boost and air/fuel ratio problems
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This is a discussion on boost and air/fuel ratio problems within the General Maintenance, Troubleshooting & Accidents. forums, part of the Tech & Modifying & General Repairs category; Hi guys, i have an Impreza sti 04, installed with a turbosmart Tee, Dump Valve and and Fuel boost valve ...

  1. #1
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    boost and air/fuel ratio problems

    Hi guys, i have an Impreza sti 04, installed with a turbosmart Tee, Dump Valve and and Fuel boost valve FSE. I have a few questions:

    1. When i step on the throttle the air fuel ratio is 24:1 in 3rd gear what does that mean?
    normally its around 14:1

    2. The maximum boost i am getting is around 15.5 psi in 3/4 gear, and i have cranked the boost tee up 6 turns, anymore and the fuel cuts off, i've heard of people in the region of 25-35 Psi. What is wrong?

    3. Can i turn the turbosmart boost tee 1/2 turn instead of the full 1 turn that thet say?
    I am using a PSi3 unit to read this data.

    Please help

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  3. #2
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    24:1!! Way too lean. Dude you are destroying your car. The number is the air fuel ratio. 14:1 is around stochiometric, meaning the "perfect burn" ratio. 24:1 is burning up your motor. From what I understand (I am still a newb to suby's) You can't just tweak your boost pressure, you need to change the map when you change the boost psi. You are essentially adding extra air, but not so much the extra fuel.

  4. #3
    Registered User justin.jordan2's Avatar
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    all ur doing is turning up the boost not adding more fuel. you have to get a protune when you turn up the boost and depending how much boost you go up you will also have to get fuel supporting mods. i would turn the boost down to about 13.5 psi, then wait til you find a tuning shop with a awd dyno, and see if they do opensource tuning or you will have to get engine management.
    COBB FLASHED STAGE 2, UPPIPE, DOWNPIPE WITH HIGH FLOW CAT, AND FULL 3 INCH CAT BACK, 160 CRUCIAL RACING THERMOSTAT, K&N FILTER. TRACK: 1/4 MILE 13.66 102.7 MPH ON THE COBB OTS MAP

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    ok, sorry i checked it again and it seems to be fine the 24:1 only comes in when i step off the pedal after acceleration.

    but what abou the boost any chance of 1/2 turn.

  6. #5
    Registered User justin.jordan2's Avatar
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    Quote Originally Posted by chinaa108 View Post
    ok, sorry i checked it again and it seems to be fine the 24:1 only comes in when i step off the pedal after acceleration.

    but what abou the boost any chance of 1/2 turn.
    if you do not have a tune to be at 15 psi then turn it back down to the stock psi of 13.5 psi in third gear at full throttle, dont blow ur engine.
    COBB FLASHED STAGE 2, UPPIPE, DOWNPIPE WITH HIGH FLOW CAT, AND FULL 3 INCH CAT BACK, 160 CRUCIAL RACING THERMOSTAT, K&N FILTER. TRACK: 1/4 MILE 13.66 102.7 MPH ON THE COBB OTS MAP

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