Front fender aero testing - Page 4 - Miata Turbo Forum - Boost cars, acquire cats.

Welcome to Miataturbo.net   Members
 


Race Prep Miata race-only chat.
Sponsored by:
Sponsored by:

Reply
 
 
 
LinkBack Thread Tools Search this Thread
Old 07-25-2014, 01:22 AM   #61
Elite Member
iTrader: (1)
 
Leafy's Avatar
 
Join Date: Jun 2012
Location: NH
Posts: 9,093
Total Cats: 90
Default

Quote:
Originally Posted by billybobster View Post
If I may threadjack back to brake ducts. I am about to mount my Trackspeed backing plates and have a question about the 2" run vs. 2.5" or 3". Would doing some of the run in 2" and the rest in bigger improve the flow at the rotor?

I'm trying to remember my fluid flow from my Mechanical Engineering degree. If it's not near sonic velocity it's a pressure drop per foot issue and not choke flow(?). So then the mixed run would help? Use an exhaust reducer for a fairly smooth transition. Of course in the real world this might be a mounting PITA.
Yes in theory running 2.5 all the way to the plate and transitioning down to 2" with a cone as close to the plate as possible should get you nearly all the flow of the 2.5" with an even higher velocity with the air being forced into the nozzle.
Leafy is offline   Reply With Quote
Old 07-25-2014, 01:24 AM   #62
Supporting Vendor
iTrader: (3)
 
Join Date: Jul 2006
Location: San Diego
Posts: 2,865
Total Cats: 492
Default

Quote:
Originally Posted by billybobster View Post
If I may threadjack back to brake ducts. I am about to mount my Trackspeed backing plates and have a question about the 2" run vs. 2.5" or 3". Would doing some of the run in 2" and the rest in bigger improve the flow at the rotor?

I'm trying to remember my fluid flow from my Mechanical Engineering degree. If it's not near sonic velocity it's a pressure drop per foot issue and not choke flow(?). So then the mixed run would help? Use an exhaust reducer for a fairly smooth transition. Of course in the real world this might be a mounting PITA.
If the transition is gradual and maintains laminar flow, you'll get an increase in velocity by a factor equal to the factor of reduction of the area of the hose. If I was trying to accomplish this I'd make a long transition piece out of a composite.

But, if you're choking it down quickly, like with a PVC pipe adapter or something similar, the turbulence created will likely cause more of an obstruction than just running 2" IMO.

-Ryan
ThePass is offline   Reply With Quote
Old 07-25-2014, 01:26 AM   #63
Elite Member
iTrader: (1)
 
Leafy's Avatar
 
Join Date: Jun 2012
Location: NH
Posts: 9,093
Total Cats: 90
Default

Quote:
Originally Posted by ThePass View Post
If the transition is gradual and maintains laminar flow, you'll get an increase in velocity by a factor equal to the factor of reduction of the area of the hose.

But, if you're choking it down quickly, like with a PVC pipe adapter or something similar, the turbulence created will likely cause more of an obstruction than just running 2" IMO.

-Ryan
Even choking it down, if you have a run of that crappy tubing longer than a foot or even have one bend in it there's going to be a significant difference in pressure drop between the 2 and 2.5.
Leafy is offline   Reply With Quote
Old 07-25-2014, 02:09 AM   #64
Elite Member
iTrader: (1)
 
cordycord's Avatar
 
Join Date: Dec 2011
Location: SoCal
Posts: 1,775
Total Cats: 148
Default CFD

Thought you guys might find this interesting. With the stock body configuration and windshield, the Catfish has the same Cd as a Miata with the top down. However, because of the flat bottom it also creates negative lift.

This has been discussed before, but aero work on race cars really depends on the class and what's allowed. Rules for everything from DTM to F1 determine all the funky stuff that gets added onto a race car, and not necessarily the most efficient method of doing so.

