How To Get Better Gas Mileage - Tell your specifics on getting the highest mpg

[harpon]

I'd still like to have a small electric motor on one of the back wheels and a couple of batteries back there- Doesn't need to go that fast 10-15 mph would do-20 would really be great- shut it off in parking lots, drive-throughs and clogged up traffic, and have emergency power otherwise to get the car somewhere in a break-down.
We could have had this feature years ago, and a real built-in external socket to an onboard charger. Gasoline selling interests keep such things down I think. And a larger car would pose greater power and weight considerations.

[meyek91974]

Engineering overtakes aerodynamics.
By this, my first car was a 1982 Vdub Rabbit 4door 5speed naturally aspirated diesel and I got 50+ish mpg. Yes it was a diesel and YES it was slow but wow! the gas mileage. - Do I want to go diesel now? No. Do I want an expensive to fix Vdub? No. BUT I have wanted to find the simplest mechanical, best mpg ford I could. The Festiva is my 30-year-later Vdub, blue oval Honda civic HF, -ish car. Well, Ive only had my Festiva a couple months but some of you have had yours for years or decades.
I want to find how to make this car 60+mpg.
So, I will work on getting the car in top mechanical shape and along the line I wonder about swapping in a Subaru Justy rear diff and axles powered by a rear mount electric motor or whatever other things to make me understand why in 1982 VW can get even better mpg than our modern cars. And, years ago I got my Ford Maverick to a regular 33mpg so I figure I can strive for this

[sketchman]

Did you look at the Aero Civic? It's fugly to a T, but it works. Really, really, really well.

Aero drag becomes the biggest thing at speed to hurt fuel economy. And yeah, you can engineer your way around that. With better aero.

[blake4591]

If you are really mechanically inclined you can try ringing up an ERG system since the cars never had them from the factory. A lot of people hate them and disable them but when working correctly they are worth at least a few mpg on engines in the 3L to 4L range. I don't know if it would be worth more or less on a smaller engine. The extra CO2 allows leaner mixtures by displacing oxygen in the cylinder.

Ultimately though the real gains at highway speeds are from areo improvements. The Cd is effectively weight at speed (since air density is just a constant in theory) so the lower the Cd the lower weight of the car.

[bhazard]

If you meant EGR, the carbies had it. The problem with displacing oxygen in the cylinder is that the air is measured well before that (VAF) and so you're still gonna get all the fuel. You would have to run a standalone.

If I managed 53 mpg on a trip across michigan following a semi truck in a stock festy with bikes hanging off the hatch, serious aero mods (wheel skirts, underbody and partial kamm-back) should easily get it to 60 mpg at 60 mph.

Of course sticking to a skinny 145-165 tire at least the diameter of the stock tires would be ideal as well.

Switching to a standalone like megasquirt would easily allow fuel map and timing adjustment at cruise, lean burn anyone? Maybe not to the extent that honda did it but cruising at ~16-17:1 AFR wouldn't be difficult.

[ryanprins13]

