Underhood temp test results

[Ronin8002]

I decided to use someone's idea on this board of measuring underhood temps with a digital thermometer with a remote sensor wire. I placed the sensor on the left side of the engine (looking at it from the front of the truck) and toward the firewall.... just about 6 inches to the right of my KKM intake. I know at least one other person has done this before...but I thought maybe someone would want to see my results. Ambient air temp was 73-74 degrees for this test

Time /Underhood air temp

Cold engine 71.6

Engine running 73.6
For 1 min

2 mins 73.8

3 mins 74.8

4 mins 75.9

5 mins 77.7

6 mins 80.2

7 mins 82.6

8 mins 84.0

9 mins 85.1

10 mins 93.2

11 mins 96.1

12 mins 99.7

13 mins 103.3

14 mins 110.5

15 mins 112.8

I then backed out of the driveway and drove a mile through the neighborhood at speeds varying from 15-25 mph. After that mile underhood air temp was at 118….though it got as high as 120 at one point.

Then I got on the highway….at speeds of 45-55 mph I was seeing temps in the 110-114 range.

After that, I got on the open highway and at speeds of 65+…was seeing underhood air temps of 100-104.

I don’t know if this was a very accurate means of measuring intake air temp, but since the sensor was so close to my KKM, I think it’s safe to assume that my intake air temp was at least close to these numbers…maybe a bit higher because the air tube goes so close to the radiator.

Also, I had removed my underhood insulation before doing this test...I was looking for good places to install some hood louvres. If I get some hood louvres and then install my ceramic coated headers I'll run another test....hopefully these two mods can lower the underhood temp by as much as 10 degrees....maybe more.

 

[aldive]

Did you test in bumper to bumper traffiv?

I would like to see the data with ambient temperature in the 90;s.

Thanks for posting.....

 

[Ronin8002]

Didn't do any bumber to bumper traffic driving...but I did drive slowly with several frequent stops in my neighborhood at one point...that's where I hit 120. Incidentally, this thermometer has a recordkeeping function where it records the max high/low it has read. I went and checked it just a min ago (it's still hooked up in my X) and the highest it read was 133.2.....which I believe was the temp under the hood after I had stopped the engine and the fan wasn't operating/no air circulation, etc. Therefore, I expect that you might see temps approaching 130 in bumper to bumper traffic...at least at the ambient temp which I conducted the test.

 

[aldive]

Originally posted by MaximumViolence
I expect that you might see temps approaching 130 in bumper to bumper traffic.

In the middle of the Summer last year, stuck in traffic in Miami, the ambient temp gauge on my truck was reading 135 F. Iwonder what the underhood temp was then?

 

[Ronin8002]

Good point....see my edit above. Also....I'm not sure on this one, but I think the relationship between ambient temp and underhood temp may be fairly constant. If that is the case, it may be possible to estimate what your underhood temp would be at ANY ambient temp without having to run another test. Someone who is better at math than me would have to figure that one out

 

[Robert]

Al we already have an Intake Air Temperature Sensor (IAT) mounted right after the MAF sensor that will show us the actual temperature of the air going in to the engine. It sounds like this is what MaximumViolence is trying to determine. His numbers match my tests pretty closely depending on the outside temperature (which I am guessing were in the 70s based on his initial temperature reading). When our outside temperature gets to about 110-115, my IAT temperature can go up to about 170 when stopped in traffic for more than a couple of minutes. You can use your scanner to find this out (which I think you have also already done).

BTW - did you get my e-mail regarding your transmission or did your e-mail address change?

 

[aldive]

I have not proved iy. yet, but, I think the underhood temp will be higher than the IAT.

No email; send to al@fdu.com.

 

[explr1]

Is it possible to put the stock airbox back in and do the same test but this time put the air temp sensor through the snorkel hole?

 

[Ronin8002]

I think I figured out of estimating your underhood temp under any ambient temp conditions. It doesn't work perfectly....probably because you would have to run several tests to get a good average set of data to work with. Anyway..here's my example (I'm wasn't a math major in college so feel free to correct me here).

When I was simulating "bumper to bumper" traffic, I was getting an underhood reading of 120 degrees. Ambient temp was 74 degrees.....so:

120/74 = 1.621 (this number represents the relationship between ambient temp and underhood temp)

Robert mentioned that during 110-115 degree weather...his intake air temp was about 170....therefore:

110 (ambient temp) x 1.621 = 178.31 (intake air temp)

The answer I came up with is a bit high, but like I said....it's not completely accurate because I'm taking the number 1.621 from data determined on MY truck, not his (i.e.....his truck may run a little hotter or colder than mine). Also, as I said before, I only did this temp test once...it would probably have to be repeated several times, maybe even on several different X's...to make it work accurately enough for everyone.

Oh...how hot was it under the hood when you were stuck in Miami?

135 (ambient temp) x 1.621 = 218.8!!! Probably somewhat less than that....maybe 10 degrees or more....due to the inaccuracies I mentioned.

Now if I am wayyyyyyy off on any of this, someone tell me to put down the glass pipe and correct my errors for me


-James

 

[aldive]

I set up my OBD II scanner to measure IAT while I was in traffic today.

Ambient temp - 93 F
IAT ( Max ) - 158 F