JMortensen Posted July 28, 2013 Share Posted July 28, 2013 I guess I'm not seeing why just cutting the far side panel out wouldn't allow the low pressure to better affect the area above the new rad duct. Quote Link to comment Share on other sites More sharing options...
heavy85 Posted July 28, 2013 Share Posted July 28, 2013 The cavity on the other side of the far panel is a stagnant area sealed off from everything. Im thinking you need to open that area up to a low pressure source otherwise how do you get any low pressure in there? Where is the low pressure coming from since its basically a sealed box? Quote Link to comment Share on other sites More sharing options...
JMortensen Posted July 28, 2013 Share Posted July 28, 2013 The low pressure is the rest of the engine compartment. Did you block off all of the holes in the rad core support? Quote Link to comment Share on other sites More sharing options...
heavy85 Posted July 28, 2013 Share Posted July 28, 2013 The low pressure is the rest of the engine compartment. Did you block off all of the holes in the rad core support? Yep all blocked off. You think there is actually tangible low pressure in the rest of the engine compartment? Quote Link to comment Share on other sites More sharing options...
Sideways Posted July 29, 2013 Share Posted July 29, 2013 (edited) Yep all blocked off. You think there is actually tangible low pressure in the rest of the engine compartment? Measure it! You can pick up a magnehelic gauge for 20-30 bucks all day off ebay. Removes all the guess work You want one that measure from 0 up to a couple inches (1-3, 1 will cover almost all the things youd want to test aerodynamically on a car it seems, but if you want to do other stuff or know youll be testing super high pressure areas- 3ish would be plenty it seems). Edit: Heck, you can just make your own device to measure presure differentials for about 10 bucks worth of parts. not as nice as a magnehelic gauge, but still very practical. Just a flat board, some clear tube, food coloring, water, and voila. Edited July 29, 2013 by Sideways Quote Link to comment Share on other sites More sharing options...
JMortensen Posted July 29, 2013 Share Posted July 29, 2013 Yep all blocked off. You think there is actually tangible low pressure in the rest of the engine compartment? That's what we're hoping for, and that's the point of the rad duct. You don't need a lot to make it work. http://www.circletrack.com/techarticles/ctrp_0707_stock_car_aero_downforce/photo_04.html Quote Link to comment Share on other sites More sharing options...
Globerunner513 Posted August 11, 2013 Share Posted August 11, 2013 Would venting air at the firewall into the cabin have any effect? I'm just shooting from the hip here. I'm guessing there isn't enough of a pressure differential to evacuate any air effectively. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted August 11, 2013 Share Posted August 11, 2013 Would venting air at the firewall into the cabin have any effect? I'm just shooting from the hip here. I'm guessing there isn't enough of a pressure differential to evacuate any air effectively. There is a reason they call it a "FIREwall". Quote Link to comment Share on other sites More sharing options...
Sideways Posted August 12, 2013 Share Posted August 12, 2013 (edited) Would venting air at the firewall into the cabin have any effect? I'm just shooting from the hip here. I'm guessing there isn't enough of a pressure differential to evacuate any air effectively. Are we venting air out of the cabin? Edited August 12, 2013 by Sideways Quote Link to comment Share on other sites More sharing options...
260DET Posted August 16, 2013 Share Posted August 16, 2013 Will have to post a pic of my bonnet vents some time, they are aero efficient as has been proven by trial and error and real time race track use in damn hot weather. Call me slack Quote Link to comment Share on other sites More sharing options...
heavy85 Posted November 6, 2013 Share Posted November 6, 2013 (edited) Test results at ~60 mph: I was a bit shocked at +0.75 " water I was equally shocked at -1" water Net 1.75" water of lift Edited November 6, 2013 by heavy85 Quote Link to comment Share on other sites More sharing options...
JMortensen Posted November 6, 2013 Share Posted November 6, 2013 (edited) So if I did my calculations right, that's .0632 psi lift for that part of the hood. Did you test the other side of the core support and hood? It shouldn't be the same everywhere, especially with your hood vents. Wonder where the pressure is coming from. Interesting stuff... Edited November 6, 2013 by JMortensen Quote Link to comment Share on other sites More sharing options...
rsicard Posted November 7, 2013 Share Posted November 7, 2013 Gentlemen: I did not mean to be "Backbiting" in my comments. If it came across that way please accept my apologies. VERY interested in testing results with a manometer, especially behind the front tires. Would like to open up the inner fender at the rear of the engine compartment (both sides) and mount a centrifugal fans to exhaust the air in the engine compartment. Would also like to fab a tunnel with small opening at grille to large one at the radiator to restrict the amount of air going through the radiator such that there is enough to cool the radiator adequately and then exhaust out the inner fenders. Also would be closing off all radiator support holes and seal above the radiator support to the hood so the only air getting in is from the tunnel forward opening. Comments Please. Quote Link to comment Share on other sites More sharing options...
heavy85 Posted November 7, 2013 Share Posted November 7, 2013 (edited) I only had time for a quick test but plan is to eventually measure all over. The pressure could be from the engine bay or possibly from the small gap between the hood and the front vertical filler plate? There is no seal as its just a close fit to the hood so mayby squeezing through there? Will tape it up tight and try again. The neg pressure above the hood is quite interesting I think - hood vent in front of the rad support anyone? Edited November 7, 2013 by heavy85 Quote Link to comment Share on other sites More sharing options...
