MPGs run, Aspire SE

[sketchman]

I love this thread.

Props on the R&D.

[TominMO]

Depending on when you go, if you need another 200+ lbs to make the car lower and a GPS unit, I can go with you.
Or you can just take the GPS unit!

Let's get together this weekend and you can teach me how to use the GPS. I'm thinking 4PM Sunday, the usual pizza-dispensing location?

BTW, several other mods I have made/will make, due to being PO'd at inconsistent results:
pass. mirror delete
windshield wiper delete (driver-side wiper in trunk, with wrench to re-attach)
blended front of SE spoiler with rear window (styrofoam/duct tape), so air only flows over it, not over and under
if I can find one of those panoramic inside mirrors, I will delete the driver-door mirror too
will connect rear underbody to rear bumper so air does not get up into the bumper (styrofoam/duct tape)
will wax and Rain-X car before test trip
will remove AC belt just before trip

If I can't hit 60 with all this, then I'll take what I get.

[bhazard]

Car said 58.5 mpg when I got to work this morning. 38 mile drive...averaged 54 mph and followed a semi for a good part of it...however my car payment plus insurance is more than most of us paid for a festy :/

[Pu241]

Depending on when you go, if you need another 200+ lbs to make the car lower and a GPS unit, I can go with you.
Or you can just take the GPS unit!

[TominMO]

Agreed as well. My next run will be 200-250 miles, starting early in the morning so I won't have to use A/C. As soon as I get the new tires on and a good-weather day.

[bhazard]

Agreed. You can not get accurate mpg calculations from small fillups. You need to use at least half a tank.

[mikeyjd]

Even with careful fill ups, I think larger sample sizes might be needed.

[TominMO]

Today I went out and put the 155/80x13 used snows on the front, stuck my new Winterforce 155/80x13s on the rear, added a little duct tape to the rear wheel arch skirt, and went for a run. Again disappointingly, I got 51.3 MPG. All I can attribute this to is either a fill error or the extreme wiggliness of the snow tires, giving much higher rolling resistance. Snow tires are a couple of pounds heavier too.

My next test will be with new Kumho Solus KR21s in 155/80x13, on my Aspire aluminum rims, probably over the weekend.

Aspire SE mileage tests
MPG.......Description
45.........stock; 185/70x13 tires
55.........small front air dam, same tires
52.7.......larger air dam, side/rear wheel skirting, 165/80x15 front tires on steelies; 155/80x13 snows on rear
59.7.......larger air dam, side/rear wheel skirting, 185/70x13s on front, 155/80x13 snows on rear
51.3.......larger air dam, side/rear wheel skirting, 155/80x13 snows all around

[mikeyjd]

59.7!

I think the difference was the lighter front tires/rims, 22 lbs vs. 33 (with adapters). Even tho the taller tires lowered the RPMs by about 10%, the negative of having a small motor push a rotating mass 50% heavier was too much to overcome.

This does seem to validate my earlier 55 MPG result. I think the side skirts, rear wheel arch skirts and skinnier rear tires gave me the extra 4.7 MPG. In other words, it seems to be mostly about a good front air dam.

My next test will involve 155/80x13 tires on the front, to see the effect of the smaller contact patch compared to my 185s. Probably next weekend. Then I want to do a test with the 155/13s all around but no side or rear wheel skirting.

Aspire SE mileage tests
MPG.......Description
45.........stock; 185/70x13 tires
55.........small front air dam, same tires
59.7.......larger air dam, side/rear wheel skirting, 155/80x13 on rear
52.7.......same as above but with 165/80x15 front tires on steelies; 33 lbs

nicely done!

[Movin]

:thumbup:

[TominMO]

59.7!

I think the difference was the lighter front tires/rims, 22 lbs vs. 33 (with adapters). Even tho the taller tires lowered the RPMs by about 10%, the negative of having a small motor push a rotating mass 50% heavier was too much to overcome.

This does seem to validate my earlier 55 MPG result. I think the side skirts, rear wheel arch skirts and skinnier rear tires gave me the extra 4.7 MPG. In other words, it seems to be mostly about a good front air dam.

My next test will involve 155/80x13 tires on the front, to see the effect of the smaller contact patch compared to my 185s. Probably next weekend. Then I want to do a test with the 155/13s all around but no side or rear wheel skirting.

