T4 Engine tin: thermal design Options

[wonkipop]

@searunner

yeah the 911 "tin" ware is a whole other ballgame (as i conceded in an earlier post).

they are fibreglass anyway. non conductive.
and the engines are dry sumped and kind of super oil cooled.
+ the fan is massive.

there is other scientific stuff going down with the old 911 engine.
but interestingly its an upright fan blowing air down over the cylinders, kind of like the original beetle.

whereas the type 4 motor (leaving aside it being dropped into a 914) is actually designed to be a compact flat package. the old "suitcase" engine or as i think americans labeled it the "pancake motor". its real parameters are to to with its application in VW sedans and station wagons. and i'm sure metal for ducting was more economical than fibreglass which back in the 60s and 70s would have been exotic.

i'll just add that the space shuttle had black tiles on the bottom of it, which was the bit that got hottest during its missions. not silver and not white. also had various little areas of black tile dotted around its upper surfaces.

and the blackbird SR-71s that flew over russia on spy missions at fairly high speed back in the 60s and 70s were black despite the intense friction on their external surfaces.

its interesting stuff. heat and how to get rid of it. (IMG:style_emoticons/default/beerchug.gif)

[wonkipop]

@searunner

to expand naively on the space shuttle for instance.
and when i say expand, i mean very tentatively, because i ain't no NASA engineer.
but.

you are re-entering the atmosphere.
and you got heated plasma (ie air turning into something else very hot) below the surface of your vehicle, the last thing you want to do is reflect that heat and add to the temp of the plasma........
so you absorb it with black stuff.
thats thick enough to suck it up.
the fabulous tiles. like space age pottery.
they suck the heat up and don't conduct it to the aluminium structure they protect.
which would soften, melt and lead to destruction of the vehicle.

then as the spacecraft slows to less than about 7 times the speed of sound and gets into the lower atmosphere the said tiles can begin to radiate the heat out to the cooler air.
no plasma anymore ( super heated air ). and the equation reverses.

so long as you don't loose any tiles!

i think that is how it worked on the space shuttle in terms of black surfaces.

with a VW engine i think it works by the black tin absorbing engine heat because its being radiated at by the engine, but on the opposite surface the air is cooler so it radiates towards the cooler body, the air and looses the same heat that its absorbing on the other side. in effect it forms a pathway for the enclosed engine to lose some heat out to the surrouding air and also to not reflect the engines heat back at itself, but rather to draw some of that heat away from the engine in the radiant spectrum.

the fibreglass on the 911 engine cooling shrouding probably does a sort of similar job because it does not reflect heat back at the enclosed engine. however it would also not form a pathway for getting the heat out. maybe they didn't need a pathway out for the heat they just worked out they needed a non reflective and non conductive surface.

?

i don't really know. just stabbing a guess at the basics.

[moto914]

My opinion for the TWO deflector underside is that Porrshe prefers to have the Air free for cooling the central OIL CUP

Good additional thought. Thanks

[Mikey914]

The 2 deflector design works very well. You have 4 vortices aligned with the cylinder areas that are creating a low-pressure area immediately behind them. The are not a scoop in a traditional sense. The do cause the air in the engine compartment to be pulled down and carried off. Increasing the efficiency of cooling. Think of the fan pushing air, and the low-pressure area sucking it.
This is one of the reasons we added "winglets" to the design. Keeping the air from rolling immediately over the edge and helping to increase the low pressure. It a 3% increase in efficiency. Not much, but if we are going to create something why just copy it??

[914_teener]

The 2 deflector design works very well. You have 4 vortices aligned with the cylinder areas that are creating a low-pressure area immediately behind them. The are not a scoop in a traditional sense. The do cause the air in the engine compartment to be pulled down and carried off. Increasing the efficiency of cooling. Think of the fan pushing air, and the low-pressure area sucking it.
This is one of the reasons we added "winglets" to the design. Keeping the air from rolling immediately over the edge and helping to increase the low pressure. It a 3% increase in efficiency. Not much, but if we are going to create something why just copy it??

Come on Mark...ya just looked over the port side of your airship on the end of the wing and thought it was a good idea! (IMG:style_emoticons/default/laugh.gif)

[914werke]

we added "winglets" to the design. Keeping the air from rolling immediately over the edge and helping to increase the low pressure. It a 3% increase in efficiency.

Interesting (IMG:style_emoticons/default/idea.gif) how did you test for the 3% ?

[wonkipop]

we added "winglets" to the design. Keeping the air from rolling immediately over the edge and helping to increase the low pressure. It a 3% increase in efficiency.

Interesting (IMG:style_emoticons/default/idea.gif) how did you test for the 3% ?

this is getting good.
if @Mikey914 is serious thats probably how you do it.....in terms of attempting to tweak some extra cooling efficiency for all you dudes who insist on hotting up the type 4.

get that air to move through.
and assist the fan to move extra volume.

i dunno what the maths is, but if you get it accurately calculated its probably where the extra cooling can be found.

(IMG:style_emoticons/default/beerchug.gif)

[Mikey914]

To be clear that's a 3% increase in the efficiency of the airfoil. Not the cooling capacity. Yes, a drop in the bucket, but a +.