Does anyone know what sets off engine heat protection / limp mode?

[GJarrett]

In the past I've overheated enough on the track a time or two during HPDE events to go into limp mode. I'm curious if anyone knows exactly what and when triggers the limp mode - is it CHT at a certain temperature (if so what temperature?), something else, or what?

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[Craig Brown]

what coolant do you have (orange/ yellow) and what thermostat do you have? Orange has been replaced with yellow. I just switched coolant and thermostat to (yellow/170 degree Reischi). Are your fans working? There are air dams on either side of your radiator, are they still in place? If you have changed coolant, did you burp the system to get all the air out?

 

[Ewheels]

I believe there are several limits in place that will trigger limp mode.
The diff can trigger it over 300° or so.
CHT will also do it but I don't know the exact threshold. I'd imagine north of 250° and perhaps if that's held for a certain amount of time.

 

[GTP]

Does anyone know what sets off engine heat protection / limp mode?

Yeah. Heat.

(Sorry, couldn't help myself.)

Me: Doctor, whenever I sip my coffee I get a sharp pain in my eye.
Doc: Try taking the spoon out first.

 

[SBR70.3]

On the 16GT in my sig, the CHT's were a massive issue on track. I think that car went into limp mode around 260 F. No idea what the oil, trans, or diff temps were.

Do you have gauges to monitor these? Definitely datalog next HPDE session.

 

[ihasnostang]

could ask Jesse, that's what you paid him for . how long did it last before going limp? Your accessport can store hours of logs

 

[mejohn50]

I pulled a 2017 Ecoboost file, that I believe is a manual, and took a look at the RPM limits based on temps.

There are a couple tables that govern this, with one defining the temps and the other defining the RPM limits.

These reference tables are 100% unmodified. If the car is tuned, I have no idea if they are modified at all. Also, I don't know your specific OSID so it's possible there could be slight variations even in OEM calibration data since there are dozens of 2017 Ecoboost calibrations, but these should give you an idea how it works and what the values are.

The first table defines the temperatures. On the x-axis, 0 = engine oil temp, 1 = engine coolant temp (which is inferred), and 2 = transmission oil temp. The y-axis defines the temperature points.

You can see, for example, at engine an engine oil temp of 295f, it references column 4 of row 0. Or if your trans oil temp is 270f, it references column 1 of row 2.

This data is then used to reference the following table. The x and y axes are the same as above, so an engine oil temp of 295f limits engine RPM to 4300 or a trans oil temp of 270f limits engine RPM to 5000.

These are likely the primary temperature-based limiters that you will run into.

 

[Skye]

Attached is the Ford description for Fail Safe Cooling.

 

[GTP]

OP To simplify things for you, usually CHT approaching 250 will limit you. We add aftermarket or DIY oil coolers for that and that usually takes care of it for up to 30 min sessions.

Once that is handled and you are driving faster the diff will overheat, at 290. Adding a diff cooler solves that.

Trans overheating is typically the final heat limit. Though I have never reached that with my A10.

Improving airflow for cooling is also something that can't hurt.

 

[horsepower addiction]

Probably CHT because the cooling system is gonna heat up faster than anything else and the oil doesn’t have a temperature sensor

 

[GJarrett]

Thanks for the healthy mixture of light-hearted smart-alec and informational replies!

Ryan Martin is my tuner and he informed me that I still have the OEM heat protection settings with tunes, but did not offer if he knew the actual settings.

I have overheated to limp mode twice, both during the late stages of afternoon sessions on hot days. The first was early on with a FP tune at VIR. I probably had a regular 50/50 coolant mix back then with stock radiator. The second time was last year during a summer session at Sebring. By then I was running 100% distilled water with a bottle or two of Water Wetter thrown in, and a larger PP radiator. Fans and air dams work and in place. Manual tranny.

I asked the question in an attempt to learn how to prevent limp mode, thinking for example if I knew that CHT at 250 degrees triggers limp mode, while on track I could monitor CHT and adjust driving to lower it when it is about to get there.

I have just hacked into my hood and installed a Race Louvers center vent which should help more. The reason I am curious about heat is that I have now upgraded my engine with a FP cam on top of my other mods and Ryan is tuning for a more spirited 100 octane tune which will produce more hp than I've ever had before, and hp = heat. I haven't dyno'd my EcoBoost but I'm sure it is now well north of 400whp/400 tq. We will see if the hood louvers help enough.

 

[robvas]

I haven't dyno'd my EcoBoost but I'm sure it is now well north of 400whp/400 tq. We will see if the hood louvers help enough.

That's how much a PP car makes so if you have the PP radiator it should handle 400hp worth of heat without issue.

 

[horsepower addiction]

You should look into ether lowering the temperature that your fans turn on or wiring a toggle switch to turn your fans on manually. The way you use your car maybe look into a larger radiator like an aluminum one

 

[GJarrett]

It only overheated during hot afternoon HPDE sessions and I assume fans don't matter when I am running triple digit speeds. How will turning the fans on help?

 

[GTP]

It only overheated during hot afternoon HPDE sessions and I assume fans don't matter when I am running triple digit speeds. How will turning the fans on help?

They won't.
Ventilating the radiator shroud

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