gretchen/jason Posted October 21, 2006 Share Posted October 21, 2006 I figured id post a new post as now i have another question about getting rid of heat under the hood . Ive tried a few things i actuall got a chin pan and it made things worse so its gone then i swaped to my electric fan so far so good 180 t stat and only 185 on a 27 degree morning .On a 50 deree day about 190 degree temp readings . Wanted to ask about my cowl induction scoop well i taped a string to the edge of it and turned on the fan it blew the string towards the windshield so i am guessing thats ok . Then i drove at different speeds from oh 35-70 mph and it still blew the string towards the windshield the only time it sucks the string inward is when i turn the fan off so i assume im venting the heat ok . Does all this sound ok like i said at the moment so far so good . Jason Quote Link to comment Share on other sites More sharing options...
MikeJTR Posted October 22, 2006 Share Posted October 22, 2006 I figured id post a new post as now i have another question about getting rid of heat under the hood ... Wanted to ask about my cowl induction scoop well i taped a string to the edge of it and turned on the fan it blew the string towards the windshield so i am guessing thats ok . Then i drove at different speeds from oh 35-70 mph and it still blew the string towards the windshield the only time it sucks the string inward is when i turn the fan off so i assume im venting the heat ok . Does all this sound ok like i said at the moment so far so good . Jason The fact that the string blows back into the engine compartment when the fan is turned off indicates the cowl induction hood is the problem. When moving at speeds over 40 mph, the ram air should blow enough air through the radiator, that the eletric fan is not necessary at speeds over 40 mph. Also, based on other statements you made with the previous fan, it makes me wonder if you had wired the fan backwards. Quote Link to comment Share on other sites More sharing options...
thehelix112 Posted October 22, 2006 Share Posted October 22, 2006 A cowl `induction' bonnet is called that because air flows IN to the engine bay via it. This occurs because the cowl entrace is right at the high static pressure zone created by the windscreen. A cowl induction bonnet will do exactly nothing to benefit engine bay temperatures. You want vents that are placed at the point on the bonnet where the airflow is fastest (lowest static pressure). I imagine this is potentially just rearwards of where the bulge starts. Dave Quote Link to comment Share on other sites More sharing options...
gretchen/jason Posted October 22, 2006 Author Share Posted October 22, 2006 The previous fan was a clutch fan it did the same thing it throws the air through the opening and over the windshield . As far as the cowl goes id assume i need to drill or add holes about the aera where the stock hood vents would be ? Id hate to cut my hood apart but if that is what it takes i guess i need to do so ouch . Would it do the same thing if i had louvered inspection lids ? Id hate to put holes in my hood then have the same problem i do now Quote Link to comment Share on other sites More sharing options...
Guest Mike Posted October 22, 2006 Share Posted October 22, 2006 I wonder if they make affordable air pressure sensors that can be mounted in several parts of the engine bay so one could accurately determine what's happening in there at speed. This would provide the data needed to determine precisely how and where inlet and outlet venting should be placed. Quote Link to comment Share on other sites More sharing options...
Sumo Posted October 22, 2006 Share Posted October 22, 2006 Why don't you try taking off the inspection lids and see what happens when you drive the car. Quote Link to comment Share on other sites More sharing options...
Guest Mike Posted October 22, 2006 Share Posted October 22, 2006 That's worth a try. If it helps, he can try adding vented lids. Why don't you try taking off the inspection lids and see what happens when you drive the car. Quote Link to comment Share on other sites More sharing options...
gretchen/jason Posted October 22, 2006 Author Share Posted October 22, 2006 Ill give it a shot and see what happens . Ive even thought of getting a small video recorder and putting it under the hood someplace and ataching strings in certain aeras and see which way they sway problem with that no room for a camera sigh Quote Link to comment Share on other sites More sharing options...
Guest Mike Posted October 22, 2006 Share Posted October 22, 2006 Here's a link to some vented lids... http://www.classiczcars.com/classifieds/showproduct.php?product=1304&cat=fav Quote Link to comment Share on other sites More sharing options...
JMortensen Posted October 22, 2006 Share Posted October 22, 2006 If you turn the fan on at freeway speeds then you have the fan moving whatever it can move, let's just say 1800 cfm. With the fan OFF, then the hood is moving whatever amount of air it can move INTO the engine compartment. Let's say that that is 1500 cfm (pulling that # straight out of my ass BTW I have no idea what the right number is). So apparently with the fan on the amount of pressure from the fan is greater than the amount of pressure from the cowl hood, so the air still comes out the hole. Don't kid yourself and think that the cowl hood is now helping to cool the car off. It is still providing lots of resistance to the air coming out of the hood, and that pressure keeps that air coming out from moving as fast as it otherwise would. So the fan is fighting the cowl all the time, and with the fan off the airflow through the radiator alone is not enough to let air pass out of the hood. If you had vents in a low pressure area of the hood the air wouldn't just be able to come out of the hood, it would be SUCKED out of the hood. When you turn the fan on with a low pressure vent, it would make the vent less efficient at removing all the pressure under the hood, like draining the sink with the water on higher, in a sense. Whether or not the hood vents could drain that additional pressure is a tough question. But without any vent in the hood at all, the air goes to the back of the engine compartment and then gets forced into the tranny tunnel and/or underneath the car, so presumably, you'd still have this happening with low pressure vents if they just couldn't evacuate all the air. I am guessing, but I think that your cowl hood/fan combo has still slowed the airflow underneath the car (which is why you are having cooling issues) when compared to a good vent design, and has probably increased the amount of pressure under the hood itself at speed when compared to a good vent design. Quote Link to comment Share on other sites More sharing options...
mom'sZ Posted October 22, 2006 Share Posted October 22, 2006 A cowl `induction' bonnet is called that because air flows IN to the engine bay via it. This occurs because the cowl entrace is right at the high static pressure zone created by the windscreen. I agree One of the most common applications of this type of scoop (from the factory) is the Chevy Chevelle. I believe they sealed the intake to it. hey... just for grins why don't you duct tape off the opening and go for a drive. Quote Link to comment Share on other sites More sharing options...
