[Tesla]

I was looking at the alternator regen braking and another idea I had was to try to manipulate cooling system, so if everyone is agreed that a grille block reduces drag, then an unblock must increase drag and give a braking effect.

Obviously greatest effect would be at higher speeds, so on good downhill overruns, but also sudden braking needs, though response times would need to be considered.

Here's the theory:
Most individuals running with a grille block are usually running hotter radiator temps because of reduced airflow, but that's fine because it is still enough to keep engine operating temps within range, if we open grille fully when decelerating, this will increase airflow through radiator and cool it down much more creating a reservoir of cooler coolant for engine to draw on as required.
When we need to get back up to speed we can switch to full grille block, stopping all airflow through the radiator reducing drag even more than a partial block and as system warms up the grille block is gradually opened again for normal cruise operation.

This could be maximised by:
1 / Using a bypass on the thermostat to actually get engine block temps down a bit too, the heater lines could be used here as they are full flow all the time in most vehicles.
2 / Increasing capacity through a larger coolant reservoir tank.
3 / Switching thermo fan on as well to pull more air through radiator and this would also load alternator up to enhance braking effect further.
4 / Using an active airdam that drops even lower to push more air back up through cooling system.

So the idea is to use cooler coolant as an temporary energy store in effect.

This may go in well with those who are already working with automated grille opening controls.