33.7 to .. 4̶6̶.̶0̶ .. 60.6 mpg!

[UltArc]

Originally Posted by elhigh

Somebody here was getting good results with adding the tiniest bit of throttle opening while decelerating, who was that? It was counterintuitive but he was taking advantage of a loophole in the ECU programming.

Jedi Sol. I'm not sure if it was actually working or if it was just a glitch with the instrument (I forget if it's SCii or UG).

[renault_megane_dci]

Originally Posted by johnlvs2run

60.6 ~
foam sheet, perpendicular to the ground, curving around to the sides;
55.9 ~
old plant pot plastic bumper cover, slanting slightly under, curving around to sides;
55.0 ~
slant back plastic bumper, 3" more forward at the bottom, curving to the wheels.

Based on my highest three trips, a perpendicular bumper shape, no lower than the regular bumper, has resulted in much better mpg than either slant back or slant under. I'm not sure why this is, other than perhaps getting the air to the side of the car as quickly as possible is more important than having a sharp angle that directs it over the hood. I'm going to experiment with this in a couple of days, which might mean trimming the plastic a bit more.

Could you sketch or pic the three different solutions in a single post ?

[j12piprius]

Originally Posted by renault_megane_dci

Could you sketch or pic the three different solutions in a single post ?

55.9 ~ slanting slightly under, curving around to sides;
60.6 ~ perpendicular to the ground to one side, open in back at bottom;
55.0 ~ slant back, 3" forward at bottom, open at back, 7" from ground, curving to wheels;
55.7 ~ almost vertical, 8" from ground, open space in back covered with pan at bottom.

[j12piprius]

The previous west trip averaged 50.7 mpg into a south wind for the first 25 miles, then turned west with a side wind, and ended up with a 60.6 mpg average. The last trip averaged 58.7 going south the first 25 miles, way ahead of record pace, quite encouraging, but then turned into a west wind the rest of the way, ending up with a 55.7 mpg average. The car was coasting so well the first 25 miles, and erratic the rest of the way. The wind was making unusually loud noise in the 1 inch gap of my window, but was it really responsible for the drop of the average?

Three possibilities are (1) the wind, (2) erratic resistance in the brakes, and (3) the bumper pan. Walking back to the car half way through an 8 mile trip today, I noticed the front bumper pan hanging down, which might have been the same way and causing resistance on the trip. The foam pan had been gorilla taped to the plastic bumper and came loose. I want to remedy all three of these as much as possible before the next trip.

My plan in the meantime is to:
1) improve coolant capacity for the hill;
2) install wheel gap strips, back wheel skirts & side skirts;
3) make sure the bumper pan is secure;
4) try several things to reduce wheel resistance.

Suggestions for any of these are much appreciated, especially regarding the brakes.

[renault_megane_dci]

You might want to check the thread about using bicycles brakes spring to space the brake pads when no pressure applied (not all cars are made equals in this department)

[j12piprius]

I'm going to order a new radiator, fan, hoses, and hope to install them before my next trip, plus wheel strips and skirts.

The foam bumper pan came loose from the tape, and the foam cover layer came loose at the top. Meanwhile, the gorilla tape still held tight to the bumper. I'm going to replace the foam with coroplast, run plastic ties through it and around the pvc spacers, plus more of the tape.

I think the main resistance was the wind, so I'm not going to bother with the brakes at this point.