JMortensen Posted November 7, 2013 Share Posted November 7, 2013 Seal it first and see what happens. I'd bet that you lose that pressure. Can't imagine where else could it be coming from. A vent right in front might still be something to mess with, but it may not be as useful right there because the flow is dirty. If you could seal the pressure out, you might find better results with another set of louvers lined up right in front of the ones you have now. Would take some testing. rsicard, I think Cameron has your duct to the rad (sans weather strip to seal air out), but no duct from the rad back out. I don't remember if we were talking about it here or in another thread, but if you duct the rad air out the wheel wells, then you have the issue of losing downforce when a car comes up close on the side. NASCARs do this and they use it as part of their strategy; drive up on the inside to make the outside car lose downforce and force them to slow in corners as the front grip goes away. The alternative is to duct it out the top, in which case you have hotter less dense air going over the top of the car and feeding the wing. Neither is a perfect solution, but since Cameron seems to be doing time trials and hillclimbs, maybe the side duct is the better choice... Quote Link to comment Share on other sites More sharing options...
tube80z Posted November 7, 2013 Share Posted November 7, 2013 The other option is similar to the WRC cars where they vent on top but have two vents close the side. A lot more work to fab but the air leaves and goes around the side of the car rather than over the top. Quote Link to comment Share on other sites More sharing options...
tube80z Posted November 7, 2013 Share Posted November 7, 2013 VERY interested in testing results with a manometer, especially behind the front tires. Would like to open up the inner fender at the rear of the engine compartment (both sides) and mount a centrifugal fans to exhaust the air in the engine compartment. Would also like to fab a tunnel with small opening at grille to large one at the radiator to restrict the amount of air going through the radiator such that there is enough to cool the radiator adequately and then exhaust out the inner fenders. Also would be closing off all radiator support holes and seal above the radiator support to the hood so the only air getting in is from the tunnel forward opening. Comments Please. I think if you open the rear of the fender so there isn't a captured area behind the tire you probably won't need any fans in the engine compartment. I have the strut area behind the strut open on my car and have been looking at possibly putting louvers in the hood over this area to help evacuate both the engine compartment and the wheel wells. It really comes down to how much area I have left after creating a radiator duct. XP rules limit this to a specific amount of square inches. For hillclimbs we have much looser rules and I can run larger louver panels. Keep up the good work, this is all really interesting and seems like there's some performance locked away we can get at. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted November 7, 2013 Share Posted November 7, 2013 The other option is similar to the WRC cars where they vent on top but have two vents close the side. A lot more work to fab but the air leaves and goes around the side of the car rather than over the top. It really comes down to how much area I have left after creating a radiator duct. XP rules limit this to a spceific amount of square inches. That is a damn good idea. I read your last post first, and was going to suggest that the exit doesn't need to be as large as the radiator. Those WRC cars have pretty small rad exhausts. The Ford ones from a couple years back that you and I talked about had to have been something like 2x12 on each side... Quote Link to comment Share on other sites More sharing options...
rsicard Posted November 8, 2013 Share Posted November 8, 2013 Seal it first and see what happens. I'd bet that you lose that pressure. Can't imagine where else could it be coming from. A vent right in front might still be something to mess with, but it may not be as useful right there because the flow is dirty. If you could seal the pressure out, you might find better results with another set of louvers lined up right in front of the ones you have now. Would take some testing. rsicard, I think Cameron has your duct to the rad (sans weather strip to seal air out), but no duct from the rad back out. I don't remember if we were talking about it here or in another thread, but if you duct the rad air out the wheel wells, then you have the issue of losing downforce when a car comes up close on the side. NASCARs do this and they use it as part of their strategy; drive up on the inside to make the outside car lose downforce and force them to slow in corners as the front grip goes away. The alternative is to duct it out the top, in which case you have hotter less dense air going over the top of the car and feeding the wing. Neither is a perfect solution, but since Cameron seems to be doing time trials and hillclimbs, maybe the side duct is the better choice... Jon: Really appreciate all the thinking and comments. Would like to NOT have to put in rear hoot vents or vents on top of the front fenders. Still really interested in manometer tests behind the front tires to see if it is a high pressure area which would force me to put centrifugal blower on the inner fender openings and extend the blower exhaust down underneath the car. Also thinking about extending a splitter aft at the bottom of an air dam such as to keep higher pressure air from going back into the engine compartment. The opening of the tunnel to the radiator needs to be enough to cool the radiator versus such a large original grille opening, large holes in core support and opening above core support with respect to hood. Still need to consider ram air openings for engine air intake and brake cooling ducts. Quote Link to comment Share on other sites More sharing options...
heavy85 Posted November 9, 2013 Share Posted November 9, 2013 (edited) rsicard - many years ago I used to travel to Tucson about once a month. Now maybe once every other year. Unfortunately it's a long ways from Illinois. This may get addictive. So sealed up the gaps to the hood and retested. Went from +0.75 down to +0.5 " so it was a contributor but not the main one. Then I moved it here and got +0.8" so confirmed its coming from the engine bay. Move the top side to here and got +0.5" (note I later rotated it 90 deg so it wasnt into the airflow but didnt take another pic - either way the result didnt change) Then finally here and got +0.5" as well Interesting that 0.5" seems to be the popular choice. I'm holding the gauge on the steering wheel so this is all referenced to the center of the steering wheel with the windows down. Not sure what all this means yet. There's a thousand areas to test it's going to be hard to focus with limited time. Edited November 9, 2013 by heavy85 Quote Link to comment Share on other sites More sharing options...
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