Milage Machine. Ideas

[tailgatewagon]

ok so this is going to be a post about my ea81 sedan that im going to make into the best milage machine i can. here is what i got and what im thinking of doing if you have any Ideas Please share.

 

1981 ea81 2wd 5speed,

car is stock with 130k on it and all factory systems intacked.

no PS and no AC

 

here are a few ideas i had.

 

spfi conversion....

 

lower it using cut 4x4 springs...w new shocks

 

165R80 13s on alloys of some kind not shure what kind yet

 

air damn of some kind on the front

 

fairing to smoth air out over rear window.

 

brakes NOT shure if Disks would be better then drums. i think disks have more drag but less rotating weight......

 

anyideas

[daeron]

lose any weight you can, and drive like there is an egg between your foot and the accelerator. Dont forget to keep your windows rolled up. Electric fans on the radiator.

 

as for brakes, I dunno... but I suspect it doesnt make much of a difference. Your front brakes are the only ones that add unpsrung load onto the engine.. the rears just roll along. You dont have drum brakes up FRONT, do you?!

 

You *might* want to think about adding some vents to the extreme rearward outside corners of the hood, or possibly the front fenders behind the wheel.. to let air out of the engine bay, yanno? i don't REALLY know how much of an effect this would have, though.. just a wild idea that I havent ever looked at, so I wouldnt know the car well enough.

[Frank B]

You won't notice any difference with alloys, I put some on a GL-10 I had and they were only 1 pound lighter than the steel wheels. Still no difference. I doubt you'll notice any difference with the brakes either. Those rear drums are so little and light that they may weigh the same as rotors.

All that air under the hood exits under the car. If you put openings in the rear of the hood(cowl area), you may get a cowl induction effect and more air will come in from there instead of thru the radiator, causing the car to overheat.

Spfi is a good idea. You'll get the same mileage as a well tuned, and perfect stock carb. But we all no that a well tuned perfect hitachi carb is a myth! They need constant attention.

The underside of the car is the least aerodynamic. An air dam and side skirts would make a big difference. So will lowering the car.

Also, if your state allows it, remove the right side mirror. Also remove the roof rack if it has one. And any other junk that will smooth out the air flow over the body.

Other than that, drive slow.

[Loyale 2.7 Turbo]

Just a Simple yet Effective Idea on the Fly: Disconnect the Secondary Stage´s Vacuum Actuator from the Hitachi Carb, and Cap it.

 

Believe me: Without the Secondary, You´ll save Gas, but your Subie will Become Lazy...

 

I Suggest you to Try it for a While...

 

Good Luck!

[RenaissanceMan]

Get the car aligned, you would be amazed what that will do if it rolls striaght down the road. Put as thin of an oil as you feel safe in the engine. 10W30 mobil one? 5W30 mobil one?

 

I saw this once at wcss7, make a water/deposit separator thing to go between the valve cover, and the PCV valve on your PCV system.

 

Run your tires up at 40 psi. (be concerned about traction in hard stopping situations)

 

Try running thinner gear oil than what you have in there now.

 

Remove any unneccesary interior, lol

 

Fresh O2 sensor, for quick and precise fuel control, faster switching.

 

thats the only stuff I can come up with for now, hope any of that points you in the right direction

 

-Mike

[idosubaru]

i know this works if you drive more freeway/country driving. city mileage may be the opposite and different vehicles would have better results than others, i don't know. now that the disclaimer has been said, you can gain significant mileage by using larger wheels/tires. larger rolling diameter allows you to travel further with the same number of rotations. of course there's a limit because as the wheel/tire combo increases there are losses to be had as well, but i've done it and gotten good gains. you have to do some detailed calculating though because your speedometer will be off...and it's inaccurate to begin with. so it's hard to get accurate numbers. your odometer will no longer show the actual distance you're traveling...you'll be going further, so you'll have to figure a way to determine how far you're really traveling.

 

skinniest and lowest rolling resistance tires you can install as well. but if you're doing this for $, then buying a set of dedicated tires won't fit the bill. but next set you get, you could down size to thinner tires. although EA81's are already insanely thin aren't they?

 

remove as much unnecessary weight as possible from the vehicle. there's a complete thread about reducing the weight of an XT6 over at xt6.net, with some interesting ideas.

[Jerry DeMoss]

Also something that you could try that I had good results with in the past is:

-Slightly larger exhaust.I gained 1-3 mpg average.

-Better coil and plug wires like msd.I could notice it had better scavanging abilities.

-Also a good free flowing air filter.

