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Brainstorming Aero ideas for Windtunnel II

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Yeah, pull the trim off; reminiscent of Mike Kelly's fender vents. He has a relatively large hole in the fender, but then he put a cowl style vent on there and it covers over the huge hole leaving only much smaller, maybe 1x6 inch hole at the end of the vent. It will work, and so will yours, but if you think you still have pressure under the hood, utilizing more of the hole in the hood should help that pressure escape.


Your comment sounded like you couldn't find the test data: http://forums.hybridz.org/topic/55944-windtunnel-test-data/


You can see by the lift in the front end on the aero testing that there was a lot of pressure under the hood, but they didn't use any rad ducts on any of the cars, which should have a huge influence. I think a few cars had a plate from the valence to the core support, but nothing to prevent air from going around or over the core support.


In terms of where to exit rad air, there are problems with any solution. If you go out the sides, then your downforce gets disrupted by cars driving next to you. This is a key to NASCAR racing. If you have it come out the top of the hood, then you're feeding hot air to the wing if you have one. No perfect solution here. You really don't want it exiting out the bottom.


Yes, low pressure under the hood, or even lower than the pressure in the rad duct will draw air through the rad. Still needs to go somewhere though, and a dedicated exhaust that takes all the air coming through and sends it out the top or the sides will help to pull air through the rad but also keeps that air from filling up the area under the hood. Add in some louvered vents to pull more air out and you should really be able to get some low pressure under there.

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Exiting engine bay air, tricky one. Side exits do involve less drag compared with bonnet top vents which however do contribute to downforce by adding to the amount of air at the high pressure point at the bottom of the windscreen. One extra reason why more power is good, less concern about drag so in effect power can be converted to more grip.

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Not sure this is the best place to post this, but relevant to the topic of:  Whats the air doing.


Before:   Oil cooler sat alone about 2" in front of radiator which was fine for street driving.

But on a road course after 20M of 4000-8000 RPM things get different.



The idea was smooth airflow through OIl then Water radiator.  So I made a little dog-house duct from 1/8" ABS plastic and created a zone for the air to smoothly pass through Oil Cooler, then Radiator without a turbulent zone in between.



In the long run I would ditch this (brand new) Arizona Z-car radiator and get something real wide and short for Maximum ground clearance and to take advantage of the inlet area which is wider than tall.  One must give credit to modern cars which run all day long and never overheat... using dinky looking 1" thick radiators and relatively small inlets and outlets.  The major auto manufacturers have cooling solved and there are good lessons there I am sure.

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  • 4 months later...

Not sure what the next step in aero will be.

I know I need a wing and splitter though... all the cool kids have them on the track.


Here's a thread that may help, http://clubroadster.net/vb_forum/89-roadster-projects/44470-my-na-becomes-track-car-build-thread.html.  It details what this guy did to his miata (all simple DIY stuff) and how much his laptimes dropped from it.  When you finish you'll want to be a cool kid too :-)



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  • 3 weeks later...

I'm really curious to see your results. My latest Z project is more of a driver/weekend racer, but I would really like to do what I can to improve aero (without ruining the look/streetability of the car) and have been following all these threads.


I know there were a few people that had talked about doing something like 1vicissitude showed in his post (on the first page) where the air is entirely ducted through the radiator and out the hood, but I never really saw results. Did anyone go through with it? My car has a ton of room up front since I swapped to an SR, and I am looking to experiment with the space. Now that you have played with shaping ABS plastic, how do you think it would handle this duty? Do you think it would get too warm near the radiator/engine and deform or does it take pretty significant heat to lose it's shape?

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  • 3 months later...

I think a good idea would be kinda like civic something ;) said, but find the optimum vent locations through the hood area to create a pressure zone in front of the windshield to help lower the cd which is by far the biggest problem on the z.


Another thing would be a rear diffuser angle, although this might be application specific.


Since i know theres a thread and plans now i'll be brainthundering on it.

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