What could cause high boost readings and bad gas mileage ?
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This is a discussion on What could cause high boost readings and bad gas mileage ? within the General Maintenance, Troubleshooting & Accidents. forums, part of the Tech & Modifying & General Repairs category; Monday morning while driving to work, I noticed my boost gauge was reading about 10-15 lbs of boost higher than ...

  1. #1
    Registered User jimbo058's Avatar
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    Question What could cause high boost readings and bad gas mileage ?

    Monday morning while driving to work, I noticed my boost gauge was reading about 10-15 lbs of boost higher than normal. For example, when going up a slight hill, it usually reads minus-10 lbs on the gauge, and it was reading +5 lbs of boost.

    The engine did not seem like it was laboring any harder than usual, but I burned about 2 times the usual amount of gas going to work and back. I was just driving along with traffic, not accelerating fast or anything. A 42-mile round trip, combination city-hwy.

    The next day, it acted completely normal, with the boost gauge reading like it should and the gas mileage going back up to normal. Since then, I have reset the ECU and re-flashed.

    Any ideas what would make it temporarily show way-higher boost and burn up twice the gas ? I eliminated things like parking brake engaged, foot on the brakes.

    '09 WRX, Catback, Cobb Stage 1, no other power mods.

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    Luke Skywalker Mikie13's Avatar
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    How does it act during other driving? Take the hill out of the equation.

    Thing is, you're not overboosting per say in that situation because you aren't over the target boost...it's hard to say. Something may be causing you to run rich. You should run some datalogs.
    The Hawk-Eye Alliance #90|The Blobeye Syndicate #0|The Stink-Eye Mob #0|N.E.R.D. Founding Member & #3
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    Registered User jimbo058's Avatar
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    It was showing abnormally high boost the entire day, like -0- when going down the highway, when it usually reads minus-15. I will run some logs if it acts up again. It is like it was stuck on the "cold-engine" mode or something.

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    Luke Skywalker Mikie13's Avatar
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    Yeah run logs anyway so you can be sure you're alright. What boost gauge do you have? Its quite possible the problem lies within there alone.
    The Hawk-Eye Alliance #90|The Blobeye Syndicate #0|The Stink-Eye Mob #0|N.E.R.D. Founding Member & #3
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    "If I have 10 ice cubes and you have 11 giraffes, how many pancakes can fit on the roof? Purple, because aliens donít wear hats" -Ying

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    Registered User jimbo058's Avatar
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    I have a Prosport "Premium Series Peak/Warning Amber/White with White Pointer clear lens" gauge. I will run some logs and look for rich conditions. Thanks for the input !!!

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    Master Baiter EJ257's Avatar
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    Confirm that your gauge is lining up with the MAP sensor
    2005 WRX STi (Mods | Virtual Dyno)

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    Registered User jimbo058's Avatar
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    "Confirm that your gauge is lining up with the MAP sensor "

    Sorry ... how would I go about doing that ??!!

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    Master Baiter EJ257's Avatar
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    Quote Originally Posted by jimbo058
    "Confirm that your gauge is lining up with the MAP sensor "

    Sorry ... how would I go about doing that ??!!
    Use the AP to log boost data
    2005 WRX STi (Mods | Virtual Dyno)

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