origionally posted by Shawndude:
Airflow basics:
1) If the car body is pushing air away from its rest position, that is a high pressure area (like the front of the hood, front bumper, windshield).
2) If the car body is pulling the air inwards (from rest position), that is a low pressure area (like the sloping rear window, rear bumper).
3) Air will flow only from high pressure, to low pressure area. How much it flows, depends on what the difference in pressures is.
Venting OUT the engine bay air.
1) The best location, as far as amount of air getting through, is a vent in the middle of the hood. See tests for details.
Air INTO the engine bay
The stock setup is fairly decent. Not much work needs to be done. The biggest difference however you can make, for the least effort, is to seal up the entire path of the air, so it cannot bypass any heat exchangers (radiator, intercooler, AC core, etc). The stock factory layout has many large holes, that need to be sealed. You can use neoprene self adhesive gasket material, as it withstands the high temperatures. Any air that passes around instead of through the heat exchangers, is cooling capacity that is lost.
Details matter
1) The factory engine undercover plastic shield makes a tremendous difference at all speeds, and even standing still. Without the engine undercover, there is 38% less volume of air flowing through the radiator at 60 mph. The test has been done without using cooling fans, to only see the difference the undercover is directly providing, so with the fans working, the difference will not be as dramatic for the radiator. However the improvement holds true for the intercooler.
2) The lower front lip on the spoiler is also very important. It keeps high pressure from building up under the car, reducing lift, and improving cooling by allowing the engine heat to exhaust into a lower pressure zone. I know they get damaged, and not many people have them anymore (including me), but it is worthwhile to get a replacement, for anyone who wants to improve cooling and aerodynamics.
Brake cooling
There really isn't anything you can do about the air exiting the brake rotors, apart from more open wheel design. We need to get more air INTO the rotors. Best way, is with a duct, running from the front grill. The duct should enter the center wheel hub, as to force the air equally throughout the INSIDE of the vented rotor. If you just duct it to one side of the rotor (like the stock little air scoop) chances are good you will warp your rotors.
How to read the tests results
All tests were done at 100 km/h, on the highway, with no traffic. Positive pressure point will have a '+' in front, negative location '-', so we know which way the air would flow (from positive to negative). All readings were very steady, unless stated otherwise. The higher the number, the more air would flow if there was a duct connecting the two locations. Cooling fan turned off for all tests (you guessed it, unless stated othewise ).
Results are in inches of water, of the totall differential pressure. This measurment is used since it makes differences easier to record. 1 PSI = 28 (rounded off) inches of water, or written as 28". For example, 1.0" = 0.035 PSI.
Hood outlet locations
All measurments are in relation to a high pressure reading at the front of the radiator. This point is lableled 'H'. All variables as in previous test description. The higher the number the more the flow, if we had a vent in that location.
Location of sensors (note that points drawn are NOT in exact position as tested, see details below for measurements):
Center of the hood measurements:
Test 1) 15" / +H - A = 1.1
So this test means, at 15" from the front edge of the hood (measuring point), the pressure difference between front of the radiator, and point 'A' is a combined reading of 1.1" of H20 (just like in previous test).
2) 20" / +H - B = 1.00
3) 25" / +H - C = 0.85
4) 30" / +H - D = 0.70
5) 36" / +H - E = 0.55
6) 44" / +H - F = 0.20
Side of the hood
These measurements were made, at 8.5" inches from the side edge of the hood (where it adjoins the fender). The same measuring baseline is used as above. Test done with headlights closed (in general, numbers improved with headlights open, but I didn't keep track).
7.) 25" / +H - G = 0.9
8.) 30" / +H - H = 0.8
(Sorry about the same use of the letter 'H'. The '- H' means the point on the hood, the '+ H' means the radiator pressure as before).
9) 36" / +H - I = 0.6
10) 44" / +H - J = 0.4
11) 48" / +H - K = 0.2
Details.
*The 'measuring baseline' is used as a reference to the test point location. It is measured in the center of the hood. The hood length maximum is 49.75", from front edge, to the rear edge (by the windshield):
* The radiator core, is located approximately 13" from the measuring baseline. Engine camshaft cover is approximately 20" from the baseline (I didn't write this down, may have to recheck it).
