Intake air temp sensor

Discussion in 'Gen 2 Prius Main Forum' started by 299K, Feb 17, 2020.

  1. 299K

    299K New Member

    Joined:
    Jan 1, 2020
    28
    5
    0
    Location:
    Cleveland, OH
    Vehicle:
    2005 Prius
    Model:
    Base
    Hello all,
    Do anyone of you happen to know what the most efficient intake air temp sensor temp is?
    Looking for the least fuel injection vs most ice ignition advance.
    Thoughts?
     
  2. valde3

    valde3 Senior Member

    Joined:
    Jun 28, 2014
    1,881
    658
    0
    Location:
    Finland
    Vehicle:
    2004 Prius
    It's not that simple. It also depends on how much power is needed from the engine. More power you need colder air becomes more efficient.

    Hot air intake is more efficient if you don't need high power. So for steady cruising at relatively low speed on a road with no steep hills hot air intake would be the most efficient.

    But I don't think this makes even as big of a difference in a Prius as it does on a normal car. Hybrid system tries to run the engine at the most efficient range always.
     
    Graeme1949, edthefox5 and SFO like this.
  3. JimboPalmer

    JimboPalmer Tsar of all the Rushers

    Joined:
    Apr 14, 2009
    12,053
    6,324
    1
    Location:
    Greenwood MS USA
    Vehicle:
    2012 Prius v wagon
    Model:
    Three
    Back when I had a gen 2, I found that the intake air was about 10 F higher than ambient, until 95F then it went to 15 above ambient.

    I confess I just watched it, and still do. I was not attempting to alter it.
     
  4. SFO

    SFO Senior Member

    Joined:
    Feb 7, 2017
    2,383
    2,664
    0
    Location:
    Northern California
    Vehicle:
    2007 Prius
    Model:
    N/A
    Can't help myself, and will now page @edthefox5 :coffee:

    On a side note, wonder when someone will do a throttle body coolant bypass on a gen4 :whistle:
     
    edthefox5 and PriusCamper like this.
  5. 299K

    299K New Member

    Joined:
    Jan 1, 2020
    28
    5
    0
    Location:
    Cleveland, OH
    Vehicle:
    2005 Prius
    Model:
    Base

    Yes, hot intake air is better for less fuel injection. That is what I am looking for, what is the most efficient intake air temp to set the intake air temp sensor at, regardless of the actual intake air temp. Dont care about emissions, just looking for max mpg, which is what should be the focus of all car computer strategies. Got a gen 2 btw.
     
  6. 299K

    299K New Member

    Joined:
    Jan 1, 2020
    28
    5
    0
    Location:
    Cleveland, OH
    Vehicle:
    2005 Prius
    Model:
    Base
    Hmmm,
    Thats interesting. Does anyone happen to have the fuel maps for the gen 2?
    Using a hot air intake with a set value resistor for a lower temp could produce mpg gains. Possibly higher nox, but more mpg defeats the higher nox.
     
  7. valde3

    valde3 Senior Member

    Joined:
    Jun 28, 2014
    1,881
    658
    0
    Location:
    Finland
    Vehicle:
    2004 Prius
    This won't work. If you trick the ECU into thinking that intake air is hot it will inject less fuel. But as the intake air is cold this will cause the engine to run lean. ECU will know that engine runs lean from air fuel ratio sensor on oxygen sensor. ECU will then use fuel trims and add fuel. So you'll get no fuel savings.

    Just concentrating on a fuel economy (CO2 emissions) would be very bad for air quality in cities and it would be bad thing globally too. If cars in cities would have more exhaust emissions cities would have to limit use of gas powered cars in there.

    This doesn't make any sense. Hot air intake could produce mpg gains. But why would you use resistor to make computer see lower temperature? If computer would see lower temperature value than it really is it would actually cause engine to run rich (that would eventually be cancelled out through exhaust sensors). Rich running engine would burn more fuel but produce even less nox.
     
    #7 valde3, Feb 18, 2020
    Last edited: Feb 18, 2020
  8. JimboPalmer

    JimboPalmer Tsar of all the Rushers

    Joined:
    Apr 14, 2009
    12,053
    6,324
    1
    Location:
    Greenwood MS USA
    Vehicle:
    2012 Prius v wagon
    Model:
    Three
    Sorry folks, I had no idea I was helping make the world worse. He is ignored and I am embarrassed.
     
