2000 GMC FastBack AeroCap Project

[Christ]

No... numerically lower ratio means lower RPM.

EDIT - Welcome to the department of Redundancy Department. (In case anyone read this before it was edited.)

[Fubeca]

Right - better for some things, maybe not for fuel economy.

The differences between our trucks on it's face are:
The steps on yours
Mech fan on yours
Lower gears on yours

I'm curious to know what other things are different and to document how similar our mileage is.

Feel free to stop by on your trip out to NY. I'm just off of i-94 just outside across the border from Minnesota into Wisconsin.

[ChazInMT]

Oh yeah, duh, a 50:1 ratio, 50 engine turns to 1 wheel turn....1:1 1 engine turn, 1 wheel turn. Sometimes going to extreemes helps understand the basics. I Bicycle too and the more ratio we have there the slower you peddle, but we're talkin 1:3 and 1:6 type ratios.

[Christ]

There's a bike with a 20:1 ratio on it that goes like a normal bike.

It has like 52" tires on it, though. LOL.

You have to remember all the parts of the equation.

Of course, that advice applies more greatly to the "overdrive" discussion in transmissions, and why it's not always necessary to have an OD gear.

EDIT - Those ratios are completely made up. They have no basis in reality, and while I've personally seen bikes with 50+" tires on them (in the past), I have no idea what gear ratios were used. Think of the tricycles with one giant front wheel, though.

[MetroMPG]

Looks great, Chaz!

Originally Posted by ChazInMT

I dunno if I'll take the time to A B A, but I'm very curious about how tuft testing will look so expect that within a week.

Most excellent. Looking forward to it.

[MetroMPG]

Originally Posted by ChazInMT

I am going to fill in some holes in the lower air dam and block some of the grill.

I think you could go with a much more aggressive air dam that would help more than just blocking the current one. Have a look at how low the dam goes on GM's hybrid full size trucks (and the XFE pickups):

[KamperBob]

Charlie, it looks sharp. Remember: your best strategy for saving gas is to curb enthusiasm. My ScanGauge paid for itself real fast on my 4.7L 4WD Tundra. Sticker says 14/17 but I get 17 +/-1 commuting (16 Winter & 18 Summer in central MA), I've repeated 22 highway and typically see 16-18 pulling a 3500# camper (Scamp 5th wheel). All that with 3.92 diffs (16" wheels) so you may have some MPG upside if you are willing to adjust driving habits.

BTW, I started a new thread today:
http://ecomodder.com/forum/showthrea...kup-12155.html
I don't want to bend these project threads but would like to discuss pickup aerodynamics more generally.

Cheers
KB

[Bicycle Bob]

Well done, chaz! And thanks for the detailed postings.

Gearheads: motor vehicles use step-down gears. Bicycles use step-up gears. The U.S. gearing nomenclature is a conversion to the equivalent wheel size on a direct-drive high-wheeler. Those were limited to about 60" diameter by anatomy, but gearing often goes over 100" now.

[Christ]

Originally Posted by Bicycle Bob

Well done, chaz! And thanks for the detailed postings.

Gearheads: motor vehicles use step-down gears. Bicycles use step-up gears. The U.S. gearing nomenclature is a conversion to the equivalent wheel size on a direct-drive high-wheeler. Those were limited to about 60" diameter by anatomy, but gearing often goes over 100" now.

Does that mean that on a bike the gear ratio is listed in the opposite?

Car - drive:driven
Bike - Driven:drive

?? That's confusing, if it's true..

[Fubeca]

Originally Posted by KamperBob

Charlie, it looks sharp. Remember: your best strategy for saving gas is to curb enthusiasm. My ScanGauge paid for itself real fast on my 4.7L 4WD Tundra. Sticker says 14/17 but I get 17 +/-1 commuting (16 Winter & 18 Summer in central MA), I've repeated 22 highway and typically see 16-18 pulling a 3500# camper (Scamp 5th wheel). All that with 3.92 diffs (16" wheels) so you may have some MPG upside if you are willing to adjust driving habits.

KB

I think it is hard to compare trucks from different manufactures - especially from different eras. Your truck has lower gears - but I think it has a 5 or 6 speed transmission vs. our 4-speeed autos and may have a more efficient final drive ratio.