Carbon fiber hood - 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 06-01-2012, 01:41 PM   #61
Supporting Vendor
iTrader: (31)
 
Savington's Avatar
 
Join Date: Nov 2006
Location: Sunnyvale, CA
Posts: 14,362
Total Cats: 1,323
Default

Quote:
Originally Posted by shanem View Post
do want the black car. does it have a build thread floating around here somewhere?
There are a couple of them, but nothing that's up to date. It's getting several big upgrades this year, and it should be ready to re-set several of the California lap records this fall.
Savington is offline   Reply With Quote
Old 06-01-2012, 01:48 PM   #62
Senior Member
iTrader: (4)
 
mr_hyde's Avatar
 
Join Date: Jul 2009
Location: Seattle
Posts: 799
Total Cats: 25
Default

Quote:
Originally Posted by jmann View Post
We need a wind tunnel.
I bought a manometer and hope to add some data to the theory later in the summer. That and tuff testing aren't as good as a wind tunnel but it's better than guesswork.
mr_hyde is offline   Reply With Quote
Old 06-01-2012, 02:03 PM   #63
Junior Member
Thread Starter
 
Join Date: May 2008
Location: Grants Pass, OR.
Posts: 449
Total Cats: 14
Default

Air flow as shown in those charts is going to change as holes are cut. Low and high pres. areas are going to change radically. Example is we all agree that the base of the windshield is a high pres. area, BUT that is with the hood sealed to the back of the eng. compartment. Remove the seal strip at the cowl and install hood risers http://www.miataroadster.com/miataro.../i-404640.aspx and I would suspect the air coming into the engine compartment by more then just the grille opening changes it to a lower pres area then the eng. compartment. Don't know for sure personally as I have never seen a wind tunnel result, but I do know that when we lived in Arkansas a few years back where the humidity is as high as the air temp., and believe me that is high, the spec miata guys are running hood risers for cooling purposes to let air flow through. It isn't probably as good as a vent located in the hood just behind the rad., but it still changes a high pres. area to a lower pres. area as the pres. from the eng. compartment is I suspect greater. Also back in the day of the rear facing cowl inducted hoods on the chevelles and other brands the intake was at the base of the windshield to take advantage of the high pres. area at the base of the windshield, BUT the hood was still sealed from the eng. comp. and the only hole in the hood for air was just a round opening over the air cleaner and it was sealed with foam weatherstripping so as not to let air pres. from under the hood effect the air flow in. Nascar uses the base of the winshield for air intake also but the snorkel on their air cleaner is sealed to the opening at the back of the hood and the hood sealed to the firewall.
As stated above Shanem's opening bottom looks to be at the transistion point of where the nose is vertical and the slope begins so there shouldn't be as much air deflection as if it was further up and even then if the opening was tall enough the air flow upward at the point of hitting the body would eventuallt turn flat as the forward air pres overtook it and deflected it into the opening, but as Bob stated a hood on the opening would catch even more. There are however other effects that would take place that you might not want if you are a serious timed track guy or racing in a class and that is decreasing down force. Nascar tapes up the upper grille opening in their noses for qualifying as they want the added down force and since thay are only out there for a couple laps aren't concerned with the lesser air flow for cooling. Also adding a hood over the opening would actually add up force if it was in the sloped area. So just going by what I have seen done for many years and what the spec guys were doing down south and not seeing a wind tunnel [which I would suspect they did as these were the national guys] result I would suspect opening the hood anywhere behind the rad and on back changes low and high pres areas greatly.So adding a relief vent behind the rad is very important to get the flow out and some areas are better then others but I think from what I have seen they all work.
jmann is offline   Reply With Quote
Old 06-01-2012, 02:10 PM   #64
Supporting Vendor
iTrader: (3)
 
emilio700's Avatar
 
Join Date: May 2005
Posts: 5,310
Total Cats: 1,333
Default

Quote:
Originally Posted by jmann View Post
Air flow over the car changes as air sources change. The base of the windshield is as high pres area as has been stated by us all, but open up the seal of the hood to the cowl with say hood risers http://www.miataroadster.com/miataro.../i-404640.aspx, and release the pres. under the hood which is being fed from the front of the car which I suspect changes the base of the winshield from a high pres area to a LOWER pres area then UNDER the hood is thus letting air flow through.
Up to about 15mph, yes. After about 15mph, I can unequivocally guarantee you that hood risers will force air from above the hood towards the underside of the hood. Doing so raises the pressure under the hood, thus reducing the differential on either side of the rad core ruining your day. Don't believe the rest of us that have tested it. Tuft test it and see.

