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Old 01-30-2013, 09:42 AM   #1
cmiovino
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2004 WRX Premium
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Default 91 vs 93 OST Map for Gas Mileage

I originally bought the car with the stage 2 93 oct map, but noticed some pinging when testing some WOT runs. I switched to the 91 oct map and have continued to use 93 oct fuel... the pinging has completely gone away, however, my gas milage has dropped to 16-18 MPG over the past 2-3 months I've been tracking it. I used to get 19-22 with the same exact driving habits and route.

Could the tune be effecting my results, or can I solely blame this on winter gas and cold weather?

2004 WRX, Cobb turboback and SF intake

Last edited by cmiovino; 03-14-2013 at 12:29 PM.
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Old 01-30-2013, 09:58 AM   #2
Cobb Tuning
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Quote:
Originally Posted by cmiovino View Post
I originally bout the car with the stage 2 93 oct map, but noticed some pinging when testing some WOT runs. I switched to the 91 oct map and have continued to use 93 oct fuel... the pinging has completely gone away, however, my gas milage has dropped to 16-18 MPG over the past 2-3 months I've been tracking it. I used to get 19-22 with the same exact driving habits and route.

Could the tune be effecting my results, or can I solely blame this on winter gas and cold weather?

2004 WRX, Cobb turboback and SF intake
First thing to do would be to get a data log (if you can do so safely) as described in the video below (if you have a version 2 AccessPORT). The version 2 AccessPORT also has newer maps (v310) that you want to make sure you are running (vs. the old v300 maps). You can find these maps in the maps section at cobbtuning.com. Regardless, the 91 octane map is not going to get worse gas mileage than the 93 map, so it is likely just colder temps and/or winter gas that is effecting your mileage. But, a data log can potentially tell us if there's any mechanical issue with your car that might be effecting mileage. You can use google docs to put up your log and then post a link. Be sure to state the approximate number of miles you've driven since you last reflash a map or reset the ECU.


Bill
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Old 03-14-2013, 12:25 PM   #3
cmiovino
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Gotcha. I actually did some testing and everything appears to be working well. DAM is good, so are my AF Learning values (under +/-%5), and knock.

I did find on your website this:
Quote:
Generally speaking, the 91 and ACN91 calibrations run slightly lower boost, have a richer fuel curve, and a less aggressive ignition advance map to help compensate for 91 octane fuel; Arizona, California, and Nevada 91 octane fuel; and/or less than ideal atmospheric conditions. The maps designed for 93 octane are the most
aggressive.
Wouldn't this richer fuel curve lead to slightly lower MPGs? I do agree it helps combat any bit of knock that might come up... I haven't had anything noticeable on my logs except a very very little bump here and there.
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Old 03-14-2013, 12:38 PM   #4
Cobb Tuning
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Originally Posted by cmiovino View Post
Gotcha. I actually did some testing and everything appears to be working well. DAM is good, so are my AF Learning values (under +/-%5), and knock.

I did find on your website this:


Wouldn't this richer fuel curve lead to slightly lower MPGs? I do agree it helps combat any bit of knock that might come up... I haven't had anything noticeable on my logs except a very very little bump here and there.
Fueling target is not any different (and ignition/cam timing is generally about the same) in closed loop (i.e. cruise/general driving/idle), so there won't be any notable difference in fuel economy. The changes are at higher load, such as when you got wide open throttle (WOT). Since that is such a small percentage of actual driving, you won't see any appreciable different in mileage with real-world driving.

Bill
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Old 03-14-2013, 01:33 PM   #5
cmiovino
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Quote:
Originally Posted by Cobb Tuning View Post
Fueling target is not any different (and ignition/cam timing is generally about the same) in closed loop (i.e. cruise/general driving/idle), so there won't be any notable difference in fuel economy. The changes are at higher load, such as when you got wide open throttle (WOT). Since that is such a small percentage of actual driving, you won't see any appreciable different in mileage with real-world driving.

