That is my primary goal, enhanced cooling on the road course. Any aero benefits will be a bonus.
Right now I don't have a problem with coolant temps. Last outing with 95* and sunny day I was seeing a max of 210 coolant. However, I still see high oil temps and I'm hoping better hood venting will help everything all around.
Were those temps the Camaro and adding the Anvil vents? Do you have a hood with undercarriage or just the top layer only?
Here's a shot. It's an AMD aluminum hood, so it still has an under structure that we had to modify a bit.
Just curious, what are your oil temps? Maybe a thermostat that opens sooner, or more oil capacity could help the issue.
Sounds like a great couple of weekends with your car Chad, congrats on that. Love seeing you and others out there beating on their cars.
I've seen your friends motorhome in the background of several pics from events out there and lust over it every time. We are still looking at getting something very similar to that at some point. It's nice having a retreat like that in the paddock on a hot day, isn't it?
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Lance
1985 Monte Carlo SS Street Car
Chad,
Which vents are you looking at...track spec?
They are currently number 1 on my list, yes. I'm still debating adding them to my current painted steel hood or getting an aftermarket carbon fiber / fiberglass hood. The thing is, that with the aftermarket hoods that are under $1k they all have the same under structure so I don't really gain anything (airflow wise) going aftermarket unless the under structure is modified. Perhaps easier to do with fiberglass.
Quote:
Originally Posted by Matt.A
Here's a shot. It's an AMD aluminum hood, so it still has an under structure that we had to modify a bit.
(removed pic)
Just curious, what are your oil temps? Maybe a thermostat that opens sooner, or more oil capacity could help the issue.
Now that I've have been studying hoods closely I have to say that thing looks awesome! How did you block out the rear cowl induction area of the hood? I'm noticing that even if I block the normal opening for cowl induction in the hood that the hood under structure still leaves a large gap in that spot for air to be pushed into the engine compartment.
I have an improved racing adapter with built in thermostat. It begins opening at 180* and fully opens by 200*. Unlike what I have read and heard about other oil thermostats this thing works really well. No matter how cold out it is I haven't seen oil temps below 195 once everything is warm and heat soaked.
I consistently see over 250* oil temps on a 20 minute road course session. My current oil temp gauge only goes to 250* so I need a new gauge to see just how high it is getting. This motor heats the oil pretty badly compared to others which is why I chased oil pressure issues until adding an oil cooler.
I'm running a 10" x 13" oil cooler which is the biggest I could fit without modifying the core support to ditching a/c. This added about another quart to the system so total capacity is about 6.5-7 quarts.
Quote:
Originally Posted by SSLance
Sounds like a great couple of weekends with your car Chad, congrats on that. Love seeing you and others out there beating on their cars.
I've seen your friends motorhome in the background of several pics from events out there and lust over it every time. We are still looking at getting something very similar to that at some point. It's nice having a retreat like that in the paddock on a hot day, isn't it?
Thanks Lance! The motor home was pretty amazing! The A/C really made a difference given how hot it was and that the pits normally don't even have shade available. Also, he has a full fridge, freezer, and TV. It rocks.
So as I indicated with my teaser pic the other day I have gotten more interested in hood vents for the cooling and potential handling benefits. I searched extensively on here and pt.com for info and found a lot of people talking about "how" to do the testing but nobody actually sharing their results. I also searched a lot online and found some cool writeups by autospeed.com on tuft testing and pressure testing with a magnehilic gauge.
So I tackled this myself and am sharing the results with you guys. This is my attempt at comprehensive hood vent testing on a first gen Camaro cowl hood. Doubt my findings would change between a 68 and 69.
First. I did the wool tuft testing shown in this pic. The taped outlines correspond to the holes in the under-structure of the cowl hood.
Here is the video with speeds up to 70 mph.
Based on the wool tuft testing the pressure wave in the cowl area was not as big as I thought it would be. You can see the last row of tufts on the hood itself are starting to deflect. I also taped two extra tufts on the very edge of the cowl portion of the hood and predictably they plus any of the tufts taped to the cowl panel itself are being sucked right into the cowl opening on the hood which is exactly opposite of what you want to happen for cooling or handling performance on a road course.
