pressure sensors for testing grill blocks?
 

From what I've read the best indicator of how much cooling a radiator will be able to deliver depends on the difference in pressure across it. For instance

Undertrays, Spoilers & Bonnet Vents, Part 1

A search of this forum didn't find any mention of people actually making this sort of measurement before and after grill blocks, and it seems to me that it would be useful information to have. The article describes various pressure sensors which read the difference in pressure between two tubes - the simplest of these is just a transparent U shaped tube half full of water. There are also small solid state sensors which can be read electrically, although I have no idea what these cost. Seems like it would be easier to run a few wires under the hood than a pair of tubes which must not be crushed.

Ok, let us know how that testing goes for you and how much it costs :)

I think the stock temperature gauge and some "get out of the car and remove that last chunk I just added if the gauge is reading hot" goes a long way.

I understand the goal is to reduce the radiator cooling when it is cool out so that the thermostat can open up more and water pumping losses will go down.

Would it be easier to create a partial coolant bypass around the radiator? Or put a bigger pulley on the water pump?

Hello,

An engine uses a LOT more fuel while it is warming up to it's normal operating temperature. And an engine will always warm up enough to open the thermostat if you drive long enough.

On my car, the temps do not change with the upper grill blocked. The remaining openings are plenty for when I'm moving, and the electric fan still comes on after I'm stuck in traffic sitting still. This is the only time the fan ever comes on -- and it did this before I blocked the upper grill.

The upper grill block and the flush fog light covers I have put on (I need to post a picture of these) have added at least 5mpg.

Ok, so what does this gain you? The purpose of the thermostat is to allow the car to heat up quickly and so you don't need to block radiators to get this.

It reduces airflow through the engine bay. With most engines today having aluminum blocks and heads this can really decrease warm up times.

Block everything and enlarge the opening in the lower grill until the fan does not kick in anymore. That's pretty much the easiest way to do it IMHO.

If minimizing engine heat losses outside of coolant flow is the goal, then the best way to do that would be insulation or a low emissivity coating (example, polished or chrome plated engine).

I'll do a test of MPG for the first 2 miles after a cold start and then repeat for a warm start. If it is a significant difference, then an electric engine heater might be worth it, even in summer.

If you do a lot of engine off coasting its not worth it as much as if you do engine on coasting. The high idle kills the milage while coasting with a cold engine. So, it'll depend on how you drive.

goal
 

The aerodynamic losses through the engine bay constitute 12-percent of the vehicles overall drag.The grille-block is an attempt to reduce this drag,without compromising engine cooling.As an aside,for those who've done it,we're experiencing more rapid warm up,and can maintain engine heat longer during winter cycle driving "warm starts".But the whole premise behind the block is drag reduction.