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Underhood Temperature Test --RESULTS!!

CobraMarty

CobraMarty

NAXJA Forum User
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Ok got a couple of cheap digital temperature sensor/readouts and tested tonight. It was cool out, 60*F ambient. Drove 15 minutes to burger king to warm it up and heat soak it with all the lights.

Drive thru at Burger King--- ambient=61.0*, underhood=155.8*, +94.8*!

Sitting idling at BK 10 mins- ambient=61.5*, underhood=184.1*, +122.6*!!!!!:flame::flamemad::smsoap::firedevil

Cruising Freeway 55mph---- ambient=58.6*, underhood= 88.3*, +29.7*

WOW!! Look at those numbers. No wonder the Cherokee runs HOT when wheeling.

I did sort of messed up and forgot to record the MAT. I will repeat this test tomorrow night and also record the MAT. Same route.

I will then add 1/2" hood lifts to the rear of the hood and test again.

More to come.
I really just want to justify a cowl hood!
 
CobraMarty said:
Ok got a couple of cheap digital temperature sensor/readouts and tested tonight. It was cool out, 60*F ambient. Drove 15 minutes to burger king to warm it up and heat soak it with all the lights.

Drive thru at Burger King--- ambient=61.0*, underhood=155.8*, +94.8*!

Sitting idling at BK 10 mins- ambient=61.5*, underhood=184.1*, +122.6*!!!!!:flame::flamemad::smsoap::firedevil

Cruising Freeway 55mph---- ambient=58.6*, underhood= 88.3*, +29.7*

WOW!! Look at those numbers. No wonder the Cherokee runs HOT when wheeling.

I did sort of messed up and forgot to record the MAT. I will repeat this test tomorrow night and also record the MAT. Same route.

I will then add 1/2" hood lifts to the rear of the hood and test again.

More to come.
I really just want to justify a cowl hood!
Click to expand...

o_O That's toasty! :scared: I'm surprised it hasn't gone kaboom yet...:explosion:skull2:
 
Well, I'd say that looks about right. Plus it all depends on where Marty took the measurement as the heat varies by location under the hood.

Consider, the cylinder head is a nice toasty 210F, the block nearly so and the exhaust manifold is most likely a cozy 600+F... And you thing 184F is hot? Looks pretty cool to me. But the ambient was low so that helped to hold the under hood temps down...

How can anyone possibly expect the bay to be cool with all the heat that is being generated. Which is why letting it out is a good thing.

The cowl induction hood will work great off road and I, for one, will be interested in the on road results should he decide to go that way.

Now take the measurement when the ambient is 100+F and see what you get...
 
The underhood sensor was taped to the underside of the hood right in the middle about directly above the oil fill cap. The ambient was taped to the windshield along with the 2 digital readouts.

It was the difference that was so impressive. On that 100* day one might see over 220* under the hood. Bolt a griddle to the hood and 'barby' a steak or bake a cake while your wheeling.

New idea- an under hood oven. 'Put it in and forget it'. Your Jeep will now cook for you.
 
i always wondered what the poor Intake air temp sensor is reading!!, i got the innovate motorsport logger a while back, in summer when its around 100F

130F driving ! 150F idling in heavy traffic which makes me think relocating that sensor in these conditions should offer a significant improvement.


and i also i think properly placed hood vents should make a significant improvement , i have a set that i'm planning to install , will update readings then
 
MAT and IAT are really the same sensor just moved/located in different positions.

When I relocated the MAT (temp sensor in intake Manifold- stock location) into the IAT position(temp sensor in the Intake tube,I have Volant CAI or air filter box area), I had to splice and lengthen the wires, I saw IAT readings 3-5* above ambient temp.

Now is that a good thing to do? Some say yes, it sends the ECU a 'colder' MAT/IAT temp reading. ?Will that richen the mixture? Will that leave it in 'cold start' mode? Will it advance the timing? Will the ECU be confused when the Coolant temp is 210* and the IAT is 90*? I don't know how the ECU is programmed. I do know that on some cars this trick works and there is a slight HP increase. I have not seen any data/testing that this is the case with the jeep.

Just finished building the 1/2" hood spacers to add in later.

Having a 'cooler' underhood temp probably won't help make any more HP but it would help with the cooling problem that the cherokee has when traveling at low speed/rock crawling. And cooler underhood temps will help with the longevity of many of the parts underhood.
 
i have an AEM air fuel ratio gauge on board, i'll try to do this trick with a new sensor so the setup is reversible and see what happens to AFRs.
 
Some more results.
Before idling 10mins ambient=61.5 underhood=184.1 difference 122.6
cruise 55 mph freeway ambient=58.5 underhood=88.3 difference+29.7

Idling 10 mins .... ambient=76.3 underhood=150.3 difference=+74.0 MAT=188.6
cruise 55 freeway ambient=75.2 underhood=112.1 difference=+36.9 MAT=121.2

With 1/2" hood spacers raising the rear of the hood 1/2" (barely noticeable, needs more)
idling 10 minutes ambient=71.2 underhood=143.8 difference=+72.5 MAT=174.2
cruise 55 freeway ambient=70.7 underhood=109.2 difference=+39.0 MAT=109

What does this show?
Today's test were with 15-16* warmer ambient
Hoodlift needs to be more.
With the rear hood seal, there was barely a 1/4" gap even though I used a 1/2" spacer.
The underhood temp was lower but the ambient was lower by nearly the same amount.
But the MAT was lower by a greater amount with the hoodlift.

I will make another set of hood spacers and try with a larger rear hood gap.
 
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I have another sensor. Where do you want me to put it?

