Safe ambient air temperature

I received and installed my new Ultragauge MX 1.4 yesterday. Today I was driving in about 90 F temps and when I pulled into a parking lot (but was still driving slowly) my UG alarmed saying ambient air temp was 120F (it is set to alarm by default at 115F). I watched this and parked and within a minute it went up to 135F (and eventually peaked at 140F after a few minutes). Once I started driving above 10mph it dropped pretty quickly.

So my question is: do these temps seem accurate? When driving at highway speeds it was in the mid to high 90s which seems about right. I know sitting in a parking lot with no airflow is going to impact temps, but with a default alarm of 115F it made me wonder if it is getting way too hot or if I should just increase the alarm temp to something like 140-150F.

2020 Tacoma with about 2200 miles. No codes or warnings on the truck. Seems to be performing fine. It did smell a bit hot, but no burning smell.

 

what do you expect? sitting idiling in high ambient temps, its going to heat up the small amount of air charge and air intake tube pretty quick. Ever notice how the outside air from the vents get warm when sitting at a stop light / idiling, thats cus under hood temps skyrocket when sitting.

Needless to say you are fine and its exactly to be expected.

 

This is all that I got:


From that, it can be assumed that some underhood temp above 160F is good to go. Most nylon parts are good to 185F minimally.

 

Thank you! This is exactly what I was looking for. I will change the alarm to somewhere in the 150s.

 

You're welcome!

Happy to help.

 

Thanks for the feedback. As I said in my post I realize that temps rise with no airflow but I wasn't sure how high I should expect them to go. The default alarm of 115F was making me think perhaps something was wrong, but the info provided by @tonered indicates to me that it is just a very low default value.

 

Interestingly... Ultragauge support seems to think that this reading should be that of the outside temp and is guessing that the code it is reading isn't actually for ambient temp, but something else. Maybe it is engine bay temp? Is there actually a dedicated engine bay temperature sensor in these vehicles? It looks like the "ambient" temp sensor is located at the front of the engine bay (in front of the radiator I believe) so it doesn't really make sense to me that this sensor should be hitting 140F even idle.

 

Yeah. The outside temp sensor is in the engine bay, so it gets some erroneous readings.

We have had a few cars with outside temp sensors, and they all are a bit different depending on placement. We had one in the lower bumper opening that got whacky number if it was hit by sunlight.

My temp sensor always reads a few degrees higher than actual. I have never paid attention to it in traffic.


In the end, it is not much different than the challenge of placing an outdoor thermometer at home and trying to get accurate numbers through the day.

 

So why do you think the MFD in the dash was still reading at 88F while the UG was reading 130F+? It is kind of feeling like there must be two independent sensors.

 

There are, Intake air temp sensor is located in the air intake tube on top of the motor as part of the MAF sensor, outside air temp is in front of the radiator behind the grill

 

Ah! I didn't realize that you were seeing a difference like that. I do believe that the MAF reads intake temps. So, UG might be picking up on one or the other? It might be good to check with another OBD app that reports all sensors, like Torque. It might give a better clue to what PID is being monitored?

 

Should the air intake temp be that hot? If it is pulling in from the wheel well I would expect it to be somewhere between outside and engine bay temps. I'm not sure how fast the air is flowing, but if it is slow enough maybe the engine bay is able to heat it up that much?

Great idea. I have a BT OBD2 reader and Torque. I will try and set up a test.

 

Yeah. The MAF is not going to be reading that high. A number in the 150s is definitely an underhood sensor.

 

All those readings/numbers are gonna drive you nuts.

 

Maf has the intake air temp sensor in it. It will absolutely read that high at low air flow when the entire couple foot long intake tract is heat soaked from so little outside air cooling it down at idle.

 

Haha. Yeah. I'm a bit OCD I guess. I really only care about transmission pan and TC temps.

 

Yeah. Mine will run super hot some times. Never anything I thought was alarming though

 

So I finally had a chance to try and test this out a bit more. I set up my Ultragauge to display both intake temp and ambient temp and guess what? They stayed in sync for the entire 10 mile drive I did! So I guess what UG thinks is ambient temp is actually just intake temp; perhaps it is supposed to just represent ambient engine bay temps. Either way, I feel like the mystery is solved.

 

I think Max ambient tops out at 120*.

 

I ran several similar experiments on my autocross car when installing a cowl induction CAI.

The high reading you are seeing is the intake air temp, which is very close to ambient when you are moving.

At idle the intake passage collects heat from the bay (heat soak) and you see the temp rise.

It's not an issue. At all. Think how many vehicles do not have a built in CAI like a Tacoma, and only draw very hot under hood air.