The name of the game is 'keeping them as close to the front as possible', as there is where the low pressure zone resides. The further back you go, the more you risk them becoming inlets, not outlets.

 

Looking down at the engine compartment (pictured below) if I put the vents at the very front edge of the hood they'll just be over the top of the radiator and cooler. I'm going under the assumption that Singular's placement a bit further back is good because it's right over the gap between the radiator and the front of the engine. If I place the top two vents above and slightly further to the side of the two lower side vents then I think they'd be somewhere in the vicinity of the wastegate actuator/turbo on the driver's side, and over the front of the intake manifold on the passenger's side - both of which seem like perfectly good places to put vents both from a heat and pressure grid perspective.

Engine Compartment

 

Ok, step back and look at the air path from the mouth. It should be (is?) ALL going through the radiator, right? So, any/all air in the engine bay is hot air. It will flow high pressure ---> low pressure. Open any panel to lower pressure than that in the engine bay, and it becomes an exit opening, the lower the pressure (higher the pressure differential between the engine bay and the outside air) the more it will flow. Even if (counter intuitively) it has to flow forward. In short, if the air can flow over the radiator, it will. If that is the area where the pressure differential is greatest, it will flow there. The provisos are that there is sufficient gap above the radiator to allow the air to flow, and that there is no air entering that space from the radiator mouth. My memory of the pressure maps over the bonnet is that the lowest pressure is at or near the font of the bonnet, so the further forward you can place the outlet the better it will work.

Whether that is a good idea depends on how willing you are to cut up your bonnet, and how much cutting you can do without totally wrecking the structural rigidity of the bonnet. The Singular vents (and all others) are necessarily a compromise, but if you think that will work with your car, go for it. OTOH, if you can improve on that location, and give yourself more cooling headroom, that is an option to be considered.

Note, if you look at the air path, and it is not all going through the radiator, fix that before you do anything else.

I am currently weighing these issues as I approach cutting up my spare bonnet. I have both RGR and Singular vents, and am considering doing some custom vents instead. Efficiency and structural compromises are front and centre of my mind as I weigh where to cut and how much. For radiated heat from the turbo impacting the bonnet/brakes/etc heat shields will be the primary protection - the vents are to maximise the air flowing through the radiator, given the oil cooler mounted behind it, and the a/c condenser in front.

 

The very front of the hood is essentially an extension of the nose (still acting as frontal area for aero puposes). The lowest pressure areas recorded were just behind the radiator and just behind the headlights.

 

Thanks Six, that clarifies the optimum positioning. Are you aware of any NB equivalent work, or was it transferred across to the new shape? Maybe I need to start exploring the search function ...

 

Spent entirely too much time yesterday trying to overlay images of various hood vent template ideas over the picture of my engine compartment. I really should get decent image processing software but I use it so infrequently. *Sigh* Thanks to the excellent information above and my own research I'm still leaning towards the Singular route - three vents across the gap between the radiator and the front of the engine, and two smaller vents above and slightly more outboard. I'll have to be careful with the driver's side upper vent to not end up on top of the intake - depressurizing that spot seems completely counterproductive. I'll probably try to put it over the turbo/wastegate actuator since I need more headroom there for the actuator anyway. I'll mirror the other top vent's placement because of course I would.

The local muffler shop was able to squeeze in both Vibrant bottle resonators mentioned previously - it no longer sounds like I have a grumpy baby elephant loudly complaining every time I bring the RPMs up. It's still too loud to hear, say, navigation prompts from my phone, but it's as good as it's going to get at this point I reckon.

Managed to squeeze in time to rebuild the hardtop latch locks with a set I picked up off of ebay:

Lock, Stock, and Four Smokin' Latches
That should Significantly Decrease the amount of Panter's tape required to keep the hardtop latches from popping open. >.>

UPS also brought A Thing in the mail yesterday:

A Thing!
My winnings from a recent 9lives scratch-n-dent auction. It's only 48" across and the mounts are waaaay too narrow for my needs but it was cheap (for a 9lives wing) and I can make it work with enough blood, sweat, and general misery. Happily I don't have to worry about it for a while because I need to get the splitter built first. I've been reading like mad and amassing splitter parts for weeks now. The splitter is getting closer to the top of the punchlist, actually. Oh, here's some photographic evidence of splitter parts. A bracket that weighs nearly four pounds. Oof.

