Quote:
Originally Posted by peakay
Hi there,
We own a Ford Expedition and I'd like to modify it to see what kind of improved gas mileage we can get.
*** Before I go further, please keep the flames and snarky comments to yourself. I realize this is a ridiculous vehicle from a MPG standpoint, but given the economy it is not one we are in a position to replace at the moment.
Anyway, its a 2005 2wd model and currently gets 13mpg city (my wife drives it) and 18mpg highway. I would love to get it to 20 and over highway and at least up to 15mpg in the city. I've been studying the Chevy Tahoe hybrid and it has a lot of mods to it for mpg that have nothign to do with the powertrain.
here are the mods I'm considering - feedback please:
1) remove roof rack (doesn't have crossbars - is it worth doing?). Tahoe hybrid does not have one.
2) remove spare tire and related jack tools. Does anyone use Slime as a preventative product or carry it in case of flats? With the size of these wheels, it just seems ridiculous to carry an extra one one around. Tahoe hybrid has runflats. FYI our current wheels are 18" wheels off of a lincoln navigator that look like this and are pretty flat on the face.
3) lower the ride height. the 03+ models are the same height whether 2wd or 4wd, but there is no reason for it to ride as high as it does. Are we likely to see an aero mpg gain on the highway? I wouldn't mind having the step in height be lower anyway and the springs are a little stiff on initial jounce, so maybe a progressive lowering spring may even ride better??
4) front air dam. Tahoe hybrid has a pretty massive one that hangs down fairly low. Ours l ooks like the one in this photo and you can see that the license plate needs to go and there is a decent lip to mount some lower material.
- would it be a good idea to mount a lower lip here or would it increase the size of the front end too much? If it would be, where can you get some material to mount here? Does anyone make some plastic to use for this purpose?
- What should I use to cover those huge lower holes (I believe they are for tow hooks on the 4wd model)? Might also try blocking that lower grill -- not sure if we need so much air intake.
5) re-map the throttle response? I can get more mileage out of it with a light foot, but for my wife it would be better of the throttle was remapped so that it didn't give as much throttle when you barely touch the gas. can this be done?
6) Gear ratio. We currently have a 3.73 rear diff ratio which could be lower. It cruises at around 2k rpms on the freeway. Due to cost and complexity, a gear change may not be in the cards, so what is the current thought on taller tires? Any benefit or do you lose it based on having to turn taller/heavier tires?
That's it for now - I really appreciate any and all constructive feedback!! |
Ill go through point by point
1) Roof rack bars, probly not worth it, will only reduce the frontal area by a few inches if it has no cross bars, and will leave holes in the roof to deal with
2) If you have AAA or something, go ahead and remove the spare and tools, I dont recommend using slime in auto tires though
3) Big YES to lowering, its one of the biggest things you can do to reduce frontal area. The underside and rear of the vehicle are where the biggest aero gains can be made, ties into number 4
4) Yes, a front lip would be a great idea, the less air that flows under the car to hit all the stuff hanging below the better. You could probly mod something like
this from a dodge ram to fit . Coroplast would work to cover the lower holes. I would leave the lower grill unblocked, and block the upper one instead, just keep an eye on temperature to make sure it doesnt get too hot. If it does, remove a bit at a time until temperature is normal. Building some kind of full or partial belly pan would also give you good results, can search on here for some examples, coroplast is a popular choice of material.
5) Remapping the computer is actually pretty easy for domestics, the superchips flashpaq
this one here will let you remap a few different ways for a reasonable price, check ebay and stuff too im sure you can find a used one for about $150. Just make sure you enter the correct tire size and stuff.
6) Taller tires would help, try and find ones in stock width with a higher aspect ratio to reduce weight gain.
Your goals are certainly attainable, and you should pass them easily. Have you read over the driving style tips and techniques? Also make sure you have your tires inflated to 35-40 psi, whatever the sidewall max is, you can go over the max, but its not recommended if you carry a lot of weight or tow regularly.
If your situation changes and you find yourself looking for a vehicle with utility for a cheap price, the old accord wagons will actually carry quite a lot and deliver decent fuel economy in stock form
example
Good luck with your project! Keep us updated
