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Thread: ECT vs CHT - coolant temperature readings

  1. #1
    Senior Tuner metroplex's Avatar
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    ECT vs CHT - coolant temperature readings

    For the EcoBoost engines, is the Cylinder Head Temperature (CHT) sensor the only actual sensor, and the Engine Coolant Temp (ECT) is just inferred from the CHT?

    If this is true, then all of the "ECT" values would actually refer to CHT?

  2. #2
    Senior Tuner Higgs Boson's Avatar
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    CHT sensor, ECT calculated. the ecm can refer to calculated values.

  3. #3
    HPT Employee Eric@HPTuners's Avatar
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    There is a lookup to convert measured CHT to ECT. Its very accurate.
    Eric Brooks
    HP Tuners, LLC

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    Senior Tuner metroplex's Avatar
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    I noticed that with the 170 tstat, my ECT never goes above 185F. Yet the cooling fans were running. I never used my A/C or defrost (ambient was 27F). The CHT ranged from 190 to 209.
    Desired ECT was set to 200F, and the ECT fan speed table started at 212F.

    With the stock 180F t-stat, the ECT ranged from 188-192, and CHT ranged from 214-218.
    Last edited by metroplex; 01-13-2017 at 03:37 AM.

  5. #5
    Ecoboost temperatures are dependent on vehicle configuration. You have to check Engine > General.

    4 Cylinders with integrated manifold have a coolant temperature sensor and an HCHT(Hi-temperature CHT) on the integrated exhaust manifold. This sensor is only used in failsafe cooling. The normal "CHT" is inferred from ECT.
    6 Cylinders instead have a CHT sensor, and no ECT sensor. ECT is thus inferred from CHT.

    The easiest way to tell is to look in Engine > General:


    If one is disabled, it'll be inferred from the other.

  6. #6
    Senior Tuner metroplex's Avatar
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    Looks like CHT is enabled, ECT is disabled. My 3V 4.6 in the GT is the same way.

    Does the ECU still look at inferred ECT for the fan settings in this configuration? Meaning, if I am asking the Desired ECT to be set to 200F, does the ECU look at when the inferred ECT is 200F or does it look at CHT instead?

  7. #7
    Looks at inferred ECT.

  8. #8
    Senior Tuner metroplex's Avatar
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    Thank you.

    The fan control has a mind of its own. I can do 3 passes back to back on the track in the winter and never have the fan running. I could do a cold start and drive around the block, and the fan would run - never ever running the A/C or defrost.

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    Sorry, I know this is an old thread, but I'm dealing with this currently. I get that there is no ECT sensor in these engines and only a CHT sensor, but what is the CHT sensing? Is it not in the cooling water also? Is it sensing oil temp in the cylinder head? I guess I just don't understand what temperature it is sensing? I put the 170? thermostat in my F-150 (I'm towing all the time) mainly to bring down my transmission temps. It definitely help with the transmission, but the ECT gauge is all over the place. The faster I go, the hotter it gets. As soon as I let off the gas to exit the highway or whatever, it quickly starts dropping. I could sit in traffic all day and it would never get over 200?. Get on the highway doing 85 (Texas) and she's up to 217?, but fluctuates a lot. I plan on using the HP tuner to change some fan settings but just trying to understand what the CHT is actually looking at and why it's so erratic. Maybe I need to replace it also. Thanks for the great forum and any help would be greatly appreciated.

  10. #10
    Senior Tuner metroplex's Avatar
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    My N/A Explorer 3.5 uses a CHT while my EcoBoost engines use ECT. The CHT looks to be screwed into the cylinder head while the ECT gets screwed into a water jacket.
    On my Explorer the CHT will generally be 10-12F hotter than the inferred ECT. I tweaked the fan settings and the CHT does reflect the change.

    I no longer have the SHO that I was discussing earlier in this thread, but it looks like my 2.7 EcoBoost in the Fusion Sport seems to work better as the fan operates as intended.

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    Quote Originally Posted by metroplex View Post
    My N/A Explorer 3.5 uses a CHT while my EcoBoost engines use ECT. The CHT looks to be screwed into the cylinder head while the ECT gets screwed into a water jacket.
    On my Explorer the CHT will generally be 10-12F hotter than the inferred ECT. I tweaked the fan settings and the CHT does reflect the change.

    I no longer have the SHO that I was discussing earlier in this thread, but it looks like my 2.7 EcoBoost in the Fusion Sport seems to work better as the fan operates as intended.
    Thank you. So the sensor that goes in CHT, does it still enter a coolant passage or is it measuring oil temp??? You said your Ecoboost does have a ECT?? That is a true sensor, not inferred?

  12. #12
    Senior Tuner metroplex's Avatar
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    I just looked for the parts online. My Explorer only listed a CHT sensor that appears to just screw into the cylinder head with a long probe. The ECT for the 2.7 has the thread sealant for what I think is the coolant jacket.

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    Okay thanks. I've seen the schematic that shows where the sensor goes. I just haven't figured out if it's in a water jacket, oil passage or just hollow cavity. I don't understand why it would create an inferred ECT if the CHT is actually in a water jacket. Wouldn't that be the same? Just hoping not to have to pull sensors to figure this out. Maybe I should just replace the CHT anyway since the swings are so radical. I've also noticed that the actual temp number (in degrees) and the temp blue bar do not track very well. The number will fluctuate 30? but the blue bar will not move, noticeably.

  14. #14
    Advanced Tuner 96gt4.6's Avatar
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    CHT sensors are screwed into a hollow void in the cylinder head casting, their sole purpose is to detect the temperature of the cylinder head metal itself. No oil or coolant is touched by the CHT sensor.
    '17 Whipple'd S550
    Too many other projects to list.....see my YouTube channel for more: https://www.youtube.com/channel/UCr7...-XfDG53sCh6tcw

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    Okay, thanks. That makes sense then.

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    Ford specifies that the CHT sensors are one-time-use. I assume that means the probe is compressed against the cylinder head surface when it's first tightened, and that interface needs to remain constant to get a valid reading.

    The 2018 2.7 has two CHT sensors and an ECT in the valley.