Phat Bracket
"But John," One might ask, "What could be more important than a splitter?"
"Oho!" I would (and am, apparently) reply(ing), "I live in the Heretofore Universally Recognized but Never Openly Acknowledged Tenth Circle of Hell Known as the Phoenix Metropolitan Area! And my track car doesn't have an Air Conditioner!"
Yes, I've been Macgyvering up a CoolShirt system.
Well, sort of.
I had it all planned out - was tracking down a latching ice chest, proper voltage submersible pump, already had the hoses, non-leak connectors, etc, etc...I even found The Perfect Shirt, courtesy of my local Wal-Mart:

THIS IS A PERFECT COOLSHIRT CANDIDATE
...and then I found one of the medical-grade coolshirt coolers on ebay for cheap.
...and then I finally tracked down a good picture of a real coolshirt and discovered they have four separate cooling loops. Not one or two or three but FOUR. Do you know how many wye connectors I'd need to munge together four cooling loops? Or I'd have to engineer a manifold, or pay a zillion dollars to buy something premade...heck with it. I returned all of the parts (except for the connectors - I'm still making hoses) and bought a coolshirt on closeout. It was cheaper to do it that way than to buy the individual parts to make one myself. >.<

Super-Duper-Mambo-Jumbo-Omega-Sized CoolShirt because it was CHEAP.
Sharp-eyed-readers will note it is rather substantial in size. I am only kinda substantial in size. It was, however, cheap. I put a light shirt on over it and tried it out in the car - works fine. Between the UltraShield seat, the 5-point-harness, and the normal shirt holding everything together it's all cozy and cool. And cheap. Did I mention it was cheap?


Hose Construction
Here's the hose I made before I discovered it was cheaper to buy a coolshirt on closeout than to buy the individual components. I can still get use out of the hose though. Official ones are crazy-expensive.

AND FINALLY...

Differential Break-In Complete!!!
The Miata is over at the Local Mechanic's getting the rear differential oil replaced because Praise-The-Lord-And-Pass-The-Ammunition, I am Finally Done with the break-in period. Driving it around overcrowded Phoenix streets to get 500 sub-50mph miles in for the past few weeks has sucked. I'm considerably better at keeping it from stalling as I work the on/off lightswitch disguised as a clutch, because this car is a red-light magnet. I swear there's a jealous traffic engineer hidden in the nether recesses of some dark government basement who has been using traffic cameras to watch me drive around and saying, "Nice Car, Man, Eat THIS!" as he flips switches and makes every light in the surrounding square mile turn red, Red, RED.

 

Picked up the car yesterday after work - it was...interesting. I don't really like interesting, but that's what it was.
Whatever break-in oil the differential shop used was...interesting. They must know what they're doing, but it was weird silvery-grey stuff. The shop saved some in a bottle just to show me:

Diff Break-In Juice

The shop also discovered two interesting additions to the break-in oil when they felt around inside the differential while changing the oil:

WASSUPWIDDAT?
The Hot Wheels car is included for scale - no, the car wasn't in the differential. The two metal bits, now...those were rattling around in the differential. The shop checked the play in the differential and it seems perfectly normal - they think this is probably some escapee chunks of one of the original bearings that hid beneath a lip during the rebuild at the differential shop. I'll have a chat with the differential people next week.

I also had them go through the alignment since the car has been sitting for so long. This was the best they could manage:

Let's not look at the front Caster, 'kay?
They basically said, "Go buy some adjustable lower control arms so we can actually set this thing up the way you want - then we'll talk."
I'll start researching those next, but I'm always open to suggestions from the Hive Mind as you know.
They very nicely didn't even charge for taking a stab at the alignment, which is nice because now the steering wheel doesn't line up precisely any more either. New, adjustable lower control arms just entered the Punchlist near the top. >.<

The car drove decently on the way home at least.

