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More thoughts on new hood design.
https://slantsix.org/forum/viewtopic.php?t=41219		 Page 2 of 2
Author:  ryandcovalt [ Wed Jul 28, 2010 10:48 pm ]
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I'm not sure if you could make this particular design look nice on a Dart, but if you designed your own setup similar to this it might be an idea.
Image
When my BMW was backed into I bought a hood almost identical to this design with the fiberglass integrated louvers. I know for sure when sitting still the louvers let alot of heat out. I'm not sure how they act at high speed. If positioned properly the design makes me think the air would pass over them in a way that would actually help draw heat out. The louvers on this setup are basically individual plates mounted slightly overlapping. I would think it would be fairly simple to design your own more "muscle car era" looking louvers to reduce the temperature without forcing more air in. Especially after you locate the low and high pressure area's on the Dart's hood. As far as water goes my car is not garage kept and is driven by my wife year round, rain, snow etc. The way the louvers are designed no water enters when the car is moving, and I have not noticed water in the engine compartment even when sitting in the rain. Building your own fiberglass louvers would be time consuming, but would definitely be unique.
Author:  Sam Powell [ Thu Jul 29, 2010 6:13 am ]
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Thanks Ryan, That is a big help. Thanks for posting the photo. That picture will absolutely get the wheels turning upstairs. I like those Z cars very much. It was on my radar when I bought my '97 Miata. And like you, somebody backed into my car recently. It cracked the bumper cover which I have not bothered to fix yet. The culprit was my business partner. He just got in his car and backed up without looking. He got a lot of teasing about that one. He offered to pay for it, but you cannot even see the damage until you press on the bumper to reveal the seperation.

You say these vents were not on the stock hood? I wonder if you could design some kind of guttering under the vents. They did this on the K cars. I guess the need would depend on where the vents sat in relationship to things under the hood. I think you are right, I need to figure out where the high and low pressure areas are. Anyplace air flows over a surface, the air pressure us reduced. It guess it "piles up" in front of the windshield, and creates the high pressure area. With the low slope on modern windshields there might be very little high pressure areas if any. The Merc SLK might be all low pressure, or relatively so.

It looks like it would be fairly simple to fabricate a set of vents similar to those you picture there. With the sqaure lines of a Dart it would look fine if all corners were square. You could make it entirely out of stock structural aluminum shapes and sheet metal. And, I suppose I could do it on the existing glass hood. It would require some pretty extensive body work, which would likely make this a winter project.

Are the plates in the vent glued in, or fastened mechanically some how?

I am looking forward to meeting you and Rick on Saturday.

Sam
Author:  CARS [ Thu Jul 29, 2010 7:25 am ]
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I'm not sure about the turbo K-cars but my Turbo Coupe T-Bird has a intake that is suppose to allow air to pass over the intercooler. I am sure they made aftermarket hoods for T-birds, so maybe you can search for a Turbo hood to see what, if any improvements they did in the aftermarket.

I don't think my hood is guttered. I think the intercooler seals up against the hood and any water just flows through the intercooler and down along the engine to the ground.
Author:  ryandcovalt [ Thu Jul 29, 2010 8:49 am ]
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Sam,
The stock z3 hood has the side vents, but does not have the louvers on top of the hood like the one in the picture. My wife has the car today, or i would look and see exactly how the louvers are fastened. I know when I received the fiberglass hood the louvers we not installed, but the ends were pre drilled for small bolts (or screws) to fasten them to the hood. The louvers are about 1/2" thick so there was enough material for the bolts to go in horizontally. The raised area of the hood around the louvers create enough clearance to run the screws in horizontally from the underside of the hood. From the top you cant see the screws and the louvers are fairly sturdy. I would think a drain system would be do-able especially with the amount of space we have to work with on the darts. Like you said Sam, I think building the louvers out of aluminum would be better, and I think fit and finish would be better than my z3 hood. The concept for the z3 hood was good, but the fiberglass fit and finish was poor. I am really looking forward to meeting you saturday as well.
Author:  olafla [ Thu Jul 29, 2010 12:59 pm ]
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I read that when the F-body (Aspen/Volare) kit car was developed, the factory made a lot of measurements (anybody seen them?) to be certain about the best place for scoop. The pressure low on the windscreen was very high, and not very dependent on a change in wind direction, so the kit car had a rearward facing scoop for some free power thanks to higher pressure in the induction system. When I open a side window on my Aspen while the cold-air ventilation ducts are open, I have a real powerful airstrem from those vents, that indicate a high pressure zone around the air intake.
To release hot air while driving, louvers along the the only low pressure site - which is on the side of the body or at the back - will work. The pressure along the side of the body will depend on wind direction, for example as a result of the car going through a curve. If you need to evacuate hot air while the car is standing still, you could use temperature activated flaps in your hood scoops, if they face forward or backward in that situation should be irrelevant, but rearward facing scoops for forced induction while driving, and flaps that let you evacuate air through the same scoop when standing still may perhaps be a solution?
I don't recall if Saab or Volvo was the first factory that fitted their turbo cars with a lubrication system that pumped cooling oil through the turbo after the engine stopped, heat surge can be real bad!

Olaf
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