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Old 01-25-2006, 10:25 AM   #1
ShawnRS
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Default noob question: Tuning for better gas Milage

Hello,

I just bought a MY06 Wagon this last boxing day. I love the power but I am wondering if anyone has done a reflash with No Mods just to achieve better gas consumption while maintaining current power levels?

I know I can just lift the right foot etc....

Shawn
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Old 01-25-2006, 01:26 PM   #2
mcowger
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You can't really do it while maintaining stock power levels. If you are willing to give up some power, you can set your boost targets to wastegate pressures, adjust fueling accordingly (e.g., add a little less) and add some timing. I'd done this, and went from 155whp on a stock car (195whp tuned @ stage 2) to more like 125whp (nice flat torque curve though!). Car was still driveable, just not very fun. Used it a few times for driving to Thunderhill or Monterey (both 3 hour drives).
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Old 01-25-2006, 01:37 PM   #3
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free up the exhaust restrictions w/aftermarket pipes and then do a retune.
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Old 01-25-2006, 01:59 PM   #4
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Quote:
Originally Posted by mcowger
You can't really do it while maintaining stock power levels. If you are willing to give up some power, you can set your boost targets to wastegate pressures, adjust fueling accordingly (e.g., add a little less) and add some timing. I'd done this, and went from 155whp on a stock car (195whp tuned @ stage 2) to more like 125whp (nice flat torque curve though!). Car was still driveable, just not very fun. Used it a few times for driving to Thunderhill or Monterey (both 3 hour drives).
That won't really effect "cruise" milage. It will only effect hard throttle milage.

TMS
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Old 01-25-2006, 02:06 PM   #5
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Another question you might want to think about is if reflashing with an economy map will void your warranty on engine and/or tranny. Anyone know the answer to this one?
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Old 01-25-2006, 02:11 PM   #6
ShawnRS
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Does Subaru still tune their car pig rich? If the car is leaned out, safely, will that save fuel.

It's not a huge concern I'm just thinking.

Shawn
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Old 01-25-2006, 02:11 PM   #7
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Get a AP and run the economy map or just keep you boost off = accelerate really slowly.

I gave up on this after a while
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Old 01-25-2006, 02:16 PM   #8
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Quote:
Originally Posted by TheMadScientist
That won't really effect "cruise" milage. It will only effect hard throttle milage.

TMS
The boost changes won't affect cruise at all, correct....I never suggested it would. But it would help during the non cruise times. The timing advance changes *would* help throughout the range.
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Old 01-25-2006, 02:18 PM   #9
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i believe ECUtek flashes now have the ability to tune for leaner conditions than 14.7:1 in closed loop/cruise situations, may want to look into that.
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Old 01-25-2006, 02:57 PM   #10
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Poor cruising mileage is due to the low compression ratio of the turbocharged engine.

On boost the car can certainly be tuned leaner and with water injection even leaner. You are current wasting >20% of your fuel as a coolant for the cylinders.

Let's say you install water injection and lean out your fuel by an average of 25%. That's only 25 mpg on what was 20 mpg. It's alot of work for a little improvement. The compression ratio (that allows you to run all that boost) is the real fuel efficiency killer.
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Old 01-25-2006, 02:59 PM   #11
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You do not want to use water injection for crusing situations. Its rediculous how quickly you could go through a gallon of water.
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Old 01-25-2006, 03:07 PM   #12
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The key word there is 'average'.

I didn't say use WI for cruising, although there are people interested in do this with low water injection rates--the so called 'lean cruise' folks that are trying to run AFRs of 20:1.

Suffice it to say if you want economy out of a 2 or 2.5 L engine you'll need a CR or 10:1 or more. You can have that and a turbo, but you'll need to either run less boost or have some pretty fancy valve-cam system to drop the dynamic CR when on boost.
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Old 01-26-2006, 10:10 AM   #13
ShawnRS
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Yes sorry I wasn't clear. I am taking cruising down the highway at 100km/h (speed limitish) with maybe a couple bursts of speed (over th whole tank of gas).

Thanks all

Shawn
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