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

[Zerohour]

So at this point, I've come to the conclusion that the "best mods" for FE may be completely backwards of what we'd all expect.

153.5 mi. @ 5.144 US gal = 29.84 MPG

As it stands...this has been accomplished by the following:




1) two lower air deflectors from an 9C1 Caprice Interceptor.
2) My rear mud of flaps are still un-installed from when I was using skirts
3) Light Bar and fog lights
4) Aluminum Pulley @ stock diamter
5) Ebay Racing header.
6) Frankenstein exhaust with 2-1/4" glass back and 2-1/4" Thrush Welded Muffler
7) DIY cold air intake
8) Anti-fouler space Mod for rear O2 (catalytic effciency sensor, read P0420 code on subaru outback/impreza/2.5L/EJ25 motor)
9) Full interior in trunk include spare tire and jack
10) no other aero mods (removed grill blocks, removed front air deflectors, removed rear skirts)
11) use of an Ultragauge (UG)

This basically goes against all eco-modder logic...but there may be a reason...

1) The ~4.3 lbs from the pulley weight reduction is obvious, less rotational mass = less energy wasted, and with the AWD system there is more than enough inertia in the drive train to keep up a good coast.
2) The header has a wider diameter port, shifting more power to top end, the stock ecu is capable of handling the header. Keep less power on the bottom end may have reduced fuel comsumption. The header has increased acceleration while in the 2.5-4K range. Reducing the duration of high fuel consumption during acceleration. The Subaru's fuel peak in 4th gear on the highway occurs around 2750 @ ~62mph, was was pre-header information, but with the intake and the Frankenstein exhaust.
3) As per the skirts and air deflectors, there may be a difference for high speed highway driving, but majority of the subaru economy is all lost in acceleration due to AWD and heavy car. Most of my commute is all 45-55 MPG and drag occurs as ~V^2. The density/viscosity of air has little effect at these speeds.
4) Neglecting my previous statement...the push bar is now giving the hood/frontal area a "breaking edge", one of which is lower than the actual hood by several inches. Similar to how divers can break water surface tension with elbows, knees, chins, etc, this forward edge may be causing a mild, but plausibly effective difference near 55 mph.
5) The UG's throttle position readout is an absolute god sent gift. I can now keep the throttle ~2% without having the auto trans kick down and out of gear. But at the same time maintain speeds while avoiding excessive fuel consumption at a 10% throttle.

Feel free to discuss. But as of right now, I'm fairly happy with this result.

[Arragonis]

Plus of course your "technique" may be getting better ?

[Zerohour]

So been a busy summer, and really haven't been focused on keep updates! I apologize. So this summer, been driving ~80 miles a day to and from work, 5 days a week. The average FE stays well above 27.5mpg. I've been hitting upper 28's if I don't use the AC heavily and I don't get caught up in congestion.

The Subaru rolled over 100K marker on 8/24/2011, which is was less than 24 hours after I signed off on this:


Needless to say, in the coming weeks I'll be cleaning up the Subaru, and placing it in the garage for sale. It was fun, but it is time to move along. My experience with Subaru has been somewhat fun, but not nearly fun enough to warrant the next 3-4 years of general upkeep as the car ages. AWD really proved not to be all that great and it is far worse than the general population makes it out to be. Hopefully the Subi will find a good home.

[Arragonis]

What the story on the flying wedge in the background ?

[redpoint5]

Originally Posted by Zerohour

AWD really proved not to be all that great and it is far worse than the general population makes it out to be.

What do you mean by this?

As I've stated before, Subaru's automatic transmission is horrible. Acceleration and FE suffer dramatically by not rowing your own gears. I've heard good things about the new CVT though.

[Fat Charlie]

I've been quite pleased with the AWD. In blizzards I generally have my own private lane on the highway (the uncleared one). My wintertime hobby is passing Jeeps. Upkeep? Aside from consumables like brakes and filters, at 167k I think I've so far had to buy some headlight bulbs and one brake light bulb.