Spent a chunk of time last night sorting the CoolShirt system in the car - I fabricated some tiedowns that attach using the passenger's seat rail bolts and did a complete garbage wire routing from the cigarette lighter to a DC converter so I could power the pump. As mentioned previously it's an old surplus medical unit so it has a plug for a wall outlet. At some point in the future I will probably change out the pump for a 12v bilge pump and simplify things considerably, but this will work for now.
Of course I completely forgot to take pictures, but here's the spot where the CoolShirt system goes:

Everything but the CoolShirt system itself

Tomorrow I pick up a rental trailer and then it's off to Chuckwalla for the weekend. Normally I'd just drive the car but since this is the first time I've been on track with it, and since it's the first time I've driven Chuckwalla, and since it would be a 200+ mile Uber ride home if things go south, I'm taking the conservative route and trailering the Miata this time.
At least I was able to learn the track virtually in Assetto Corsa - that one blind, off camber whatever-you-call-it corner would NOT be fun to discover the hard way...

 

Somethings fucked up on the FL, you shouldn't be able to get down to 2.5* of caster. Either your brake didn't stay set during the alignment, you have a bent arm, or some/all of your bushings are worn out. At this point, any NA rubber is next to useless unless it's a bone stock car driven only occasionally, which yours appears to be a bit past. If stock rubber bushings are still there, replace them. Replace all the eccentrics while you're in there.

They either didn't know how to adjust caster, or they don't know miatas, or both. There's no adjustable control arm that's going to fix your caster as far as I'm aware.

 

It's Sean's old car, so there's a bunch of delrin in there - the car has been sitting for years though - not sure what that would do to the soft-ish bits. I'm reasonably certain the shop doesn't know miatas that well - they're a general-car-repair shop, but all of the miata guys are on the opposite end of town (Tempe/Mesa) which makes for logistical nightmares.

 

Chuckwalla Pits
At Chuckwalla this weekend with the group I drive with. First time on the track with the Miata, and first time at Chuckwalla! I definitely don't plan on setting any land speed records. If I make it through with better knowledge of the car and track and without anyone hitting me then it's a Win in my book.

 

First time on the track with the Miata, and first time at Chuckwalla. Kept it shiny side up and got my lap times down from 2:41 to 2:17 over the course of two days. Oh, and no one hit me. Success!

Chuckwalla Turn 2


Chuckwalla Turn 9


Chuckwalla Turn 9 too

The car handled great, and the low amount of boost with the current tune was rock solid and more than enough to help keep up with, well, one of the NA miatas with a student driver. >.>

Miata Chase
The headrest peeking out from behind the driver's helmet in the green miata makes it look like he's got Popeye forearms and has his left elbow up above his head. He doesn't, and he doesn't. It kinda looks like he's changing radio stations too. All this while logging considerably better times than me (for the first day at least.)

I had some challenges loading the car on the rental trailer before heading to the track and ended up having to take the exhaust tip off before the ramp tore it off. When I got the car unloaded at the track I looked at the exhaust and said, "Eh, it's close enough to the edge of the bumper to be Ok."
Nope.

Crispy Bumper
After a few sessions I noticed some smoke coming from the back bumper. It was a bit more discolored and crispy than it had originally been. Back on went the exhaust tip. Problem solved.

Here is a video of my fastest lap of the weekend. Clearly I have a lot of room for improvement, but for a first track weekend with the car I'm pretty happy. The beer cooler in the passenger seat area was handy, but hard to get into with the tiedowns. Incidentally the car is going back to the shop tomorrow so they can do a better job of straightening the steering wheel after they tried aligning the car last week.


Near the end of the weekend I decided to try Sean's "All of it" alternate tune table. (Hey, I had a trailer for the car, right?)

The car had noticeably more power...until it started smoking. Happily when I got the hood open I could see it had just blown the dipstick out and was spraying oil into the engine compartment. Ok, that's not exactly ideal but at least it was obvious, easily caught, didn't start a fire, etc. I remember Sean had this exact issue back when he first put the new rings in and it finally went away when the rings fully seated. Obviously that's not going to happen on it's own at this point, so it's back to lower boost. If this is really being caused by blow-by, though, I wonder if there are other options. Hmmm...

 

Nice work, good seeing this thing on track already!

I doubt it's the rings, and more likely, your valve cover breathing. For example I had to open mine wayyy up, I was filling catch cans and puking oil out of just about everywhere until I addressed that.

 

I decided to drive the Miata to class tonight to see if anything else was out of sorts before taking it to the shop tomorrow - good thing I did!

