Optimizing the Cooling System
So far in 2024 I have attended three trackdays @ Rudskogen which has been a blast. The Fab9 EFR turbo kit has been working flawlessly and with the added power I’m doing low 1.40s but with much less capable tires so pretty sure I can match the 1.38 with the FMSC and R888r’s
But with more power comes more heat and the current coolant setup is not up to the task:
- CSF 32mm (core) radiator
- OEM oil cooler/warmer
- Bonnet vent and battery relocation
This setup worked fine for N/A. I did not have the same problems with the SC, but that was lower power and the small HE was less of an obstruction for the radiator than the full size IC in the FAB9 kit.
Graph from trackday with N/A Esslinger Stage2.
~ 110C oil temps, mid 90C coolant in ~20C ambient.
Compared to my last session in July.
The graph starts with 1 lap with maximum attack, then 1 cool down lap. 25C ambient temps.
Looking at the graph I let go when my dash alerted me of coolant >100C where it maxed out 103C. The oil temps followed the coolant temps to 103C but as visible in the graph it only cooled down ~2C to 101 during the +2min cool down lap while CLT was cooling down much faster. So the oil is basically heat soaked. Further testing in the next session showed that even 2 cool down laps (4 min..) was not enough. The OEM donut cooler do not have the capacity AND we are trying to cool down 100+ temp oil with 100+ temp coolant…
Ideally this might have worked if I could keep the CLT at max 95C so the HE could work with a temp differential that actually did cool the oil. There are bigger radiators out there but the CSF rad is already a capable unit.
So what can be done ?
Obviously an external oil to air cooler is the way to go here. Separate cooling loop, actual temperature differential, does not tax the engine cooling system. There are also two not so well known benefits:
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The coolant bypass that feeds the donut cooler from the back of the engine is also routed trough the cabin heater core. This is a constant flow system for the donut cooler to work which means some heat is always radiating into the cabin regardless of isolation/ducting/flaps in the hvac system. This Might work for AC cars, but for non AC cars it is very noticalbe in hot weather. Since the donut is no longer needed a valve can be added to stop flow to the heater core on track/summer.
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The hot coolant bypass exiting the donut cooler never goes trough the radiator exits in the low pressure zone right in front of the water pump impeller. This is to get suction trough the bypass via pressure differential, but at the cost of lower coolant efficiency. By blocking off the flow when not needed all coolant will go trough the radiator increasing cooling capacity and flow.
I’ll make a post on the upcoming oil cooler install when it’s done.
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