Guest Mike Posted October 22, 2006 Share Posted October 22, 2006 mom'sZ is right. Most, if not all, of the factory cowl induction setups were sealed off from the engine compartment. After all, the idea is to bring fresh cold air directly into the carb(s). You should follow that principal and seal it to the hood somehow. Otherwise it's just for looks rather for function. Have you tried removing the inspection lids yet? Does this help? Quote Link to comment Share on other sites More sharing options...
PapaCreech Posted October 22, 2006 Share Posted October 22, 2006 hmm i cowled mine but have the cowl moved out about 5inches from the window aways from static zone b/c after i upgraded my ignition system and headers bla bla bla i was having heating issues. I put the cowl on then in the way it hsould have been close to the window, no good. Sold that cowl to some mustang kids and bought a smaller sitck on AVS single hood scoop. Turned it around backwards, moved out away from static zone. Then made sheet metal scoops under the engine bay(risky but effective) to push air up around headers and block and out through the now *sucking* cowl(i try tostay off rocky roads and or large potholes os water and speedbumbs dotn want to chance throwing something up in there that would be bad ) . Works fairly well was heating to over 200+ every drive now i run 180 to 190 on nice hot georgia days just me 2 pennies on it! Quote Link to comment Share on other sites More sharing options...
Guest Mike Posted October 22, 2006 Share Posted October 22, 2006 PapaCreech... Aren't you concerned about the air getting hot before it reaches the carb(s). A cowl induction system is intended to bring COLD air into the carb(s), right? Your scheme will probably help keep the engine bay cooler but then it's function is no longer for cowl induction, rather a cooling vent for the engine bay. I'm no expert by ANY means but this seems correct to me. Quote Link to comment Share on other sites More sharing options...
gretchen/jason Posted October 22, 2006 Author Share Posted October 22, 2006 I did try to tape off te cowl opening no diference there so i left the tape in place and then took the inspection lids off no difference there either . So i removed the tape left the lids off and nothing happend . It is strange as ive always dealt with cars that overheat when standing still at a light or something but mine is the opposite if i drive 40 mph for 10 miles non stop it hits oh about 190 with a 180 stat now if i sit at a light or my case my driveway i can let it idle for a hour and it will never go over 175 !!! Ive yet to get the t stat to work properly as watter always flows past the stat no matter how i seal it . This may be my issue . I ordered a new stat and neck from chevy then i put a bit of good silicone in the grove where the stat sits then on the gasket itself i torqued the neck down let it dry for 24 hours filled it up and bang the watter flows past the stat once again . besides what someone mentioned cutting fins off the pump impellar is there another way to slow the watter down . im still working on getting close to stock vents back in place but untill then maybe i need to slow the watter down to keep it in the rad longer . Quote Link to comment Share on other sites More sharing options...
gretchen/jason Posted October 22, 2006 Author Share Posted October 22, 2006 Scoops under the ride huh befor or after the front cross member ? from frame to frame ? not sure how it would act with snow on the ground but a pic would be good as my engine never ever went over 195 with the hood removed maybe the under car scoops can force the air out the cowl even more as it blows it out somewhat decent now ill try anything twice Quote Link to comment Share on other sites More sharing options...
Sumo Posted October 23, 2006 Share Posted October 23, 2006 Can you take pics of the cars engine compartment, underneath hood up, hood down. Maybe we can spot a problem you haven't seen or get a better idea, another set of eyes doesn't hurt. Quote Link to comment Share on other sites More sharing options...
PapaCreech Posted October 23, 2006 Share Posted October 23, 2006 PapaCreech... Aren't you concerned about the air getting hot before it reaches the carb(s). A cowl induction system is intended to bring COLD air into the carb(s), right? Your scheme will probably help keep the engine bay cooler but then it's function is no longer for cowl induction, rather a cooling vent for the engine bay. I'm no expert by ANY means but this seems correct to me. Fuel injected my friend Quote Link to comment Share on other sites More sharing options...
PapaCreech Posted October 23, 2006 Share Posted October 23, 2006 Scoops under the ride huh befor or after the front cross member ? from frame to frame ? not sure how it would act with snow on the ground but a pic would be good as my engine never ever went over 195 with the hood removed maybe the under car scoops can force the air out the cowl even more as it blows it out somewhat decent now ill try anything twice ill try to get some pics taken today tomorrow this weekend just got in from work, gonna have a busy week, but verbal explanation goes liek this. The scoop is about 4 1/2 inches wide and runs the bredth of the frame. The ending lip (which is aimed into the bay) is about 3 inches behind crossmember. so far no flapping issues have had it on for abotu 2 weeks now. I know it will blow the rain that falls infrotn of the cowl straight onto the window now, so its pushing lots more air then before. thanksFor the interest! Quote Link to comment Share on other sites More sharing options...
Guest Mike Posted October 23, 2006 Share Posted October 23, 2006 Oops... mea culpa. Still... isn't the cowl suppose to bringe cool air to the throttle body... or is yours intercooled? Fuel injected my friend Quote Link to comment Share on other sites More sharing options...
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