[Thaddeus_the_Bold]

Hi,

I have a 2017 Forester XT.

It gets OK mileage when I'm careful.

But it could be better.

I rarely use Sport Sharp because the CVT shifts are too harsh and the turbo is too peaky. Not pleasant, really. Sport is sporty enough for me.

What I'd really like to do is replace the Sport # mode with a hypermiler option -- some sort of economy tune that would keep my MPG's above 32 in mixed driving-- something I know is possible, because I've achieved it the hard way.

Is there a way to apply a custom economy fuel mapping to just one of the selectable modes? Global climate change is pushing me to do things a little differently.

Thanks.

 

[FozzieBalou]

I've been trying to drive my 2.5i Limited in ways to up my mileage, as well. I drive mostly (all) surface streets with little to know steady-state cruising, so I rarely see an average over 20 mpg - by the built in MPG meter - overall. Some trips are more mpg, some are less.

I didn't by the XT for 2 reasons - the dark interior (I live in the deserts of SoCal, so heat-gain is an issue) and I didn't want another turbo.

I don't know if there is a way to reprogram the XT CVT SI Drive to an eco-mode. Not sure if there is much of a market for that, either, as most XT related posts on here are more about "more power!" as Tim the tool man Taylor used to say.

 

[Thaddeus_the_Bold]

At the end of the day, fuel mappings just define how must pressure the turbo is going to be told to produce and how much gasoline to add to the measured charge of air.

I wonder if there would be a way to tell the turbo not to boost, so there would be less air passing through the MAF, and the fuel added would decrease? Basically, set the machine to run naturally aspirated? An NA 2.0 might do better than the NA 2.5.

Might be worth a weekend's tinkering...

 

[Siouxbie]

lol its hard to find words for this post. Sell your XT and go by the smallest engine you can find. There are many 1.5 liter economy cars out there. Seriously you buy a turbo XT and want to hypermile?

 

[pleiad7]

Ok guys... I've removed some posts that were non-relevant to the question posed by the OP. Please stay on topic - this is not the place to discuss climate change, and the OP doesn't have to justify his reasons for wanting a high mpg tune. Thread has been re-opened.

 

[sleepstate]

Find a pro-tuner that will do what you want, you'll have to ask around.

May not be able to OpenSource tune it, so you might be out the cost of an Accessport to have a Cobb pro-tuner do it. (~$600, which may negate a lot of hypermile savings)

No, you cannot just "disable the turbo" to run it NA. This will cause more problems and issues than it will solve.

 

[jzmtl]

lol its hard to find words for this post. Sell your XT and go by the smallest engine you can find. There are many 1.5 liter economy cars out there. Seriously you buy a turbo XT and want to hypermile?

It's simple, crawling along with rush hour traffic in town, I might as well turn off the turbo and turn it back on when I want the power. If I buy a 1.5l engine I can't swap the engine by flipping a switch.

This is also why I don't like the small turbos used in new cars that reaches full boost as low as 1.5k rpm, but fall flat on its face at higher rpm. Gimme a bigger turbo that doesn't run out of breath in higher RPM and raise the boost threshold to 3k rpm, my pedal is essentially the switch that says turbo or no turbo.

 

[Thaddeus_the_Bold]

I'm wondering if a simple mod of the boost controller would be of benefit; put a cap on how much it can boost (say, cap it at 11, instead of 14 psi), and leave the rest to the computer.

I don't think wanting a car that can be economical during the week's commute and fun when desired is that big of a stretch. Nobody's always Sunday morning, and nobody's always Saturday night.

Back in the dawn of time a lot of cars had 4 barrel Rochester carbs that, when driven normally, used 2 teeny little barrels that allowed a V8 to get 18 mpg, and when you got on it would open up the big barrels and drop you down to 6 mpg (plus tire smoke).

I guess you had to be there....

 

[FozzieBalou]

An NA 2.0 might do better than the NA 2.5..

You would think, but this isn't necessarily so... An easy comparison? The Crosstrek vs the Forester.

Crosstrek shared platform (prior to 2018 redesign) with the Forester. Main difference - 2.0 vs 2.5 motor (and height, some weight, market, etc.).

You'd think that the Impreza and Crosstrek would be mileage champs compared to the Forester but not so - there is just 1 MPG difference between CVT Limited models for both.

In some ways, if you want to get the best mileage possible, it's going to mostly be about driving style and habits and situations.

Remember, also, that the typical turbo process is to get more power from smaller displacements. This is why a shift in the industry is towards smaller turbo motors rather than larger N/A motors. Look at Ford and all of the "eco-boost" engines. They've replaced bigger V8s with smaller I4 and V6 motors with turbo boost for better MPG. So theoretically a smaller turbo motor will give you more MPG then a larger N/A with the same outbut, but at what cost? And the MPG gains may be minimal, at best.

Keep us all informed as to what you find and how it works out.

 

[jzmtl]

Forester was available in Europe and Asia with 2.0 NA motor, would be interesting to see the consumption rating comparison.

 

[FozzieBalou]

Just found this chart on a Subaru dealer site -

2018 Subaru
Outback Forester Crosstrek

Horsepower
175 170 152

Fuel Economy (city/highway mpg)
25/32 26/32 27/33

Maximum Towing Capability (lbs.)
2,700 1,500 1,500

Remember that the Forester and Outback use the 2.5 motor and the Crosstrek is the 2.0. This would be for base engine and not the XT turbo or 3.6R models

 

[x05]

A few simple concepts for increasing fuel economy that can be applied to any vehicle:

*Weight reduction (especially wheels/tires and other unsprung weight)
*Aero improvement (keep windows /sunroof closed, antenna removal, mudflap removal, get aero wiper blades, keeping exterior surfaces clean and paint sealed with ceramic or wax, etc.)
*Friction reduction of any rotating component contacting another (use full synthetic lubricants & fluids wherever possible)
*Top tier E0 (non-ethanol) fuel containing detergents (highest octane generally available)
*Use an air/oil separator (AOS)
*Periodic fuel treatments like Techron or other that protects against ethanol (if E0 fuel NA)
*Optimize electrical system to keep accessories (AC, cooling fans, defroster, wipers, headlights, etc.) from increasing engine load unnecessarily

More controversial concepts (some things obviously only apply to turbocharged vehicles):
*Warm air intake
*Intercooler removal (replace with single hot pipe)
*Warmer heat range spark plugs
*Throttle body spacer
*Extremely low viscosity oil (0W-20, 0W-16)
*Oil & fluid friction reduction treatments like CERMA
*Water/alcohol injection
*Electrically disconnect wastegate solenoid to run only WG spring pressure (will throw DTC) and/or change to a weaker spring
*Adjust WG actuator arm to keep WG open (may throw DTC)
*Learn other extreme hypermiling techniques from hybrid vehicle forums
*Tune closed loop entirely with fuel ratios above stoichiometric in low load areas

Note that I’m not explicitly recommending any of the above, only showing what is possible. I’m sure there are other strategies.