Bartman Posted October 2, 2008 Author Share Posted October 2, 2008 So I'd really like to understand how this cowl area venting works and how the air is delivered to the stock HVAC blower. I currently have my cowl panel removed and I'm not seeing how the air flows though and gets where it needs to go. The only openings I found are the ones for the drains. Quote Link to comment Share on other sites More sharing options...
Guest 280ZForce Posted October 2, 2008 Share Posted October 2, 2008 All the air for the heater, defroster, and the AC unit come through the cowl vents. Is there a diagram or drawing, anything that shows how the cowl area supplies the air for all those? I was picking my brain and looking at my Z (which is a 78, and also looking at Bartman's last night, which is a 73 to confirm between early and late models) and they are setup the same and I don't see how it supplies air for anything. I don't see a reason the vents in the cowl are needed, but correct me if I'm wrong. Not saying you're wrong, but would be a nice piece of learning knowledge for all of us here on Hybrid if we knew how the air flow through the cowl works. I was trying to figure it out, but all I see is 2 holes inside the cowl area and they are water drain holes that dump out behind the fender. The rest is all solid inside there. The air that is supplied for the a/c, heater, defroster, etc enters from the front of the engine bay area right behind the core support and then travels through a chassis tunnel along the upper inner fender and then out under the dash. Quote Link to comment Share on other sites More sharing options...
johnc Posted October 2, 2008 Share Posted October 2, 2008 Man, you guys need to get more curious. Lie on your back on the passenger floorboard and look up at the bottom of the cowl. There is an opening in the bottom of the cowl under the metal shield in picture 2 above. Its under the lettering in the picture that says: "Passenger side water drain hole (dumps out to the inner fender area)." In picture 3 above you can see some of the sealer around the hole on the bottom of the cowl just above the lettering: "Cowl drain tube (dumps out behind fender)." When you pulled the heater/fan box out of the car, didn't you notice the opening on top that sealed to the bottom of the cowl? Quote Link to comment Share on other sites More sharing options...
Guest 280ZForce Posted October 2, 2008 Share Posted October 2, 2008 Man, you guys need to get more curious. Lie on your back on the passenger floorboard and look up at the bottom of the cowl. There is an opening in the bottom of the cowl under the metal shield in picture 2 above. Its under the lettering in the picture that says: "Passenger side water drain hole (dumps out to the inner fender area)." In picture 3 above you can see some of the sealer around the hole on the bottom of the cowl just above the lettering: "Cowl drain tube (dumps out behind fender)." When you pulled the heater/fan box out of the car, didn't you notice the opening on top that sealed to the bottom of the cowl? haha that makes sense... but how well does that air get pulled into the cowl to that boxed up area? The vent in there is all boxed up almost from every angle, it's very crammed. The vent goes straight up and dead ends into the cowl structure (metal shield area), the vent is a box shape that rises to about 1" or less from the underneath the metal shield and looks to be surrounded by more shield everywhere around it. I understand the raised, mostly enclosed box is to keep water from getting inside of it, but the area and position it's in really makes it seem hard for air to really flow nicely into it, it's not like it can be ducted into the box either, cuz of the water issue. Yes. air can get in there eventually, but aerodynamically it seems like a very crapatastic way from my point of view. Am I missing something here as well? I would think the frontal core support vent areas are more efficient as they are ram induced air and a straight shot through their fender tunnels and seem like the more important vents by far. Either way, I haven't had an a/c or heater setup in my Z for probably close to 3 years now so the vents in the cowl are not needed in my case. Quote Link to comment Share on other sites More sharing options...
Bartman Posted October 2, 2008 Author Share Posted October 2, 2008 ... When you pulled the heater/fan box out of the car, didn't you notice the opening on top that sealed to the bottom of the cowl? No I don't remember seeing that opening when I removed my stock blower, but now I know I should block that opening off. It looks like a smooth cowl will work just fine for my application. Quote Link to comment Share on other sites More sharing options...
johnc Posted October 2, 2008 Share Posted October 2, 2008 Yes. air can get in there eventually, but aerodynamically it seems like a very crapatastic way from my point of view. Am I missing something here as well? Yes. Airflow is based on pressure differential not how smooth the flow path is. You can have the smoothest flowing air intake in the world but nothing will flow through it unless there's a difference in pressure. The cowl area in front of the windshield is a high pressure area, one of the highest pressure areas on the outside of the car. The car's cabin is a low pressure area in comparison (windows up or down). There is a large amount of air flow between the cowl and the heater/fan box at speeds from about 10 mph on up - more then enough to do heating, defrosting, and cooling. Its a very effective and time proven solution to getting cabin air for the HVAC system and its used on 90% of the production cars build today. Quote Link to comment Share on other sites More sharing options...
