This month, amid all the talk of war with
Iraq, the horrible economy and the standoff with Korea - I thought I would
lighten things up by telling you of a project or two that I'm working on
for the racecar.
One of the things that always concerned
me when I started driving my car in Driver Education events was the possibility
of breaking something. It just seemed inevitable that with a car with 130,000
miles on the odometer that something would go. It turned out that my suspicions
were correct after my first few events, with a coolant hose popping off
of the throttle body at Lime Rock (and slicking down the track) and an
alternator going south for the duration at my first Zone 1 event at the
Glen! Luckily neither of these events caused serious damage to my car (or
anyone else) and I was able to repair them rather quickly.
Of course the faster you go, the more
you have to worry about maintenance and enhancements. In my humble opinion,
brakes are by far much more important for safety and performance on the
track than horsepower although the ideal world is to have plenty of both!
These days I do all of the upgrades and general maintenance myself, partly
because I like knowing how it all works, but mostly because I learn something
in the process of understanding how to develop the car.
One of the few weak points on our cars
for track events is cooling. Although Porsche designs their cars to be
driven hard, the track can stress even a well-maintained street Porsche
beyond what the factory intended. Oil and brake cooling are two areas that
can be enhanced to cope with the harsh environments of racing. On my car
for example, the factory installed an oil cooler in the front right (passenger
side) of the nose. This cooler is great for driving on the road or an occasional
autocross, but long stretches of flat out driving will bring up the oil
temperature readings in excess of 250 degrees F. At this temperature the
oil thins out and lubrication suffers because of it - just when you need
it most!
As for brakes, when they are overused,
they can become so hot that they can be ineffective at stopping your car
- and usually this happens at the end of the longest straight. This is
not the place to feel a squishy brake pedal (boiling brake fluid) or fade
(degraded stopping power). One of my first events at the Glen, I overused
my brakes and didn't cool them down appropriately after coming off of the
track. Instead I sat in the car discussing the run with my instructor -
with my foot on the brakes. This caused my rotors to warp since they cooled
unevenly with a portion of the disk in contact with the pads.
Without going into too much detail, a
brake system on a car (or racecar) functions by turning kinetic energy
- or motion - into heat. When the brake rotors on a car attain a certain
temperature they become less effective at absorbing more heat and therefore
do not have the same ability to slow the car, no matter how hard you push
on the brake pedal.
So how do you solve these two heat problems?
Generally, better airflow is the solution.
Fortunately, I was able to utilize factory parts to increase the airflow
to the front brakes by adapting 968 cooling ducts. The two piece brake
duct redirects air under the front of the car to the center of the brake
rotors. With a little adaptation (drilling holes in the deflector) and
the creative use of zip ties I was able to mount the deflector on the control
arm in a similar way to the 968. The upper portion of the duct bolts right
on to the strut without any modification. The best part of this whole addition
is that the pieces are cheap and the modification fairly easy to do.
Porsche part numbers for the pieces are
as follows:
Right side deflector (18 in drawing):
944.341.051.01
Left side deflector: 944.341.052.01
Right side duct: (22 in drawing)
944.341.556.01
Left side duct: 944.341.555.01
There are other options for brake cooling
that involve air-ducting, scoops etc that may be more effective at cooling,
but will cost significantly more money. These kits are not offered for
my S2, so the 968 pieces were a good starting point. I want to thank Mark
Keefe for showing me this particular trick.
As for bringing down oil temperatures,
one of the solutions that I am considering is to add an additional cooler
to the factory setup. There are several ways to do this, in series so that
the oil flows from one cooler to the next and then back to the engine.
Or in parallel with the stock cooler, meaning that the oil lines are split
at the engine and go to each cooler individually.
There are issues to solve (or at least
ponder) with each of these methods. The parallel method offers less overall
resistance to the oil pump in the motor and is an excellent choice if both
coolers are the same type. The drawbacks are the number of fittings required
to make the connections and more overall plumbing. Also if the coolers
are not of the same type, one of them (the cooler with the least resistance
to the oil flow) will do more of the cooling, and the benefit will be lessened.
For the series method, the oil pump in the engine will have more work to
do, so any additional cooler added should be as free flowing as possible.
If you are adding an oil cooler to a car
without a factory cooler, you can use an oil filter sandwich adapter to
add an external cooler. Make sure if you do this that you also have an
oil thermostat so that the cooler doesn't get used until the oil is up
to temperature. Oil that is too cool won't flow well enough through your
engine.
Well, that's my current thinking on the
subject of oil and brake cooling. I have yet to implement the oil cooler,
but when I do I'll let you know how it comes out. As always if you think
there is a flaw in my logic or just a plain mistake in what I'm doing,
feel free to send me an email at Stephen.w.Berry@verizon.net
Of course as I write this in mid January,
the permafrost on my driveway makes me wonder if I'll ever get the car
warm again, never mind need to cool it down! Keep warm and be careful on
those salt covered roads... |