One sensor is located- taped to the underside of the hood, centerline, 10" forward of the back edge of the hood.
 
So...

Another "Blast from the Past" from one of the resident olg guys.

When I was a kid and my family went up in the hills of NorCal for the day, my Dad would wrap potatoes in "tin foil", place them on the intake manifold of the '40 Ford flattie we had so we would have baked spuds for lunch.

Just sayin...

Marty, you might consider checking just inboard of the throttle body as that is where most cut the hood for the vents.

I'll be honest here, I placed them there for clearance reasons. Did not want to cut the supporting structure.

Here is where I cut them in...
P9090002.jpg


As you can see, they are just in front of the rear supporting member. This made bending up a set of drip pans easier to do. And, they dump any water that gets in out of the way of the electronics.

The front outboard corner of the vent sits at about the midpoint of the throttle body. So, the vent is inboard and aft of the TB.
 
CobraMarty said:
MAT and IAT are really the same sensor just moved/located in different positions.

When I relocated the MAT (temp sensor in intake Manifold- stock location) into the IAT position(temp sensor in the Intake tube,I have Volant CAI or air filter box area), I had to splice and lengthen the wires, I saw IAT readings 3-5* above ambient temp.

Now is that a good thing to do? Some say yes, it sends the ECU a 'colder' MAT/IAT temp reading. ?Will that richen the mixture? Will that leave it in 'cold start' mode? Will it advance the timing? Will the ECU be confused when the Coolant temp is 210* and the IAT is 90*? I don't know how the ECU is programmed. I do know that on some cars this trick works and there is a slight HP increase. I have not seen any data/testing that this is the case with the jeep.

Just finished building the 1/2" hood spacers to add in later.

Having a 'cooler' underhood temp probably won't help make any more HP but it would help with the cooling problem that the cherokee has when traveling at low speed/rock crawling. And cooler underhood temps will help with the longevity of many of the parts underhood.
Click to expand...

Yes, a lower IAT reading will affect the PCM. No, you will not confuse the PCM with 210 degree water and 90 degree air, or you couldn't drive your car in the winter. No, it will not affect loop operation.

http://www.angelfire.com/my/fan/IAT_sensor.html

And yeah, cooking on engines has been going on for as long as man has made engines. ;)
 
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CobraMarty said:
New idea- an under hood oven. 'Put it in and forget it'. Your Jeep will now cook for you.
Click to expand...

it's an old idea, it's pretty common to take a frozen burrito and wrap it in foil, then toss it on top of your intake manifold and go for a light trail run. by the time you get back to camp your manifold burrito lunch is ready :D
 
I really like what ur doing here. I tend to get 'vapor lock' on my '01 XJ when parking after sitting ideling or in traffic for a while. I get hard & stumbling starts and it takes about 1 to 2 minutes of driving for that to stop & normal running start.

I'd love to add some vents but not sure how I feel about cutting holes in my hood. If vents are done right they look great, so we'll see. I like the spacer idea but that doesn't look to good, although functional & reversible so it's an option.

I think if I could figure how to get the fan to run for about 15min after I turn the ignition off would solve my issue too.
 
GrimmJeeper said:
it's an old idea, it's pretty common to take a frozen burrito and wrap it in foil, then toss it on top of your intake manifold and go for a light trail run. by the time you get back to camp your manifold burrito lunch is ready :D
Click to expand...

Will this work if I have a 30 minute commute to work in the interstate?
 
Redsnake said:
I really like what ur doing here. I tend to get 'vapor lock' on my '01 XJ when parking after sitting ideling or in traffic for a while. I get hard & stumbling starts and it takes about 1 to 2 minutes of driving for that to stop & normal running start.

I'd love to add some vents but not sure how I feel about cutting holes in my hood. If vents are done right they look great, so we'll see. I like the spacer idea but that doesn't look to good, although functional & reversible so it's an option.

I think if I could figure how to get the fan to run for about 15min after I turn the ignition off would solve my issue too.
Click to expand...


Next time I will put my third temp sensor right near the fuel rail/injectors. After my drive test, I will take temp readings every 15 minutes during cool down and see how long to cool after driving.

I will post pictures of the hood lift tomorrow.
 
bigalpha said:
Will this work if I have a 30 minute commute to work in the interstate?
Click to expand...

Not sure if you were serious... but during high school, I used to make miniature burritos and freeze them. I would put them on the intake manifold and drive to my morning class at a different school across town (~25 minute drive), and let them sit/thaw for the hour long class. Then I would drive back to my high school for the rest of my classes, park, and throw them on top of the cat for 5 minutes while I waited for the bell to ring. By the time I had to head into school, they would be nice and toasty!

I even had a few "customers" in my class that I would sell them to. Good times, good times.

:cheers:


EDIT: a few months ago I tried making a b-fast burrito on the way to a snow wheeling trip (although the weather was probably ~70*). Bought burritos at Safeway and immediately threw them on the manifold. Drove 1 hour and 15 minutes on the highway and when I checked them they were still frozen... So, I wedged them between the headers :D. Drove for about a minute and smelled them burning. Pulled over, peeled off the burnt part, and enjoyed the best breakfast burrito I have ever had!
 
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I am dead serious about cooking on the intake. It is a time honored tradition going back to, well, the first gear head realizing he could do it. Say, circa 1911?

Redsnake, see my response to your thread...
 
o-gauge-steamer said:
I am dead serious about cooking on the intake. It is a time honored tradition going back to, well, the first gear head realizing he could do it. Say, circa 1911?
Click to expand...

there are even cookbooks about cooking under the hood :D I am a real fan of the manifold burrito just make sure you take the plastic off and wrap it in foil :gee:
 
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