Not sure whats this does but i've been noticing alot of hoods being lifted in the rear, like on drift cars and on others? where the hood mounts to the hinge. Like maybe a half an inch or so. Is this possible on an 2nd gen 86 and if it is how to do it and what is the purpose of this is?

Thanx

 

Haha. You can use flat washers if you want, or a machined spacer. ANything that works really.

Its supposed to be for better cooling so the air flowing through the radiator has a place to escape better, and realease engine bay temperatures. Honestly, It probably doesnt help as much as a real hood made to do this, but I guess it might help a little.

The other reason is some people like that style

 

Actually, that's wrong.
The base of the windshield is a high pressure area...from the top.
Take a look at the aerodynamic pressure pic of the FC profile somewhere in here.
Then it'll make sense...

The airflow gets pushed UNDER the hood edge back there.


-Ted

 

i stand corrected. Thanks

BUt that is not going to stop me from humping your avatar!

 

Hood propping is main done by stupid people who don't understand basic automotive aerodynamics (I've noticed it's popular in drifting...). Pretty much any car made in the last 50+ years has taken advantage of the high pressure at the base of the windshield to force air into the cabin for ventilation. Since the pressure at that point will always be higher than the pressure under the hood, if you raise up the back of the hood air will always be pushed into the engine bay, as opposed to letting it out. This can actually reduce radiator airflow be increasing underbonnet pressure.

 

Downforce to the front, yo.

 

http://www.aerodyne.net/ was selling these at one time...

 

Also it's very unsafe. The stock hinges are designed to keep the hood from entering the cabin in the event of a head on collision. Bringing the back of the hood up above the level of the firewall and changing the angle of the hinge means that it will try to cut through the a-pillars...thus removing your head if it succeeds.

 

I had my hood propped on my turbo FB and did notice a huge drop in underhood temps and water temp dropped an average of 5*. Mostly it was propped cause how hight the carb sits on top of the s5 intake manifold it hit the hood w/o it propped. I took a bunch of yarn one day and taped it all over the hood to watch the air flow as I was driving. And right as any one knows it was clearly sucking air into the engine bay. But the question is where does it go from there? Right under the car and out causing extra turbulance under the car, drag, and lift. And you deffinatly feel the difference with the hood propped at speeds over 100mph. It might look cool, but the negitives out weigh the good.

 

some people belive it helsp with venting . some people think if they have a V mount it'll help air travle threw and out better. but . to each their own.

 

Thats with the aerodyne hood brackets

 

where are the decapitation theorists?

 

They still sell them. Just call.

There was already one decapitation post above.

 

Dang it....

 

Beside all this above... everybody will say "hey why doesnt your hood latch all the way?" and... "Hey man I think somebody ran into your car and drove off!"

I tried this for a couple months and noticed that the under hood temps were cooler. I wouldn't really say it looks better at all.

If there was an actuator you could install to raise the hood automatically when at low speeds or a complete stop to let the heat rise out it would be quite functional I would think. It does creat a vortex of air above like 30MPH though so it may mess up the cooling a higher speeds.

-Water leaks inside...
-dumb comments from others...
-gimmicky...

 

When wanting to lower engine temps without buying a new hood, wouldn't one do better to cut holes between the back and middle of a stock hood, and craft something to let the air from that area come out the top? that way, there would be no pressure towards the front of the car (maybe?) to push air down in, and hot air would be able to escape up and out.
Plus, no one would get decapitated.

Any thoughts on this?

 

I think we can consider actual decapitation very unlikely, but I'm pretty sure we can agree that the windshield coming through the windshield would be a Very Bad Thing. It would be foolish to assume this couldn't happen. You only have to look at what happens to property mounted hoods in a frontal impact to see there's more than enough force to push the whole thing backwards if it's been raised at the rear.

You're absolutely right, properly located bonnet vents would do a much better job of lowering temps, because the engine bay pressure would be lowered instead of raised. This increases the airflow though the heat exchangers (radiator, oil cooler and intercooler, top or front mount). The proper way to locate the vents is too measure the static pressure (while driving) at various points on top of and underneath the hood to find the spot with the greatest pressure difference.

 

hood proping is so lame.

normal engine temperatures are there for a reason. if you prop your hood to cool your stock car, if it even does cool it, it brings down the engine temperature, and doesnt let it warm up to functional useage.

retarded.

 

Hmmm.
I'd like to see the hood design - be it vented or "proped"- that made a rotary run too cold...especially on a car with a functioning thermostat.

 

I find it funny that people are claiming the hood is going to suddenly chop your head off if you do shim the rear...

Have any of you seen an FC hood fold?
I've seen one in a front end collision that managed to crumple the hood.
The rear hinges are designed to bend and not break.
Even if you do shim the rear, it'll still do it's job and not allow the hood to come through the A-pillars.


-Ted

 

The hood's designed to bend by holding the rear fixed. Raising it up seriously compromises the strength of the rear hinges in a fore-aft direction by turning the force on the hinge from shearing to twisting. You only have to look at the pic of the red FC above to see what's likely to happen...

 

Many years ago the NTSB & the insurance institute for highway safety mandated that hoods be designed to: not come loose at the rear, and to fold on front impact.

About cooling - jacking the rear of the hood will help below ~20 MPH & work in reverse above ~30 MPH.

It's like the opposite of the TMIC - it works well above 30MPH and poorly below 20.

 

if you jack up the rear of the hood on a TII with a top-mount, wouldnt it be very counterproductive by un-sealing the hood vent with the top of the intercooler, no longer forcing air thru?

 

Good point - You'd have to make an adapter gasket.

 

:Quote:
Quote:
Originally Posted by NVConvertible

You're absolutely right, properly located bonnet vents would do a much better job of lowering temps, because the engine bay pressure would be lowered instead of raised. This increases the airflow though the heat exchangers (radiator, oil cooler and intercooler, top or front mount). The proper way to locate the vents is too measure the static pressure (while driving) at various points on top of and underneath the hood to find the spot with the greatest pressure difference.
:Quote:

NZ Convertible, how does one measure static pressure?