Aspire SE mileage tests
MPG.......Description
45.........stock; 185/70x13 tires
55.........small front air dam, same tires
59.7.......larger air dam, side/rear wheel skirting, 155/80x13 on rear
52.7.......same as above but with 165/80x15 front tires on steelies; 33 lbs

[TominMO]

so capri 14's would be an ideal swap if i wanted to use my current break setup without any kind of adapters?

Yes, as long as you have Aspire Monroes on the rear, and don't go with too tall a tire; a 185/60x14 will fit fine with the Aspire rear struts. But if you are going for MPGs, I'd put good-quality 155/80x13s on the rear (both to clear Festy KYBs, which are much better than Monroes, and for lower rolling resistance), and perhaps a 185/70x14, or 185/65x14 on the front for a little extra height/lower revs. Any slight differences in sidewall height (and therefore flex) between front and rear can be addressed by adjusting tire pressure.

The Kumho Solus KR21 comes in all the sizes mentioned in this post BTW....

http://www.kumhousa.com/tire/category/car/A554FF1F-6F0E-4A7B-B4F2-F117F7942A2D

[TominMO]

To answer both of you regarding engine efficiency at a given RPM, my best mileage in a Festy was 62.5 MPG @ 45 MPH. My engine speed was 1800 RPM in 5th, and of course at 45 there is little air resistance to contend with. But that's not to say that 1800 is max efficiency; more extensive testing would have to be done to determine that.

Concerning my fill technique, I noticed yesterday that the pump I was using placed the filler neck downhill, the way that gas station lot is laid out; so at any point I might have gotten an air pocket. From now on I will use a specific pump that puts the filler neck uphill from the rest of the tank. My 55 MPG figure might have been due to an air pocket when refilling at the end of the run.

I do find it hard to believe that rolling resistance would be that much of a factor here; especially going from a 185-wide to a 165. But there was a distinctive pull to the right, and I'm not sure what that means. Perhaps because the tire had such tall sidewalls it caused issues? Shouldn't have happened tho; I did have the tires inflated to 44, so the sidewalls should have been adequately stiff.

Taking it out on another run in about an hour, with the original 185/70x13s on front and yesterday's 155/80x13s on the rear.

[Movin]

If the rolling resistance is not abnormally high the sweet spot should be 1700 to 2100 for best
MPG's. Even with a trailer on cruising on the hiway is around 2 grand.

[mikeyjd]

Just came back a little while ago from doing another MPGs test. Same 99.1-mile hwy course, same perfect weather. Changes to the car were taller 165/80x15 tires, and more aero mods. I even made rear-wheel skirts this morning, out of some styrofoam I had laying around and the last of my white duct tape. Total aero mods to date have cost less than $30 in materials.

See pic below. (Included is a bonus pic of the cat who owns me.)

The results were surprising and disappointing. It took 1.88 gallons to refill, at the same pump I always use. This came to a MPG figure of 52.7! This despite the fact that on a roll-down test, it took a long time to lose speed, and was significantly quieter inside the car (lower radio volume needed), indicating less air disturbance. Engine RPM was down from 2700 to 2400, the same as my Festy's @ 60, due to the taller tires.

What I am thinking is: fill error. Need to do a longer test to get better results. It could also be that I had a fill error on the previous run (when refilling), so that my result of 55 MPG was not accurate. So for now the jury is out. I just need to do a longer test.

The other possibility is that the 15" steelies and tires are so heavy that it took more gas to keep them rolling than was gained in lower rolling resistance or lower RPM; but I don't really believe that. BTW these tires are just too tall for everyday driving; lotsa scraping of the fender liner happened on turns or small bumps.

Tmw I will do another identical test with my regular 185/70x13 tires on front to see if that was an issue. It will raise RPM back to 2700, but on the other hand it will also lower the front of the car by about an inch. Possibly that was also a factor, but again I doubt it based on how quiet the car was.

Also be aware that rolling resistance can vary allot from tire to tire. Things like tread wear and pattern play a huge roll. Some people report as much as 3-4 mpg change from same size tires in different brands just based on the rolling resistance of specific brands. I think that it's even possible that you may have dropped your rpm's to the point where you would need to go even faster to hit maximum engine efficiency load. I'm no expert and don't know what the bfcs's for the 1.3 is but it could be closer to 2700rpm than 2400rpm. If that is the case you would actually just be moving your ideal speed into a higher mph range. Some engines operate at max efficiency at over 3000 rpm's! My guess is that is likely an issue of increased rolling resistance along with moving outside the ideal rpm range for that speed. It's hard to imagine since these seem to be geared somewhat short, but from what I've been told the way the engine is designed limits what can be achieved with taller gearing.