It is all quite simple:
1. Force the air through the correct sized hole in the bumper skin to go through radiator core.

2. Eliminate all other intakes to engine bay except those directly ducted to cooling or engine intake. Full coverage front under tray is a huge benefit.

3.
Know where the Miata engine bay exhausts waste heat and help it. For the record, that's:
a) Around the trans and out the trans tunnel.
b) Properly located hood vent. For the record that's a V shaped area from between the cam gears /rad and angling back towards hood hinges.
c) Through the gap between the subframe and frame rail and out through the wheel opening. Note: Factory MSM is almost completely covered from oil pan to mid point of trans. This improves cooling.

4. Reroute

5. Properly sized radiator

Note that I listed radiator last. Some of our endurance cars use OEM replacement plastic Koyo's. The rest if the mods are so effective that even without a vented hood, we have trouble getting enough temp on <75° days.

This image shows the opening sufficient for a 170whp endurance racing engine in 110° ambient, with a mesh grill that has 81% open area. The net area is about 35% of core area. What is not seen in this picture is the formed and fully sealed duct direct to the rad core we later added. The plenum is made of ABS plastic and riveted together. Just a simple rectangular box with divergent walls. No I don't have pics of the plenum, sorry.

As Andrew mentioned, NASCAR feeds 800whp engines with an opening barely larger than this. I almost feel sorry for the Miata track guys I see that have the front of their cars all hacked up with drag and lift inducing holes, misplaced vents, no reroute and still complain of cooling issues. Argh.

Attached Thumbnails
Carbon fiber hood-4567d1335670726-nasa-buttonwillow-4-21-22-564885_351629258223972_302480113138887_960947_13865034.jpg  
emilio700 is offline   Reply With Quote
Old 06-01-2012, 02:12 PM   #65
Junior Member
Thread Starter
 
Join Date: May 2008
Location: Grants Pass, OR.
Posts: 449
Total Cats: 14
Default

Sorry for the double post, thought I had accidentally deleted the first one, my bad.
jmann is offline   Reply With Quote
Old 06-01-2012, 03:25 PM   #66
Junior Member
Thread Starter
 
Join Date: May 2008
Location: Grants Pass, OR.
Posts: 449
Total Cats: 14
Default

I would have thought the spec guys would have tufted or even wind tunneled this before they did it and why does Bill at miata roadster and others sell the risers? Guess I well have to put my stock hood back on and stack some washers and remove the cowl seal and tape some tufts on and see for myself.
jmann is offline   Reply With Quote
Old 06-01-2012, 03:35 PM   #67
Junior Member
iTrader: (1)
 
Join Date: Aug 2009
Posts: 48
Total Cats: 0
Default

Some cars are setup to take advantage of the air coming in through with a missing hood seal - typically they'd remove just a portion of it and have that area ducted for an intake. Others just have no idea and think it looks race inspired. Others use it to cool the car when they're hard parked. It does let heat escape from the engine bay when not moving. Drifters use it because they spend their time sideways and sitting in the grid.
SmokeSR is offline   Reply With Quote
Old 06-01-2012, 04:47 PM   #68
Moderator
iTrader: (11)
 
sixshooter's Avatar
 
Join Date: Nov 2008
Location: Tampa, Florida
Posts: 15,662
Total Cats: 1,560
Default

Hood risers would see air coming into the engine compartment from the base of the windshield and then exiting into the lower pressure area of the transmission tunnel. This would likely raise the pressure under the car reducing available downforce as well as reducing the deltaP between the front and rear of the radiator and other coolers. None of that is a good idea.

Many people performing a modification based upon faulty understanding does not increase the validity of the modification.
sixshooter is offline   Reply With Quote
Old 06-01-2012, 04:48 PM   #69
Elite Member
iTrader: (10)
 
rccote's Avatar
 
Join Date: Jan 2008
Location: Buffalo NY
Posts: 1,595
Total Cats: 17
Default

Quote:
Originally Posted by jmann View Post
I would have thought the spec guys would have tufted or even wind tunneled this before they did it and why does Bill at miata roadster and others sell the risers? Guess I well have to put my stock hood back on and stack some washers and remove the cowl seal and tape some tufts on and see for myself.
Quote:
Originally Posted by emilio700 View Post
Up to about 15mph, yes. After about 15mph, I can unequivocally guarantee you that hood risers will force air from above the hood towards the underside of the hood. Doing so raises the pressure under the hood, thus reducing the differential on either side of the rad core ruining your day. Don't believe the rest of us that have tested it. Tuft test it and see.
End of story. Sure, lower underhood temps are nice but you're essentially trying to aircool your water cooled engine. I'm still confused as to why people can't grasp this. Those vents on shanem's car are improperly designed, hood risers suck and don't work, and really consider taking the free R&D people like Sav and Emilio provide.
rccote is offline   Reply With Quote
Old 06-01-2012, 05:07 PM   #70
Junior Member
Thread Starter
 
