Engine cooling and outlets

Formula1 engines have 10 cylinders running at nigh on 19,000rpm and pumping out 900bhp, kick out a lot of heat. Cooling of the engines is taken care of by water and oil radiators, housed in the sidepods cooling air is fed in to the inlets either side of the driver and the relatively fast flow is slowed down by the radiator duct diverging after the inlet, to about a third of the speed it was before entering the duct. This slower air passes over the radiators core and cools the fluid circulating inside the core. The heated air then is left fairly free (i.e. without a closed to direct it) to exit the sidepods.


In earlier times this outlets simply needed to larger than the inlet to accelerate the flow back up to road speed and placed in a convenient location. The increased sophistication of aerodynamics and the advent of “coke bottle” shaped rear ends forces some compromises in the outlets placement.


The basic design for sidepods lets the heated flow exit at the opening at the end of the sidepods (between the rear wheels), with extra holes let into the body work for when additional extraction was required. This forced the end of the sidepods to be wider between the rear wheels, upsetting the increasing trend for slim rear ends. To allow the flow to exit further forward placed the outlets in areas that would increase drag or upset flow to the rear wing.

McLaren soon realised that a vertical outlet placed on top and the edge of the sidepods could direct its flow either side of the rear wing and as the outlets was above the main flow passing close to the sidepods surface the outlet wouldn’t upset the cars aerodynamics as much. Additionally the outlet further forward allowed the sidepods to be narrower between the rear wheels.
This solution has become known as a chimney an has been adopted by almost all the teams at some point, either as a permanent fixture or as an aid to tuning the cars cooling requirements.


A second solution used the flip up ahead of the rear wheels, to shroud an outlet, Ferrari and McLaren adopted this format in 2001 and only late in 2003 had most teams discarded it. As the flip up was already functioning to direct airflow up and around the rear wheels (and away from the rear wing) adding some of the cooling flow to this area created some gains in efficiency. By making the area of bodywork ahead of the flip up and detachable panel teams could replace the panel with versions that created different sized outlets to aid the tuning of the cooling package, also as the engine often has only one oil cooler placed in one of the sidepods, one outlet needs to be larger to cope with the increased heat rejection of both the oil and water. Most of the following solutions also adopt an asymmetric layout because of the single oil cooler.


By 2002 Ferrari had placed a winglet to add some downforce on top the sidepods, by placing the wing In front of the outlet the low pressure created under the wing helped draw flow from within the sidepod.


Ferrari then made use of a aerodynamic effect that used the very fast flow from the exhaust pipe to accelerate cooling flow through a duct, effectively acting as a pump to scavenge hot air form the sidepods, the distinctive tall arched outlets around the sidepods became adopted by others again both as permanent and optional cooling solutions. The downside of this solution was that both the exhaust and cooling flows went directly into the rear wing, hindering its efficiency.


Allied to the Exhaust fairing outlet Ferrari placed the radiators at a compound angle in the sidepods. Usually the sidepods are angled in one dimension vertically or horizontally, usually placing both oil and water cores into a single panel. By angling the radiator in such a way Ferrari were able to increase the size of the core surface area (more important to cooling than the thickness of the core) without making larger sidepods.


Just as the flip up exits used in 2001 used the winglet to extract air form the sidepods Renault found a solution for the their 2003 car that placed a chimney outlet ahead of the winglet, while at first this appeared to be detrimental to the winglets efficiency, Renault found the strong trailing vortex created by the outer edge of the winglet also pulled air from the chimney, this improved upon the Ferrari exhaust fairing as the flow was directed away from the rear wing.