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Thread: atmospheric pressure

  1. #1

    atmospheric pressure

    How much difference in tuning would there be at these levels= 12.9psi/3500ft. when seal level is 14.7psi?
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    Last edited by carotene; 6 Days Ago at 07:29 PM.

  2. #2
    I am having one hell of a time trying to get rid of backfire on the let off.
    I did some searching and found out it's possible to either break the turbo shaft or destroy the vanes.
    With all the knowledge on this forum somebody should know what I might try. I have reset everything I can think of I even tried canceling dfco. It goes very lean on letoff, that's why it backfires. If I cancel the 02 sensor it goes rich and it won't backfire but I don't want to run it at 9.5/10.0 afr.
    Last edited by carotene; 6 Days Ago at 07:39 PM.

  3. #3
    Tuner in Training
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    What's up with your engine coolant sensor? The log says it's stuck at -40?C, is the sensor connected?
    I assume it has an automatic transmission. And can you pinpoint at what point in the log the backfire happens?

    The default turbo on these engines has no vanes, and it's wastegate controlled. So you can't destroy them.


    Quote Originally Posted by carotene View Post
    How much difference in tuning would there be at these levels= 12.9psi/3500ft. when seal level is 14.7psi?
    No real difference in tuning, only lower final power output because of the limitation of the turbo. The exhaust manifold is quite small and it can't flow well at higher RPM, therefore it can not compensate for the lack of atmospheric pressure. At the sea level it can flow about 135-140 g/s air at high load.
    Last edited by sbarisic; 4 Days Ago at 11:30 PM.

  4. #4
    I didn't say anything before because I wanted to see if anyone might know what I was talking about.
    That is exactly what I was talking about no power from idle till the turbo kicked in. It is so bad that it is dangerous to pull out into traffic.
    I have moved around and changed everything I can think of but so far nothing has improved the problem. I have gone over and even changed the temp sensor but it won't come off of -40. If I am right it should not have any effect on this particular problem, temp from what I know effects fuel, timing and throttle pressure which can be changed from other tables. I have tried to get the turbo to respond a little lower than 2000 but it doesn't go lower. I just put most everything back as close as I can to stock settings it won't run at all with everything at stock settings because my air filter and exhaust system are not stock. The engine isn't shrouded like it is in a car so my engine and components run a lot cooler. I have tested the temp of the intake when the engine is hot, it only reads 115* to 126*f and that's with the outside air temp at 104*. These ecm's are designed to compensate for a lot but I am thinking that I might be outside of it's parameters a little.
    One more item where did you get those flow numbers for the exhaust manifold?
    Last edited by carotene; 4 Days Ago at 11:22 AM.

  5. #5
    Senior Tuner cobaltssoverbooster's Avatar
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    not having a coolant reading is a big issue. Coolant temp reading negative values kicks in a heavy fuel multiplier as the ecu thinks the motor isn't warm enough to 1) properly seal and 2) correctly flash the fuel into a vapor when injected.
    If you cant pull out into traffic because of power loss, its not becuase of the baro is 12.9 instead of 14.7, its becuase your likely having sensor and wiring issues that are causing extreme fueling control.

    A stock motor shrouded vs. unshrouded is a negligble concern. Revisit all of your sensors and make sure they are reporting reasonable values. Any that aren't, go fix them before you continue forward.
    2000 Ford Mustang - Top Sportsman