A Quest for 35mpg (Subaru Outback Limited Sedan 2.5L auto)

[evilskillit]

I must say this thread is inspirational as well as informative. You've actually got me kicking around the idea of fiberglassing something. I've put it off up to this point due to materials cost, but I found a place online where you can get something like a 36"x25 yard roll of chop mat for like $38. That seems cheap, and should be enough to do anything I'd want to tackle any time soon. Then I just need everything else... where does one get cheap resin?

[VegasDude]

Your car has the same city and highway rating as my 3.5L 5 speed Altima rated at 250 bhp/ 249 lb ft. I think that says a lot about the energy loss inherent in an AWD auto, the tires don't help either. I think your best bet is to slow way down; a scanguage would really help you determine your most efficient speed. I think 35 MPG is doable, but probably not on the freeway.

[cfg83]

Zerohour -

Beautiful work.

I wonder, do you have the "FWD mode" fuse holder in your engine bay? :

Disable all wheel drive? - i-Club

fwd fuse

Originally posted by Paisan

4EAT w/o VTD:
Have the FWD Fuse. It can be used for short distances when the temp tire is in place. I you run it like this on a semi-regular basis you will break your tranny. Power split is 80/20 under normal conditions and can go up to 60/40 during slippage, pre-00 4EAT used speed sensors to detect slippage only, post-00 speed, weight and computer pre-emptively splitting power was established. Uses clutch packs to vary torque. When in "1" the ATF line pressure is increased to max pump as well as the clutch fluid pressure, this will give it a faster reaction time according to the factory manuals. Pre-96 4EAT had an initial split of 90/10.

5MT:
No FWD fuse, cannot disable AWD via fuse or easy means. Center diffy is viscous and will vary power. 50/50 initial split with up to 80/20 and 20/80 under slipping conditions.

XT6 5MT:
Same as 5MT but has manually controlled locking center differential that will lock power in at 50/50 no matter what slippage occurs.

4EAT w/VTD:
No FWD Fuse. This has initial split of 45/55 torque and can vary it up to 80/20 and 20/80 during slippage. Uses planetary gears along with clutch packs to vary torque. Also uses speed sensors, weight sensors and computer pre-emptive torque distribution like the 4EAT.

4EAT w/VDC:
Same as VTD but adds: Yaw sensors and use of brakes to stop slippage of individual wheels.

4EAT w/VTD & Sportshifter:
Same as VTD but adds tiptronic like controls for changing gears.

What vehicles have what ATs?
Imprezas/Forester up to 01 had 4EAT w/o weight and Ecu sensors.
Legacy up to 99 had 4EAT w/o weght and ECU sensors.
02 WRX has 4EAT w/VTD
VDC has 4EAT w/VDC
03 Legacy GT has 4EAT w/VTD and Sportshifter
00->03 Legacy and Outbacks have 4EAT w/ weight and ECU sensors
88,89,91 XT6: 4EAT w/o weght and ECU sensors or 5MT w/Locking center diffy.

4EAT non VTD/VDC units have electronically controlled clutch packs (3)
4EAT VTD/VDC units have electronically controlled clutch packs (6) plus a planetary gearset.

Manual Button, and Power Light:

Vehicles with "power" mode light can engage "power" mode when you hit the accelerator quickly, even if you are in the "2" "3" or "D" positions, this will raise your shift points to redline.

Vehicles without the "power" light do the same thing, except there is no light to indicate this.

If you have the "manual" button on your car, then you hit the manual button and place the car in "2" or "3" and the car will be held in that gear regardless of where the 4EAT thinks it should be.

Vehicles w/o the "manual" button, you can start out in 2nd gear by placing the shifter in the "2" slot, this will start you in 2nd gear and bounce you off the rev limiter.

I recently took my '92 SVX to Limreock Park for a track day. I tried several different combinations of gear slections. Finally settled on "2" which kept me in 2nd gear most of the track, when I hit the straightaway, it hit redline and upshifted to 3rd.


Hope this helps.

There you go. Everything and then some you could want to know.

//Mark

It may not help MPG, and the fellow above states that it is not good for your drivetrain, but it might be worth testing if you have the option.

CarloSW2

[brucey]

CFG:My testing showed that fuse did nothing but make the front tires spin:
http://ecomodder.com/forum/showthrea...awd-10755.html

Vegasdude: I know it's odd, but my scangauge consistently shows best MPG at 45~50 mph. Below that, the torque converter comes unlocked too easily on the slightest of slight inclines and is a major loss in efficiency. On a manual it might be different though.

[VegasDude]

45-50 is pretty quick to see your mileage at its best. The auto tranny and AWD system must be sucking power. Any way to manually lock the torque converter? Anecdotally, I can report my car does best at 33-36 mph in very hot weather. The 5 speed is the best thing I have going for me.

[Zerohour]

Actually I was getting ~34 on the highway on a trip to newyork.I hit ~285miles on ~8.5 gallons of gas. And the first 25-30 miles were around town miles. I was also going 70-75mph.

35mpg is well within reach. Maybe not all the time, but on highway portions. City mileage will probably always remain around 20 because of the AWD. And disabling the AWD is NOT healthy for the components of the car. The AWD Fuse is actually for towing purposes or flat tires. The car is designed to operate at a 50/50 split in first, and normally 40/60 or 20/80. Putting all the strain on the front differential will cause premature failure. The gear rings are only about 4" on a subaru, and they are not intended to use put up with all that abuse. At least those built for the outback.

[VegasDude]

Oh snap! 34 MPG@70-75 MPH! That's more like it. Any way to convince you to try 60? Maybe even 55? Once you experience MPG nirvana you will be changed forever.

[Zerohour]

If you do 60 in a 65 in NY you will cause an accident. So no.

[cfg83]

brucey -

Originally Posted by brucey

CFG:My testing showed that fuse did nothing but make the front tires spin:
http://ecomodder.com/forum/showthrea...awd-10755.html

Vegasdude: I know it's odd, but my scangauge consistently shows best MPG at 45~50 mph. Below that, the torque converter comes unlocked too easily on the slightest of slight inclines and is a major loss in efficiency. On a manual it might be different though.

Thanks for the correction!

CarloSW2

[euromodder]

Originally Posted by brucey

Vegasdude: I know it's odd, but my scangauge consistently shows best MPG at 45~50 mph. On a manual it might be different though.

Not quite.
It's also a very efficient speed in many manual european cars I've driven.

It's at the sweet spot where the engine can rev fairly low but efficiently without a long (top) gearing strangling it and where aerodynamic drag isn't such an MPG-killer yet.

In my own car I get the best mileage between 42-47 mph in 4th gear.
In 3th gear at the same rpm it'll get similar mpg, but it's not getting anywhere fast then.
In 5th (top) gear at the same rpm I'll still get good mileage, but not the number I see in 4th due to increased aero drag at the higher speed - and any incline will make the mpg drop like a stone .


Driving my sister's Skoda Fabia 1.4L TDi again, I was getting a solid 2.2 L/100km @ 70 kph .... or over 105 mpg at 43.5 mph
Sweet