You probably don't want to hear my two cents about each piece of aero, but I do find it extremely interesting, especially the balance between wing and splitters.
Attached Thumbnails
Front fender aero testing-cfd.jpg   Front fender aero testing-cp_bottom.jpg   Front fender aero testing-cp_front.jpg   Front fender aero testing-modelforcfdstp21_mesh7nocellqualityrem_visu_speed.jpg   Front fender aero testing-sep_side.jpg  

cordycord is offline   Reply With Quote
Old 07-25-2014, 02:20 AM   #65
Supporting Vendor
iTrader: (3)
 
Join Date: Jul 2006
Location: San Diego
Posts: 2,865
Total Cats: 492
Default

Sexy flat bottom is sexy. ^
ThePass is offline   Reply With Quote
Old 07-25-2014, 02:33 AM   #66
Elite Member
iTrader: (1)
 
cordycord's Avatar
 
Join Date: Dec 2011
Location: SoCal
Posts: 1,775
Total Cats: 148
Default

Quote:
Originally Posted by ThePass View Post
Sexy flat bottom is sexy. ^
Sir Mix-a-lot likes his big and round, son.
cordycord is offline   Reply With Quote
Old 07-25-2014, 02:46 AM   #67
Supporting Vendor
iTrader: (3)
 
Join Date: Jul 2006
Location: San Diego
Posts: 2,865
Total Cats: 492
Default

I just re-read it

Last edited by ThePass; 07-25-2014 at 02:57 AM.
ThePass is offline   Reply With Quote
Old 07-25-2014, 08:11 AM   #68
Moderator
iTrader: (11)
 
sixshooter's Avatar
 
Join Date: Nov 2008
Location: Tampa, Florida
Posts: 15,679
Total Cats: 1,561
Default

Catfish has a windshield?
sixshooter is online now   Reply With Quote
Old 07-25-2014, 12:05 PM   #69
Elite Member
iTrader: (1)
 
cordycord's Avatar
 
Join Date: Dec 2011
Location: SoCal
Posts: 1,775
Total Cats: 148
Default

Quote:
Originally Posted by sixshooter View Post
Catfish has a windshield?
Building one now...
cordycord is offline   Reply With Quote
Old 07-25-2014, 12:48 PM   #70
Junior Member
 
Join Date: Nov 2009
Location: SF, CA
Posts: 49
Total Cats: 2
Default

Good input Leafy and ThePass.

The engineer in me wants to build a test bench to try various configurations of brake ducts.

The sane person in me finally spoke up and said put in the full 2" SCAT run and see what happens. If it stops my rotor cracking, great. If it doesn't or the cracking reappears as I (hopefully) get more pace, do something else then.
billybobster is offline   Reply With Quote
Old 07-25-2014, 01:10 PM   #71
Senior Member
iTrader: (1)
 
Join Date: Jun 2006
Location: Sweden
Posts: 1,391
Total Cats: 58
Default

Quote:
Originally Posted by billybobster View Post
Good input Leafy and ThePass.

The engineer in me wants to build a test bench to try various configurations of brake ducts.
Starting with the TSE duct, there is nothing preventing a 2.5" hose attachment, if you spend some time making the it. 2" fits all but even with ABS you can make something that will have more area and positioned more center than a round 2".
TSE made something that fit all and could be made at a decent cost.

As mentioned; airflow in the brake duct hose can be one parameter to measure if the pressure is to be lowered in the wheel well. The positive pressure in front can be seen as a constant.

I'm not sure if the airflow could be easier to measure than the absolute pressure difference. Measure whatever swings a cheap meter the most.
Anyone with a spare MAF (that of course can be killed by debris)?
or a Pitot tube attached to a differential manometer?

