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Fender Vents, General aero Questions


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#21 Nelsonian

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Posted 25 November 2012 - 08:44 PM

OK, not sure how to link photos now that the site has changed...
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#22 roger280zx

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Posted 26 November 2012 - 03:44 PM

The firewall is also structural. Its much easier to brace a fender (bracing off of firewall or off of lower part of fender) to compensate for holes drilled, than it is to brace a firewall.

#23 Nelsonian

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Posted 26 November 2012 - 07:09 PM

Yeah I was thinking it would just be easier to go the route of the lower fenders with the necessary strengthening added. I must be a complete simpleton as I have yet to figure out how to link photos now.
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#24 JMortensen

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Posted 26 November 2012 - 08:19 PM

...I have yet to figure out how to link photos now.

Me too. Don't think it's working as of right now. You can link to photos stored elsewhere, but can't add them as attachments here anyway.

Edited by JMortensen, 26 November 2012 - 08:19 PM.

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#25 Sideways

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Posted 27 November 2012 - 03:04 AM

Id suggest using photo bucket if you dont already have an account with them, super easy to use and its free.

#26 Mikelly

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Posted 24 May 2013 - 02:12 AM

I'd gotten these scoops from John Washington when he was making them in CF and had planned to use them on the fenders, so I finally installed them.  I chose to go lower for the extraction point.

 

922858_645066602176434_276221131_n_zps61

img_7349_zps18641221.jpg


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#27 JMortensen

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Posted 24 May 2013 - 08:09 AM

Those vents are meant to be used in smooth airflow. You'd do better taking them off, as they essentially cover 90% of the hole, which is positioned in a low pressure turbulent flow area, as you can see in the 27th test of the last wind tunnel outing.


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#28 Mikelly

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Posted 26 May 2013 - 04:36 PM

All I can tell you is that flowing air with my large shop fan and yarn on the openings showed a BUNCH of air moving thru those openings.

Mike

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#29 JMortensen

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Posted 26 May 2013 - 04:56 PM

Is your point that you can test airflow with a shop fan in your garage, or that those vents work, or that it would work as well as an open vent, or that the area behind the wheel isn't a turbulent low pressure area of the car? We can prove that it is a turbulent low pressure area by using the photos from the last test. Since we know what the flow looks like there, we can make some assumptions about what kind of vent to put there. FWIW, I wouldn't put a NACA there either. 

 

http://i51.photobuck...el/PICT0288.jpg

http://i51.photobuck...el/PICT0570.jpg

http://i51.photobuck...entsUntaped.jpg

 

 

This spot needs a big open hole to let the air out. Here is a good example:

 

http://www.google.co...Q9QEwAQ&dur=356


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#30 Mikelly

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Posted 26 May 2013 - 05:51 PM

My point was that the vents went where the airflow showed they would work based on the data I had and what I could mimic in my own shop. I will be happy to test these in the wind tunnel and prove your point for you, but they are on the car now and wont be coming off until I have a better solution to cover the now rather LARGE holes in the fenders. My eventual goal is to replace the fenders with fiberglass versions, so I wasnt concerned cutting them up. That said, I placed them where I saw the need in my shop with my crude testing.

My goal was to help out the fenders by removing the trapped air in those sections behind the doors since I dont have fender liners currently.
Mike


Edited by Mikelly, 27 May 2013 - 04:32 AM.

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#31 260DET

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Posted 20 June 2013 - 11:22 PM

This setup didn't work. Huge aero understeer at speed - almost drove off the track on the second lap. A splitter needs to be no more then 2" off the ground if you want it to work as a splitter. You can alway angle the splitter down and just have it work as a spoiler.

btw410paddock1.jpg

(The car looks like its about 6" off the ground but there's a jack under the car behind the door)

 

Coming from a long way back but, as I have now worked out through experience, a splitter should be just part of an aero package which at the front must include an undertray, at least. And if you have an undertray on a S30 then, if it  all is working properly, engine bay vents will be essential for both cooling and aero purposes.


Edited by 260DET, 20 June 2013 - 11:23 PM.


