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Thread: battery / ambient air temp scale

  1. #1
    Supporting Member Turbo Mopar Contributor
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    battery / ambient air temp scale

    i've looked at a lot of the old posts regarding logging and cannot find an answer on how to convert the battery temp / ambient air temp sensor volts to degrees (F or C). from what i can gather currently it looks like 2.5v = 75F and 3.0v = 60F(maybe). its the last scale i really need to finish out the settings in mpscan. neither the coolant temp or charge temp sensor scaling seem to work.

    i've been able to determine all the proper scaling for coolant temp, charge temp, baro pressure, tps position, bat volts (pretty close), inj pulsewidth, and a few others.

    any input would be appreciated.
    89 Voyager LE, 2.5T2 - rest in peace
    87 Charger Shelby T2 (2.4 conversion in process)

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    Supporting Member Turbo Mopar Contributor
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    Re: battery / ambient air temp scale

    just had me a "you're so stupid moment"..........

    i thought, hey, why don't i just monitor the voltage and temp on my drb2 as i heat up the ecu with my wife's blow comb!!! then i can figure out the scale myself. so, plug in the blow comb, turn it on HIGH (don't ask), and hold it a foot or two from the ecu as i gleefully watch the volts drop (and temps rise) on my drb2. as i'm watching blindly to the volts drop from 2.5 (75F) to around 1.5 (110F) i'm thinking this is brilliant. then as the gauge rapidly crosses 125F+ or something like that my ecu goes completely whacky and now when i hook it up i've got all kinds of lights flashing on my smecstim. so needless to say, i'll be searching for another ecu to use for testing. dammit.... i'm blaming it on some bad chinese food i had tonight.

    at least i know the scale works similarly to the charge temp, but not at the same readings. oh well.
    89 Voyager LE, 2.5T2 - rest in peace
    87 Charger Shelby T2 (2.4 conversion in process)

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    Supporting Member Turbo Mopar Contributor
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    temp scales

    just to document this (thanks to naj):

    battery temp charge temp coolant temp

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    Last edited by wowzer; 10-22-2015 at 09:50 AM.
    89 Voyager LE, 2.5T2 - rest in peace
    87 Charger Shelby T2 (2.4 conversion in process)

  4. #4

    Re: battery / ambient air temp scale

    What are you doing with this information exactly, specifically the battery temp? I'm not aware of how it is used in relation to tuning.
    [SIZE="3"] [B]Jon Trotter[/B][/SIZE] [B]1985[/B] Dodge Shelby Charger, Currently decommissioned [B]1987[/B] Shelby GLHS, #937 [B]1987[/B] Shelby Lancer, #628 [QUOTE=Reeves;587010]I can be ready. Please send pics of wife. _____DodgeZ add comments here______[/QUOTE]

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    Supporting Member Turbo Mopar Contributor mopar-tech's Avatar
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    Re: battery / ambient air temp scale

    Quote Originally Posted by minigts View Post
    What are you doing with this information exactly, specifically the battery temp? I'm not aware of how it is used in relation to tuning.
    Voltage affects injector P/W if my memory serves me correct and charging voltage will vary depending on what the ambient temp is.


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  6. #6

    Re: battery / ambient air temp scale

    Quote Originally Posted by mopar-tech View Post
    Voltage affects injector P/W if my memory serves me correct and charging voltage will vary depending on what the ambient temp is.
    Right, right. That makes sense. I don't know much about the different tables and what all does what.
    [SIZE="3"] [B]Jon Trotter[/B][/SIZE] [B]1985[/B] Dodge Shelby Charger, Currently decommissioned [B]1987[/B] Shelby GLHS, #937 [B]1987[/B] Shelby Lancer, #628 [QUOTE=Reeves;587010]I can be ready. Please send pics of wife. _____DodgeZ add comments here______[/QUOTE]

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    Supporting Member Turbo Mopar Contributor
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    Re: battery / ambient air temp scale

    my primary goal is just to figure out the scaling so the mpscan display gauges make sense. even with the air temp scale i now have it doesn't seem to quite match up yet. it displays low around 7 to 8 degrees F from what my drb2 was showing. weird
    89 Voyager LE, 2.5T2 - rest in peace
    87 Charger Shelby T2 (2.4 conversion in process)

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    Moderator Turbo Mopar Staff Vigo's Avatar
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    Re: battery / ambient air temp scale

    System voltage affects injector latency / opening times but I think the battery temp signal JUST alters the charging system control, right?

