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Keeping Cool at Speed
By Steve Grosekemper
One of the great benefits of owning a Porsche are the wonderful driving events PCA offers. They range from slow relaxing tours on forgotten back roads to high-speed events at real racetracks. Both are great fun, but the high-speed driving events are our focus today.
To run at these events most of us just need to empty the accumulation of junk out of the car and go. But, as the afternoon temperatures rise and the run groups get longer, our cars may run hotter than they should. Fortunately, there are a few very simple tricks to help your car keep its cool.
First, determine if your car is getting the proper amount of fuel delivered to the engine (a slightly rich fuel mixture helps the engine run cooler). After a practice session remove a spark plug and check its color. It should look like well-done toast. Lighter color indicates too lean a mixture and black means the mixture is too rich. This is a very basic test. If you have any concerns, you should consult your Porsche technician.
After determining all is well with the fuel mixture you're ready for Step 2: feed the engine cooling system the largest possible amount of cooling air. Here are a few simple modifications that can be made in just a few minutes.
356/912/914--These models draw air in through a squirrel cage fan. These fans often get debris caught in them, thus restricting airflow. For 356/912s, reach around the fan housing and feel inside the fan for debris. Remove any foreign objects (paper or plastic bags are the most common obstructions). Make the same inspection for 914s. Their fan is on the front of the engine near the passenger compartment. Also, check that the insulating blanket has not fallen against the fan. This will greatly restrict airflow. This is were I say don't forget to turn the engine off before making this inspection, or be forever known as "LEFTY!"
Now that all is well with the fan, it is time to add more air. 914s have a very small air inlet. When the factory went racing with 914/6 GTs, they doubled the air intake for the engine. These engine lids are all grill instead of just half grill. They are hard to find (and not cheap). The simplest solution is to remove the engine cover. This takes two people and about four minutes. First, open the engine cover and mark the hinge with a pen. This helps position the lid during reinstallation. Second, loosen the hinge bolts with a 10mm socket and ratchet. Both people hold their end while removing bolts. Set the lid aside and you now have a huge passage for that cool air to get to the engine.
356/911/912s can get more air by fabricating a spacer that holds the rear deck lid open about 3 inches. As air passes over the top of the car, it makes a u-turn down towards the license plate. If the deck lid is cracked open, air will be forced in. We have all seen this on hot rod VWs.
Also, any spoiler added to the back of a 911 will increase airflow into the engine. That high-pressure air is just looking for someplace to go... right into the air intake grill!
964 C2s and C4s have belly pans under the engine and transmission. Many people think they trap heat. They can be removed to increase airflow around the engine. This is a job best left to your mechanic (unless you can jack up the car. There is minimal ground clearance).
944s and 928s stay fairly cool. Their biggest enemy is the bra. Many of them restrict airflow to the radiator. So, if you're getting hot, go bra less! (We're still talking about cars aren't we?) You can also increase airflow by turning the cooling fans on all of the time. This is as simple as 1-2-3. First, turn on the headlights. Second, reach below the left headlight and remove one wire from the A/C low pressure switch (looks like a soda can). Third, turn the A/C switch to position #1. Doing this turns the cooling fans on at high speed, but there is no heat load because the wire you pulled disables the A/C compressor. This operation has a lesser effect on '85 and newer cars. Their fans will only run at half speed.
'87-'89 911s have oil cooler fans which can be manually activated by bridging the switch. Remove spare tire. Locate the small two-pin white plug next to the larger two-pin black plug in the right forward corner of the trunk. Unfold a paper clip and insert it into the terminals of the white plug. The fan will now run whenever the engine is on.
'74-'89 911s with front oil coolers can get a blast of air by removing the fog light or turn signal assembly. Plugs need to be installed to easily disconnect the wiring, which is a more complicated modification and is material for a separate article.
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