Air under, over, or on either side of the car?

[mcrews]

typically, you are blocking thr grill.
But with that said, new cars have underbelly pans and open grills so the designed (on new cars) air flow works correctly.
here is the underside of the 2011 Audi A8

[California98Civic]

Originally Posted by mcrews

typically, you are blocking thr grill.
But with that said, new cars have underbelly pans and open grills so the designed (on new cars) air flow works correctly.
here is the underside of the 2011 Audi A8

I'll do an undertray at some point. But... are those resonators or catalytic converters on the exhaust pipes just aft of the engine bay? With grills blocked and the belly enclosed, I would think heat builds up more, especially if the CAT is still in the bay, no? These cars have more cooling capacity in some other way? Better pump or radiator?

[mcrews]

the stock A* does not have a blocked grill. And those are the cats.
On my Q45 there are actually 2 cats per side. One right at the manifold and one just as the exhaust pipe goes paralell to the road.
Because of that, I double checked and the A8 has only one cat per side and it is what you see in the pic.
(as a note, my Q45 had a resonator in that exact spot!) I removed it and put in an x pipe.
as a final thought the little puff section is a flex piping. Wish my Q had that since I had developed a crack where the pipe entered the resonator. That was a common defect on the Qs.

[Rokeby]

mcrews,

Thanks for the photo of the A8 underside. Georgeous!
Now we know what a world class belly pan shoud look like.

I know it's not the case, but it almost looks like it has golf-ball dimples!

[brucepick]

Originally Posted by muffildy

I was wondering,
if you create an underbody for an ICE car, would the enclosing of the engine bay create more drag because the air coming in through the grill will only have the wheels as an exit option?

I found real benefit from adding the belly pan to my Civic. In my gas log, see the entry for 2011-13-21 and the subsequent fillups as I gradually finished building the belly pan.

If you use a grill block I recommend a digital engine temp display so you can see when it gets too hot in there. I get mine from my ScanGauge !! but I'm sure there are other ways. Grill block certainly helps reduce amount of air entering the engine bay.

If drag actually is created as you suggest it might, the net result is still a benefit, as you can see from the gas log.

I suspect though, if air can't easily get out due to a belly pan, it builds pressure in the engine bay, which would reduce the amount of air entering. In other words, it would be a self-correcting problem. At least that's what I think.

[mcrews]

Originally Posted by Rokeby

mcrews,

Thanks for the photo of the A8 underside. Georgeous!
Now we know what a world class belly pan shoud look like.

I know it's not the case, but it almost looks like it has golf-ball dimples!

otherwise know as 'eco-modder porn'!!!!!!

[Rokeby]

FWIW, the under/belly tray of the LEAF ;flat, ribs, diffuser.



What's not to like?

[California98Civic]

Originally Posted by Rokeby

What's not to like?

Nice. Here is the 2012 Civic Hybrid, which shows much more open area around the engine bay.

[Fat Charlie]

Originally Posted by California98Civic

I'll do an undertray at some point. But... are those resonators or catalytic converters on the exhaust pipes just aft of the engine bay? With grills blocked and the belly enclosed, I would think heat builds up more, especially if the CAT is still in the bay, no? These cars have more cooling capacity in some other way? Better pump or radiator?

Those are cats.

[mcrews]

Originally Posted by Fat Charlie

Those are cats.

right....read post #13