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Thread: TPS% on '11 5.7 challenger

  1. #1
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    TPS% on '11 5.7 challenger

    My TPS % is showing only 86.7 on WOT pulls, and 13.7 at idle. Is this normal with throttle spark tables zeroed out, power % requested and expected power have been adjusted as well.

  2. #2
    Tuner Mattechperf's Avatar
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    That looks pretty normal. For whatever reason, that 86% number seems to always be the max. It bothers me, but many have said that there is no difference in TB airflow from 86% to 100%.
    At idle, mine tends to be in that 13% range too.

  3. #3
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    That settles my nerves a bit, thanks for the reply.

  4. #4
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    The scanner is setup on a 0-5 volt basis for TPS % which is SAE standard. Your throttle body is fully open before 5 volts, roughly 4.3 volts, hence the 86% readout. For sure, you are full throttle

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    For WOT that does make sense, but how or why would it read 13.7% at idle? Does the throttle body not fully close at idle, or is that another SAE standard not mixing well with voltage readings?

  6. #6
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    If it was fully closed, how would the motor run? It needs air to idle. Dodge doesn?t have an IAC system like GM that allows air past a closed throttle body.

  7. #7
    Advanced Tuner coanan's Avatar
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    Quote Originally Posted by toxic5.7 View Post
    For WOT that does make sense, but how or why would it read 13.7% at idle? Does the throttle body not fully close at idle, or is that another SAE standard not mixing well with voltage readings?
    Mine sits at 14.9
    2018 Trackhawk PCM/TCM tune by Dusterhoff.
    Flex Fuel, MMX faux 95mm TB, GripTec 2.85, 10% ATI lower, FIC1200, ARH 1 7/8 w/cats, 180 T-stat

    13 Chrysler 300S, RAM BGE 412 stroker, cam motion 232/246 619/619 118 +4, ATI 18% OD pulley
    Whipple Gen5 3.0, 2.50 upper pulley, Smooth Boost controller, FIC 1200 inj. Nick W 108mm TB, FORE dual return fuel system, E85, FTI 2800 stall(SRT83380), SHR WAR Viking trans and valve body, Getrag 3.73, 1 7/8 kooks w/hi-flow cats, 3" Magnaflow Cat-back 943rwhp

  8. #8
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    Wow...please stamp "dumbass" on my forehead please.. I guess I completely forgot to think about air intake at idle. Thank you for the stamp sir.

  9. #9
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    Also consider the fact that most 0-5 volt sensors typically have an effective voltage range from 0.5 volt minimum to 4.5 volts maximum (or an effective 4 volt range). You'll notice this is especially true of pressure transducers (think MAP sensors) if you ever start playing with MAP sensor rescaling and you look up the data sheets for the sensors. A TPS has a bit more variability in it than a pressure sensor since it is literally just a potentiometer. But it's still pretty typical to have a minimum voltage of around .5 and a maximum voltage of around 4.5.

    Since the parameters you're viewing are simply displaying a percentage of a 5 volt range, 0.5 volts is 10% of 5 volts, and 4.5 volts is 90% of 5 volts. Then, 06300CSRT8 already explained the need for airflow at idle and the lack of an IAC circuit, hence the 13-15% idle position.

  10. #10
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    Thanks for all the info, its super helpful. I have spend most my life building small and big block carb engines, so this is a completely different animal for me. It doesn't seem to be too difficult, but definitely a learning curve to tackle.