 

I did all of the above things to my previous ea81 hatch and I got 5-8mpg better.Good luck:)

[idosubaru]

exhaust work may depend on what kind of driving is done. on highway, country driving, an AWD automatic XT6 with a straight through muffler helps a good deal. the stock XT6 mufflers suck, not sure about others. i've swapped out cats, hollowed out the cat, installed high flow cats, custom headers, run straight pipe only, aftermarket mufflers and stock mufflers. with all the different exhaust set ups i've had it fairs best for my type of driving with just a simple muffler swap. all that other stuff provided unnoticeable gains or even losses (straight pipe).

 

a simple google search would probably aid alot too.

[subie_newbie]

Here's the pretty classic formula for fuel economy, I think this has all been mentioned by different people before:

 

1. Taller (lower ratio) differential gears, or at least 5th

2. Skinnier tires at maximum or a bit above pressure

3. Reduced mass, and in particular reduced rotating mass such as wheels, flywheel, crank and accessory pulleys.

4. Remove all exterior trim, antennas, mirrors, door handles etc

5. Reduce parasidic engine drag such as AC, power steering, and get/build an underdrive crank pulley

6. Do an engine tune-up

7. Use fuel injection with a management system like MegaSquirt the GD is always talking about. Go with a maximized fuel economy setup.

 

A final thought about intake/exhaust: open intake and large diameter exhaust are meant to make power by getting more air into the cylinders per stroke, but this more air must be accompanied by more fuel = less economy. Also, when you make these changes they are often at the expense of low end torque, meaning you will have to use more throttle off the line and run at higher RPM's to make the car driveable. While you don't want to have overly-restrictive intake or poor flowing exhaust, a good muffler on the stock sized exhaust and a reasonable air filter are probably your best bet economy-wise

[Milemaker13]

Speaking in theroy only, Would removing the cat on a vehicle reduce back pressure? And would that make more power and/or MPG? Its illegal to remove a cat, ya know, but what are the thoughts on it?

[baccaruda]

lots 'o good advice here... don't forget to keep the car clean and waxed!

[GeneralDisorder]

If you really want to push the limits, you will need to install and tune MegaSquirt. While the SPFI is a great system, there are gains to be had when using it with the EA81 due to the EA81's smaller valves and tighter flowing heads. While it is the same displacement, it is NOT the same on the performance end of things - the EA81 can use less fuel than the EA82 so the SPFI computer's fuel maps are slightly too rich. Not enough to hurt it, but definately enough to notice over an entire tankfull. I would guess you would gain about 5 MPG or more if you tuned the SPFI properly for the engine.

 

It's not a small amount of work, but the gains would be more than any other single modification.

 

GD

[idosubaru]

Speaking in theroy only, Would removing the cat on a vehicle reduce back pressure? And would that make more power and/or MPG? Its illegal to remove a cat, ya know, but what are the thoughts on it?

i already answered this question in general format in my earlier post and am speaking from experience, not theory. it would likely depend on the vehicle, but in general no. reduction in "back pressure" does not mean higher gas mileage.

 

GD brings up a good point about the fuel maps. dylan (a member here but not very active) drives a dodge neon and says the right year and FWD manual trans can get 50 mpg highway of course. he said there's a modification you can do to the O2 sensor that allows the ECU to run at a better mixture than stock....something very similar to what GD said. at that point you'd want to closely monitor to make sure you're not running lean. his is a very simple mod that retains the stock ECU but still leans the mixture out. i always wondered if and how it could be done to a soob. i don't have time for megasquirt but would love to learn it and build one. it's really annoying that i can't find his emails about that. i just sent him an email, hope he replies and i'll follow up with more info.

[Frank B]

i already answered this question in general format in my earlier post and am speaking from experience, not theory. it would likely depend on the vehicle, but in general no. reduction in "back pressure" does not mean higher gas mileage.

 

GD brings up a good point about the fuel maps. dylan (a member here but not very active) drives a dodge neon and says the right year and FWD manual trans can get 50 mpg highway of course. he said there's a modification you can do to the O2 sensor that allows the ECU to run at a better mixture than stock....something very similar to what GD said. at that point you'd want to closely monitor to make sure you're not running lean. his is a very simple mod that retains the stock ECU but still leans the mixture out. i always wondered if and how it could be done to a soob. i don't have time for megasquirt but would love to learn it and build one. it's really annoying that i can't find his emails about that. i just sent him an email, hope he replies and i'll follow up with more info.

 

Probably something like this,

http://better-mileage.com/products.html

 

I want to make one, but I suck at such things :-\ .

 

I hope Dylan does reply, I'd like to know what year Neon can get 50 mpg.

[idosubaru]

good brakes (not dragging)

well greased, synthetic grease in the cv's and hub bearings.

[tailgatewagon]

i have a pp6 that i plan on using

[WoodsWagon]

Dropping the viscosity of the oil in the tranny might have a big effect. I know a number of manufacturers went to using ATF in their manual trannies so that there was less drivetrain drag.