22mpg with my old 2.3L manual, but after coming here to TRS I found guys getting 28.
I hope my new 2.3L will get as good or better than my old one. Nevertheless I'll be happy with anything over 20 with an "aerodynamic" (read: brick shaped) truck using "oxegenated" gas here in commiefornia.

 

[snake]

24.5 inch tires? Thats the size of a 18 wheeler! I've got 15's on mine. Am I missing something here?

My ranger does best locally for some reason. Normally gets 20-22 around here, but on a road trip it barely gets 20.something. I guess I've got the hammer down passing on the two lanes too much or whatever. Odd phenomenon though, never had a vehicle do worse MPG on the highway than around town.

 

[MAKG]

Snake, more likely you have 28 or 29 inch tires, if stock.

It's TIRE size, not WHEEL size.

 

[Will]

Will thats not true. All of the Maritime Academys in the US teach celestial navigation. But im an engine cadet so I just turn wrenches. I however cannot celestial navigate, but I can pull out my charts and using a compass a watch and a speedometer, plot my location. Its a little harder when your sailing and having to figure in current and wind but I can still be pretty close.

I wasn't talking about professionals. Even then, it's a cutsie class--like making Navy midshipmen train on a tall ship.

You are talking about dead reckoning. That's not plotting your position--it's just an educated guess about where you will end up.

 

[VaGent]

I'm driving a '90 Bronco II 2.9 with automatic running 215/75R/15 tires. The stock tire aize is 205/75R/15 from the factory. I've tuned the engine as best I can for stock, I don't get on the gas hard at all anywhere unless I just have to. I drive mostly in town & occasionally on the highway. I'm getting 16.5 mpg but if I am driving open road running 65 mph, I get at the most around 21-21 mpg. I have no idea what else I can do to get better mileage out of the 2.9. Anyone got any suggestions? This "LIQUID GOLD" everyone has to buy these days is getting harder to afford.

 

[Yettoblaster]

...Anyone got any suggestions? This "LIQUID GOLD" everyone has to buy these days is getting harder to afford.

Go taller on wheels/tires is all I can suggest. My brother used to get the tallest oversized tires he could and ran them rock hard.

If you're getting over 20mpg out of a 4wd I'd say you're doing real well. My new 2.3L 2X4 w auto gets 25 when I baby it.

 

[MAKG]

Go taller on wheels/tires is all I can suggest. My brother used to get the tallest oversized tires he could and ran them rock hard.

If you're getting over 20mpg out of a 4wd I'd say you're doing real well. My new 2.3L 2X4 w auto gets 25 when I baby it.

Huh? Taller wheels, if it does anything, REDUCES fuel mileage by increasing the profile the truck presents to the wind.

Running them rock hard might improve mileage, but I hope you don't drive Hwy 17 that way, especially if it's a bit drizzly.

 

[Speedwagon]

The accuracy of the GPS is irrelavent. It is a trip he has done multiple times, with other methods backing up the distance. He has his wife's car, the truck's odo, the GPS, and hell, you can mapquest the dang distance too! That's 4 ways to come up with the distance travelled. I'd say that is fairly accurate measurement of distance right there.

Me, I get about 25mpg highway, and I'm no granny on the acceleration. '92 3.0 5spd, 220k+ miles. Worst I've measured is 16mpg delivering pizzas in town, or pulling a very heavy load highway.

 

[VaGent]

OK what if I went with 235/75R/15 tires instead of the 215s? AND will the the A4LD 4X4 tranny with 3.73 gears pull those bigger tires OK? I also have a Hypertech chip that was given to me as a gift but I have not installed it yet. Is there any truth that those things really work? I've heard they don't do much at all for gas mileage but do make the engine perform better. Anyone know anything one of them?

 

[MAKG]

I put P235 75R15s on my 1986 Bronco II with 2.9L and 3.73s. It was JUST fine. That's a miniscule difference in size, less than 1 inch in diameter. Though I had a stick.

The change is just about half a tooth in the speedo drivegear, so you may need to change it.

 

[VaGent]

Thanks for the info MAKG Do you think the automatic will handle them OK? I've heard it puts a strain on the tranny & I don't want to mess it up until I can change out the 2.9 to a 4.0 5 speed along with the 4.0 clutch setup. The A4LD I have in it now was just rebuilt & has less then 5,000 miles on it. Where I live there aren't much hills or mountains to climb unless I go about 75 miles west of here. Would you recommend the HyperTech chip for the 2.9?

 

[MAKG]

I wouldn't recommend any modification without some idea that you might actually need it.

The change in tire size is so tiny that it won't make any difference to much of anything, except some 1/2 inch extra ground clearance.