Last edited by NiklasFalk; 07-25-2014 at 01:21 PM.
NiklasFalk is offline   Reply With Quote
Old 07-25-2014, 06:32 PM   #72
Junior Member
 
Join Date: Mar 2011
Location: Melbourne, Australia
Posts: 152
Total Cats: 40
Default

BEAVIS is offline   Reply With Quote
Old 07-26-2014, 01:25 AM   #73
Senior Member
iTrader: (1)
 
Join Date: Dec 2008
Location: Manassas, Virginia
Posts: 1,247
Total Cats: 57
Default

So vent the fender on the top slightly ahead of the center of the hub with some louvers and remove some material from the behind the wheel starting at the bottom. That about what we've decided so far? Also, should the rear wheel wells be treated the same?
mx5autoxer is offline   Reply With Quote
Old 07-26-2014, 01:59 AM   #74
Senior Member
Thread Starter
iTrader: (1)
 
Join Date: Sep 2006
Posts: 738
Total Cats: 86
Default

Theorized, not decided!
Keith@FM is offline   Reply With Quote
Old 07-28-2014, 02:50 AM   #75
Supporting Vendor
iTrader: (3)
 
Join Date: Jul 2006
Location: San Diego
Posts: 2,865
Total Cats: 492
Default

Yup, no conclusions at this point.

I've done some pressure testing in my track car's fenders, but that car's airflow is too far removed from a 'typical' miata for data from that car to be relevant to much more than just itself.
I'm hoping to find some time to fully map inner/outer fender pressures of a much more stock NA that I have here soon.

-Ryan
ThePass is offline   Reply With Quote
Old 12-08-2016, 09:35 AM   #76
Junior Member
iTrader: (5)
 
Join Date: Oct 2014
Posts: 473
Total Cats: 23
Default

Not trying to necro post but this seemed like a great topic. I currently have my fenders spaced, this was more for wheel fitment rather than aero advantage since autocross car, but, I am in the process of making a front splitter and would like to cut my fenders to accompany. Have you all done anymore testing on the theories proposed here? I have used ThePass's car often as a reference for my build and wanted to mimic his fenders until I read that it requires two sets of fenders to achieve that result. Just not in the budget.
90civichhb is offline   Reply With Quote
Old 12-08-2016, 11:41 AM   #77
Senior Member
 
Join Date: Oct 2011
Location: Northridge, CA
Posts: 655
Total Cats: 282
Default

Not sure if you've seen it or not, but the vented fenders on Morpheus use one fender -







Filler panels can be done from FG to reduce cost -






Finished product -





Blackbird is offline   Reply With Quote
Old 12-08-2016, 02:51 PM   #78
Supporting Vendor
iTrader: (3)
 
Join Date: Jul 2006
Location: San Diego
Posts: 2,865
Total Cats: 492
Default

Welllll yeah, you used one set of fenders, but then you had to make a new rear section from scratch... it's a great execution and lighter weight but it's also the more complicated option of the two, not the simpler one. The point was you can't just cut up one set of fenders and be done - you've got to either scavenge a back section from a second pair of fenders OR you'd have to make new rear sections from scratch.

That said, plenty of guys HAVE done similar stuff with just one set of fenders that takes only simple cutting and no significant fabriction... they just don't have a rear section

ThePass is offline   Reply With Quote
Old 12-08-2016, 02:51 PM   #79
Supporting Vendor
iTrader: (3)
 
Join Date: Jul 2006
Location: San Diego
Posts: 2,865
Total Cats: 492
Default

On the fender venting subject in general, we have some cool stuff in the works. Nothing ready for public release yet.
ThePass is offline   Reply With Quote
Old 12-08-2016, 02:54 PM   #80
Senior Member
 
Join Date: Oct 2011
Location: Northridge, CA
Posts: 655
Total Cats: 282
Default

Well excuse me, Debbie downer
I was just giving the guy another option...

Got a call this morning asking if we're going to make the filler panels available, and it wasn't the first call I got about them.
If there's enough interest, I can make it happen.
Blackbird is offline   Reply With Quote
 
 
Reply

Related Topics
Thread Thread Starter Forum Replies Last Post
Project Gemini - Turbo Civic on the Cheap Full_Tilt_Boogie Build Threads 59 Yesterday 09:00 PM
1991 special edition with hard top full part out JC, NJ russian Miata parts for sale/trade 6 10-08-2015 04:01 PM


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



All times are GMT -4. The time now is 01:43 AM.