#32 JMortensen

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Posted 21 June 2013 - 02:54 PM

How far back did you run your undertray? Lots of racing classes limit it to the axle centerline.


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#33 duragg

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Posted 06 July 2013 - 06:42 AM

This setup didn't work. Huge aero understeer at speed - almost drove off the track on the second lap. A splitter needs to be no more then 2" off the ground if you want it to work as a splitter. You can alway angle the splitter down and just have it work as a spoiler. btw410paddock1.jpg(The car looks like its about 6" off the ground but there's a jack under the car behind the door)


John,
Which part didn't work?
Was that frontal plain airdam a problem
or the splitter?

The fascia looks just like what the Miata guys do and I was going to try.

------------------------------------------------------------------------------------------------------------------------
1973 S30 (Gutted & caged NASA ST3) 2252lbs (dry & vacant) / VQ35HR/ 4.375 CLSD R200 / GC-Koni doubles / 275 R7s / Safety is a priority.


#34 Tony D

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Posted 07 July 2013 - 01:46 AM

At Bonneville we call that 'the snowplow'! The big opening effectively lets the air the spoiler up front dams up go straight into the hood, and then  pressurize the underhood and lift the car up (adds to understeer.) 

 

It may work better with about a 4" slot and the entire front covered with the 4" slot properly ducted to the radiator...

 

The key is getting air out from under the hood once it's in there. One way is to limit the amount entering, another is to duct the underhood area to low pressure to let that air out.

 

It's in the aero testing about taping up the front end.

 

Actually, http://forums.hybrid...ir-money/page-2

 

Go to post 35 about the comments, it's encapsulated there pretty well, and references the test runs in the original aero data tests so you can refer to it.


Edited by Tony D, 07 July 2013 - 02:00 AM.

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#35 Mikelly

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Posted 07 July 2013 - 03:22 AM

Over the last several weekend events my hood has become looser and looser at the pins.  We will have to adjust the pins, and probably re-mount the rear pins lower since I'm out of thread to adjust down further.  We will likely have to extend the spoiler lower to try and remove as much of the clearance ot the ground as possible.  I think our hood vents will work properly, but as with any piece that is constantly take off the car, constant attention ot fit is mandatory.

 

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#36 duragg

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Posted 07 July 2013 - 05:35 AM

Thx TD, good links set me on course again.

Its funny how little time I spend on Aero for my Aeroplanes versus my car. I guess the planes are closer to begin with.
Controlling air through our air-cooled motors is key. Looking at the TINY 1.75" annular duct around the spinner on a 4000hp Unlimited like Rare Bear with 3,350 cubes and max-performing each molecule even to the point of trying to gain thrust from its newly acquired heat while exiting the cowl.

So, answer to my question seems to be: its what happens AFTER the airdam (which is kinda funny in a "Ya, N/S" way).

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#37 Tony D

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Posted 07 July 2013 - 05:48 AM

I remember helping construct some Honda CVCC Powered Pushers back in the mid 70's that used (get this) 1974 Chevrolet Impala Harrison Air Conditioning Evaporators in the wings as radiators! 

I was in the 7th grade, and the way it was explained was the speed vs the density of the exchanger allows the evaporators to cool the engine just fine at speed. the holes in the wings were DINKY compared to the size of the cores, and of course a duct opened up to let the air through the core. Same as your 'what happens after the air dam' comment. Small opening to control inlet air, and get efficient flow through the exchanger, then blocking the rest as best you can.

 

I always wanted to use smaller, thicker radiator on a Bonneville Car with minimal opening but Class Rules make it prohibitive. And for a street car, unless you are making a Vegas Runner dedicated to live about 80mph all the time.... I doubt it would be practical on a street car. Though we can dream, right?


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#38 duragg

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Posted 07 July 2013 - 10:15 AM

What about venting through upper firewall into (now empty) cowl area?

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#39 Tony D

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Posted 08 July 2013 - 03:37 AM

Cowl Area is high pressure, not low pressure.

 

Now, using stovepipes through the interior and out where the plate used to go....


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#40 socorob

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Posted 08 July 2013 - 01:36 PM

Did any of you see how the new Ferrari F12 vented thru the fenders on top gear last night?


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