Underhood Temperature Test --RESULTS!!

I wonder if it may cook more thoroughly if placed between the wheel well and exhaust, just underneath the intake manifold. When Top Gear went to Africa Jeremy and Richard threw some type of steak in James' engine compartment, not sure of the exact placement or result. This reminds me of the ham-shaped sub enclosure thread that was so delicious a while back....
 
Not to dump on the intake cooking twist this has taken... But I'm really interested in the OP's test results and pics...

Any updates not cooking related? :)
 
1/2" Hood Lift Spacer
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1/2" Hood Lift
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1" Hood Lift
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UnderHood Temp Sensor Location
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Fuel Rail Temp Sensor Location
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Above are the pictures.
1/2" hood lift- too low, was barely off the weatherstripping, no gap.
1" hood lift- good gap, aesthetically looks too high, need to lower to 3/4"
Under hood temp sensor location
Fuel Rail temp sensor location

With the 1" Spacer, The Results-

10 min idle at BK ambient=73.6* underhood=127.9* DIFFERENCE=+54.3* fuel rail=151*
Freeway 55mph ambient=62.6* underhood=86* DIFFERENCE=+23.4* fuel rail=99.5*
 
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Thx! Am I reading it right that a the 1" hood spacer the temps were 54.3 degrees cooler after idling 10 min vs No hold lift (or stock)? If that's the case that's a pretty big difference & I'd imagine would really help w low speed driving/crawling & also my vapor-lock hot start problems.
 
So what does this show?
1/2" didn't make much difference in the underhood temp but did lower the MAT 10-14*
1" lowered underhood temp by 20* but looked too high and need to make 3/4" spacer

Plan is to make a 3/4" spacer and retest stock vs. 3/4" spacer, Measuring ambient, underhood, fuel rail and MAT.

Up to now it has been trial and error to see what thickness spacer works and where to take temp readings at. Now that it is worked out I can do a back to back apples to apples test.
 
Redsnake said:
Thx! Am I reading it right that a the 1" hood spacer the temps were 54.3 degrees cooler after idling 10 min vs No hold lift (or stock)? If that's the case that's a pretty big difference & I'd imagine would really help w low speed driving/crawling & also my vapor-lock hot start problems.
Click to expand...

I think that stock the underhood temps were 74* over ambient and the 1" lift was 54* over ambient or 20* cooler than stock.
 
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.

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.
Click to expand...

With the 1" Spacer, The Results-

10 min idle at BK ambient=73.6* underhood=127.9* DIFFERENCE=+54.3* fuel rail=151*
Freeway 55mph ambient=62.6* underhood=86* DIFFERENCE=+23.4* fuel rail=99.5*
Click to expand...

I think that's definitive proof that the hood spacers do allow a massive amount of heat to be vented out of the engine compartment at idle. At freeway cruising speeds the effect is much less as you'd expect.
 
At freeway speed, the results were exactly what I was expecting. The cowl, at speed, becomes a high pressure area and should be forcing air into the bay where at low speeds it allows air out of the bay.

Cowl induction hoods have been used by the Muscle Car Crowd (yes, I had a 69, Raven Black, 429 Boss Mustang...) for just that reason. To get more air to the intake. So the results indicate that the air flow is stalling compared to the low speed application which, truth be known, is exactly as it should be.

The air flow through the bay is all about pressure differentials. The reduction of resistance to flow will gain the best results. Here is the kicker. At highway speeds, the vents in the hood need to be just behind tha radiator to get the best results, at low speeds, they need to be further back.

Do the yarn test. Tape 2" pieces of yarn in a no more than 6" grid to the hood and take it for a drive. The low pressure areeas will cause the yarn to stand up. What you will discover is where the low pressure areas are as well as the actual air flow over the hood. In the past, I have used the areas of the highes velocity to locate NACA vents. The fast moving air will create a large low pressure area over the relief wich results in a positive flow from under the hood. It may surprise you as the where the best location is.

My installation is just for low speed and the vents may not be large enough. We will see this summer as it is alleged that it will be warmer than last... Should they prove inadequate, I will go larger.

Do not ask what I had to pay for the Mustand back in 80. Let's just say it was more than when it went off the show room floor...
 
Very interesting. So a cowl hood/scoop thingy like this is really needed:
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Just move the 'reverse hood scoop thingy' forward a bit.
 
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The issue I have with these and for that matter all of the others is that they do not come with Drip Pans. And you need the pans to keep the water out of the electronics. But, the Hylines are nice. Being cut in several areas will change the flow through them when at different road speeds.

They look like some one actually took measurements of the air flow across the hood.
 
i put vents in without drip pans. things under your hood get wet- I don't see the difference between water splashing up from the ground, or dripping in from the top?
 
They're genright "louvers" http://www.genright.com/ProductInfo.aspx?productid=LVR1006

I'm pretty happy with them, and my temps have never crept too high. I'd say hood vents are absolutely worth it depending on how comfortable you are cutting into your hood

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one piece of information I wish someone had told me- careful working on your hood. Its more delicate than it appears. Between cutting out the vent holes, and banging down one of the supports to fit my poorman's cowl intake, I kinda warped it- and I really didn't think I was being that rough on it.
 
Thanks for the pics and info. What did you use to cut the holes in your hood? I'm thinking about picking up a pneumatic saw to use with my air compressor... but not sure how 'clean' of a cut that would make. I have a cut-off saw and dremel... but always nice to get another tool that I 'need'... :)
 
No problem; I used an angle grinder. A dremel would probably look nicer, but I didn't have the patience. My thought was, the cuts are going to be hidden by the vents anyway, so I didn't really care what they looked like. Just remember to spray them with some rustoleum(you can see the diff color in first pic) before putting vents on.
 
here's my setup, I used nearly the same aluminum louvers but those were made by Poly performance.
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I made a paper template using the vents to design my cutting line in reference to the vent shape,
3M double sided tape to temporarily fix the ventson the hood and make markings,
drilling 3mm rivet holes on the perimeter of each vent,
then used a jigsaw on low speed and a bosch 118A metal cutting blades,
the cutting quality was amazing, so smooth with no paint chips, i only did very minor deburring with a flap wheel.

Testing results are very impressive, coupled with a spectre cowl intake the Temp guage is now down by at least 5deg c. i'm running at a solid 100deg c in heavy traffic and 85 to 90 at highway speeds. I'm living in 38-40 deg c sunny weather.

The other observation is that the engagement time for both the clutch and AC fan is reduced and the intervals where they engage are much less frequent.

I can also feel a noticeable performance gain which i think is because the intake air is not getting super heated as before. The amout of heat that comes out of those vents is just scary, i can't imagine all that was kept under the poor hood.

the only down side is that i have to put a rubber mat under the hood while washing the car to protect the TPS and other electrics, water did get in at the 1st wash.
 
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