Nice move going to the Mini, though. That's going to be a blast.

[Zerohour]

@arragonis - The TR7 is in a state of repair. It is making its way around. I've been meaning to get the brakes fixed so I can drive it outside to sand a majority of the body. The pass. rear wheel cylinder let go, so I ordered new wheel cylinders. Got the rear up in the air, ended up ordering a new rear hose, and needed new pads because the brake fluid soaked the bottom pad when it leaked. When to assemble and needed new clips because the pads didn't come with them, finished up one side, went to install the other new wheel cylinder, found out I got one 4spd and one 5 spd wheel cylinder, had to send back/receive new parts...needless to say fixing the rear brakes and buying a mini have been the last 6 weeks worth of automotive fun for the time I could get devoted.

@ Fat Charlie, you have an 2005 Legacy, which is a completely different vehicle, you have a 3rd gen, your traction control is standard. My 2nd gen Subaru with automatic w/o traction control and with ABS was worse than my Ford automatic FWD without ABS and lowering springs in the snow. Neither one could deal with ice.

As for upkeep, you do realize the timing belt on a 2.5 is due at 105K Ditto on the waterpump while you are there. Also, old generation outbacks are plagued by failed head gaskets, which if you made it to 100K without replacing, you might as well do those when you do the timing chain. Not to mention after 100K of driving things like the suspension need a serious look over and watching. the Subarus with welded control arms need to be inspected to make sure the suspensions will continue to remained attached. The newer models have aluminum cast control arms. There is alot to consider for upkeep...include stuff like brake lines, fuel lines, the fuel system in general, the emission systems. If you made it to 167K on the Outback and haven't seen P0420 CEL you one of the few lucky ones.

[brucey]

Cool car man! I'm sure the cooper will get better mileage being driven hard than the Subie will being driven easy! Probably the best way of doing it if you just aren't happy with the car.

Although I've honestly been impressed with the AWD on mine. If you don't need it or aren't happy with it, no use in carrying it around with you all the time!

[Arragonis]

The TR7 looks good. I've been looking at Retro Rides to get my classic mojo back and started the process of emptying my garage of the cr@p in there so hopefully I can get my MGB GT started again - also it means I don't have to veg in front of the TV I only have a small, single garage though and the driveway is a steep slope so moving it around to get at different bits is a PITA - and Mrs A doesn't like ger Gardening shed full of removed parts...

Plan is an imperfect but usable fun car, maybe with a Sebring kit but more likely not, but probably looking more "Cafe Racer" than concours. I'm also going to give it the $50 paint job with Rustoleum but I have to plan when we have enough heat here - what am I tapping, this is Scotland...

Moss do complete rebuild kits here for stuff like brakes and I tend to go for those, plus they match them based on the VIN / reg plate so usually fewer mistakes - not always though - I often get 2 LHS parts instead of one of each . You get more parts than you strictly need but you don't have to waste time getting anything else which may be missing or broken by the DPO.

Subaru - I haven't seen a huge amount of evidence of them being particularly good for FE despite people claiming that they are - of course this could be relative, they are thirsty cars compared with the competition here, maybe not so thirsty compared to models in the US.

On the other hand that list of maintenance issues is no worse than for a TDI VW IMHO - belts and water pumps at 40K intervals, oil pump on the 2.0 at 100K or risk a failure, DPF issues, injector issues, suspension bushes go on the estates, electrical problems on smaller cars.

Good luck with the BINI - is it new ?

[Zerohour]

Yep Mini is 2011 new. Build in late May of this year. The used one with 25-20K are worth considerable close to what I paid for a new one. Given mine is a base model without technology packs other things that raise up the price, I think I got away with a good deal! I'll probably start up a new thread for the Mini. I think a healthy goal it to aim for 40mpg tanks! Right now I'm not sure what it will get, but I've got alot of eco-modding practice with the Subaru. After I sort out the 6 gears ideal, and button up my shifts, I would imagine 40 should be obtainable!