  9. 299K

    299K New Member

    Joined:
    Jan 1, 2020
    28
    5
    0
    Location:
    Cleveland, OH
    Vehicle:
    2005 Prius
    Model:
    Base
     
  10. 299K

    299K New Member

    Joined:
    Jan 1, 2020
    28
    5
    0
    Location:
    Cleveland, OH
    Vehicle:
    2005 Prius
    Model:
    Base
    You should be embarrassed. 100 years of data is not enough to think the sky is, or is not, falling.
     
  11. 299K

    299K New Member

    Joined:
    Jan 1, 2020
    28
    5
    0
    Location:
    Cleveland, OH
    Vehicle:
    2005 Prius
    Model:
    Base
    Not looking to spoof a lower temp, looking to spoof a higher temp. Where the least fuel injection and the most ICE timing advance meet.
     
  12. TMR-JWAP

    TMR-JWAP Senior Member

    Joined:
    Aug 12, 2016
    2,763
    3,278
    0
    Location:
    Columbia, SC
    Vehicle:
    2007 Prius
    Model:
    Touring
    Soooo.....doesn't the Gen 2 mass air flow sensor have the temp sensor in it? Or did I learn this lesson incorrectly?

    IMG_5032.JPG
     
  13. TMR-JWAP

    TMR-JWAP Senior Member

    Joined:
    Aug 12, 2016
    2,763
    3,278
    0
    Location:
    Columbia, SC
    Vehicle:
    2007 Prius
    Model:
    Touring
    Your plan is to spoof the IAT to think that air temp is always at a fixed "ideal" temperature, then also spoof the air-fuel ratio sensor in the exhaust manifold to make the car think it's always running at a specific mixture? Or just the IAT and then let it do it's normal loop control thing?

    There's a lot that goes into fuel mixture. What about engine coolant temperature?

    This sounds like something that can get out of hand fast.
     
  14. TMR-JWAP

    TMR-JWAP Senior Member

    Joined:
    Aug 12, 2016
    2,763
    3,278
    0
    Location:
    Columbia, SC
    Vehicle:
    2007 Prius
    Model:
    Touring
    Some info for you....this is in the engine control section of the repair manual. Around page 92.

    Any P0110, P0112 or P0113 (IAT sensor problems) will cause temperature to be set at 68F in the ecu.
    Any P0115, P0117 or P0118 (engine coolant sensor problem) will cause engine temp to be set at 176F.

    Those may not be 'ideal' but apparently they're safe values to start with.

    The IAT thermistor range is 98.5 ohms at 284F and 156K ohms at -40F. It is close to linear between -4F and 212F, with 68F being around 2k ohms and 104F being right around 1k ohms.
     
    SFO likes this.
  15. valde3

    valde3 Senior Member

    Joined:
    Jun 28, 2014
    1,881
    658
    0
    Location:
    Finland
    Vehicle:
    2004 Prius
    You don't need to look at climate data to see that air quality problems in cities like Los Angeles in the past when there was no exhaust emission limits. With no limits on exhaust emissions you would need to limit the use of fuel burning cars in places like that.

    But if you drive your car in rural area some reduction in fuel consumption with some increase in local toxic emissions might actually be beneficial. But even then you would need to keep a limit to do net good.

    Ignition timing could actually be changes by changing the intake air temperature that ECU would see. But in some temperatures you might actually want to spoof the temperature to be lower to get more ignition advance and better fuel economy. Then one thing that you have to take into account is a possibility of knock. Knock would be bad for an engine and because of knock sensor retarding ignition timing would also reduce fuel economy. So if you would spoof intake air temp to get better fuel economy you might need to run higher octane rating fuel. Higher octane rating fuel is more expensive and the amount of fuel saved is small so that would make no sense. Or perhaps you could mix in a bit of e85 to boost the octane?

    Fuel injection amount can't really be changed by spoofing intake air temperature, coolant temperature or something like that because engine is running in closed loop. You also really want to keep the engine running in closed loop as that's needed for fuel economy to remain the same during the use without constant manual adjustment.
     
    #15 valde3, Feb 25, 2020
    Last edited: Feb 25, 2020
Loading...