Grille Unblock to aid Regenerative braking.

[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.

[Tesla]

So what you are saying is that a grille block is just as effective as taking that fly off the windshield.

[pete c]

Bad idea. The coolant system running a little warm is a good thing. Fluctuating the temperature is a bad thing. It also adds complexity and weight.

The idea would have some merit if you were racing where added cooling/braking might come in handy.

[radioranger]

got to agree , up and down temps stress everything

[H-Man]

The problem with bypassing the thermostat is that the engine's efficiency goes through the floor when cold. The end result of this coolant temperature micromanagement system would be that there would a drop in efficiency if it was to drop the coolant temperatures by any meaningful amount, so much so that any gains from drag reduction with the grill fully closed would be lost ten fold.
Coolant reservoirs don't have the contents circulated through the coolant system, it is merely draw upon when the system cools down and has fluid pushed into it when the system heats up (minimal amount, 100 ml on my Geo Prizm.)
What you plan to do is about as useful as an exhaust turbine driven alternator (read: unicorn corral material.)

[Tesla]

pete c:
I think you'd be doing really well to significantly alter engine temp even with thermostat by passed with a good downhill overrun situation and there is no significant weight gain or complexity if you do not add the larger reservoir and if you are already looking at implementing an adjustable grille block.

Frank Lee:
The A-B-A testing and literature is already there for the cooling system drag so there is little doubt that the benefits are there, but as you say would the intermittant selective operation of the grille block be quantifiable, I'd tend to agree it would be hard to show a benefit.

Unlike many other questionable mods where it is hard to show a benefit, I believe this concept has a better chance of giving a positive return as it is based on known benefits of grille blocking, although it would likely be quite small and could easily be lost through adding unnecessary complexity as pete c suggested.

Using the KISS principle, if someone is already doing the automated grille block controls to allow quicker warm ups, then incorporating this idea does not add further weight or complexity.

[Tesla]

Originally Posted by H-Man

The problem with bypassing the thermostat is that the engine's efficiency goes through the floor when cold. The end result of this coolant temperature micromanagement system would be that there would a drop in efficiency if it was to drop the coolant temperatures by any meaningful amount, so much so that any gains from drag reduction with the grill fully closed would be lost ten fold.
Coolant reservoirs don't have the contents circulated through the coolant system, it is merely draw upon when the system cools down and has fluid pushed into it when the system heats up (minimal amount, 100 ml on my Geo Prizm.)
What you plan to do is about as useful as an exhaust turbine driven alternator (read: unicorn corral material.)

Let's say you forget the thermostat by pass, if I put ice water in my radiator, that will have no effect whatsoever on engine temp as it is regulated by the thermostat, so engine efficiency will not be affected.

Therefore if I can get all the coolant outside of the engine down to half it's temperature, the engine will only need to draw half the rate of flow and I could keep the grille fully blocked for twice as long and gain the benefit of reduced drag for that period.

Oh, and I think your suggestion of unicorn material on this idea puts the entire concept of grille blocking in the same place. As I said the gains would probably be small, but the theory is rooted in evidence of cooling system drag studies.

[Tesla]

Originally Posted by radioranger

got to agree , up and down temps stress everything

My radiator temps are always up or down depending on whether I am pulling hard up hill "pedal to the metal", or free falling down a big hill, so i imagine the radiator is designed to have this type of temperature fluctuation, the engines heat output is constantly fluctuating.

Although as said bypassing thermostat may not be appropriate, so if we leave that out engine is fine and will maintain efficiency.

[H-Man]

You have a bad thermostat chances are if the temperature fluctuation of the coolant is that noticeable, replacing the thermostat would yield a bigger gain in MPG.
My car has 2 temperatures of the coolant: Cold engine and running engine, unless I yank the heater valve open the temperature gauge never moves. It would go up and down when I had a bad thermostat, I got horrible FE in the cold.
Flooring it on hills may kill FE if you have an ECU that enriches the fuel air mix at WOT.

[Tesla]

Originally Posted by H-Man

You have a bad thermostat chances are if the temperature fluctuation of the coolant is that noticeable, replacing the thermostat would yield a bigger gain in MPG.

Sorry, my point was radiator temp fluctuations not engine coolant temps, I run a seperate temp gauge on radiator outlet, that is the one that fluctuates, the engine coolant temp is fine, very steady, so thermostat is working perfectly fine.