Join Date: May 2008
Location: Grants Pass, OR.
Posts: 449
Total Cats: 14
Default

rccote to begin with that is not my hood, I bought a carbon fiber hood from chasers and the vents are up front right behind the rad. where the best spot is. If Shanem's hood opening is ducted to the rad. then he isn't just air cooling the motor as you put it. Go out and drive around and see how many cars have a lower and upper opening in front of the rad. and I'm sure some pretty smart engineers designed atleast some of those vehs. In fact there are some that have a opening in a very sloped section of the nose. I'm not saying anyone is wrong and anyone is right and I don't take anyones advise lightly. I just brought up some points as to what others are doing. Have you ever did a test for the air flow personally and would be interested to see some pics of the results. I plan on doing a tuft test myself to see the results.
jmann is offline   Reply With Quote
Old 06-01-2012, 05:45 PM   #71
Elite Member
iTrader: (10)
 
rccote's Avatar
 
Join Date: Jan 2008
Location: Buffalo NY
Posts: 1,595
Total Cats: 17
Default

Quote:
Originally Posted by jmann View Post
rccote to begin with that is not my hood, I bought a carbon fiber hood from chasers and the vents are up front right behind the rad. where the best spot is. If Shanem's hood opening is ducted to the rad. then he isn't just air cooling the motor as you put it. Go out and drive around and see how many cars have a lower and upper opening in front of the rad. and I'm sure some pretty smart engineers designed atleast some of those vehs. In fact there are some that have a opening in a very sloped section of the nose. I'm not saying anyone is wrong and anyone is right and I don't take anyones advise lightly. I just brought up some points as to what others are doing. Have you ever did a test for the air flow personally and would be interested to see some pics of the results. I plan on doing a tuft test myself to see the results.
I get what you're saying, but I'm just far more likely to trust the word of the people out there flogging the ---- out of their cars and finding real proven solutions. Also, I'm too lazy and don't see a benefit in reproducing an experiment that others who are far more capable than I have already performed and produced results. Point is the hood riser thing has been beaten to ----. Doesn't matter if the hood opening is properly ducted to the rad, if the pressure differential isn't right you're going to have insufficient flow through your heat exchangers. Jesus we stopped debating this hood riser garbage years ago I thought.
rccote is offline   Reply With Quote
Old 06-01-2012, 05:46 PM   #72
Elite Member
 
Join Date: Jul 2005
Location: Anacortes, WA
Posts: 2,476
Total Cats: 114
Default

Quote:
Originally Posted by sixshooter View Post
Hood risers would see air coming into the engine compartment from the base of the windshield and then exiting into the lower pressure area of the transmission tunnel. This would likely raise the pressure under the car reducing available downforce as well as reducing the deltaP between the front and rear of the radiator and other coolers. None of that is a good idea.

Many people performing a modification based upon faulty understanding does not increase the validity of the modification.
FWIW I have seen string tufts placed on the back edge of a Simpson cowl "INDUCTION" hood with the opening cut out the back. At approximately 20 mph the strings get sucked into the engine compartment.

Hood risers are a total poser Idea reserved for the hard parkers.

I dare anybody to drive 100 mph without there hood being latched or pinned. I did that by mistake with my Erebuni hood with a properly placed hood duct and the hood stayed shut. A hood with no opening would have flew up and smacked the windshield.

Single inlet needs to be at the stock location. It does not need to be any larger than stock for a track car even at 3 to 400 hp. Stock exit is at trans tunnel. Best place to increase air flow for cooling through you’re heat exchangers and reduce both drag and lift is to put an opening in the hood as far forward as reasonable where the pressure on the external surface is lowest.

