kurt_1

Matt: I see what you mean with your reference to the old British racers.
With the straight-sixes the flow of air around the engine was a little different but still very interesting designs.

Alan is right, one would need to create two different air flow paths and the hot rad air would have to be routed down and out the back of the belly pan. According to my understanding,extracting the hod air more effectively was one goals of the belly pan design.

Unfortunately, I lost the auction of the used hood so I will have to wait and see if I can get another one that fits my budget.


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Kurt
90 S4 satin black metallic
928 OC Charter Member

The Fixer

That depends on your definition of "lingers". But i disagree.

Diverting all that volume of hot radiator air down would cause a lot of lift at speed don't you think?

Out of the sides of car behind front the tires or out of the top of hood is better imo. Maybe a combination of what Sean R's Customer did and some added venting further back and out.

The heat from the exhaust manifolds are forced down and out at speed but at slower speeds that heat must go straight up into engine bay heating the intake runners etc..

I do a lot of stop and go here in suburbia and would like this heat to freely go out of the hood at slower speeds. So for my use my design will work i think.

Edit:

If all of the hot radiator air could be vented up and over the hood through on vent like a Porsche GT3, that would be a great looking and working setup.

But there isn't the room.

Alan

Where do you think it goes in a stock car?

All I'm proposing here is to try to avoid it circulating up to the top, so you can have a seperate loop up there - absent any venting it all has to go down & under eventually so this is no different.

Alan

The Fixer

I see what you're saying Alan,

but there would be an air pressure difference if it were controlled and ducted quickly down to the road way up front.. causing more unwanted lift than letting it find its way out as it does now wouldn't you agree?

I wonder if it IS possible to divert most of it up (via a duct) and out over the hood where Sean's Customer located his vents.

That would be nice. I think i will try it.

I'm done, brain is tired.

Speedtoys

It is pulled down, not forced down..hot air being pulled thru the radiator via low pressure under the car is 1/2 of how a cooling system works for the most part.

Alan

I think most of it goes straight down & out on a stock car - with a full belly pan the exit is likely just diffused across a longer distance.

If you just look at what's behind the radiator it has a major incentive to go straight down - it's the widest opening, its the shortest path to where is has to exit. This flow is pressure differential driven at speed & fan driven at a standstill. I'm sure there are minor paths taken around the engine top & sides & even under the intake - but as those are longer more tortuous paths they will also be far less travelled.

Up & out for most of the rad flow would probably a bad idea - you still need significant manifold/header, oil pan, down pipe & cat cooling. The post radiator flow is still relatively cool enough to achieve this.

Alan

The Fixer

Yes, I get that.

But that wasn't what we were disagreeing about.

Alan was saying that he'd like to duct that entire volume of hot radiator air ramming through at speed directly down in front of the oil pan. I think that would cause lift like an airfoil..

I think up is better Alan. But i also know you're very smart and will think about what you are saying

But I think i know now how to make my preferred method work very well now that i've had to think about this and without decreasing the flow of cool air through the radiator or around the motor.

It would most definitely work.

We will have to end this in disagreement.

But I still think you're a genius
and respect how you help so many here

Speedtoys

Nah..not at all.

It's not as much air as you think it is..besides, the engine will never be cooler than the water and oil in it..so its not saving any heat to the engine to duct it out ahead of it.

Proper under plates help all that, a lot...on all cars.

BPG_Austin

Kurt, I machined a hood with vents quite a few years ago and have since sold my S4. I did all the work on a cnc machining center and the hood/vents look very nice. As the Fixer mentioned, once you shut the car off you can literally watch the heat vent out of the engine compartment. (my car had Devek L2 headers and I live in Texas) Its currently hanging in my garage. Not sure what its worth, but I'd be happy to let it go if you're interested and it fits your needs. I haven't updated my membership and RL won't let me post pics right now. Please feel free to e-mail me and I'll send you a couple pics. legendgarage@gmail.com

Best,
Ben

kurt_1

Ben,

that sounds exactly like it would fit the bill perfectly ... IF ... I wasn't located in Germany.
Sending a hood overseas might be doable but I very much doubt that it would arrive in a condition similar to the one you sent it off.

Anyway, thanks for offer and if someone on this side of the pond has a hood lying around gathering dust, let me know.

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Kurt
90 S4 satin black metallic
928 OC Charter Member

The Fixer

We should read how Jim Hall solved these sort of issues.

Look at Chaparral 2, he was really ahead of his time.

Attention to these sort of details made his cars competitive.

Alan

Are you suggesting putting the engine behind you? ...

Not sure how that's relevant here.

Alan

The Fixer

Yes Alan,

That would seem the easiest way to solve the issue.

We've come full circle in Porsche terms.


Jim Hall is relevant here because he, unlike

you, thought outside of the box.

(see i can be rude also)

Matt

hacker-pschorr

One particular Aston Martin V12 that has hood vents, also has heat shields around the manifolds with chimneys going up to the hood vents.
It wasn't retained on later models so I question the effectiveness.

Making a set of stainless heatshields for the manifolds and / or having them coated by an outfit like SwainTech will be far more effective than hoping all that heat will just find it's way out those small vents in the hood.


If you want to keep heat out of the engine bay, the #1 and probably only significant way is to cut a hole in the hood and create a duct that seals off the radiator form the engine compartment and flows the hot air up and over the hood. Like the nose of the F40, Ford GT / GT40 etc...


You can see the heat "chimneys" in this photo, this is a 2007 or 2008 Vanquish:

Speedtoys

I guess you would have to ask WHEN you want manifold heat to go away.

Going down the road with the undercovers and front spoiler intact...that air is going out under and behind the engine just fine.

Parked..different story. But just like my planes..when I park, I open the cowl to vent it nicely.

Plane = oil fill cover.
Car = At home unlock the hood.

Both are free mods.