    Dont push the red button.You hear me?

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    Re: battery / ambient air temp scale

    the bat temp is also used in determining when to turn the fan on but i don't think much else.

    and from minimopar.net ----

    "The logic module uses this sensor to determine the ambient air temperature near the battery. The sensor is located inside the power module (or SMEC) and measures the air as it flows through the module. This information is used to calculate the target charging system voltage and intake air density."

    ...and allpar....

    "The battery temperature sensor is actually inside the power module (or SMEC). It measures the air temperature as it flows through the power module, using the temperature to calculate the intake air density and target charging system voltage. The battery temperature sensor reacts to different temperatures by producing a voltage between .04 volts and 4.96 volts DC, based on an input voltage of 5 volts DC. Because the logic module is so close to the battery, these readings can be used to estimate the temperature of the battery itself. Knowing the temperature of the battery is important because batteries are sensitive to heat, and the logic module will reduce the power sent to the battery by the alternator to prevent “cooking the battery.”
    If the logic module detects a voltage outside the normal range (0.04 to 4.96 volts), it triggers a code 44 and the charging rate is set to 14.0 volts as a “safe” option. If the output of the sensor returns to the normal range, the logic module will return to normal operation and it will use the output from the sensor to adjust charging rates."
    Last edited by wowzer; 10-23-2015 at 10:55 AM.
    89 Voyager LE, 2.5T2 - rest in peace
    87 Charger Shelby T2 (2.4 conversion in process)

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    Supporting Member Turbo Mopar Contributor Turbo Joe's Avatar
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    Re: battery / ambient air temp scale

    Ok wondering why that gauge wasn't jiving with what I was expecting, So if I understand this correctly Charge Air Temp is NOT the manifold temp sensor for the air temp in the intake? then what one is so I can monitor my intake temps and see how my water/air cooler is doing vrs the air/air I used to have
    Turbo Joe
    ----------------------- 87 CSX #175 TIII powered, MegaSquirt3 Pro Ultimate, GTX3076R, Turbo Joe header, Lengel intake, Menegon ported head, the list goes on

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    Supporting Member Turbo Mopar Contributor mopar-tech's Avatar
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    Re: battery / ambient air temp scale

    Quote Originally Posted by Turbo Joe View Post
    Ok wondering why that gauge wasn't jiving with what I was expecting, So if I understand this correctly Charge Air Temp is NOT the manifold temp sensor for the air temp in the intake? then what one is so I can monitor my intake temps and see how my water/air cooler is doing vrs the air/air I used to have
    Charge air is in the intake manifold.

    Its primary function is to modify the fuel calculation based on air temp. The colder the air in the intake, the denser the air and the more fuel is required.

    The later TI's don't have them since they have no intercooler to pull the air temp down coming out of the turbo.
    Last edited by mopar-tech; 11-08-2015 at 09:23 PM.


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    Supporting Member Turbo Mopar Contributor Turbo Joe's Avatar
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    Re: battery / ambient air temp scale

    Quote Originally Posted by mopar-tech View Post
    Charge air is in the intake manifold.

    Its primary function is to modify the fuel calculation based on air temp. The colder the air in the intake, the denser the air and the more fuel is required.

    The later TI's don't have them since they have no intercooler to pull the air temp down coming out of the turbo.
    ok that's what I thought it was.. so in that case something is up with my charge temp sensor then...OR the scaling in MP Scan is off alot..
    Turbo Joe
    ----------------------- 87 CSX #175 TIII powered, MegaSquirt3 Pro Ultimate, GTX3076R, Turbo Joe header, Lengel intake, Menegon ported head, the list goes on

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    Re: battery / ambient air temp scale

    joe - if you would send me a log file i'll take a look to make sure it is picking up the correct ram addresses.
    89 Voyager LE, 2.5T2 - rest in peace
    87 Charger Shelby T2 (2.4 conversion in process)

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    Supporting Member Turbo Mopar Contributor Turbo Joe's Avatar
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    Re: battery / ambient air temp scale

