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Old 01-05-2017, 01:35 AM   #1
striktlysubie
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Default Cobb OTS maps versus gas mileage

Looking for input: seems like ever since loading up the Cobb Stage 1, 93 octane map on the '15 WRX, gas mileage has gone down quite noticeably. I have NOT changed driving habits, pedal mashed, or even changed routes that much, but I've noticed at least a 2-3mpg reduction, getting about 250-275 miles on a full tank. Most folks say that changing the maps to an OTS one smooth out power caused no mileage dips at all, but I beg to differ. Anyone else have this issue? Getting avg 17mpg city isn't good.
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Old 01-05-2017, 12:06 PM   #2
HinshawWRX
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Driving style + winter fuel blend + moar boost = less mpg.
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Old 01-05-2017, 01:21 PM   #3
mrsaturn7085
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Being in a perpetual state of warm-up enrichment is never good. This 17 is bad? Try 12.
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Old 01-05-2017, 04:13 PM   #4
Miggy-Verlander
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That is pretty terrible 17 in the city for these new WRXs, i was getting slightly better mpg on Cobbs tune (27 city, 35 hwy) over stock.
Just running the stock map I assume, no mods?
It might just be driving style on this new tune combined with the terribleness of winter gas.
Your AP is fully updated and the map is the most recent version, correct?
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Old 01-05-2017, 10:12 PM   #5
hondaeater69
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consider it insurance. i don't know for sure about 2015, but i know in years past one of the major improvements in the cobb ots map over stock was the removal of the cl/ol fueling delay. this allows you to run into richer points of the map without hanging at 14.7 under boost. your engine and wallet will thank you in the long run.
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Old 01-08-2017, 09:43 AM   #6
RckSti
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Quote:
Originally Posted by mrsaturn7085 View Post
Being in a perpetual state of warm-up enrichment is never good. This 17 is bad? Try 12.


I guess you have an STI?
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Old 01-09-2017, 01:17 AM   #7
mrsaturn7085
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Yep - I've yet to do a full freeway tank test to see what I can get out of it since having it tuned.
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Old 01-09-2017, 10:26 AM   #8
BartNJ
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I can only tell for STI:

COBB Stage 2 vs Stage 2 ProTune = ~2mpg difference
COBB Sage 3 vs Stage 3 ProTune = ~3mpg difference

both in ProTune favor
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Old 01-09-2017, 02:58 PM   #9
mrsaturn7085
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^ This assumes you keep an OEM-based ECU which is VERY good as closed loop fuel fueling reduction.
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Old 01-10-2017, 01:53 AM   #10
striktlysubie
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Quote:
Originally Posted by Miggy-Verlander View Post
That is pretty terrible 17 in the city for these new WRXs, i was getting slightly better mpg on Cobbs tune (27 city, 35 hwy) over stock.
Just running the stock map I assume, no mods?
It might just be driving style on this new tune combined with the terribleness of winter gas.
Your AP is fully updated and the map is the most recent version, correct?
I saw the drop in mpg even before winter was here, so I don't think its the blend. And yes, stock map with no bolt-ons yet, and no change in driving style. Map is fully up-to-date. I've even noticed on conservative long highway drives that my 33-34mpg on a full tank now barely reaches 30-31mpg.
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Old 01-10-2017, 03:11 PM   #11
Miggy-Verlander
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Take a few logs, maybe there's a leak or something. Monitor your AF Learning 1, and your AF Sensor 1 Ratio. (AF - Air/Fuel)

AF Sensor Ratio 1 is going to be the readings from the front 02 sensor, which can be used as a wideband for these cars. You're wanting 14.7ish cruising, dropping to 11 or so under full boost WOT, and usually low 12s to 11s for mid boost situations.

AF Learning is going to be your long term fuel trims, IE what it takes for your engine to keep the correct 14.7/1 AFR - negative values indicate fuel being removed and positive values indicate fuel being added. Normal variance on these DITs is between +/- 13% - according to my emails with Cobb, so if you frequently see high numbers past that while cruising it could indicate a leak. With that being said, I was frequently seeing my AF learning jump to -15 while sitting at idle on Cobb's map, but when I got E tuned my tuner said there is no evidence of any leaks - so keep that in mind. WOT your AF learning should be 0.00 - your car switches to open loop fueling so it's not longer using information from the 02 sensor - it's basically speed density at that point (ie each rpm gets assigned specific AFR values, rather than relying on sensor).

My suggestion, take a 2-3 minute log - keep it under 2-4 lbs of boost - just light driving and take a look at your numbers (or post them here). Also, take a 3rd Gear, 2500-6500RPM pull at 100% accel and see what that looks like. If you're AF Sensor is not close to 11 - if it's really rich or lean that could indicate a leak or a restriction.
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Old 01-11-2017, 09:40 AM   #12
Chris808
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Default Small drop

I noticed a small drop in gas mileage on the stage 1 tune but only cruising high speeds when boost was starting to build around 3500rpm
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Old 01-16-2017, 04:25 PM   #13
striktlysubie
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Thanks for the suggestions Miggy. I'll see what I can log...
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