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WonkoTheSane (Forum Supporter)
WonkoTheSane (Forum Supporter) SuperDork
6/10/20 11:59 a.m.
jfryjfry (Forum Supporter) said:

I made some scoops for my brake ducts on my vette.  Not the same thing at all but figured it would help a lot. 
 

this is an old pic when I hadn't done much to the car but you can see the scoop in the former foglight hole
 

Those look great!  Luckily mine is still on the front, so there's probably less than 1/4” difference between inside and outside edges, so I'm not sure how much of a benefit it would be to add the outer scoop profile.

Keith Tanner
Keith Tanner MegaDork
6/28/20 9:49 p.m.

Only took a month! This thing is pretty sexy in person.

apexanimal
apexanimal New Reader
6/30/20 7:30 p.m.

2.5" outlet?

if so, where do i buy them?!

Keith Tanner
Keith Tanner MegaDork
6/30/20 9:53 p.m.

FM, soon. And yes, 2.5". 

I'm trying to think of a science fair experiment to do with it this week :)

WonkoTheSane (Forum Supporter)
WonkoTheSane (Forum Supporter) SuperDork
7/1/20 1:19 p.m.

Well that's pretty!

sleepyhead the buffalo
sleepyhead the buffalo Mod Squad
7/4/20 4:07 a.m.

I should probably note, that it's apexanimal's car on the first page that I posted a photo of

I look forward to seeing the science experiment, Keith

Marcus_NineLivesRacing
Marcus_NineLivesRacing New Reader
7/7/20 9:12 a.m.

Late to the party here.

 

I actually had this convo with a miata buddy the other day. My idea was to keep drag low on the front, so I have plans to route my brake ducts inlets in the mouth/inside the sturdy bois. Emilio had this method on one of his w2w cars years back with decent results iirc. The advantage is less harsh bends in the tubing to get to the brake shrouds. Something like a naca duct at a ~45* angle, like this: https://www.summitracing.com/parts/qcr-60-003 
 

Scott Robertson's GLTC car pictured earlier in the thread has been the tried and true method, though. My idea is my attempt at being cool, haha get it?! ............ I'll see myself out.

Keith Tanner
Keith Tanner MegaDork
7/7/20 1:59 p.m.

Science fair experiment on Facebook Live Thursday at 2 pm Mountain! Tune in live on the FM Facebook page.

If you have questions you want me to answer or things you want me to try, ask now.

WonkoTheSane (Forum Supporter)
WonkoTheSane (Forum Supporter) SuperDork
7/7/20 4:11 p.m.

Wow, cool science experiment!


I guess my first questions will be "what's the flow difference between that and the straight porthole," of course.  Followed quickly by "what's the difference between perfectly perpendicular to forced air (i.e., pointing straight forward on the car) and then 5, 10, 15 degrees off axis?"

WonkoTheSane (Forum Supporter)
WonkoTheSane (Forum Supporter) SuperDork
7/7/20 4:13 p.m.
Marcus_NineLivesRacing said:

Late to the party here.

 

I actually had this convo with a miata buddy the other day. My idea was to keep drag low on the front, so I have plans to route my brake ducts inlets in the mouth/inside the sturdy bois. Emilio had this method on one of his w2w cars years back with decent results iirc. The advantage is less harsh bends in the tubing to get to the brake shrouds. Something like a naca duct at a ~45* angle, like this: https://www.summitracing.com/parts/qcr-60-003 
 

Scott Robertson's GLTC car pictured earlier in the thread has been the tried and true method, though. My idea is my attempt at being cool, haha get it?! ............ I'll see myself out.

I had actually thought about using NACA ducts on the bottom of my splitter as a dual purpose "generate a low pressure area/feed the brakes" thing, but I didn't want to hinder getting the splitter off quickly an I was worried about packaging.. But I was going to use that exact NACA duct.  Maybe I'll revisit it? :)

apexanimal
apexanimal New Reader
7/7/20 4:48 p.m.

we started off ducting from the rad ducting, but more care and thought needs to be put into that placement.

you'll want it far forward in the ducting before the size really starts openting up, and you'll want some sort of a scoop around the sides and rear of the duct opening to help actively funnel the air into the duct work. 

we've found it was easier to mess up than to do it well... 

 

dangit keith just sell me a set already!! you and your science ;)

Keith Tanner
Keith Tanner MegaDork
7/7/20 5:38 p.m.

It took me a month to get the one I'm playing with, you think I can get it into the FM catalog that fast? ;) 

The Skyline uses NACA ducts on the bottom to cool the diff, IIRC. I don't remember the generation number, it's the one before it came to the US. Also, various Lotuseses do the same. In fact, you can get a nice little snap-in pre-formed duct from Lotus for under $10. There are two lengths, here's one of them: https://www.lotuspartsonline.com/p/Lotus_2005_Elise/NACA-DUCT/62882242/A116A0143F.html 

My Facebook thing is going to be titled "when experiments don't work". I can't get good data. But I'm having fun.