You can also see that the raise hump on the cowl hood has the smoothest laminar airflow. Based on this test alone it was clear to me that the best location for a hood vent is the cowl hump immediately after the radiator. The problem is that an OEM styled cowl hood doesn't have much of an opening in this area in the under-structure of the hood. The taped outline of the opening in that area is about half in front of the radiator fan opening and half behind. So you can only use half that space which is a tiny area.
I was feeling inspired after reading the autospeed article on using a magnehelic gauge so I ordered one that measured between 0 and 1.0 inch of water.
In hindsight I should of gotten a gauge that went to 2" or more of water. I pegged the gauge in some of my tests. There are areas of the hood with what appears to be significantly greater than 1" of water pressure differential between under the hood and above the hood on a first gen Camaro cowl hood.
I did two types of tests. Test 1) the pressure difference between the top of the hood and the interior of the car with the windows cracked an 1" on either side. Test 2) The pressure difference between the top of the hood and directly opposite underneath the hood.
Here are the readings from test 1 (hood is lower pressure compared to cabin except for position 3).
Position 1.
Reading at 50mph - fluctuated .3 to .4 inches of water
Reading at 70mph - fluctuated .8 to 1+ inches of water. Average of 1.0" I haven't even started measuring underhood pressure differential and am already maxing the 1" gauge.
The little piece of tape sticking in from the left below the black tubing is where my radiator fan shroud ends.
Position 2.
Reading at 50mph - fluctuated .2 to .4 inches of water. Average 0.3"
Reading at 70mph - fluctuated .4 to .8 inches of water. Average 0.6"
Position 3 (pressures differential reversed and is now higher on hood than cabin).
Reading at 50mph - held fairly steady at .1" I wasn't that interested in this location so I didn't measure at 70mph.
Test 2 with tubing to both sides of the hood.
This is what it looks like in Position 2 (note the openings I've done a tape outline of on the top of the hood).
And the Test 2 measurements.
Position 1.
Reading at 50mph - fluctuated .6 to 1.0 inches of water. Average of 1.0"
Reading at 70mph - Pegged the guage. Didn't even wiggle. Because the gauge was pegged I compared to the underhood pressure to the cabin. The hood was fluctuating between 0.4 - 0.8 stayed mostly between 0.6 and 0.7. Adding the above hood pressure in test 1 to this test would be a differential of 1.6-1.7".
Position 2.
Reading at 50mph - fluctuated .4 to .6 with momentary spikes to .8 inches of water. Average of .5+"
Reading at 70mph - fluctuated .9 to 1+ inches of water. Average of 1.0"
The Magnehelic confirmed the instincts I had from the tuft testing. The center of the hood immediately behind the radiator fan shroud (Position 1) is the best place for a vent and significantly better than vents to the side of the cowl hump farther back. BUT this location benefits best from either cutting the understructure of the hood or a high dollar hood with no understructure. However, the side location (Position 2) would still provide excellent venting with 0.5" pressure differential at 50mph which is significant and requires no cutting of the understructure!
For random comparison I took the pressure readings from the front of the A/C condenser and back of the radiator with the car off and fan on (12v instead of 14v) and the radiator fan was pulling 0.36" of water.
Conclusion TL;DR
Position 1 is best but benefits from modified or no understructure.
Position 2 is a great alternative and doesn't require modifying the understructure.
Regardless of which position block off the cowl hood opening and get a super thick cowl to hood seal!
Remove 6" for cowl pressure and you have about 2016 square inches.
An average of 0.75 inches of water pressure differential over that surface.
You are looking at about 55 lbs of lift on just the hood. No wonder my hood latch failed with two track days with speeds of 150+ and 130+
If you are able to route a lot more air out the top of the hood rather than under the car then I'm guessing that can result in a downforce change of a lot more than 55 lbs. But that probably requires a lot larger hood vent opening a la one lap camaro.
good to see some pictures of the testing. and the reason i want a flat hood now that the carb is gone. cowl hood is really only good for a carb setup or if you need room in the bay. some like the looks also. looks like what chevy found when the did the areo for the 2014 camaros with the hood vent . http://mixmotor.eu/wp-content/upload...Camaro-016.jpg
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1970 El camino
1969 camaro
1996 civic
I would be curious about the pressure difference if you vented the side of the fender instead of the top of the hood...like a second gen Trans Am. Seems to me you would be pulling the air that is packing up against the fire wall.
Great work, by the way, thanks for taking the time!
Brian Hobaugh SCCA National Tour June 2014
First Hemi 'Cuda Convertible Ever Built
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