Bill
Makes sense

Appreciate the explanation.
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Old 10-21-2013, 02:37 PM   #6
cmc2154
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Quote:
Originally Posted by Cobb Tuning View Post
Fueling target is not any different (and ignition/cam timing is generally about the same) in closed loop (i.e. cruise/general driving/idle), so there won't be any notable difference in fuel economy. The changes are at higher load, such as when you got wide open throttle (WOT). Since that is such a small percentage of actual driving, you won't see any appreciable different in mileage with real-world driving.

Bill
A little late in the thread but question to cobb... if I run the stage1 91octane map (for the cobb intake that I have) but put 93 octane gas in every time, am I helping/doing harm? I saw it had a slightly lower boost than the stage1 93 octane and I figured running the 91 map might give me a little more knock resistance... what do you think?
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Old 10-21-2013, 04:17 PM   #7
Cobb Tuning
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No harm would be done at all. You would give the car a little more of a safety buffer and leave a little bit of power on the table.

It's a good combination for the guy who is more concerned with reliability/longevity and doesn't necessarily care about getting every bit of power out of the car.

- Chris
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Old 10-21-2013, 04:52 PM   #8
cmc2154
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Join Date: Apr 2013
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Location: Rockland County, NY
Vehicle:
2002 wrx sedan
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Quote:
Originally Posted by Cobb Tuning View Post
No harm would be done at all. You would give the car a little more of a safety buffer and leave a little bit of power on the table.

It's a good combination for the guy who is more concerned with reliability/longevity and doesn't necessarily care about getting every bit of power out of the car.

- Chris
Awesome! That's what I'm going for since this is my daily driver and I commute 70 miles round trip a day.
Now if (more like when) I buy the cobb downpipe and go stage 2 I'm guessing the same applies?

Also thanks for the speedy reply... I've been trying to contact someone from cobb all day but keep getting the voicemail after 10 minutes of waiting on the phone and no email response. All I need is the usb cord that connects the accessport to my laptop since the person I bought the AP from failed to give me it.
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Old 10-21-2013, 05:12 PM   #9
Cobb Tuning
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Yeah, that same thing applies if/when you go to Stage2.

I'm sorry you couldn't get through to us. Mondays are usually pretty crazy for the guys up front answering the phones and our support emails. The USB cable we supply is nothing special and can be picked up at any electronics store. If you have the APv2 then you need a USB to USB mini B cable. If you have the new APv3 then you need a USB to USB micro B cable.

- Chris
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Old 10-21-2013, 05:48 PM   #10
cmc2154
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Join Date: Apr 2013
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Location: Rockland County, NY
Vehicle:
2002 wrx sedan
blue

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Quote:
Originally Posted by Cobb Tuning View Post
Yeah, that same thing applies if/when you go to Stage2.

I'm sorry you couldn't get through to us. Mondays are usually pretty crazy for the guys up front answering the phones and our support emails. The USB cable we supply is nothing special and can be picked up at any electronics store. If you have the APv2 then you need a USB to USB mini B cable. If you have the new APv3 then you need a USB to USB micro B cable.

- Chris
Sweet!

Chris, your the man dude thanks again for getting back so fast.
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Old 11-18-2013, 10:12 PM   #11
cmiovino
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For the record too, I've been running the 91 octane map with 93 octane fuel since this thread was created. I've put nothing but Shell V-Power in... same gas station, same pump.

So far, so good. Gas mileage is usually around 19 city driving. It drops with my winter tires and I let it idle 3-5 minutes when it's below 32 degrees. I attribute my initial drop in MPG to this, not the change in map.
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Old 11-19-2013, 11:31 AM   #12
cmc2154
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2002 wrx sedan
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Default

Quote:
Originally Posted by cmiovino View Post
For the record too, I've been running the 91 octane map with 93 octane fuel since this thread was created. I've put nothing but Shell V-Power in... same gas station, same pump.

So far, so good. Gas mileage is usually around 19 city driving. It drops with my winter tires and I let it idle 3-5 minutes when it's below 32 degrees. I attribute my initial drop in MPG to this, not the change in map.
Nice! I have a cobb downpipe on the way and am interested in how much of a decrease in mpgs I'll get once going to the stage 2 91oct map running 93 oct fuel. Currently Im running the stage 1 91 oct map only putting 93 oct and am averaging 25-27 highway.
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