It's primary purpose is to shield the heat radiating from the engine, not to block the hot air.

So what is the grey felt lining for?

S

 

WOW, it's easy to just drop something like that.
What is so ignorant about this?
Perhaps you would you like to indulge us with your view and understanding of the correct purpose of the cover? Something that is based on the pure facts ad not speculation please?
Or are you going to counter the fact that the hit energy can be transmitted via other means than matter to matter?

But then again, your opinion in this forums is aways sided with the opinion of the majority. I have never seen you to post anything more that a smirky comment, that has something similar in content. It is either that, or you just sit there quietly with your mouth shut, pretending to look smart.

Let's hear the voice of the genius

 

Isn't the felt lining a fire retardant material?

 

I'm not defending anyone but if you're going to ask anyone for proof you should be prepared yourself. Where is the flaking, peeling, faded, whatever hood? And further more you'll have to prove that it's because the engine cover was off, not oxidation, abuse, or any other variable.

Everyone gets so defensive and hot headed for nothing but a little testosterone rush. If you're wrong you're wrong. If you can't prove something and believe it anyway, good for you.

Edit: And yes the felt is for heat but more so noise. The cover does nothing. Ok, that's a lie, it looks nice to some people.

 

Ze Goggles - Zey do NOTHING....!!

 

Yep, that was actually my other thought.
It is there just to look pretty.
But it will provide an additional level of shielding from heat produced by the engine.

I've seen plenty of those (Not on the 8, 8s are farely new), and in most cases the cars I've sen with peeling paint didn't have the covers.

I don't have to prove anything.
I stated what I reasonably believe to be true. Everyone is entitled to think differently.


How was I proven wrong?
I was called ignorant without any explanation or reason.
That was just rude. If I am wrong, offer me a reasonable explanation why, i am wrong. I nave no problem accepting other people opinions.
We had disagreements with MM, CRH, Mysql before but never at any point we called each other ignorant or anything like that. we argued and defended out opinions, ad it was informational. Ind in some cases I was wrong, and I admitted it without any problems.

And there you go yourself saying what i said in my original post...

 

Pretty poor engineering materials choice to use that horrible waxy-black plastic as a heat shield.......

S

 

Uh... your reading comprehension skills might be worse than mine. Nobody said you were wrong. Likewise, nobody said you were right. I'm signing out right... here.

 

Comprehension skills... Not wrong, not right... So what the f*** are you saying then? Do you even have a point, or you just sitting there barking at shadows?

Some conflict mediator you are

Consider your responses more carefully next time, and people will have no trouble comprehending.


You gotta love it! Come up with something that's beneficial to others and in return they call you at first a *****, then ignorant, and on top of that it turns out that my comprehension skills are not there. WTF?

 

People don't like having their preconceived notions challenged. Get used to it.

 

Some got real pissed off because it would make them look stupid to drop $800 on a CF vented hood, using an excuse that it provides improved cooling. Now they'll just have to do it for rice.

 

Im open to logical discussions.

One more thing to consider is that under the car is not the low pressure zone, under the car is the high pressure zone. So, naturally air will be wicked up to the lower pressure faster moving air going over the top of the body of the car. Thats just common sense. Thats how airplanes fly, and after all a car is merely a wing shape that never leaves the ground.

airplanes fly because they have high pressure on the bottom of the wing because the air has no obstructions as it passes under the wing. But since the top of the wing has a large bump on it air wants to move more quickly over this bump to exit at the same rtime as the air going under the car. As the air moves quickly though space it spreads out and becomes less dense, this is what is called a low pressure system, and this is what the entire top of the car is in comparison to the underside of the car. Air moves from high pressure to low pressure, never the other way around.

Now in airplanes and some very fast cars, the high pressure under the car becomes so great that it can lift the thing off the ground, almost like magic.

Therefore, air wants to move out the hood toward the top of the car. But though clever ducting and blockoffs we channel this under the car to cool the catalytic converter and tranny.

but generally air wants to move out the hood, and generally we like cool engines and transmissions, which is why the engine cover is in place, to divert air trying to excape the hood down to cool the headers and the coils.

but seriously, if you want to prove it, just buy some dry ice or a smoke bomb, put them in your undertray in front of the radiator and see where the smoke comes out with/without spacers.

