Best mpg with your festiva?

[mikeyjd]

OK, yesterday I went and picked up some tire irons/spoons, one 30-inch and two 18-inch. Today I spent about five minutes less than eternity removing one of my space-saver tires from its 15x4" rim. I broke the bead by jacking up the Festy with the tire's sidewall as the base for the jack. Festy didn't go up, tire went down, as planned/hoped. Had to go mostly around the tire to git 'er done. Then had to do the other bead, but this went much quicker.

Then to work with the irons. I've done this on bicycle tires, so I understood how to do it. Just a matter of scale. Long story short, from start to finish I probably took about an hour, maybe a little less.

Went back inside and saw that my wheel adapters came! I just ordered them on Monday. Went out and put one on, then mounted my other space-saver, which still has air in it even. Really fills up the wheel well. Plenty of clearance from the strut now. I'll have to see how it goes with the fender liner. Took pics, but photobucket is acting even weirder than ever. Can anyone recommend a good site to upload pics to?

BTW the label that identifies my wheel as a space-saver wheel peels off very nicely, if you are patient. Then a little Goof-Off or Goo Gone or WD40 will get off any remaining glue.

Diameters:
155/80x12 = 21.8"
165/80x15 = 25.4"
An increase of about 15%, i.e. your motor is turning 15% slower at hwy speeds with these tires. So 50 MPG at a given speed should be 57.5 now.

If you have the Aspire swap and use these wheels, you need to carry an extra spare with this bolt pattern (4x114.3). Or you could just do a front Aspire swap, add the wheel adaptors, and carry only one spare. Or you could have a dual-bolt pattern spare. Or have a prybar or equivalent handy so you could remove the adapter when you put the spare on. (Assuming you are alone when you get a flat, there will be no one to press the brake pedal for you to immobilize the brakes so you can get the adapter nuts loose. Hence the prybar, which you wold place between two studs and have the other end touch the ground, to immobilize the adaptor so you could remove the nuts holding it to the hub.)

Also bear in mind that since this tire is much taller, you might want to have a 2x4 or two handy to put under the stock jack.

it won't be as good as that estimate because you have added frontal area from the tire width and tire exposed to aerodynamic forces. You have also slightly increased your rolling resistance by having a wider tire. And slightly increased the weight by having a larger tire. And although your cruising rpm should be roughly 13-14% lower with these tires you also have to factor in that you will spend less time in 5th gear which will diminish the overall gains slightly as well. All this to say that you should still see impressive gains. I wouldn't be surprised to see a 10% improvement at the pump if you do mostly highway driving. Please keep me informed about your results as I am strongly considering doing this very thing for myself

[TominMO]

it won't be as good as that estimate because you have added frontal area from the tire width and tire exposed to aerodynamic forces. You have also slightly increased your rolling resistance by having a wider tire. And slightly increased the weight by having a larger tire. And although your cruising rpm should be roughly 13-14% lower with these tires you also have to factor in that you will spend less time in 5th gear which will diminish the overall gains slightly as well. All this to say that you should still see impressive gains. I wouldn't be surprised to see a 10% improvement at the pump if you do mostly highway driving. Please keep me informed about your results as I am strongly considering doing this very thing for myself

a. Width difference is negligable--155 vs. 165. But in fact I currently am running 185/70x13s, which are wider than the 165s. I used the typical 155/80x12 tires size for comparison since that is a very common Festy size.
b. Weight is not much of a factor either, as long as the car is not accelerating. When moving at a steady pace, the tire/wheel acts as a flywheel. Its own momentum keeps it moving, to a degree. A 4" steelie with a narrower tire is probably about the same weight as my 13" tire on the 5.5" wide aluminum rim. I will try to get a weight on the final setup.
c. On the hwy, I will be spending all my time in fifth gear, barring traffic slowdowns.

I suspect my results will not be as good as 15%, because I am currently running a tire that is taller than the 155/12", so some of the gearing improvement has already happened. But the 15" tire is narrower, and with aero mods I may do better than I expect. Even a 10% improvement is worth $350 over my expected lifetime of these tires (40K miles). Refer to post #4 for my fuel cost calculations.

