robertp

Since my 1981 911 SC Targa, I have used a fan to help cool off the engine when I parked my Porsche in the garage. Once I pulled the car into the garage, I would place a fan next to the read of the car blowing air under and into the engine compartment to help cool off the engine.

Now, 25 years later, I still seem to want to place the fan behind the car and blow air into the engine compartment.

Am I the only one who thinks that this is really doing something beneficial? I guess my engineering background in thermal dynamics has subconsciously driven me to do such an act.

Comments, suggestions, criticism?

Kiko

My engineering backround tells me you're right and Porsche thought the same that why my TT has a fan on the rear lid which sets off sometimes well after I turned the engine off! I say drive slowly the last couple of miles and do the 2 min. idle routine together with the OEM engine bay fan and you're fine!

ebaker

You can also just open the engine cover. The hot air rising should circulate a lot of air.

robertp

My 2005 turbo S has the same fan, but the read engine deck lid remains warm for an hour or two after shutdown. That is why I use an external fan when I park it in the garage.

robertp

I did that on my air cooled cars, but now with the build in fan, I just have an external fan blowing air for a few hours.

Shark

Yeah, remember a water cooled engine has much better heat transfer properties....that combined with the on board fan should be fine.

tkerrmd

I do it after track runs

Dock

I think that the fan blowing air over the engine is a better heat exchange than just the radiant cooling that occurs with the deck lid raised.

1999Porsche911

Just simply istall a timer relay that will turn on the engine lid fan for a few minutes whenever you turn the key off. Problem solved. Blowing air over the top of the engine will cool things alot faster than letting the hot air escape from the bottom.

Virtigo

Curious. How does the built in fan know to start up after you shut the car down. Is it an internal sensor or an external sensor.

Made me think what if your plugged to the wall external fan is throwing off the sensor and it does not turning on the engine fan when it should. Maybe a problem? That would be the only problem I could think of, other than that you can't hurt it so why not?

tkerrmd

there is a temp sensor on the right side of the engine compartment and this is what it runs off of, not like the water or oil temp
My question is does the engine cool faster with the deck lid closed and the fan on or off by the factory setting or does it cool bette with the lid open, then no fan help
At the track I have a large fan on the engine with the lid open!!

1999Porsche911

If I were tracking the car, I would do my fan mod (described somewhere in the 996 forum) and run the fan at ALL times. This will reduce underhood temps by as much as 15 - 20%. Openning your lid versus running the fan after a run will INCREASE engine temperatures.

I found it:

Radiator Fan and Engine Compartment Fan Switch Mod


The 3.4 996 runs extremely hot when driving around town in temperatures higher than 75 degrees. This mod is a way to reduce coolant temps back to a safer level, helping to reduce oil temps and improving performance.

The mod consists of installing a switch that will allow you to turn on the high speed radiator fans at any time, while maintaining the automatic operation of the fans. We do the same for the engine compartment fan.

Radiator Fans

Connect a wire to the ground of the 2 high speed fan relays located on the relay carrier located in the driver’s side foot well. The relays are #20 and #22. Feed this wire to where your switch will be located. Connect the wire to one side of the switch. Connect another wire from the other contact on the switch and then connect the other end of this wire to a chassis ground point.

With key on, this switch will now immediately turn on both radiator fans providing maximum cooling. When you turn the key off, the fans will continue to run for about 5 seconds until the relay shuts down. Your fan operation remains normal when the switch is off.

Engine Compartment Fan

Connect a wire to the ground of the relay located in the relay carrier behind the passenger seat, driver’s side. Relay #8. . Feed this wire to where your switch will be located. I simply fed the wire along the driver’s side of the car and under the door sill. Connect the wire to one side of the switch. Connect another wire from the other contact on the switch and connect the other end of this wire to a chassis ground point.

With key on, this switch will now immediately turn on the fan drawing air into the engine compartment. When you turn the key off, the fan will continue to run for about 5 seconds until the relay shuts down. Your fan operation remains normal when the switch is off. This mod helps keep the engine compartment much cooler when driving around town and is particularly beneficial to any engine that draws its intake air from inside the engine compartment, such as the EVO SC.


If you are adventurous, you can automate the operation of these switches so they will switch off at a specific speed, or operate when vacuum is present only, etc. You can choose any style switch you want and even use Porsche switches. I simply used 2 toggle switches that I installed in the batwing,

Jim

robertp

I did that on my air cooled cars, but now with the build in fan, I just have an external fan blowing air for a few hours.

Jim, since I live in Orange County the temp is always above 75 for 6 to 9 months of the year. I am going to set up the switch.

Tom, I will still have the fan on the engine after I park it. I keep the lid in the closed position because I still hear the fan cycling on and off a few times after I have parked the car.

On my S600 Benz, I will open the hood and place the fan in front of the car, blowing air into the engine compartment. I also have the garage door open a few inches to allow air to circulate.

This just something I have been doing on all of my cars over the last 25 years (F360, 69 Mach 1).

Dock

The Turbo's engine compartment fan runs any time the engine is running.

1999Porsche911

Did not know that. Thanks. The ones I have worked on did not run at all times.