Vent Puking Oil

The dipstick is staying in, but the vent on the driver's side valve cover is puking oil all over, well, everything, whenever the RPMs come up. The catch can is staying relatively clean. The part I don't get is I just I ran this engine pretty hard for six 20-minute sessions on a track and it was fine. I ran Sean's higher tune for half a lap, popped the dipstick, and went back to the regular tune. If it was a ventilation issue that hadn't been a problem at the lower boost levels before, I would have thought it wouldn't have been an issue after going back to the lower boost levels again. This makes me think something let go during that half lap - is it time for a compression test?
(I didn't make it to class.)

*Edit* I've been reading through the various PCV threads and...now my head hurts. And I'm more confused than before. >.<

 

I'd once over the PCV system in general just to make sure, then do a leakdown test, just to be sure. And go from there.

I agree with your logic though, unless something clogged or the PCV got stuck you shouldn't be having blowby issues on the street like that. My issues only happened at the track.

 

I went through the rest of the system - Sean has a pretty big line coming out of the driver's side valve cover, through a check valve that allows airflow to a very nice catch can which has a hose going to the passenger's side valve cover. Everything looks good, the catch can isn't filling any faster than usual, and the check valve passes the "blow on the hose" test. I threw together a rough catch can for the other vent so I could get the car to the shop tomorrow without spraying oil all over the exhaust manifold and turbo.

Catch Can
AZ Iced Tea Can for the Win! It's even green, if not the right shade. A short drive around the block indicates this will work long enough to get me to the shop at least.

 

Damn, I guess I commented on the wrong build thread. I know I just told someone else to swap out their breather like last week. I pointed the same thing out to a guy at autocross a couple weeks back and he hadn't even realized he was dripping oil all over his manifold.

In 4 janky catch cans. FWIW mine only accumulates at a decent rate if I'm at larger autocross venues and seeing lots of limiter. Otherwise I probably empty it every couple thousand miles or even less frequently

 

He didn't notice he was dripping oil all over his exhaust manifold? Wasn't there, like, smoke? I have a general rule of thumb that if my car suddenly starts smoking I stop and try to figure out what's causing it...
I remember you saying in your build thread that the repurposed blender bottle got plenty of comments from people! Mine is just temporary - a more permanent one would have a lid like yours.

Oooh, I could put this one in the same spot and it even has a lid! I'd probably skip the steel wool and use a bigger hose based on the stuff I read in the PVC/Catch Can threads. $35 to the door with an amazon coupon. I can't take The Girlfriend to lunch for that any more. >.>
EVIL ENERGY Oil Catch Can

 

The Miata is off at the shop getting the steering wheel sorted and some "where's all this pressure in the driver's side valve cover coming from?" diagnostics - aka a dry and wet compression test. In the meantime I'm resuming work on the hood vents. (Well, I'm also researching valve jobs, ring jobs, 1.8 engine swaps and other fun stuff, but I won't be doing any of that until the diagnostics come in. I can chop up a hood now if I want.)


Current Best Guess on Vent Placement
Occam's Racer suggests placing the vents 2" behind the radiator - I can squeeze the three primary vents in at the 10 1/2" mark right where the radiator, oil cooler, and fans end - any further back and the middle vent is going to run into the hood bump. If I flow with the outer line of the side vents and go up 3' then I can place the upper vent on the driver's side just above the wastegate actuator which gets it about as far away from the intake as I can manage while taking care of the hood clearance problems with the wastegate actuator, and also venting a medium-pressure area, venting turbo heat, following the same general placement of the singular vents, and hopefully encouraging good airflow through the intake by providing a path for high pressure air behind the headlight to flow towards the intake and then to the vent. *Whew* I'm thinking that's the best I can manage. What do you all think?

 

@douginjenison Here you go!

Hood Vents are IN!
Did I really need gurney flaps on those top vents? I dunno. I had the materials and the other vents had 'em so why not?
Because I'm Certifiably Insane, I went ahead and left the bottom layer in place - I just swiss-cheesed it. I can always cut it out later if I want, but I liked still having a place to seat the hood prop and the additional rigidity it provides. It looks awful of course.

Not winning any concours awards with this hood...
You can also see I didn't use most of the predrilled holes on the vents - the holes on the leading edge didn't line up the way I wanted with the gurney flaps, and I couldn't even see where most of the other ones were since they were sandwiched between hood layers. The swiss cheese holes were added using the highly scientific "yeah that looks about right" method with a step drill bit.

