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One of the fastest, and most notable small aircraft of it's day was the early Beech Bonanza. As it grew, and got ever more higher HP engines, at a point the plane started having trouble shedding heat in climb. The solution provided by Beech, and approved was to cut louvers in the lower gill doors to release heat from the cylinders below the engine. Of course, not a direct correlation, but worth looking at:
From the factory, these gill doors were just a flat sheet of metal. Punching the vents in them improved the cooling and had little to no effect on the aerodynamics. It was either luck, or serendipity that this worked as well as it did, because I don't think there was a ton of engineering done. They basically went out and punched some slots in the gill door, and fitted it back to the same plane and took measurements.
Wildbilly, on your C4Ss, do the vents from the radiators also lead to openings below the car as on Carreras? Or are they blocked of like on the MkII GT3?
RS: There are openings beneath car which if you reach inside towards the front of car you can feel the rad fan blades. I have not felt in this area to verify radiator air flow. However, I do know if the fans are running you can feel the warm air exiting the wheel well vents!!?? Could it also be a way for the air that enters to center grill to exit the car? After all these noses are designed for the center radiator.
RS: There are openings beneath car which if you reach inside towards the front of car you can feel the rad fan blades. I have not felt in this area to verify radiator air flow. However, I do know if the fans are running you can feel the warm air exiting the wheel well vents!!?? Could it also be a way for the air that enters to center grill to exit the car? After all these noses are designed for the center radiator.
I installed the center radiator kit a while back. I didn't buy the whole kit as I wasn't happy with the intake boot ducting. There is no ducting out the back side and it's left to discharge down and back under the car. i wondered about the effect of the air under the car now, but before installation, there was just that indented rubber insert in the front bumper, so I knew it couldn't be much worse than bone stock.
I have no idea about the airflow past the radiator, but presume that it just flows down and back. I could be entirely wrong though. However, it does not flow to the side as far as I can tell. The front shape of the frunk well is tapered back somewhat, but not V shaped so it would promote flow to the sides.
Below are pics of my solution about radiator/fan bracket mods from 996 mkI, where they're orginally veted downwards ahead of front wheels. As 997 GTx and Cup/CupS (plus also some 996s) cars have vent to wheel wells, the solution must have some benefits over the initial set up of 996/986. I haven't wasted much of thoughs about the theory (don't think too much, it hurts your head.. ), just copied working solutions. Study factory solutions from racers, there's lot to be gained if you're not hysterically into keeping your car 100% original.
While the mkI radiator/fan bracket has a diagonal brace behind the fan, later models do not, the bracket is almost square for the vent to open unobstructed backwards. So I cut it away and spotwelded it inboards. And the frame is square... Next step is to cut out and form the opening to fender liner, v2.0.
v1.0 had two triangular openings both sides of that diagonal brace, but now I can cut out a bigger and square one. Equipped of course with a wire mesh screen like racers have. Air will be quided out from wheel wells race car style in this v2.0.
Another reason for doing this v2.0 is to fit 10x18 et37 wheels with 265/35-18 MPSC2s. With 40 mm LCA shims. Well, not really 40mm of shims, just 25mm and 997 Cup LCA inner ends, which are 15 mm longer than 996's.
__________________
Pete
Power. Lots is good, more is better, too much is just right...
'87 951, RIP '00 996 C2 L92U AQ / IXAA IXRB IX54 M96/7.xx G96/7.88 M030 M375 M376 M436 M476 M601 M983 ... + 991 GT3 brakes, 997 GT3 sway bars, fully monoball'd suspension, Bilstein Cup Car coilovers, do88 Big Pack ICs. 10 & 12 x 19" BBS CH-R wheels with 265/30 & 325 /30 -19 MPSC2s.
Could it also be a way for the air that enters to center grill to exit the car? After all these noses are designed for the center radiator.
Originally Posted by docmirror
I installed the center radiator kit a while back. I didn't buy the whole kit as I wasn't happy with the intake boot ducting. There is no ducting out the back side and it's left to discharge down and back under the car. i wondered about the effect of the air under the car now, but before installation, there was just that indented rubber insert in the front bumper, so I knew it couldn't be much worse than bone stock.
I have no idea about the airflow past the radiator, but presume that it just flows down and back. I could be entirely wrong though. However, it does not flow to the side as far as I can tell. The front shape of the frunk well is tapered back somewhat, but not V shaped so it would promote flow to the sides.
I'm a bit confused. My understanding is that on a C4S or 40AE, the air that enters the center opening in the bumper is mostly blocked by a very obstructive black plastic grill from going any further. And any air that makes it through has no where to go but down.
But if you have a turbo, or a 3rd radiator on a C4S or 40AE, then there is an open grill instead of this obstructive one. The air that flows through it then passes through the radiator, and then has pretty much no where to go but down (unless you have GT3RS style openings above). For both the obstructive grill and the open grill, see post 47 in this thread: https://rennlist.com/forums/996-foru...it-work-4.html
And in neither case could any air enter a duct that leads to the wheel wells. Or indeed to a duct that leads anywhere.
I'm a bit confused. My understanding is that on a C4S or 40AE, the air that enters the center opening in the bumper is mostly blocked by a very obstructive black plastic grill from going any further. And any air that makes it through has no where to go but down.
But if you have a turbo, or a 3rd radiator on a C4S or 40AE, then there is an open grill instead of this obstructive one. The air that flows through it then passes through the radiator, and then has pretty much no where to go but down (unless you have GT3RS style openings above). For both the obstructive grill and the open grill, see post 47 in this thread: https://rennlist.com/forums/996-foru...it-work-4.html
And in neither case could any air enter a duct that leads to the wheel wells. Or indeed to a duct that leads anywhere.
Make sense?
Don't know about the diff in the 40AE, but on a 99 C2, the bumper has a block off center duct which is removed. The air then goes through a duct, past the center rad, and exits downward. One could put a grill on from a car with tip, which has a center rad as standard. I chose to leave the center opening bare for now.
Barely read through any of this but I can tell you my C4S wheel liners have open air fins behind the front radiators. Not sure if that was a 996.2 deal or what.
The center inlet on the C4S/TT front bumper barely lets any air in and there is no where for it to go but down without a GT2 conversion or center radiator (which both C4S/TT don't need)
I did want to just pop in and leave this here for those interested. This excerpt is taken directly taken from the Porsche Intro book for the 987:
Also, it's interesting that frontal area was increased which is usually bad. However, with the 987 improvements the drag coefficient was actually lowered. Not sure how much of that improvement was the vents in the wheel wells, but I'm sure it accounts for some of it.
I did want to just pop in and leave this here for those interested.
Very interesting post as well - thanks!
Do you know if the 987 (or the 997)'s vents into the wheel well are shaped and positioned like the 996 turbo's (as shown earlier in this thread)? Or like the 996 GT3s? Or ... ?
01-05-2017, 03:39 PM
), just copied working solutions. Study factory solutions from racers, there's lot to be gained if you're not hysterically into keeping your car 100% original.