 

sleepyhead the buffalo
sleepyhead the buffalo Mod Squad
7/7/20 6:21 p.m.

In reply to Keith Tanner :

I'm not real sure what the test apparatus is... besides the bell housing, and the Miata intake meter.  Those are a MAP, and not a MAF, right?

off hand, I wonder if that sensor requires "fully developed flow" for accurate measurements.  Background Wiki on that... and of course, being at altitude, we can't assume '1976 standard sea level values' when calculating Reynolds number.  They maybe putting you way down towards the 'funny' part of the Reynolds numbers regime.

Keith Tanner
Keith Tanner MegaDork
7/7/20 6:55 p.m.

Spoiler alert for tomorrow :)

So that's a bilge blower in the box blowing inward. The Miata meter is an air flow meter, a big flappy door with a pot to measure the displacement. It's measuring actual airflow, which is good. But I wasn't seeing the difference between the bellmouth and a flush inlet.

I then turned it around so the bilge blower was evacuating air from the box. At the very least, this means the top isn't trying to blow off anymore and it's much easier to change inlets :)

 

Didn't help, which had me thinking the spring on the AFM was too tight because even a 116 hp 1.6 pulls a lot of air at WOT. I backed the spring off and even disabled it, but I couldn't measure small differences. 

So then I decided to get rid of the AFM and look at pressure differentials. Runs about 0.60 on the gauge with a certain amount of noise. I think the problem is my fan. Looking at this article, a mention is made of similar test rigs pulling 28 inches of water. In my experimentation, I'm pulling more like 0.60. That must be it. I'm simply not moving enough air through for the inlet design to make a difference. Maybe I should get Brandon to print up one with a 1" throat. I will experiment with a longer pipe as well to see what that does.

WonkoTheSane (Forum Supporter)
WonkoTheSane (Forum Supporter) SuperDork
7/7/20 11:19 p.m.

You may want to build a more sealed box (a large PVC pipe works well) and use a shop vac to pull vacuum.  That's how cylinder head ports are measured, not by forcing air through it...

Use the magnehelic gauge to determine pressure differential.  The greater the difference, the greater the flow, after that, it should be some easy math to figure out flow based on the cross sectional area. 

Otherwise, figure out how to have a certain volume of compressed air to force through that hole and then measure how long it takes to equalize pressure inside and out, but it's going to be a shiat-ton of air on something that size.  You probably are right that you want to shrink that down to 10 or 20% of your current size.  Rummaging around my shop, I'd probably use my yellow harbor freight air tank filled up to 50 PSI or something, and have a coupler on a PVC pipe that would allow me to thread on ends as needed for a straight flange vs the tapered one.

Keith Tanner
Keith Tanner MegaDork
7/7/20 11:31 p.m.

I did change to pulling a vacuum - that's the second and third setup I tried. Didn't think of a shop vac, though. That's a good suggestion.

The magnehelic gauge is 100% being used to determine pressure differential. That's what it does :) Problem is, with the size of that hole, there's no difference in the pressure differential with and without the bellmouth.

We're going to print a 50% scale unit. That's 1/4 the cross section. I'll have it tomorrow. Hopefully with the shop vac that'll move enough air that we'll start to see some effects.

Honsch
Honsch New Reader
7/8/20 1:58 a.m.
Keith Tanner
Keith Tanner MegaDork
7/8/20 8:59 a.m.

Yup. Linked to it above, referenced it in the test apparatus and I'm using that profile. 

Justjim75
Justjim75 Dork
7/8/20 11:21 a.m.

In reply to Keith Tanner :

I asked on page 1 about using my NB1 foglight holes but got no answer.  Do you know if that works at all for brake cooling?  I have empty holes and extra shop vac hose so I thought it was worth a shot.  Do fender vents help brake cooling or just reduce pressure?

Keith Tanner
Keith Tanner MegaDork
7/8/20 2:18 p.m.

It should work reasonably well. 

Fender vents help brake cooling by dropping pressure and thus increasing the airflow though the brake ducts. 

Justjim75
Justjim75 Dork
7/8/20 10:46 p.m.

In reply to Keith Tanner :

So doing both should yield results? I didnt say good results on purpose, for the investment if it does much at all I will be happy, I'm not chasing tenths or trying to make it X laps/events on a set of pads 

Keith Tanner
Keith Tanner MegaDork
7/8/20 10:49 p.m.

The ducts are the main thing, but the fender vents should make them work better. 

Justjim75
Justjim75 Dork
7/8/20 10:50 p.m.

In reply to Keith Tanner :

Thank you very much sir.  I'm excited to see the results of your experiment 

Keith Tanner
Keith Tanner MegaDork
7/9/20 1:53 p.m.


Scale is the key. We have a measurable effect. 

WonkoTheSane (Forum Supporter)
WonkoTheSane (Forum Supporter) SuperDork
7/9/20 2:37 p.m.

So you're just going to leave that there with no data? cheeky

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