I once managed 52mpg US (63mpg UK) in my festiva on a road trip with no modifications and without trying too hard. I believe like everyone says aero modifications are very important to get much better but its also engine design. Your diesel VW probably made 30hp? Diesels are also more efficient, but small engines obviously can use less gas than larger ones, we just all want to go fast so manufacturers put bigger motors in cars. Thats in general, im sure we all know of large motors that took tons of fuel but still made no power... Theres a guy on youtube with a 0.5L diesel yanmar motor in a festiva, he gets like 75mpg with it floored everywhere he goes but it takes a few miles to speed up...*
I think your best bet after you make sure all your maintinance is up to date and your tune is proper is a system where you can adjust AFR. It wont pay off but your numbers will go up but time. You should be able to lean out to 17:1 while cruising. I would think adding methanol injection would allow you to lean out more but you would have to look into that yourself. I think that would net you the best improvement after maintinance and adjusting driving style for fuel economy.*
I think if you want to add batteries, generator, extra drivetrain and all that you would have to plan to use it most of the time for it to offset the additional weight for when its not used. It would never pay off of course and hopefully you live somewhere warm. I calculated out the cost difference of an electric car vs gas for where i live a while back, i think i used a prius, but anyway, when it gets to like -20 or below with my daily commute it would cost more on electricity than my festiva would on gas and i wouldnt make it to work on a full charge. I think only 2/3 of the way when it gets that cold, but i cant recall.*
Anyhow, i think either a full electric swap with no gas motor other than maybe a small emergency gas generator or an engine swap such as the geo xfi, the diesel mercedes smart car engine, diesel tractor motor... Would be best. I would never drive a vw or audi for the reasons you mentioned but mercedes are just about as bad. However a diesel from a smart car in a festiva with a setup so you could adjust fuel ratio, turbo output, ignition timing and all that like the guys with big diesel trucks do would be cool. You could get great fuel milage after only a few years of wiring... For something simpler look up that youtube video with the yanmar lawn tractor motor and see what the motor is, then find out if yanmar made a slightly larger motor that will still mate up to the transmission so you can do highway speeds easier. Or get the same one and get a big turbo old lawn tractor deisels are pretty simple.*


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[blake4591]

If you meant EGR, the carbies had it. The problem with displacing oxygen in the cylinder is that the air is measured well before that (VAF) and so you're still gonna get all the fuel. You would have to run a standalone.

If I managed 53 mpg on a trip across michigan following a semi truck in a stock festy with bikes hanging off the hatch, serious aero mods (wheel skirts, underbody and partial kamm-back) should easily get it to 60 mpg at 60 mph.

Of course sticking to a skinny 145-165 tire at least the diameter of the stock tires would be ideal as well.

Switching to a standalone like megasquirt would easily allow fuel map and timing adjustment at cruise, lean burn anyone? Maybe not to the extent that honda did it but cruising at ~16-17:1 AFR wouldn't be difficult.

yes EGR, I hadn't had my coffee yet. Haha

Since additional air is be added in the manifold it should reduce the total air flowing into the engine through the VAM. Basically the cylinder fill total will be EGR plus fresh air from the VAM. The ECU would then fuel for total measured fresh air which will be less than the total cylinder fill. There are tons of MAF cars that use EGR and inject the exhuast gas after the MAF sensor.

Yeah I think if you want to seriously pursue mileage improvements tuning is a must. On a trip with one of my friends we leaned out the 302 in his 91 mustang out to about 17.5 AFR at cruise and got 31 mpg at 80MPH over about 350 miles. The car was cammed, with gears and wide sticky tires so it wasn't exactly setup for highway cruising.

[bhearts]

If you are really mechanically inclined you can try ringing up an ERG system since the cars never had them from the factory. A lot of people hate them and disable them but when working correctly they are worth at least a few mpg on engines in the 3L to 4L range. I don't know if it would be worth more or less on a smaller engine. The extra CO2 allows leaner mixtures by displacing oxygen in the cylinder.

Ultimately though the real gains at highway speeds are from areo improvements. The Cd is effectively weight at speed (since air density is just a constant in theory) so the lower the Cd the lower weight of the car.

The real gains of oxygen displacement would come from steam. Instead of egr. Steam displacement.

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[lessersivad]

I have attempted to achieve maximum MPGs once in my Festiva.

It was during a 728 mile trip, 364 miles each way. On the way to my destination I kept the speed 50-55 mph. consumption of 50.2 MPG was recorded.

On the return trip I drove 55-60 mph. Consumption of 45.5 MPG.

This was with stock everything and 2 adults and 2 suitcases.

Actually the 'stock everything' isn't a fully true statement as I was (and still am) running P155-80R 13 tires.

So without correcting for the larger diameter tires those are the numbers I was able to get.

[nitrofarm]

Install an Aspire Head & Header,free Hp less friction.