The biggest takeaways I got from this are:
1) If you don't want to spend hours on planning and placement, then pony up the cash to buy the Singlular Hood Vents and use their template. Seriously.
2) The part where almost everyone says to use a right angle grinder rather than a dremel? There's a reason for that.

Here are the boring details for those who are interested.
Based on the previous feedback and with my own (quite possibly bad) ideas of how I wanted things to work, I finalized the vent placement last weekend. I ended up scooting the middle vent forward a smidge to ensure I cleared the hood bump. Turns out I didn't need to, but I'd rather it was a bit farther forward than not far enough.

Final Placement Plan
My next challenge was figuring out how to align the vents properly, both on the hood and in relation to each other. I'm not that OCD, but eyeballing it and saying, "Ehhhh, close enough" wasn't going to cut it. So I did a ton of careful measuring to make sure the center vent was exactly where I wanted it, and then broke out a tripod and laser level I picked up from Amazon a few months ago.

Frickin laser beams!
I placed the remaining vents using the center vent, tape marks, and a tape measure for placement, and verified everything was level and properly oriented with the laser level. Once everything was placed properly I got out a marker and traced the inside of each vent to use as a cutting template.
Here's how it ended up looking.

Cutting marks in place
The next part was going to be really time consuming and noisy (well, pretty much the rest of the entire process was noisy) so I had to wait until Sunday afternoon when I had some free time and my neighbors weren't asleep. Then it was off to the back yard for drilling and cutting.

First vent cuts
I hit the corners with a punch so the step drill wouldn't wander, drilled them out to the marks (more or less - I got better with practice) and then cut through the top layer with a dremel and metal-cutting wheels. It worked, but the cuts weren't that clean, the dremel kept overheating and shutting down to cool off, and when I went to cut the middle layer I couldn't get the body of the dremel down far enough to make clean vertical cuts. *Sigh* Happily I also have an old right angle grinder with a cutting wheel from decades ago. Out comes the grinder.

All the layers
The grinder made much cleaner cuts. It also happily blew through multiple layers and scuffed up the top later instantly if you weren't really, really careful. I wasn't overly worried about the bottom layer, but I didn't want to make the top layer any uglier than it already was.

Kinda Janky...
The end result wasn't terrible but the cleanly cut lines on the vent really highlighted how janky the cuts in the hood looked. Carpenters use moulding; CarPeoples use rubber trim. Or silicone trim in this case. It wasn't a big leap to make since virtually every hood vent manufacturer provides the option to also buy rubber trim. Clearly this is why. Happily I had a bunch left over from when I added silicone trim to the heat shield so that became the New Plan.
Then there was more drilling and cutting. Much, Much More.

More Cuts. More Drilling.

And More...

Onions, Ogres, and Miata Hoods have Layers

Getting closer

Finally getting better at the drilling part

Avengers (Dis)Assemble!
And FINALLY, hours later, the cuts were done.

*Whew!*
Then it was time to add the rubber (silicone) trim and to slip the vents in between the layers. Fortunately I hadn't pre-bent the vent fins because that would have made sandwich making impossible.

Much better looking with the trim!
More trimming and sandwiching ensued, along with some vent fin bending.

Work in progress
Then it was time to rivet stuff together. Once the vent fins were bent the vent assembly wasn't prone to moving that much but I wasn't taking chances. Mark a hole for a rivet, hit the mark with a punch, drill the hole making sure the vent didn't move, put in one rivet, then move on to the next one. Repeat. For Hours.

A Riveting Photo
As I mentioned in a previous post, the leading fin on these vents was larger so I suspect they were intended to be sacrificial gurney flaps. I wanted as much vent-y love as possible so I just bought some 1' aluminum angle at Home Depot and made my own gurney flaps with a hacksaw, an old Buck Bros mitre box, and a hand file to take the sharp edges off. I trimmed the, well, trim, on the leading edge of each vent back so there's wasn't a gap between the vent and the flap - Singular just has you leave the trim off the front edge entirely but my cut lines were janky enough that I really wanted that trim there. So there it stayed.

First Gurney Flap in Place
Once all of the gurney flaps were in I broke out the Mother's Mag and Aluminum polish yet again and went to town.

Flapped and Polished

The Girlfriend looked at it and said, "It's better looking than I expected for home work."

Indeed it is.

 

Looking good man. Ill get a set coming. I might just install the 3 initially as the area behind the head light also leads to my air filter #rain