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Old 10-12-2004, 04:27 PM   #1
kiltjim
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Member#: 60002
Join Date: Apr 2004
Location: PA, USA
Vehicle:
2000 Impreza OBS
Running at OC'ed 900MHz

Default Better gas mileage, then tuning

I want to work on my gas mileage right now, than when I get some improvements, I would like to work on my overall performance (speed, torque, ect.) My question to all the ezperts out there is how to start.

What are the best/cheapest/easiest ways to increase gas mileage without risking performance. I know this may be asking how to do the impossible, but there has to be some ways out there.

What I would really like to be able to do is increase my gas mileage so that when I am ready to tune the car, and lowering my gas mileage by increasing performance I won't dip below the stock MPG.

If I am asking the impossible, just tell me, and I'll stop botherin' ya.
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Old 10-12-2004, 05:08 PM   #2
Black_Rain
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I'm not 100% sure...but i'm pretty sure that once u start modding...the gas mileage will go down below the stock mpg anyway... this idea sounds good on paper...but i think that once its applied it will just be a waste of money on the "gas saving" mods...

My suggestion is to change the oil regularly, keep the tires to the correct psi, dont go WOT to the supermarket (keep the revs in check until racing or when u wanna have fun) Maybe check ur head gaskets, try that tornado thing that u put in ur intake... just basic stuff to help maintain the mpg, but also the car Good luck though
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Old 10-12-2004, 05:46 PM   #3
RS_to_WRX_swap
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I laughed at first when i read the first paragraph. but really performance is a oneway road, full of trade offs. The only thing i can think of that helps performance and mpg is maintence. However if you are paying someone to clean, and maintence your motor then bad mpg will cost less.

I would say go for performance, and for daily driving dont get on the gas and you will still be very close to stock. however with me the more i mod my car the more i want to floor it...."just to see how shes runnin today"......
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Old 10-12-2004, 07:08 PM   #4
jasona
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If you do a nice efficient full exhaust and have it dyno tuned you can probably pick up a little power and gas mileage...
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Old 10-12-2004, 08:24 PM   #5
kiltjim
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See, that's what I was thinking. I knew that once I started modding the car, I would lose effeciency. I also knew that the cars are pretty well tuned to start with, and knew I would get a few laughs. Although, you never know if soeone knows something unless you ask. I was hoping someone would chime in and say, "you know if you switch to this higher performance exhaust, or such-and-such you'll get about 10% better." That would get me both of what I'm looking for in one shot.

Along the lines of an exhaust, will maybe a borla or stromburg help with this? I'm not looking for any particular sound....yet. I would probably be better off searching first, but any suggestions as to which one is the most effecient?
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Old 10-12-2004, 10:33 PM   #6
suby_driver57401
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SRP

Default Increase mpg, and HP!!

I may not be an expert but I had some physics in college. The conlcusion that I came to is that you can increase power and gas mileage. The best way to do this would be to put on a lighter flywheel, and lighter pullies. These mods are somewhat simple except the flywheel can be difficult. The reason this works is simple: you decrease rotational mass which in turn means your engine does a lot less work. Putting on a differant exhaust and intake doesn't work because your car needs more fuel to run at stachiometry which is 14.7 to 1 air to fuel ratio. More air=more gas=more power. Running all synthetic fluids makes sense in theory, but I never felt the increase in power, and never saw an increase in gas mileage.
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Old 10-12-2004, 11:58 PM   #7
Crash477
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slow down
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Old 10-13-2004, 03:52 AM   #8
evorev
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tuning your car and buying parts that suit your needs [like the right exhaust for the type of driving, etc] will definitely increase your HP and your MPG. it's not always a 1-way road. ...but usually it is

good luck!

-brett
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Old 10-13-2004, 08:35 AM   #9
droogz
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Blue

OMGHi2U

Not sure about anyone else but It seems as though I got a small bump of MPG after I put the unorthodox lightened under driven pulley on my 04 OBS. I also have a cobb intake but that was on the car for 2 weeks before the pulley with not much if any increase in MPG. At this point I have put 300 miles on the car from the last fill up and I have just under a quarter of a tank left. This included some spirited driving. Normally I would only have a 8th of a tank left at this point. I had prev gotten about 340 or so miles when the fuel light came on. I drive about 90-120 miles a day. My normally cruse speed to work is 80-85at 3.5k rpm. I have had the car about 5 or 6 months and have 18,000 miles on it.

I also have a yakama bike rack on top of the car so that did not help with my MPG.

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Old 10-13-2004, 09:26 AM   #10
chip4761
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AS

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After pullies, flywheel, and exhaust, I would think about a PnP if you have the money, or the know-how to do it yourself. That just makes the car run more effeciently all together. IIRC, with an intake, you should get worse mileage, as the ECU would be putting more fuel into the engine to compensate for the larger quantity of air. At least that's how it works on a MAF car. Not so sure about a MAP.
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Old 10-13-2004, 01:26 PM   #11
DoinkMobb
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- lighter rims/tires
- overall weight reduction
- lighter pullies might be worth a shot
- freer flowing exhaust might help too
- try to cruise in 5th as much as possible
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Old 10-13-2004, 02:37 PM   #12
Crash477
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well I have COBB CAI and Cat-back, and I noticed my gas mileage changed a little. but not to noticable. But when I put my Rota T2's on, i noticed quite a change in mpg. The wheels weigh 18 lbs each, not sure about the tires. But mpg on 87 octane was about 22-23. My last 2 tanks have been 93 octane, and my mpg was 25.9. In the next week I should have my COBB headers and high flow cat on, so I will see what that does to MPG.
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Old 10-13-2004, 06:54 PM   #13
jasona
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I average 28mpg with NO o2 sensors, short ram intake and a headerback exhaust with no cats. I would probably get 30+ city/highway mix with the sensors...
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Old 10-13-2004, 06:55 PM   #14
DreddRS25
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BRP

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I've installed borla headers, custom catback, Ganzflow intake, and even a grounding mod. My mileage has never dropped and I actually believe my car gets slightly better mileage than when I purchased it. (BTW my car came with a Unorthodox Underdriven/Lightened pulley)

Started with 63k and I am almost at 83k.

Edit: I average 24.65 MPG. Lowest 18.69 MPG and Highest 29.75 MPG.
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