How to improve our V6 Miata’s cooling? Hood vents.

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Update by Tom Suddard to the Mazda Miata project car
Mar 26, 2024 | Miata, V6 Miata, Hood Vents

After a Lucky Dog endurance race at Carolina Motorsports Park, it was clear that our Miata’s cooling system needed some attention.

[What you learn from your first time racing a new car]

Why? Well, blame us: We swapped a LFX V6 under the hood with a V8 Roadsters swap kit, meaning we were now cooling 300 horsepower with a radiator space originally …

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Comments
Colin Wood
Colin Wood Associate Editor
3/26/24 9:37 a.m.

Whether or not they are needed, a (well-installed) set of hood vents looks rad on just about every car.

KyAllroad
KyAllroad MegaDork
3/26/24 11:15 a.m.

I did the SuperMiata 3 vent set on my turbo NA and installed them from the underside.  It's MUCH more of a PITA to do with all the webbing underneath the hood skin that needs to be trimmed back but I like the way it looked afterward.  It makes a huge difference in keeping it's cool on hot days, I don't love that rain can get in and the noise from the engine bay is much more noticeable now.

Miata hoods are a dime a dozen, y'all could have saved track day time by having the louvers installed already and simply swapping hoods in the pits for the back to back comparison.

Tom Suddard
Tom Suddard GRM+ Memberand Publisher
3/26/24 11:21 a.m.

That's a good idea for a stock car, but a Miata hood won't fit on ours--it interferes with the swap. This is a fiberglass swap hood from Treasure Coast Miata. 

https://grassrootsmotorsports.com/project-cars/1996-mazda-miata/does-lfx-v6-swap-fit-under-hood-na-miata-project-e/

wspohn
wspohn UltraDork
3/26/24 12:17 p.m.
Colin Wood said:

Whether or not they are needed, a (well-installed) set of hood vents looks rad on just about every car.

The problem is that they are so frequently installed for looks, not function.  Usually the best place is up front, right behind the radiator level, but people seem to prefer them further back and in many cases far enough back to get into the high pressure region in front of the windshield and then they actually take air in rather than venting it out.

 

Colin Wood
Colin Wood Associate Editor
3/26/24 12:49 p.m.

In reply to wspohn :

I hear on the looks. I feel like hood vents fall into a similar category as a rear wing. If it's not making your car faster/handle better/etc., it tends to look a little out of place.

Msterbee
Msterbee Reader
3/26/24 1:26 p.m.
KyAllroad said:

I did the SuperMiata 3 vent set on my turbo NA and installed them from the underside.  It's MUCH more of a PITA to do with all the webbing underneath the hood skin that needs to be trimmed back but I like the way it looked afterward.  It makes a huge difference in keeping it's cool on hot days, I don't love that rain can get in and the noise from the engine bay is much more noticeable now.

Miata hoods are a dime a dozen, y'all could have saved track day time by having the louvers installed already and simply swapping hoods in the pits for the back to back comparison.

I was looking at photos of a first-gen BRZ with some of these earlier and I would do the same as you - mount them from underneath.  They look too square and clunky on most modern cars.  That said I can't argue with their functionality, and the manufacturing looks really simple and clever. I'm assuming they are either laser cut or water jetted from a single sheet and then the flaps are bent to their final position.

DavyZ
DavyZ New Reader
3/26/24 1:57 p.m.

Some hood vents do look better mounted from underneath and the same goes for some hood "pins" like Aerocatch latches.  The less on the surface of the hood, the better.  For pure function, however, does it really matter?  I don't think it does.  I like the fact that the Miata hood vents are black, which contrasts nicely with the red paint, just like the wheels, etc.  Sweet little track car that.

ShawnG
ShawnG MegaDork
3/26/24 2:14 p.m.

Vents on the hood look sexy but the hood tends to be an area of positive pressure

You want air in through the grille and out underneath or through the wheel openings.

An extractor vent in the fender with a duct if needed works well.

You can also make the front edge of the wheel arch protrude further than the rear edge to create a low pressure area to draw the under hood air out.

wspohn
wspohn UltraDork
3/26/24 4:54 p.m.

On the Fieros some used to put small vents (c. 3" across) right behind the radiator level on the hood - very effective.

Keith Tanner
Keith Tanner GRM+ Memberand MegaDork
3/26/24 5:38 p.m.
ShawnG said:

Vents on the hood look sexy but the hood tends to be an area of positive pressure

You want air in through the grille and out underneath or through the wheel openings.

An extractor vent in the fender with a duct if needed works well.

You can also make the front edge of the wheel arch protrude further than the rear edge to create a low pressure area to draw the under hood air out.

Depends on where on the hood, it varies quite a bit. Also, what matters is if the pressure on the upper surface is lower than the pressure in the engine bay, because it's that pressure differential that will drive airflow.  I think we have a pretty solid body of knowledge that venting out the top of the hood can work. 

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