I went to Brainerd Raceway this past weekend and participated in the road course event, the weather was perfect @ 77 Degrees.

I logged my runs with the JB4 as well as a GoPro. Throughout the runs, the Boost would be limited when the water temp exceeded 235F. I ran the JB4 on Map 0 (stock) for my last run and still saw 3 periods where boost was reduced. I have not seen any options for improved radiators on the F54. Has anyone else had this cooling issue?

Here is a video that shows 8 minutes of a 20-minute session.

 

Pretty sure the thermostat is electronically controlled to a temperature set point, just like previous models. If the temperature set point is 220°F, that doesn't lend itself to much headroom before dropping boost. I'd be curious what the temperature control is during normal driving.

That being said, a proper tune can also adjust the thermostat control temperature to a lower operating level, and should help with reduced power output. With simple bolt-ons, I would think a tuner like @Lou@Prototype-R could adjust boost levels to a moderate level, and give you a lower operating temperature. Might be worth having a conversation with him to verify.

 

I am preparing to get boostmod3 flash tune, I'll inquire about changing the thermostat setting for daily driving. The car did cool down to 205 between each run, and I usually see it in the 210 range around town.

If it could be cooled lower between each run it would help delay the power reduction but it would still overheat within a 20-minute session at 75F+ Ambient Temps.

 

I raced cars for many years with the SCCA. Unfortunately, I haven't had my Mini on a track, so I can't tell you whether or not this is typical. But before blaming the radiator, I'd look at a more common culprit: ducting. Make sure that all of the air that goes into the grille is ducted into the radiator, and that there aren't any major gaps that could allow that air to escape around it. The most common issue here is that your lower trim might have been knocked loose from a tall parking curb or something, this allowing air to escape below the radiator.

If you are confident that the radiator is properly ducted, then yeah, you're on the right track.

 

I replaced the Intercooler with a bigger one this spring, this requires the bumper and front ducting to be removed, everything went back together smoothly. I checked and the primary duct behind the bumper is in place.

The Wanger intercooler is a very tight fit in the bottom inlet, it required some of the ductwork to be trimmed but everything was very snug on the bottom, and the radiator mounts on top of the intercooler. I am going to check the fan shroud to ensure it is still mated close, but I suspect that the majority of the cooling was due to the car moving, most of the track was over 45 mph with several sprints to 100+.