 

Thank You! Finally someone who understands basic aerodynamics!!

 

One thing you guys didn't mention when you do this mod is that you need to put screws or something back in the holes to stop the plastic cowl thingy coming loose .....

I might have to test this mod at the track next time I go .

 

airplanes and race cars go real fast. in 45mph traffic and idling in slow traffic--airflow is a different animal.
When I come off a track session the engine bay temp is very mild--hell the cooling fans dont even come on when i park it.
When I drive home from work with the a/c on etc, the cooling fans come on when I park and if you lift the hood--- it is hot--- real hot, surface temp on coil packs at 160-170F.
So-i did this little mod and repeated a drive home on a 95f day in georgia. Surface temps on my coil pack was 150-160F . Thats enough for me, Aint worried about the small part of paint on the hood that MAY get a little warmer---hell my dash gets 150F!
This is one mod I say "Good job" this one works!
olddragger

 

WTF ! are you kidding me ? What sort of old lady drivers track are you on ?

 

come--- on check us out anytime. We are at Road Atlanta running laps at around 1:50s, Roebling Road lapping at 1:26 or so. Maybe our gearing is a little better, keeping the rpms down? Ya think? Coolant temps on track are around 220F, oil temps 220 to 230F. Even on a 100f ambient day.
you are welcome to join us anytime.
olddragger

 

and to add coolant temps are down to below 200F after the cool down lap.So no fans on in the pits.
OD

 

I just did this mod in a way that takes care of this concern. LINK

 

he he - sorry for the wind up OD . 220 is still pretty hot though - your fans would definately be on . I'll try doing a cool down lap properly next time i'm out rather than just the last 1/2 mile .

 

LoL --np man---I know what ya mean as far as it's hard to do a full cool down lap
OD

 

the air going over the top of the wing actually leaves the wing before the air going under. The 'it exits at the same time" is a myth, but one that makes it intuitive as to why the air speeds up.

The other problem with that theory is when you apply it to thin wings.

Referring to the Mercedes CLR Le Mans flip? That was because the high rear downforce and the way/amount of front downforce is generated is highly pitch sensitive. A few degrees change in rake (aka angle of attack) to the oncoming air turns the front from a huge downforce generator to a lift generator, but the rear wing still forces down, causing spin, which further increases AOA which further increases lift at the front, and so on, feeding back into itself till separation.

The front of the car is a high pressure zone, ditto the underbonnet region - so yes, it'll want to move to a lower pressure region, but not everywhere on the top of the car is lower pressure, thats why you don't place vents designed for high speed cooling near the base of the windscreen.

it is a water cooled engine, if you want to keep it running cooler then you cool the coolant. Cooling the surface of the engine really makes zero difference to the engines actual operation. (Why do you want to cool your exhaust headers? usually you heat wrap/coat them to keep te heat in)

The engine cover is a pretty piece of trim, but it does no work in directing air - the underboonet air is not flowing nicely, it is all turbulence in there - the stock bonnet would perform the same role in directing air as the engine cover. The engine cover is there because without it that area looks like ***, same reason some ugly V8s have them, same reason Ferraris, Veyrons and Supras (OK, I'm biased in that regard ) don't have engine covers like that (just trim pieces to cover our ugly plugs/coilpacks)

If all you want is to keep the underbonnet temps down during slow/regular driving or when the car is stopped, then any topside vents would help.

 

Here's a proper explanation of lift over an airfoil and the typical theories used to describe it.

http://travel.howstuffworks.com/airplane5.htm

I agree the most effective ducting would be directed at removing the air from behind the radiator ala lotus Elise or Ferrari F50. Having a duct and exit vent from right behind the radiator and ditto for the oil coolers.

 

So what about washing your car or intense rain after doing this mod? Are you allowing water to get into your engine bay?

Of course you could do this like expo1, where you can screw on and screw off the bumpers. Note- Also black bumpers would look better.

https://www.rx8club.com/attachment.p...5&d=1186341710

 

I have the same question as sosonic...does water ENTER the engine bay after you do this mod?