Guest 280ZForce Posted October 2, 2008 Share Posted October 2, 2008 awesome, good to know info for those wanting this cowl panel but still have their a/c and heater stuff. then again, this is a carbon fiber "race part," a/c, defrost, and heater are usually not present on race cars, let alone race z cars so the cowl vents are not usually needed unless it was a street car with these features still hooked up. Quote Link to comment Share on other sites More sharing options...
johnc Posted October 2, 2008 Share Posted October 2, 2008 defrost, and heater are usually not present on race cars, Depends on the rules. All ITS racing 240Zs have the heater and fan installed. I kept the fan in my old race car because defrost and a fan are a really good things to have when racing in the rain and sitting in grid baking in the sun. Quote Link to comment Share on other sites More sharing options...
Guest 280ZForce Posted October 2, 2008 Share Posted October 2, 2008 Depends on the rules. All ITS racing 240Zs have the heater and fan installed. I kept the fan in my old race car because defrost and a fan are a really good things to have when racing in the rain and sitting in grid baking in the sun. Good to know, glad this was all clarified. I'm going to talk to my carbon fiber/fiberglass guy some more on how difficult or easy it'd be to still incorporate the vents on the cowl panel when making a mold for it. Quote Link to comment Share on other sites More sharing options...
sickboy Posted October 5, 2008 Share Posted October 5, 2008 I put in a bid for $280 and got it. No heater in my car so don't need the vents. Hopefully it matches my CF hood somewhat. I'll let you know how the quality is. Quote Link to comment Share on other sites More sharing options...
BurnoutZ Posted October 6, 2008 Share Posted October 6, 2008 Hmm, I posted a topic similar to this months ago but didnt get many replies. So if the cowl vents are covered, Will you get no air? very little? Moderate? Quote Link to comment Share on other sites More sharing options...
Guest 280ZForce Posted October 6, 2008 Share Posted October 6, 2008 Hmm, I posted a topic similar to this months ago but didnt get many replies. So if the cowl vents are covered, Will you get no air? very little? Moderate? thanks to johnc for pointing this out, but if you're running an a/c, heater and/or defroster you'll definitely want vents in the cowl as the air that enters the cowl is a crucial and major part of any air that enters into the cabin for those sources. Tomorrow I'll be going over details with my shop on getting a mold made to allow vents to stay in the panel with production and at a more affordable price. Quote Link to comment Share on other sites More sharing options...
Sparky Posted October 6, 2008 Share Posted October 6, 2008 Justin, Will you be looking at producing both panels or just the vented piece? Quote Link to comment Share on other sites More sharing options...
BurnoutZ Posted October 6, 2008 Share Posted October 6, 2008 thanks to johnc for pointing this out, but if you're running an a/c, heater and/or defroster you'll definitely want vents in the cowl as the air that enters the cowl is a crucial and major part of any air that enters into the cabin for those sources. Tomorrow I'll be going over details with my shop on getting a mold made to allow vents to stay in the panel with production and at a more affordable price. So you will get no air if the vents are covered? Quote Link to comment Share on other sites More sharing options...
ZXT_bean Posted October 6, 2008 Share Posted October 6, 2008 Good to know, glad this was all clarified. I'm going to talk to my carbon fiber/fiberglass guy some more on how difficult or easy it'd be to still incorporate the vents on the cowl panel when making a mold for it. any interest in making one for the 280zx? Quote Link to comment Share on other sites More sharing options...
sickboy Posted October 22, 2008 Share Posted October 22, 2008 Here it is, took a little bit of dremel work on the tabs to fit up. It's a nice piece IMO, no ripples, gaps are even. CF matches my hood perfectly (pattern and angle). Quote Link to comment Share on other sites More sharing options...
TrumpetRhapsody Posted October 22, 2008 Share Posted October 22, 2008 Next stop, CF inspection lids Quote Link to comment Share on other sites More sharing options...
janaka Posted October 22, 2008 Share Posted October 22, 2008 very nice! Quote Link to comment Share on other sites More sharing options...
sickboy Posted October 22, 2008 Share Posted October 22, 2008 Next stop, CF inspection lids Funny you mentioned that, they said they are working on lids right now. They also plan on producing a cf hatch. Don't know any prices yet. Quote Link to comment Share on other sites More sharing options...
Tony D Posted October 23, 2008 Share Posted October 23, 2008 Go take a look at the F-Series Trucks from a while back...they have a very nice perforated grille to let air in instead of punched slats. Very sanitary and smooth looking. With a drill press, some backup wood, a nice grid pattern to lay it out...I don't see any reason why someone couldn't get creative and even 'punch' in designs using holes of different diameter for shading/etc on a solid piece and get plenty of air into the cabin for ventilation. Who says they have to be in a straight line, either...sketch some arcs that conform to the windshield or cowl... Or hell, even drill a "Rising Sun" pattern of fine holes radiating outward on the cowling... The pressure is all over the front of the lower windshield area...even making long thin slots with a 'rotozip' tool would accomplish venting adequate to let air in there and be relatively inconspicious. C'mon guys, I didn't even think about these ideas, they just popped into my head. Why be stuck on the way they were done 40 years ago? You're starting with a blank plate...you're free to do whatever you wish! For that matter, all you guys with louvres on the inspection covers should be clamoring for one with closed center area and matching louvres outboard... Those ideas just keep rolling in as you think about it. Cogitation...try it some time! LOL Quote Link to comment Share on other sites More sharing options...
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