Partial front grill cover for winter

I blocked off the lower grill for the winter in hopes of warming up the engine quicker.

A piece of black foamcore 4x30" behind the grill:



I’m hoping to save a little gas by warming up the engine faster.

I take mostly short (10-20mi) trips.

Does anyone else do this besides semis?

Frankly I doubt if it is going to do you much good.

You car has a thermostat that prevents much water flow though the radiator until the temperature is already hot. Of course if you have a bad thermostat or if someone has removed it, then that might help you out.

If your car is a diesel, it may help out, since diesels make far less waste heat. Blocking air flow around the engine helps. That is why you see such things on a semi and not on cars. They semis use it to a great degree to keep the engine temperature up at idle.

I would also be careful what materials I used around hot parts. Make sure your foamcore can handle the heat.

Semis do it because they have diesel engines. On a gasoline burning engine, I don’t see the point.

Semis do this because their diesel engines run cooler, and blocking part of the radiator can improve heat inside the truck, especially when the truck is idling or running at low RPMs. They don’t do it to save fuel, because it doesn’t save them fuel, and I seriously doubt it saves you any fuel.

I think a block heater would be much more effective in achieving your goal.

If this was a good idea, and could really save fuel, there would be at least one car that did this automatically with some kind of motorized device that blocks the radiator. Maybe it would be a specialty vehicle for driving in Antarctica or the Arctic Circle, but there would be at least one example.

Another reason to use a block heater instead - what if you get a warm snap and forget to take out the foam core? Overheating is not a good thing!

Block heater is not feasible since I live on an urban street.

Had no trouble on a recent drive at 74F ambient.
Remember the cooling system is sized for Death Valley.

The thermostat is good, but in stop and go traffic below freezing I can make the temp gauge drop a little by putting the cabin heater blower on medium or high.

The foamcore is ~ 6in from the radiator.

Remember the cooling system is sized for Death Valley.

That should not make any measurable difference.

yes, ice racers. they couldnt survive without it.

You arent going to kill the engine thats for sure, so go ahead, try it this winter.
it may not raise mileage, but it will keep the engine warm.

I remember that the school bus drivers (owner-operators) who drove their prewar buses when I was in elementary school tied burlap sacks across the grills of their buses. I heard that this was so the buses would warm up more quickly, but I don’t think this was the case. The buses were always cold inside.

A grille cover will certainly save fuel. Not so much for the effects on warm-up as for the fact that reducing the cooling inlets reduces that car’s aerodynamic drag considerably. As aero drag increases at the cube of speed, the effect will be more pronounced for high-speed driving vs. stop-and-go.

Since manufacturers cannot afford to make vehicles that overheat (ever), or that require seasonal maintenance to the grille, they size cooling for the “worst-case scenario.” If you are willing to pay closer attention to your temperature readings (and make the block easily removable by the roadside), you can probably afford to close off some cooling air flow.

The electric fan in your car will give you a margin of safety if you close off too much, but you’d lose most of the gains if you have the fan running all the time.

This has worked for me, and I’ve noticed both better fuel economy and better “coasting” results when measuring the quantitative effect.

I don’t know if you looked at the pictures, but he put the cover behind the grill not in front of it, so I seriously doubt there is any aerodynamic advantage.

All you’re likely to do it toast your engine, and then you’ll want to blame someone else.

Do you think the Toyota engineers haven’t tested this vehicle in cold climates?

You’re crazy. Let me reinforce that; You’re crazy!

Your Matrix does not need any of this foolishness. It will warm up just as quickly with or without the black foamcore, which is 6" from the radiator.

You’re fooling yourself.

Good luck with that.

The thermostat regulates the engine temperature, not the radiator. You don’t know what you’re doing. Your Matrix is not a Peterbuilt, and Death Valley has nothing to do with anything.

Stop this foolishness before you do serious damage to your Matrix’s engine. Remove the foamcore and allow the cooling system to operate as designed by the Toyota engineers.

Or perhaps you know something they don’t.

Not likely!

Yes, I suppose I should have said “A properly designed grille cover will certainly save fuel.”

My old SAAB two stroke benefited from doing this. It needed all the Help it could get. I would like to know where you live that you feel you need to go to such extreme measures. DC ? You have to be kidding. Why not do a little test with an egg timer with and without to see if that extra minute or two is worth the potential problems…like all of a sudden, stuck in traffic and the sun comes out and your car starts to overheat and…you get the idea. I wonder too if car is still under warranty and any engine problems would be covered if dealer knew you were doing this.
When I do winter plowing, we sometimes block the grill of “some” of the diesel equipment. But we never blocked the grill of the car we drove to the that equipment. And we kind of think we know what we are doing.

Reread mcparadise’s reply.

Your grill cover will make zero difference while the thermostat is closed.
When the thermostat begins to open it might make a very tiny unmeasurable difference in the rate of coolant temperature rise (as the cold water in the radiator mixes with the hot engine water). But there is such a small time window there, the difference is likely measurable only with precision lab equipment.

You also don’t know how your ECM changes the injector flow for the different cooling temperatures. Is the amount of fuel based solely on cooling temperature values, or does it also include ambient temperature. The EPA also has rules for how long a car can run in the “cold warming up” stage.

Covering radiators was more common years ago (often a band-aid for something else). It also caused many engines to overheat. Do you really want to be adding that risk?

This has been my impression of why truckers do it.

And it shouldn’t matter if the cover is behind the grille-- it’s still restricting the airflow into the engine compartment. The actual bumpy part of the grille isn’t what’s causing the drag, it’s that the air goes into the very non-aerodynamic engine compartment.

While I definitely agree that this shouldn’t be even remotely necessary on a car with a functioning thermostat, I don’t think it’ll even do anything since on modern cars most of the airflow for cooling gets scooped in from the front air dam thing not through the grille (because of the above-mentioned aerodynamic problems). Many cars don’t even have grilles in the traditional sense and the only reason why this one does is because of styling. I’ve noticed on some cars, the ornamental grille doesn’t even line up with the radiator.

I think blocking off the grill in cold weather was more common in the days when we ran 160 degree or 180 degree thermostats in the cars. The engines in today’s cars run at higher temperatures, so the heaters work more effectively.

“You’re crazy!”

Would you talk to me face to face like that?

Lighten up!

So maybe it’s not a Good Idea. No excuse for you to talk to me like I’m an idiot.

In the good old days of fans that were driven by a fan belt off the engine pulley, blocking off a radiator may have helped the car warm up more quickly because the fan was always turning. Today’s cars have thermostatically controlled electric fans or thermostatic clutch controlled mechanical fans. These fans don’t run until the engine is warmed up, so the engine warms up more quickly. Hence, there is less need to block off the radiator as there was in the good old days.

Thanks to all those who gave their opinion in a polite, civil manner.

I’ll be taking the mod off.

And next time I have an idea outside of the routine of this forum I’ll be sure not to share it.