Side fender outlet locations
1) +H - L = 0.7
2) +H - M = 0.9
3) +H - N = 1.0
Airflow basics:
1) If the car body is pushing air away from its rest position, that is a high pressure area (like the front of the hood, front bumper, windshield).
2) If the car body is pulling the air inwards (from rest position), that is a low pressure area (like the sloping rear window, rear bumper).
3) Air will flow only from high pressure, to low pressure area. How much it flows, depends on what the difference in pressures is.
Venting OUT the engine bay air.
1) The best location, as far as amount of air getting through, is a vent in the middle of the hood. See tests for details.
Air INTO the engine bay
The stock setup is fairly decent. Not much work needs to be done. The biggest difference however you can make, for the least effort, is to seal up the entire path of the air, so it cannot bypass any heat exchangers (radiator, intercooler, AC core, etc). The stock factory layout has many large holes, that need to be sealed. You can use neoprene self adhesive gasket material, as it withstands the high temperatures. Any air that passes around instead of through the heat exchangers, is cooling capacity that is lost.
Details matter
1) The factory engine undercover plastic shield makes a tremendous difference at all speeds, and even standing still. Without the engine undercover, there is 38% less volume of air flowing through the radiator at 60 mph. The test has been done without using cooling fans, to only see the difference the undercover is directly providing, so with the fans working, the difference will not be as dramatic for the radiator. However the improvement holds true for the intercooler.
2) The lower front lip on the spoiler is also very important. It keeps high pressure from building up under the car, reducing lift, and improving cooling by allowing the engine heat to exhaust into a lower pressure zone. I know they get damaged, and not many people have them anymore (including me), but it is worthwhile to get a replacement, for anyone who wants to improve cooling and aerodynamics.
Brake cooling
There really isn't anything you can do about the air exiting the brake rotors, apart from more open wheel design. We need to get more air INTO the rotors. Best way, is with a duct, running from the front grill. The duct should enter the center wheel hub, as to force the air equally throughout the INSIDE of the vented rotor. If you just duct it to one side of the rotor (like the stock little air scoop) chances are good you will warp your rotors.
How to read the tests results
All tests were done at 100 km/h, on the highway, with no traffic. Positive pressure point will have a '+' in front, negative location '-', so we know which way the air would flow (from positive to negative). All readings were very steady, unless stated otherwise. The higher the number, the more air would flow if there was a duct connecting the two locations. Cooling fan turned off for all tests (you guessed it, unless stated othewise ).
Results are in inches of water, of the totall differential pressure. This measurment is used since it makes differences easier to record. 1 PSI = 28 (rounded off) inches of water, or written as 28". For example, 1.0" = 0.035 PSI.
Hood outlet locations
All measurments are in relation to a high pressure reading at the front of the radiator. This point is lableled 'H'. All variables as in previous test description. The higher the number the more the flow, if we had a vent in that location.
Location of sensors (note that points drawn are NOT in exact position as tested, see details below for measurements):
Center of the hood measurements:
Test 1) 15" / +H - A = 1.1
So this test means, at 15" from the front edge of the hood (measuring point), the pressure difference between front of the radiator, and point 'A' is a combined reading of 1.1" of H20 (just like in previous test).
2) 20" / +H - B = 1.00
3) 25" / +H - C = 0.85
4) 30" / +H - D = 0.70
5) 36" / +H - E = 0.55
6) 44" / +H - F = 0.20
Side of the hood
These measurements were made, at 8.5" inches from the side edge of the hood (where it adjoins the fender). The same measuring baseline is used as above. Test done with headlights closed (in general, numbers improved with headlights open, but I didn't keep track).
7.) 25" / +H - G = 0.9
8.) 30" / +H - H = 0.8
(Sorry about the same use of the letter 'H'. The '- H' means the point on the hood, the '+ H' means the radiator pressure as before).
9) 36" / +H - I = 0.6
10) 44" / +H - J = 0.4
11) 48" / +H - K = 0.2
Details.
*The 'measuring baseline' is used as a reference to the test point location. It is measured in the center of the hood. The hood length maximum is 49.75", from front edge, to the rear edge (by the windshield):
* The radiator core, is located approximately 13" from the measuring baseline. Engine camshaft cover is approximately 20" from the baseline (I didn't write this down, may have to recheck it).
Side fender outlet locations
1) +H - L = 0.7
2) +H - M = 0.9
3) +H - N = 1.0