Hi everyone,
I picked up a Cobb Accessport (AP) to dip my toes into ECU tuning to eek out some more mpg's on my 2013 Wrx Sti. The "word" in the Subaru forums is that the AP will increase 15 HP and 53 lbs torque while not losing any mpg's. Some users are even claiming 2-3mpg increase. All of these mpg claims were anecdotal, so I decided to put the claims to the test.
You can find these used for about $300-350, depending on which "version" you get. Mine is an older "version 2" that I bought used for $330.
Testing Info:
0.75 mile loop in an industrial park, Set cruise control at 30mph in 5th gear, drive around in circles making notes of "trip mpg" on SG II at pre-determined "start" and "end" points, Reset SGII after every lap.
I did 3 laps of every "tune," and here are the averages
Stock Tune: 35.53 mpg
Stage 1 (91 octane, 47 state tune): 36.5 mpg
Stage 1 (91 octane, Arizona, California, Nevada tune): 36.67 mpg
Economy Tune: 37.43 mpg
Just for fun, I ran 3 more variables (while on Economy tune)
A/C On: 32.6 mpg
Windows full down: 36.5 mpg
Windows half down: 36.9 mpg
Impressions:
Stock vs. Stage 1 (Ariz, CA, NV tune): 1.14 mpg (3.1%) increase compared to stock. it's not quite the 2-3 mpg increase as claimed, however, an extra 15hp and 53lbs of torque with no loss in MPG's is amazing.
Stock vs. Economy: 1.9 mpg increase (5%) compared to stock. It's closer to the 2-3 mpg increase as claimed, however, there is definitely lack of power (peak boost is only 8lbs).
A/C vs. Windows: it appears to be more fuel efficient to run your windows half down than it is to run your A/C. However, at highway speeds, I suspect aerodynamic drag will come more into play with the windows rolled down.
Conclusions:
Perhaps, the 2-3mpg increase on a Stage 1 tune can be found somewhere else on the rpm/load/bsfc range such as at highway speeds and in 6th gear? However, there are too many variables to do accurate testing on the highway. I also don't know the best BSFC for this car yet, so perhaps 30mph in 5th gear is not quite the most "efficient" in terms of BSFC.
Is $330 worth it for a 1.9 mpg increase?
How about, is $330 worth it for 1.14 mpg increase, with EXTRA POWA?!
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On a side note, I got pulled over by the police because a security guard thought that I was scoping out the place because I was driving around in circles, lol! The cop told me there have been reports of robbery in the area, i explained to him what I was doing, he let me go on my merry way.
Today
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