The 10 degree fan mod is a very interesting option for more coolant and intercooler loop cooling. I have read complaints about the fan running at high speed and causing much noise though.
10 degree fan mod link
I've done some testing and here is what I know:
I removed the stock thermostat, rated 87 degree C, and stuck it in a pot of hot water.
The thermostat begins to open at 87 C.
The thermostat is full open around approximately 94 C.
I blocked the radiator with cardboard and checked the fan setpoints, monitoring coolant temp via OBDII.
The fan control is variable speed.
The fan starts to rotate at 93 C.
The fan turns off when the coolant drops to 92 C.
At 101 C, the fan gets very loud.
When driving, I've observed coolant temps from 87 C minimum, to low 90s typical, to high 90s on a very hot day.
On a 65 degree F ambient day, I have observed coolant temps of 87-89 C while driving, then the coolant and intake air temps start climbing when I come to a stop until the coolant reaches 93 C and the fan comes on.
At the drag strip, the coolant temp usually sits around 93 C (200 F), which is the fan on setpoint, and may climb a degree or two during the run.
The 10 degree fan mod would have the fan come on at 83 C, 4 degrees before the thermostat opens, and go to loud speed at 91 C, in the middle of the thermostat's operating range. The advantage is that once the car is warmed up, the fan would ALWAYS BE RUNNING. Which means constant airflow for the intercooler heat exchanger. This is great for sitting in the staging lanes waiting to run at the drag strip or sitting at red lights. With the stock settings, the fan will not provide any airflow to the IC HX until the coolant warms up to 93 C.
I think a 5 DEGREE FAN MOD might be a better option. The fan would come on at 88 C, just after the opening of the thermostat. The fan would shut off if the coolant temp gets down to 87 C, which is where the thermostat would close as well. Sitting still, the coolant temperature would be controlled down to 88 C, 5 degrees lower than stock. The thermostat hasn't changed, so temperatures with driving airflow will be unchanged. Cooling for the intercooler heat exchanger while sitting still will be significantly improved, and heat soak at the drag strip will be reduced. The loud speed setpoint for the fan would move to 96 C, which should only be encountered on the hottest of days.
Any thoughts?