fan under whale tail

[mickster8888]

i was wondering if it would be beneficial to mount a fan under the tail next to the intercooler that could be switched on manually after car is shut off? what direction would be better- blowing into engine compartment or exhausting out? thanks in advance, mick

[TRE Cup]

if you are using it to cool off the intercooler while parked, then blow outwards. It will help cool the top of the motor.
It has very limited benefit while driving (unless sitting in bumper to bumper, but how much boost can you get at a standstill ).

[mickster8888]

tre cup, was going to use it solely to cool the engine compartment after shut down. with the turbo and muffler it gets pretty hot a few minutes after the engine is shut off. so you think i should have blow air out instead of blowing air into the engine compartment?

[TRE Cup]

i would blow the air up and out- there will be enough cool air getting sucked into the compartment mixed with hot air from the engine

[bonkers]

Yup. Since hot air rises, you'll want to push it up and out, which will in turn cause cooler air to get sucked in from below.

[euro911sc]

The only problem is that the air coming in from the bottom will have to pass the exhaust system first, heating that air up in the process... If you blow it the other way, you cool the engine first then the exhaust/turbo with the heated air going out the bottom...

Something missing in the above posts here is that the engine compartment is supposedly sealed from the bottom exhaust area by the sheet metal and rubber seal. so ... Theoretically ... little air should be coming up from the bottom anyway and you'll just end up pushing the air around the engine compartment unless you have a specific inlet and outlet. Pushing it around is not entirely bad, just inefficient.

Obviously, the sheet metal and piping gets nice and warm in the engine bay, but unless you cut a hole you probably would find it easier to mount the fan on the decklid with air blowing in through the fan and escaping out any other possible orifices This gives you a dedicated inlet which assures cool outer air makes it into the compartment. A second benefit of this is that you can aim the fan and flow at your item of interest, where in the reverse setup you are hoping that air just goes through where you want it.

Another concern might be are you blocking flows that would otherwise go through your intercooler while at speed by mounting a fan? I do not own a turbo so you will have to answer that one

If you have one of those nifty GT2 wings with the side scoops you could duct the air from those...

Just some thoughts

Best regards,

Michael

[Rob G]

Cant you just open the lid and let all that HOT air out. I assume you are talking about after you park the car at home after work or a long drive.

[Oracle]

the 964 and 993 will start the rear blower (with the car off) automatically and blows air from the fan intake down to the heater flappers and you can feel hot air coming out thru the wheels.. the principle is to cool down the heat exchanges drawing the heat from the heads... pretty cool... except that it can kill your battery.. details....

[1100sport]

Is there any reason why you would want to better the cooling system after the engine has been switched off? I mean is it sustained by any rationale from a mecanical stand point like preserving the engine heads or anything? I would have thought that once switched off, the reason why the engine heats up is gone, so why worry?

[bkreigsr]

+1 on just popping the lid, no fuss, no muss
Bill K

[911st]

If you actually had a good seal around your motor, there is still a clear path up past the cylinders and out the fan housing.

Might be interesting to trigger the aux heater motor in the motor compartment with a turbo timer or something to pull air in the fan housing and out the heater valves at the end of the heat exchangers. This would cool the exhaust, heads, cylinders to a degree and pull some air in and around the IC.

[euro911sc]

Originally Posted by 1100sport

Is there any reason why you would want to better the cooling system after the engine has been switched off? I mean is it sustained by any rationale from a mecanical stand point like preserving the engine heads or anything? I would have thought that once switched off, the reason why the engine heats up is gone, so why worry?

The engine bay will actually get hotter before it gets cooler. A lot of turbo cars run a turbo timer to allow their cooling systems to even out the temperature in the turbos so they do not cook the oil in the turbo and destroy bearings and such. Even my NA car gets hotter after I drive it in to the garage and turn it off. I just pop the tail though. I do not pop it at work though.

Originally Posted by 911st

If you actually had a good seal around your motor, there is still a clear path up past the cylinders and out the fan housing.

Might be interesting to trigger the aux heater motor in the motor compartment with a turbo timer or something to pull air in the fan housing and out the heater valves at the end of the heat exchangers. This would cool the exhaust, heads, cylinders to a degree and pull some air in and around the IC.

I like this idea the best. Very subtle and easy. A little relay and RC work and you could get it done and totally out of sight.

Best regards,

Michael

[bkreigsr]

Originally Posted by 1100sport

Is there any reason why you would want to better the cooling system after the engine has been switched off? I mean is it sustained by any rationale from a mecanical stand point like preserving the engine heads or anything? I would have thought that once switched off, the reason why the engine heats up is gone, so why worry?

lemme guess, you've never owned an air cooled turbo?
heat actually continues to build on the upper side of the motor as the exhaust and turbo unit try to cool down. I've seen my (surface metal) temps rise as much as 50 degrees after shut down.
Bill K

[911st]

The heater blower would also be sucking air from under the motor.


Heat soak of the IC can be a real concern in traffic but few worry about it after shut down.

Investing in a good IC temp probe might be money better spent. It is a classic story about the guy sitting in traffic with his A/C on and a 1 bar boost spring that blasts away from the stop light with a heat soaked IC and detonates his motor.

It is always best to idle a turbo for a minute or so before shut down to cool the Turbo bearing and prevent cooking. If one was going to put a fan on something, the turbo would be the place.

Just some thoughts.

[safe]

I would do it as TRE says, I think that would cool the engine more evenly and efficiently. I would rig a button up that I could push and let it run on a timer 4-5 minutes.

[mickster8888]

all good points\. the only reason why i want to do this is to cool the engine compartment as it gets hotter bfore it starts to cool. the engine is a huge heat sink and without air movement the rear valence and bumper are so hot you can't touch them. i don't want to harm the paint. when i turn the car off at first it's fine then gets hot after a few minutes. i thought that by installing a fan next to the innercooler hanging it on the deck lid i could at least draw some air through the engine compartment thus keeping the bumper and rear bodywork(all fiberglass) from getting cooked. maybe even mounting a time delay relay(delay on break) to control the fan on and off. i'm not trying to cool the intercooler, engine, heads,ect. just want to keep bodywork cool. lifting the lid would work but i don't feel like hanging out with the lid up everytime i park the car. i guess the consensus is to pull air up through the engine compartment and out the decklid next to the intercooler?