I will run two tests--one with just the tire change, and then another after adding mild sero mods to my Aspire, to reduce turbulence under the vehicle.

Here is my one-and-only Aspire test to date--it was done on my other white Aspire SE, now owned by Festyboy. It got 48.2 MPG, but this is slightly better than real-world, I think. With the same car, I got 46 MPG over the course of most of a tank, driving cross-country.

http://www.fordfestiva.com/forums/showthread.php?24409-MPG-Run-1995-Aspire-SE&highlight=aspire

[mikeyjd]

a. Width difference is negligable--155 vs. 165. But in fact I currently am running 185/70x13s, which are wider than the 165s. I used the typical 155/80x12 tires size for comparison since that is a very common Festy size.
b. Weight is not much of a factor either, as long as the car is not accelerating. When moving at a steady pace, the tire/wheel acts as a flywheel. Its own momentum keeps it moving, to a degree. A 4" steelie with a narrower tire is probably about the same weight as my 13" tire on the 5.5" wide aluminum rim. I will try to get a weight on the final setup.
c. On the hwy, I will be spending all my time in fifth gear, barring traffic slowdowns.

I suspect my results will not be as good as 15%, because I am currently running a tire that is taller than the 155/12", so some of the gearing improvement has already happened. But the 15" tire is narrower, and with aero mods I may do better than I expect. Even a 10% improvement is worth $350 over my expected lifetime of these tires (40K miles). Refer to post #4 for my fuel cost calculations.

I will run two tests--one with just the tire change, and then another after adding mild sero mods to my Aspire, to reduce turbulence under the vehicle.

Here is my one-and-only Aspire test to date--it was done on my other white Aspire SE, now owned by Festyboy. It got 48.2 MPG, but this is slightly better than real-world, I think. With the same car, I got 46 MPG over the course of most of a tank, driving cross-country.

http://www.fordfestiva.com/forums/sh...ghlight=aspire

If your decreasing your width then you should actually have less drag than currently. I tend to shy away from the reliability of small refills as the margin for error increases exponentially. If you are going to do a small tank test I would recommend using the same pump at the same station in the exact same manner as each pump can have slight variances which are enough to make a large difference on a small test sample. The most accurate way to do small A-B tests would be to add another A run to see if any other factors are contributing such as ambient temps and engine temps. Also if you want to get instrumentation for your fuel economy endeavors this guy is making one compatible for pre obdII ecu's http://www.dschmidt.com/MPGuinoJBD.html I look forward to your results!

[TominMO]

If your decreasing your width then you should actually have less drag than currently. I tend to shy away from the reliability of small refills as the margin for error increases exponentially. If you are going to do a small tank test I would recommend using the same pump at the same station in the exact same manner as each pump can have slight variances which are enough to make a large difference on a small test sample. The most accurate way to do small A-B tests would be to add another A run to see if any other factors are contributing such as ambient temps and engine temps. Also if you want to get instrumentation for your fuel economy endeavors this guy is making one compatible for pre obdII ecu's http://www.dschmidt.com/MPGuinoJBD.html I look forward to your results!

I'm not quite that conscientious. I just do these short MPG runs as baselines, not gospel truth, and of course I know that my results are a little high. But my real-world test across country in the Aspire was only 2.2 MPG less. I know my methodology is good tho, because my results have been very consistent with the changes I have made, mainly in speed traveled.

Lemme go find a thread summarizing my results....
Here you go. See post #6. http://www.fordfestiva.com/forums/sh...-MPG-Run-NA-B6

Now I'm thinking I should do a Festy B6 MPG run at 60 MPH with the skinny 15s, to see how much of a factor that would be! 41.9 vs. ? BTW I have run an MPG test twice with the B6 Festy at 60 with these 185/60x14 tires, and got the same results, right to the tenth! So I know I get consistent results.

[mikeyjd]

U da Man

I'm not quite that conscientious. I just do these short MPG runs as baselines, not gospel truth, and of course I know that my results are a little high. But my real-world test across country in the Aspire was only 2.2 MPG less. I know my methodology is good tho, because my results have been very consistent with the changes I have made, mainly in speed traveled.