Bob
bbundy is offline   Reply With Quote
Old 06-01-2012, 07:14 PM   #73
Elite Member
iTrader: (12)
 
GeneSplicer's Avatar
 
Join Date: Sep 2009
Location: Birmingham, AL
Posts: 2,006
Total Cats: 147
Default

Quote:
Originally Posted by emilio700 View Post
I almost feel sorry for the Miata track guys I see that have the front of their cars all hacked up with drag and lift inducing holes, misplaced vents, no reroute and still complain of cooling issues.[/IMG]
At least I don't complain of have cooling issues... if anything, too cold - so I'll complain about that - which on a serious note can be/is just as bad - was no fun driving with 90% of my radiator covered up so get proper temps on cold track days, but the churbo loved it.
GeneSplicer is offline   Reply With Quote
Old 06-01-2012, 08:01 PM   #74
MT Pony Underground
iTrader: (6)
 
Nagase's Avatar
 
Join Date: May 2009
Posts: 1,811
Total Cats: 0
Default

So reread this a few times... the best option for a CF vented hood is the Autokonexion without gills, right? (On the original topic)
Nagase is offline   Reply With Quote
Old 06-02-2012, 10:23 AM   #75
Moderator
iTrader: (11)
 
sixshooter's Avatar
 
Join Date: Nov 2008
Location: Tampa, Florida
Posts: 15,662
Total Cats: 1,560
Default

Quote:
Originally Posted by Handy Man View Post


The Miata has a windshield with less rake angle likely making the area at the rear of the hood an even more pronounced area of high pressure than represented in this pic. That makes it worse for hood risers.

It appears that one might see beneficial flow characteristics without cutting the hood if the trailing edge of the headlight doors were raised 3/4 inch or so.

The bumper cover on the Miata needs to be sealed to prevent lateral movement of air between it and the hollow ABS bumper underneath (as I have done). If you remove the turn signal, you can stick your fist in the open void above the rigid bumper and under the bumper cover's top edge. That opening and others like it allow air to easily exit the nose past the headlight into the engine compartment without going through the heat exchangers. That is for the benefit of those who have never opened that up and made modifications to seal it. It is at least twelve square inches of leakage on either side.
sixshooter is offline   Reply With Quote
Old 06-02-2012, 03:31 PM   #76
Senior Member
iTrader: (1)
 
Join Date: Nov 2010
Posts: 951
Total Cats: -252
Default

On the bottom side of a stock NA hood there are 3 circles. I think by cutting those out with a holesaw that they are in about the right location-about 15 inches from the front edge of the hood.
wannafbody is offline   Reply With Quote
Old 06-04-2012, 08:04 PM   #77
Junior Member
Thread Starter
 
Join Date: May 2008
Location: Grants Pass, OR.
Posts: 449
Total Cats: 14
Default

Lets try these hood photos again, Chaser hood, click to enlarge.
Attached Thumbnails
Carbon fiber hood-016_1200x900.jpg   Carbon fiber hood-014_1200x900.jpg   Carbon fiber hood-013_1200x900.jpg   Carbon fiber hood-012_1200x900.jpg  

Last edited by jmann; 06-05-2012 at 01:02 PM.
jmann is offline   Reply With Quote
Old 06-05-2012, 03:06 PM   #78
Junior Member
 
Join Date: Jun 2011
Location: Houston
Posts: 409
Total Cats: 17
Default

Emilio; I would do very dirty things to you in exchange for pictures of that ducting
Handy Man is offline   Reply With Quote
Old 06-05-2012, 07:35 PM   #79
Elite Member
 
Join Date: Jul 2005
Location: Anacortes, WA
Posts: 2,476
Total Cats: 114
Default

Quote:
Originally Posted by Handy Man View Post
Emilio; I would do very dirty things to you in exchange for pictures of that ducting
I saw crusher running a half width radiator. looked like a 3 row ebay civic radiator. car runs cool.

Bob
bbundy is offline   Reply With Quote
Old 06-06-2012, 03:18 AM   #80
Supporting Vendor
iTrader: (3)
 
emilio700's Avatar
 
Join Date: May 2005
Posts: 5,310
Total Cats: 1,333
Default

Quote:
Originally Posted by Handy Man View Post
Emilio; I would do very dirty things to you in exchange for pictures of that ducting
No revelations. Just a cobbed together plastic box that mates the bumper opening to the rad core.
emilio700 is offline   Reply With Quote
 
 
Reply

Related Topics
Thread Thread Starter Forum Replies Last Post
Raleigh: Fiberglass headlight scope, 1.6L ECU, AFM, Hardtop latches, more bigmackloud Miata parts for sale/trade 13 09-22-2017 01:34 PM
Project Gemini - Turbo Civic on the Cheap Full_Tilt_Boogie Build Threads 57 07-19-2017 05:11 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
Expected intake temps on the track? tazswing Race Prep 20 10-03-2015 12:04 PM
Are my coils failing? viriiguy General Miata Chat 5 09-28-2015 08:39 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 09:51 PM.