My new hopefully more aero Metro front bumper

[Coyote X]

I think the trend is going in the right direction. Today I drove about 250 miles on a trip. It was all in WV so no flat roads it was all up or down hill. I was driving between 55 and 60mph. No wind and running ethanol free gas Both windows down and the rear wing windows open. I managed to get 65mpg on the trip. I filled up before and after and the numbers matched the mpguino as usual with this car and filling up on the same pump.

For today's trip I was easy on the car and didn't race anyone off the lights, except one time I think with a few tweaks the car could easily get 70mpg on this trip just driving it easy. If someone was to take this car and go all out hypermiling I bet it would be impressive.

The list of mods I have done to the car:
Weight reduction, no back seat, spare tire/jack, no rear seat belts.
Aero is as shown in this thread
Crower 181 duration cam, ignition at 6 degrees
Yokohama 145/12 tires at 36psi
injector kill switch and engine start button on the shifter

I am really thinking the cam is what is making the mods have a bigger effect than usual. It is a pretty good cam. To really get the car right I need more gearing so either go to 155/13 tires or find a 3.52 trans. This cam basically is out of power at 3000, it's power range is probably 500rpm lower than the stock xfi.

If this car was a bit lighter I think it would be at 70mpg right now. It has a complete non working a/c system, power windows and locks, and 2 layers of soundproofing under the carpet. All that stuff together is probably 100lbs so it offsets the stripping of the interior. The frame horns and important parts of the car are made out of 10ga steel so the car will hopefully never rust out again. For now I will probably just drive it a bit and see where the numbers settle before doing any more mods.

I guess the next step is to work on a belly pan but that will have to wait till I get some more free time.

[freebeard]

Looks good. Where on the graph did you roll the bottom edge of the air dam?

[Coyote X]

I Filled up the car the day after I built the front bumper but during that tank I also rolled it under and added the back. Those low 50mpg readings I have on the chart are from me not having to drive anywhere and basically the entire tank is short trips of normally 3 miles and a max of up to 15 miles. School is out in May so I mostly just didn't have to do any commutes or go anywhere. Those short trips really kill the mileage.

Today I filled up again and this tank is pretty good. It is a lot of short trips with one longer 80 mile trip in the middle. I managed 62mpg. I can easily maintain 67mpg on the highway doing 55-60mph.



I am thinking I might go ahead and make a full bellypan for the car and maybe try out some taller tires I have laying around to see if it makes a difference. I might be able to make this car get 70mpg out of a tank. I had to drive a bit today so right after filling up I tried a bit of hypermiling for about 20 miles. Lots of engine off and coasting. I had 85mpg at 20 miles of driving before I got bored and gave up. The mpguino is still sitting at 68mpg with 120 miles driven today

[Coyote X]

I can never leave well enough alone



I am debating on trying a set of 13 inch tires if I can round up 4 good ones to test with. With all the mods done to this car I am sure it needs taller gears to really take advantage of them. I just hate to put taller tires on these horrible brakes and I don't want to put all the time into swapping to larger brakes just to test it out.

[deejaaa]

what size are you running right now? from the look of the ones now, they look old. if running 15's, i would try a set of Cooper CS's, pumped to 50 but make sure they are T rated. H is a waste of money. helps me out. i almost have 60,000 on 2 of them and can go a lot longer. tread wear is rated 80,000 miles.
also, i can't help but comment. the rear bumper, is it going to help or hurt? have read of no benefits at from it. http://ecomodder.com/forum/showthrea...mpg-20113.html

[Coyote X]

A small update, I took the underbody panels off and my mileage is now back into the mid 60's. So it looks like putting those covers on the bottom is dropping me up to about 4mpg. I never would have guessed that is what caused my slight drop in mileage. I assumed it was some oddball problem like a dragging brake or something I just wasn't able to find.

So for now back to a regular underside with my ventilated back bumper. I will have to get the car in the air sometime and try and figure out why it was worse with the underbody panels than without. I would think that at worst it just would not gain mileage but I never expected it to be that much drag by smoothing the underside.

[Coyote X]

I forgot to put up pictures of the minor update I did to the front end.





The headlight covers are attached at the bumper and the top is just resting against the headlight bezel. The center section is attached at the hood and just resting on the bumper. That way I can still open the hood without a huge amount of work. It seems like it made the car a bit quieter but I have not seen a mileage increase. Mostly because the gas tank is leaking and I have a bad O2 sensor. I am holding around 59mpg with those problems so I think it is doing pretty good. Now that the weather is good I will probably change over to a 4 wire O2 and fix the gas tank soon.

I still have not figured out why it gets worse mileage with the underbody panels than it does with the ventilated bumper but it works good enough I am probably just not going to mess with it anymore. I am thinking the next thing would be to add to the rear sides and make bigger rear wheel skirts. But I think the easy gains are all done now so it is going to be expensive to really push it much higher with normal driving.

[freebeard]

I would think that at worst it just would not gain mileage but I never expected it to be that much drag by smoothing the underside.

That is curious. Since it's two partials you could add back one or the other at a time and maybe isolate the cause that way.

[2000mc]

I'll vote for trying the front section only, which Seems like it should help. I'm imagining that the rear creates some weird air channel, because of the rear bumper vents, I think the leading edges of the rear section would have to be sealed up air tight to not create a problem.

[Coyote X]

I sealed up the back bumper for a test with the underbody panels and it didn't make any difference. I figure something in the rear of the Metro design isn't liking the rear sealed up. I would guess the only way to test it would be to get a video of the back end on a rainy day at speed and see what is going on. I might put the front section back on this summer when I have the car up in the air but I have other experiments to work on first.

At least I did fix the O2 sensor and upgraded from the bad 1 wire sensor to a 4 wire sensor so that should help some. I just need to fix the gas tank and I am hopefully back into the mid 60mpg range.