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Discussion Starter · #1 ·
I was wondering what kind of engine mods would actually improve gas mileage as well as add a little power. I've heard people talk about better mileage with samco hoses and an uppipe. If I get only an uppipe I know it won't help as much as it would if I had an MBC as well, however, would I still get 5-10 hp out of it? I'm just looking for a very modest increase in power and a very modest increase in fuel economy. That way the cost of the mod is offset by buying a little less fuel. Has anyone actually compared fuel usage before and after mods?

Thanks
 

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I think the Vishnu Performance stage 0 kit increased gas mileage on Roberto's car. I think you shouldn't really worry about gas mileage because heck you spent so much money on your car already so you might as well drive it w/o worrying about gas mileage. If money is an issue then I would suggest that instead of spending money on mods just drive your stock WRX hard becuase it's got more than enough power for most people out there.
 

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Discussion Starter · #3 ·
It's just kind of a rationalizing thing. Also while I think a unichip upgrade works well to get power, I somehow doubt it is more efficient than stock (doesn't it only use two sensors while the stock ecu uses like 6). On my 911 turbo I get like 17 mpg highway. The rex is more of a commuter car. So I don't want to put on mods that will reduce mileage, however I would love to have a little boost in power over stock, and BETTER mileage would give even more reason to do it.
 

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it stands to reason that SOA has programmed the ECUto give you the best possible economy at the given level of performance...there are all sorts of government incentives for them to do so.....especially if they decided to conform to LEV standards....therefore it ALSO stands to reason that the only way you're going get more power is by burning more gas. I think this is pretty much true with all performance mods. In a reasonably efficient motor, getting more power out of it means burning more gas.
 

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Well, in one way when you ADD power, you burn more gas, however, when you FREE horsepower, you can get better milage.

Usually mods like exhaust and underdrive pullys and ignition upgrades and intakes will often give more power/torque AND raise fuel economy.

Because we have direct coil on plug ignition, there is little we can do but maybe put in a better plug, however, I think their already pretty good.

Underdrive pully might not raise you MPG's but it wont take away either.

Exhaust and intakes just make the engine more effecient with what fuel it already has, so those in general are good ones to start with. I'd say turbo back and uppipe, you'll be more of a polluter, but it'll probably raise your MPG's pretty good.

Intercooler Hoses might be another good one for effeciency.

Maybe get an Apexi S-AFC so you can dyno tune it for optimum burn, a little more power and economy, just don't go too lean with it.

That's all I can think of.
 

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WRX's run rich from factory, actually a little too rich to make good power. However this is the safety margin that they factor in - along with complying to the LEV rules. Lots of the Unichips out there increase your power by leaning out your fuel mixture, and this is affective as your stoich air/fuel ratio maynot be ideal for fuel economy or for power.

Basically gas mileage is a direct function of how heavy that right foot is ;)
 

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I think any mods that reduce weight or free up HP will give you better mileage and more speed.

Uppie ......................... lighter and free up the spooling
Downpipe ................... lighter and free up the spooling
Underdrive pully .......... lighter and free up the rev.
Light weight exhaust.....reduce weight = more speed
Light weight rims.......... reduce HP lose.

200 lb killer sub .......... add weight and reduce speed
Full body kit ............... add weight and reduce speed
3 sweet lady friends .... add weight but increase classyness :D

But then once we got the extra power we will push the car more and negate the mileage gain :D
 
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