To be or not to be?

when A/C is active it forces both radiator fans to run so it cools down system more aggressively. On other side - it eats up engine power and adds a bit of its own heat.

What is the best option?

 

I have run my AC at the track, yes it does take a little bit of power away, however I find that I am more alert and on the ball when my body isn't over heating. It is a track day, not a race, a few extra HP won't make or break your cars performance.

 

In my experience, most A/C units are designed to cut off the compressor - does anyone know if this is true for Porsche? If so, then there should be no noticable performance hit from running the A/C.....

 

When you are going above a certain mph the forced air will be more effective then the fans. Also, the water draining from the a/c system is never good for the track and the cars behind.

 

How much water does your car dump when it is driving?

Mine drops if any a few small drops, and with the tarmac well over 100F it will evaporate very quickly, shouldn't be an issue.

 

I've run with and without AC on the same day and I have noticed a big difference.

When I don't run the AC on a hot day I get hot and tired. When I run the AC I don't. As NorthVan said, it's not a race. I haven't noticed a car performance difference. Just in the driver.

 

I always run mine, way to hot to be comfortable and alert

 

AC will zap 5-25 HP depending on how hot the car is running, outside temp.. blah blah (told by race team).

Our 997 AC systems run of a compressor attached to the engine in the lower rear of the engine.

You can get a underdrive pulley and this will help the power loss.

The new 2010 Cup Cars now have AC, but they are a electric unit and does not use the engine for power.

In our cars the following runs off the engine:
AC
Heater
Power Steering
power everything

Next time you are on grid, put your windows down and listen to the engine with the ac off and then with the ac on.. you will hear a difference and see the rpms rise.

Now i just need to drop my engine and take out the:

ac
heater core
power steering

ahh to be insane is blissful and expensive

 

I agree, the radiator fans are only for when the car is stopped (built for stop and go traffic)

Actually when the car is above 30 mph.. the impede better cooling to the radiators (hence why mine are removed)

 

why do you remove power steering? isn`t 997 still a bit too heavy to run without it? how much weight does it save?

 

no just change the power steering to electric like the cup car so you get pure HP from the engine... basically getting rid of all the piggybacking on the engine so it can do just 1 thing.. push the car faster!

 

i see, now it makes perfect sense. i imagined you decided to revert it to 100% mechanical no assist somehow - that would be quite odd...
well, you are working on one really great project. good luck! do you think you will be able to get it done this season?

 

Unless those run solely from an independent battery, they use engine power, though indirectly. Attaching an electrical load to the car, converts into mechanical load at the alternator.. so the engine has to work harder to turn the alternator. You still get the engine load from an electrically driven A/C system, if its powered by the alternator, just an indirect pathway.

Same goes for power steering.

All those electrical things need their energy from somewhere... the rules of physics you learned in high school do still apply. The added load on the output of the electrical generator becomes more forces needed to turn that generator - so the alternator becomes a bigger load on the engine.


Its certainly easier to add an A/C by tying it into the power system, rather than having to add it to the serpentine belt pathway.

 

HUH? I am really confused. The AC compressor is on TOP of the engine almost right in the middle. The heater core is behind the dash, and has absolutely nothing to do with the engine other than the waterpump that pushes coolant through the system (which it is pushing already to the front radiators, so remove the heater core won't save you anything). Power steering....yes, a slight hp robber, but in most cars PS is faster on the track than manual steering. The PS pump is also on top of the engine. Underdrive pulley for the crankshaft can be install simply by removing the rear bumper cover.

 

porsche says the compressor fluctuates and will almost turn off when you need full power

i ran AC and no AC and did not notice a difference in temps FWIW. no way could i tell a difference in power, but i was warmer