How does a Grill Block help with engine warmup?
 

Genuine question.
I see people post it all the time but it's not something I can see happening.

I have a UG monitoring my intake temperature. I also have a WAI that pulls air from directly behind the radiator. So, basically, I can watch the intake temp and it never moves from ambient temp UNTIL my engine reaches operating temp (190 Deg F) AND the thermostat opens which lets hot coolant into the radiator. Then and only then does hot coolant flow through the radiator. When my tstat opens I can see my WAI start to work in that the intake temp rises quickly. Until then intake temp is sitting at ambient.

Point is that nothing happens until the engine gets warm anyway. A grill block would do very little to quicken engine warmup, wouldn't it? I mean, if the radiator isn't trying to radiate engine heat it makes no difference whether there's air flow through it or not? Maybe in VERY, VERY cold temps it might make a difference in that there'd be less airflow across the actual engine rather than the radiator? Jes' wonderin'!

Grille blocks increase the temperature of the coolant leaving the radiator. Exit coolant temps vary greatly from summer, around 120 degrees, to temps below freezing where the temp can be as much as close to 100 degrees colder. That cold coolant sucks heat out of the engine when it enters the block, and the restriction to flow in very cold temps means it is moving slower in its circuit.

In severely cold temps you can probably keep the engine cool with just the heater core.
Less heat dissipated into the atmosphere means more heat energy to push the pistons for useful work.

Another factor is grille blocks tend to help aerodynamics.

regards
Mech

I'm still not getting it .... if the coolant coming out of the radiator is so cold then the engine will cool off AND the tstat will shut off and then NO coolant goes to the radiator thereby warming up the engine again. Seems like a grill block wouldn't make a difference in this control system unless the problem is one of the engine getting up to temp and then the very cold coolant bringing it back under temp over and over again. That would make sense in that a grill block might stop that from happening.

Not questioning the aerodynamic benefits of the grill block just the statement of fact that a grill block helps keep the engine warmed up.

Keeps as much cool air from getting into the engine bay as would without the block. The air not only cools the engine by going through the radiator, it also cools the engine by hitting it directly.

If the engine bay is warmer, the engine should warm up faster. If you keep as much air from going in there, the engine bay should be warmer.

-soD

It may be because the general air flow through the engine bay is reduced and so all the hot parts of the engine get hot quicker and that heats up the coolant more quickly?

It's a good question, and I don't know if anybody has done any AB testing.

I installed my block in order to keep the engine at a consistent temp. On the freeway the thermostat would close and sometimes the ECU would go to open loop briefly. This wasted a massive amount of fuel. I bet the increase in fuel economy I saw wasn't from aerodynamic but just the fact the engine would stay in open loop... Plus a side bonus is it protects the radiator from damage. I have seen many bugs splattered on it and a few dings from rocks...

With no block, in winter my engine often wouldn't get any warmer than 172ºF. With block, it stays between 182º-195ºF. Belly pan up front also helps. My belly pan came off due to snow damage and since then, both coolant and intake air temperatures have been down a bit.

It seems to be that forcing the air over, rather than through the engine bay means you get less cooling done at the Radiator.

consequently, the temerature gradient from "in at the top" to "out at the bottom" is lower, and you lose less heat from the block to the coolant (to get it back "upto temp" for going to the rad.

Warmup is mainly affected becasues you stop the colder air entering the engine bay and keeping the engine block cold.

as far as Ic an see.

that reminds me, better price up a thermostat!

On a cold start it takes some time before the thermostat valve to the radiator opens, but the engine does start to heat up right from the start.

The grill block causes less air to flow though the radiator. Therefore the intake takes in air that is heated by the engine, especially when in town.

I see this happen when I take my kids to school (I have a LGB but no UGB): Engine heats up, the air under the hood gets slightly warm.
Drop off the kids, get back into the car, intake air is 10 C above ambient initially.
Stays up at +5C while escaping from suburbcatraz.
Once out of town the intake temp drops to ambient as more air flows through the (stiill cold) rad.

The thermostat will not "shut off". It will restrict the outlet coolant flow which makes the coolant exiting the radiator even colder which exacerbates the issue with engine heat being lost to the now much colder coolant.
Try to understand this if you can, the cooling system is designed for the worst case scenario which is 120 degrees ambient, with maximum load, climbing a significant grade. Under this circumstance the coolant exiting the radiator will be about 30-40 degrees lower than the coolant exiting the engine and the thermostat will be wide open.

Anything less than that and the coolant exiting the radiator will be colder than 140-160 degrees. As I said before, and I have tested it which you can do also if you have difficulty believing simple physics, the coolant exiting the radiator is where huge temperature differences occur. In winter with very cold ambient temps and hypermiling that temp can drop to close to ambient, even below freezing under extreme circumstances.

Every degree you can add to that coolant temp by reducing the effectiveness of the radiator means more heat is available for combustion pressure versus heat absorbed into the cylinder walls.

Several new car manufacturers are doing this with automatic adjustable grille blocks. Thye would not waste the money if it was not effective.

regards
Mech