jsmirand

My 2003 Cab 4 has three radiators, which I understand is standard for this model. Many other 996's do not have the 3rd radiator.

I was curious (no other reason, other then trying to know the car better) if anyone knew the engineering reason on why some models would have the additional radiator...

SH || NC

Tips and x51s get the 3rd radiator from the factory, unless its an C4S

ivangene

Some cars have all the luck

dallasboats

c4 has radiator

knfeparty

not all x51s have a third radiator. 40th anniversary editions don't because of the added cooling from the turbo/c4s style nose.

Mother

Mine was added for inter-cooling of the Supercharger but was not factory.

SH || NC

Yes, I should have been more explicit; this is why none of the C4S front bumper installed cars have the 3rd radiator from the factory

jsmirand

Thank you all for the replies, but I was trying to understand from Porsche's perspective, from an engineering perspective:

WHY their engineers might have opted for a 3rd radiators on a TIP but not on a 6 speed, as an example.

In the example, do TIP equipped cars inherently have an engineering need to support greater cooling capability?

wwest

Automatic transmissions ALWAYS have a requirement for ATF cooling. That is often done in regular passenger vehicles via a simple ATF flow loop inside the standard radiator. Even some power stearing systems have a small "radiator" for cooling the PS fluid.

Pac996

I take it then that the 3rd radiator could also be called a stand alone transmission fluid cooling radiator? I find it hard to navigate the service manual for a quick and easy answer most of the time since the search function is ate up with the way index's are arranged in seperate files.
1hr 57mins till new years. whoopy.
Happy new years

SH || NC

Just bull****ting here, but here is my guess: the tip generates more heat, and it transfers more heat to the engine, thus requiring more cooling capacity for the engine?

C4CRNA

My C4 only has 2

Pac996

Automatic transmissions are not direct gear drives. They are using belts and fluid between plates with fins where the current invoked on the fluid is imparted on the receiving plates. No metal contact so the fluid is taking the 300hp of pressure to move the weight of the car. There is a lot of heat imparted on the fluid. 3rd radiator for sure.

Manual gears can get by with the mass of oil and all the absorbing heat with gears making the oil flow on them cool thing by spreading the heat in the case around enough. Like a heat sink for electronics would spread heat away from the source.

wwest

The primary HEAT generation in an automatic transmission is via the compression of the ATF. Either the gear type ATF pump itself or the torque converter. The only other serious heat source is the SLIPPING of the various clutches as they are engaged but that CANNOT be for a sustained period.

Modern day automatic transmissions no longer use the power stearing type ATF pump and pressure relief valve but have substituted "real time" control of the ATF pump's pressure relief function.

Google for:

wwest abolition hesitation -dfg

For information about the FLAW in that approach for which Ford has a solution(***) but Toyota refuses to acknowledge the FLAW.

Ford uses a variable displacement ATF pump much like the one Porsche now uses for the engine oil lubricating pump.