    Quote Originally Posted by wowzer View Post
    joe - if you would send me a log file i'll take a look to make sure it is picking up the correct ram addresses.
    Ok but that will have to be tomorrow, since I deleted those logs cause I thought maybe I wasn't recording the right thing... but I can send you a log of the last run I did for today. I have most of the knock gone except for one little part.
    Wideband says slightly lean first getting into it but gets in the zone and even gets slightly rich now. car feels pretty good for low boost but it's the over 6k rpm mark that keeps haunting me.
    Turbo Joe
    ----------------------- 87 CSX #175 TIII powered, MegaSquirt3 Pro Ultimate, GTX3076R, Turbo Joe header, Lengel intake, Menegon ported head, the list goes on

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    Supporting Member Turbo Mopar Contributor Turbo Joe's Avatar
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    Re: battery / ambient air temp scale

    ok wowzer check your yahoo mail. I sent you a log of the last drive around i did. also can you check the map sensor scaling cause it reads like -4 vac when it should be reading -8 vac and the boost side reads about 1 psi under from my autometer gauge.
    Turbo Joe
    ----------------------- 87 CSX #175 TIII powered, MegaSquirt3 Pro Ultimate, GTX3076R, Turbo Joe header, Lengel intake, Menegon ported head, the list goes on

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    Re: battery / ambient air temp scale

    Quote Originally Posted by mopar-tech View Post
    Charge air is in the intake manifold.

    Its primary function is to modify the fuel calculation based on air temp. The colder the air in the intake, the denser the air and the more fuel is required.

    The later TI's don't have them since they have no intercooler to pull the air temp down coming out of the turbo.
    Oh my, I just got done being facebook "schooled" by a Chrysler Gold level tech and an aerospace engineer that Chrysler used inlet air temp sensors in everything from 88-2000. I only knew the 3.0's didn't after 87-88 or so but what a brilliant man.
    As if when completely disassembling harnesses, each time I mysteriously never found the sensor they know is there.

    My assumption is that the ECU guesses using ambient and coolant information.
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    Supporting Member Turbo Mopar Contributor mopar-tech's Avatar
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    Re: battery / ambient air temp scale

    Quote Originally Posted by Ondonti View Post
    I only knew the 3.0's didn't after 87-88 or so but what a brilliant man.
    None of the 1988-1992 2.5 Turbo I had them.

    My assumption is that the ECU guesses using ambient and coolant information.
    I'd have to peek at the code again but I don't think so. The CAS value is fixed on the later Turbo I vehicles.

    Which makes sense as the air temp out those little mitsu turbos is always on the hot side due to their size. The probably found in testing that even from the hottest ambient temp to the coolest there wasn't enough shift in the air/fuel ratio at WOT to impact engine durability and they could justify removing the sensor and saving money.


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    Re: battery / ambient air temp scale

    Quote Originally Posted by Turbo Joe View Post
    ok wowzer check your yahoo mail. I sent you a log of the last drive around i did. also can you check the map sensor scaling cause it reads like -4 vac when it should be reading -8 vac and the boost side reads about 1 psi under from my autometer gauge.
    joe - the boost gauge in vacuum reads different then what you are expecting because it is showing psi in vacuum. you probably want to switch the vacuum to InHg. so you need to edit the gauge by setting the following for the lower break point items:

    value: 0
    units: InHg
    multiplier: -2.036254 (make sure you include the negative sign)

    as far as the gauge being "low" in boost i don't know really how to fix that (i.e. which is more accurate - the external gauge or the ecu reading?). anyhow, in the new version of mpscan i have added an option in the gauge settings for a "constant". this constant would add/subtract from the calculated value to account for offsets (map sensor error, ground voltage issues, etc). i was holding off to release it to verify some LM things but i think will go ahead anyhow. there is also some changes to be able to display the ambient and charge temps correctly as well as throttle position.
    89 Voyager LE, 2.5T2 - rest in peace
    87 Charger Shelby T2 (2.4 conversion in process)

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    Supporting Member Turbo Mopar Contributor mopar-tech's Avatar
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    Re: battery / ambient air temp scale

    Joe have you had your CSX on the scales?

    I'm trying to make an educated guess on what mine will run this weekend but need more data.


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  20. #20
    Supporting Member Turbo Mopar Contributor
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    Re: battery / ambient air temp scale

    joe - are you using the cal option to use your wideband instead of your narrow? it would be interesting to see your AFR on your logs.

    the log you sent me only has the Coolant temp on it, not the charge temp or ambient air temp.
    89 Voyager LE, 2.5T2 - rest in peace
    87 Charger Shelby T2 (2.4 conversion in process)

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