Just finishing a 2003 996 tiptronic cabriolet ls1 swap, and due to space requirements had to make the rear air deflector/spoiler fixed in the down position. I am attempting to keep the rear compartment temps as low as possible, and was looking at getting an aftermarket spoiler or wing that will introduce as much air into the compartment at speed as possible. Any suggestions?

I have mounted 2 fans to pull air , switched at 165, but it would be nice to take advantage of the natural airflow at speed. Thanks

 

Gt 2 type after market wing. they have air ducts designed into the outside edge of each wing pillar for extra air intake. would fit your two fan concept as well.

 

The most aggressive and tested scoop for incoming air at speed would be the gt3rs decklids.

However for a street driven vehicle, wouldn't you want a design that let's the most amount air out and diffuse it?

I've seen others modify the stock decklid to stay in the open position all the time. Couple this with gutting the underside and you should have adequate ventilation.

 

Since I believe the stock fan brings air in from the top., and the vents on the stock spoiler direct air in, I thought the best way to go would be pulling air from the top side and directing it to the bottom. I could be wrong though.

 

The stock fan is a joke. It hardly goes on and sometimes it will go on after you park the car if your engine bay gets hot enough. But if you notice, this fan hardly goes on most of the time. I think I've only heard/seen my fan turn on only a handful amount of times during the last few years. YMMV

The stock spoiler serves both purposes as a scooping effect at higher speeds and ventilating diffusing effect at lower speeds. Just place your hands over the top with the spoiler manually raised after a long drive to see what I mean.

The later 997 decklid design seems to have a more ventilation and diffusing effect as the fins are channeled rearward.

 

Do you guys have pics of these wings I'm entrusted in getting a new one, as my stock deck lid I do not like. I was thinking something like this

 

I think that most of the heat on a stock 996 and 997 is at the bottom where the exhaust manifolds are. The engine pretty much shields the top of the bay from the heat. With the V8 the manifolds are up at the coolant tank level, and the heat is up higher. I was thinking of pushing the heat down, instead of pulling up warmer air from the bottom, I think it may keep the bay and everything cooler.

On my 996 turbo, the fan has come on a few times with the a/c on and longer drives, but the 997 turbo I have, I haven't had it come on. The engine bay seems to stay cooler on those, but I need to confirm with temp gun.

It would be easier to build scoops under the engine compartment to pick air up from the road, but. I can only imagine that air being pretty hit in the middle of the summer at 3" to 4" above the pavement, so I think the air would be cooler 3' off the ground. Leaving the trunk fans on all the time is pretty loud, but keeps the bay cool.

 

Hard to know for sure. The stock setup "spoils" air flow over the back of the car to reduce lift which has the added benefit of increasing air pressure over the engine compartment lid to force air down through the louvered lid to help remove air from the engine compartment.

Otherwise when working hard the engine compartment would get way too hot and something bad would happen.

Off hand I'd say something from the factory, some TechArt (?) spoiler/wing setup would be preferred as this would replace I assume the stock automatic spoiler and thus have to provide what it provides which is to reduce lift and as a by-product increase air pressure over the engine compartment lid and thus help cool the engine compartment.

 

That the engine compartment fan hardly goes on when the vehicle is being used is a good sign the factory did something right. Air flow (via sensible aerodynamics) over (and under) the car is such that air flow (down) through the engine compartment is keeping the heat down without having to run the engine compartment fan. That's going to prolong the engine compartment hardware life and without the need of working the alternator harder to supply the electrical power the engine compartment fan requires. Sure not lots but every little bit helps.

 

I agree with this. What I was trying to get at is that the stock fan doesn't really do a whole lot most of the time compared to fans in other cars that run more often. As you said this is due to good engineering on their part.

OP, do you have your headers wrapped? That would def help if it isn't already done.

Have you looked at the duck bill style spoilers? Those have a good surface area in the openings. Not sure if it's your style though.

There's LS 996 guys that's been running a couple years without any issues just gutting and reusing the stock spoiler.

I guess the methodical way would be to measure under good temps at various points on a stock 996 compared to your LS setup. Engines are meant to be in hot conditions. If it's within operational parameters, I wouldn't really make a big deal of it personally.

 

Interested in the build man! I love LS-swaps. If not for living in CA I'd consider doing it but don't want to deal with the smog referees and technicalities.

 

I would do it in a heartbeat with a manual car, the automatic was a little more of a challenge, but it is for my wife and she requested an auto. The car doesn't sit any lower, it has much more torque, and if the ls1 breaks,( which it more than likely won't) it won't cost $10,000. I bought the car to do the swap, having purchased the engine 8 or so years ago, and really doesn't seem to be any downside, besides the added heat up top, which I would fix before installing the engine next time with heat shield.

I did this swap as a practice round for the 996 turbo I have. I am looking at a twin turbo aluminum LS or newer LT ( if the DI pump is affordable) swap. At the minimum it will get the purists panties in a bunch!

 

i have wrapped the whole exhaust, which did help, and purchased a Blazecut extinguisher, which is an automatic extinguisher that activates above 284*, just for reassurance. Hopefully that is never needed, but it is compact and easy to install. Just want to get all the heat I can out of the rear bay.

 

I have a Gemballa spoiler that has a ton of room. Sent you a PM

 

Thank you, it looks to have lots of room and would work well, but it may be a little much for the stock cab narrow body look. I showed the pic of the wing to my wife, and she said something I have certainly never heard from her, "it's too big":