Lemme go find a thread summarizing my results....
Here you go. See post #6. http://www.fordfestiva.com/forums/sh...-MPG-Run-NA-B6

Now I'm thinking I should do a Festy B6 MPG run at 60 MPH with the skinny 15s, to see how much of a factor that would be! 41.9 vs. ? BTW I have run an MPG test twice with the B6 Festy at 60 with these 185/60x14 tires, and got the same results, right to the tenth! So I know I get consistent results.

I wasn't trying to cast doubt. I was just merely pointing out the pitfalls of small test samples. I appreciate your ardor towards what I view as a fine cause. I'm sure you will help people save money if you find out that this produces anything statistically significant. :cheers:

[mikeyjd]

501.8 miles on 8.021 gallons = 62.63mpg!! My best full tank yet

[TominMO]

501.8 miles on 8.021 gallons = 62.63mpg!! My best full tank yet

Wonderful! BTW I am waiting on my 165/80x15s to arrive from tirres-easy. Hope to do a MPGs test pretty soon.

[FestYboy]

165/80/15?!?!?!! dude are they going on a truck? that's 4" taller than normal! and a nearly 18% differance.

[TominMO]

165/80/15?!?!?!! dude are they going on a truck? that's 4" taller than normal! and a nearly 18% differance.

Exactly....

[TominMO]

501.8 miles on 8.021 gallons = 62.63mpg!! My best full tank yet

What was your average speed, and other relevant details?

[FestYboy]

ok, so it's a truck, that makes me feel better now. just remember to mind the load capacity.

oh and i averaged 40mpg (39 up with a steady 20mph head wind and 41 back with negligable tail wind all at 70ish mph) for the ohio trip. this is in Skippy who has a ported and -.020" milled head and FMS comp cam (not a fan of the cam). i was hoping to get the stage 2 dickmeyer cam in before the trip but it hasn't shipped out yet.

[kumalaba]

501.8 miles on 8.021 gallons = 62.63mpg!! My best full tank yet

wow!

[TominMO]

Gearing. The ultimate would be lowering your overall hwy RPMs by using 165/80x15 tires made for older VW Beetles. You would need appropriate VW wheels. The 4-lug ones are 4x130mm, so you would need a pair of adaptors (no need to go to this expense for the rear wheels).

155/80x12 = 21.8" diameter
165/80x15 = 25.4" diameter
A difference of about 15% reduction in engine speed; so 60 mph would be like 51 for RPM purposes. 55 would be like 47.
At 45 mph over a distance of 86 miles, I got 62.5 MPG.
At 55, same course on the hwys around St Louis, I got 58 MPG. So 55 is a pretty good sweet spot; only a 4.5 MPG difference with a 10 MPH difference. These results reflect both RPM and wind resistance, of course.

Adaptors: http://www.ezaccessory.com/Wheel_Ada.../4000-4000.htm
Wheels: http://www2.cip1.com/ProductDetails....D601%2D025%2DG
Tires: http://www2.cip1.com/ProductDetails....C%2DC10%2D6654
Total cost looks like about $400. But with these gas prices....saving 15% in gas over 40,000 miles might be worth looking into. Plus you just have to replace the tires, not the hardware.

40,000 miles / 40 MPG = 1,000 gallons
1,000 gallons x $3.50/gallon = $3,500 for 40K miles!
$3,500 x .15 = $525. This setup more than pays for itself in 40K miles.

Here ya go, Arty....post #4 in this thread. See post #25 for what wheels I am actually using.

[mikeyjd]

501.8 miles on 8.021 gallons = 62.63mpg!! My best full tank yet

What was your average speed, and other relevant details?

55 hwy (glide down to 45 when traffic permitted)
allot back road driving with pulse and glides from 55-35 (all in 5th gear)
switched to mobile 1 full synthetic 0W20 in the engine and tranny.
warmer temps and good weather made this tank possible

[Prafeston]

Just did 388 miles in my car at 44mpg...I thought I was going good!