rpm reducing

[roosterk0031]

Don't recall the name exactly, "gear reducer" but you can install an extra gear box between the tranny and rear diff to reduce hwy rpm, I think they are $2,000 plus the driveshaft rework. It will never pay for itself with one truck, but if you keep it long enough through several trucks maybe.

I'd focus on low hanging fruit, drivers mod & tires.

[mcrews]

Originally Posted by roosterk0031

I'd focus on low hanging fruit, drivers mod & tires.

this!

[MobilOne]

Gearvenders overdrive/underdrive? And $3k I think.

[Lonesome Trail]

Bear in mind it's a 4x4, if you intend to use 4WD you'll need to regear the front axle as well. My personal gear rates are $250 in labor plus parts per diff, but you can easily sink $300-600 into each diff depending on how many bearings need replaced, the gear set, if you're going to install a new limited slip or locker (it's a 4x4)...

And in the end, you now have a 3.0L Ranger that is perhaps the most doggy truck on the planet that you'll HATE driving because it can't get out of it's own way, and you might get 1-2mpg highway out of it, potentially losing city economy because of how much harder the engine must now work to accelerate.

I'd personally stick with improving your eco skills (try the Torque Pro program with a Bluetooth device/adapter, it's cheap and fun!) and doing some efficiency upgrades to the motor. If you want to spend a lot of money, consider some lower rolling resistance all season M&S street tires (mudders not the best for economy, lol), then some aero mods like splitter and belly pans.

Good luck!

[Ecky]

The engine working harder to accelerate generally improves economy, rather than the other way around.

[Frank Lee]

"Pickup gearing" LOL, remember George Wiseman? http://ecomodder.com/forum/showthrea...ere-28068.html

On a serious note, it is possible to gear too tall, not just from a driveability standpoint but from a fuel efficiency standpoint as well by dropping too low off the BSFC peak. Searches will reveal many discussions of that here.

[bentring]

Any time forum threads are focused on gearing, I feel compelled to post this gear calculator link.

[Lonesome Trail]

Originally Posted by Ecky

The engine working harder to accelerate generally improves economy, rather than the other way around.

Hi Ecky, I'm curious about this statement. Are you saying that an engine working harder is more efficient, or are you saying that a vehicle reaching cruising speed in a shorter duration run-up is more efficient, probably due to the engine working harder for a shorter span of time to reach the same cruising speed?

In this case going taller on the gears could in fact cause the engine to work harder for a longer duration because it lacks the power to weight ratio to effectively get the vehicle to speed quickly, ergo working harder longer decreasing economy?

[Ecky]

Lonesome Trail, to some degree I mean both, but mostly the former. Here's a BSFC chart for my car:




I'm not sure how familiar you are with these sorts of charts, but it's an RPM vs torque chart, with the amount of fuel needed to produce a given amount of power printed on contour lines over the load and rev range. Lower fuel consumed to make the same amount of power is better.

I'm going to draw some lines on this chart, and then explain them:




One important thing to note about this chart is that it is not a power (kwh or HP) chart - as you move from left to right, horizontally, you have a roughly linear increase in horsepower, because power = torque * RPM.

Another important thing to note is that the contours are elongated horizontally. Increasing or reducing load has more impact on efficiency than RPM does, meaning it's nearly always better to upshift.

Hypothetically, let's say you shift up at about 2500rpm, as I do, and the next gear brings you down to about 1750rpm. You accelerate at around 75% load, which you can determine with instrumentation, such as a vacuum gauge or scangauge. By doing this, you'll be moving back and forth alone the green line, staying in the engine's peak efficiency range. How long it takes you to accelerate is irrelevant, but ideally, you want to spend the greatest amount of time in the highest efficiency range.

The red line I've drawn represents (very roughly) a fixed amount of horsepower. If you need 20HP to cruise on the highway, you could do it at 6000RPM with 10% load, resulting in an incredibly poor BSFC of over 800, or you could do it at ~2000RPM with 80% load whit a BSFC closer to 200, which is 4x more efficient.

The only time taller gearing is not better is when you can't use it because you simply can't produce enough power in that gear.

Downsizing an engine is another matter. I used to be under the impression that downsizing an engine was always better. However, if I needed to produce 50HP, a 2.0L engine (all else being equal) would almost certainly do so more efficiently than my 1.0L engine, as long as it is geared correctly.