34MPG in a 2002 Grand Cherokee diesel

[AdrianD]

Originally Posted by nemo

Thinking maybe a little less on the width maybe align it with the last groove of the tire. Just speculation on my part as most I see don't go to the edge of the tire. How far off the ground is the bottom? Don't forget about curb stops and driveway angles. Maybe others will chime in.

It's not yet on the edge, this is as big as I would go but I won't mind making it smaller. It's going to be strictly for highway use, only connected with 2 screws.

Originally Posted by DSMHondaGuy

Maybe angle it back some to direct the air around the tire some, that would allow you to not need it to be so wide, reducing surface area.

Noted, I really like idea.


Thanks guys, I will update next week once I cut it from plastic

[AdrianD]

The plastic version of the side panels :
Looking along the edge of the tire


Looking along the angled edge of the side panel:


A week from now I should have some results. It won't be an a-b test, it will be a comparison with the previous trips

[AdrianD]

Raising this back up from the dead:
The trip was a mess, windy, cold and the instant MPG showed no improvement of the side panels. So they came out.

Now with some extra instrumentation and different tires I will do some testing before the annual ski trip. Maybe I can squeeze a reliable 7.0 L/100km

I also need to reinforce the mounts for the lip, it bends back if I go over 80mph.

[AdrianD]

Looking over my previous data for the trips, I had one trip with 29.7 MPG (7.92L/100km) total (that includes going to the ski slope and back) and I remember now that it was with a lower grille block installed.

From what I remember it did not show much improvement over the warm-up times so I did not use it later on. But looking back at mpg data, it did help. Another thing to test.

The grille inserts to block the upper grille are cut and ready for testing.

So far on the list to test:
Front tire deflectors
Rear tire deflectors
Gas tank to rear bumper transition
Lower grille block
Upper grille block
Some sort of rear spoiler (inspired from here: https://ecomodder.com/forum/showthre...mph-13476.html)

[redpoint5]

Those tires don't look particularly good for snow, and certainly not for MPGs. 30 MPG from a Jeep is incredible though. I had a crappy Liberty that got 18 MPG with me somewhat trying to get good fuel economy. One tank was 14 MPG.

[Taylor95]

All terrains are pretty good in the snow. I have BF Goodrich and they are incredible for snow driving. The tire in the picture has a similar tread pattern. They aren't good for fuel efficiency though. I think the OP was trying to mitigate that with the extended air dam.

[Taylor95]

I think the lower grill block you have planned will make the biggest difference in fuel economy. Personally I would not block the upper grill openings.

[AdrianD]

Originally Posted by redpoint5

Those tires don't look particularly good for snow, and certainly not for MPGs. 30 MPG from a Jeep is incredible though. I had a crappy Liberty that got 18 MPG with me somewhat trying to get good fuel economy. One tank was 14 MPG.

They were ok in the snow, I can't complain. The mileage penalty was over 1L/100km, so down from 29.7 mpg full trip average to 26.4 mpg.
My original plan was to use them for winter and off-roading and they were not aggressive enough for the kind of off-road we do. My summer tires were pretty worn, so I sold the all-terrains and bought a set of Vredestein Quatrac 5. Much better suited for pavement driving, much better on the rolling resistance.

Originally Posted by Taylor95

All terrains are pretty good in the snow. I have BF Goodrich and they are incredible for snow driving. The tire in the picture has a similar tread pattern. They aren't good for fuel efficiency though. I think the OP was trying to mitigate that with the extended air dam.

They were General Grabber AT2. I really liked them but they were taking up space...growing pains while I got to learn what I want from the car. The airdam went on way before I had the AT2's

This is where I thought I could use the all-terrains...

[euromodder]

Originally Posted by AdrianD

I also need to reinforce the mounts for the lip, it bends back if I go over 80mph.

Don't go over 80 then
You'd do even beter on the FE

[AdrianD]

I set my cruise speed at 60 mph. But when I have to pass a truck, depending on traffic, I might have to get up to 80 mph.