More grill block = better MPG

[bsn1989]

I just filled up the Kia last night and this was the first fill up with the lower grill almost entirely blocked shy of a 5x5 square hole in the center.

Last time I filled up was with the initial small grill blocks I was at 41mpg with my normal route to work. My normal route to work is relatively flat and mostly highway.

Last night when I filled up, half of the miles on my tripometer were mostly hilly highway roads versus my normal flat drive to work.

When I filled up, I was shocked that my car achieved 43.95 mpg! I accredit this new high MPG to my Torque App, wheel covers, grill block and right foot discipline.

I'm excited to see what I get as MPGs with my normal flat highway drive to work!

[Daox]

Nice job!

[MetroMPG]

Congrats! It's lots of fun when you're on the steep part of the improvement curve!

[TimV]

I also found out that i could hold my upper grill block longer.
Previously I removed it when it is 20 degrees celcius.
Now it stays on until 23 degrees if i do stop and go. And 27 degrees when i do lots of highway

[Katmandu]

Originally Posted by bsn1989

I accredit this new high MPG to my Torque App,

What's your Torque App ?

[bsn1989]

Originally Posted by Katmandu

What's your Torque App ?

Torque is an app for Android that connects to your car's OBD2 port via bluetooth and a bluetooth adapter. It lets you view all kinds of diagnostics.

Simply google Torque app Android and you'll find it's page.


I have an ELM327 bluetooth adapter plugged into my Kia. They can be found on Amazon for under 10 dollars.

[RedDevil]

I keep track of my air intake temperature as it is related to the general under hood temperature. If it goes over 40°C on a regular basis I remove some of my grill blocking.

The reason (apart from having EGR, which adds heat and reduces the effectiveness of a WAI) is the battery.
Lead acid batteries don't last long if they get over 40 degrees.

My advice would be to choose the blocking in such a way that the 12V battery benefits from the air stream through the remaining unblocked parts.
And, of course, measure that under hood temperature. I used a cheap in/out digital thermometer before I got my UltraGauge.

[Nautilus]

Originally Posted by RedDevil

My advice would be to choose the blocking in such a way that the 12V battery benefits from the air stream through the remaining unblocked parts.

If the engine bay temps are high enough to damage the battery, the airflow from the front of the car is too little to improve anything, even on highway, leave alone city traffic.

The best way to pump air through the battery box, if the car has a closed box: use the engine intake. Drill a hole about 1 inch through battery box and another in the air filter box, and fit a pipe (either plastic, or a wire-reinforced hose between them.)

A 1.6-liter engine draws thousands of liters of air per minute even at slow rpm, enough to bring quickly the inside of the battery box at outside temperatures.

Originally Posted by TimV

I also found out that i could hold my upper grill block longer.
Previously I removed it when it is 20 degrees celcius.
Now it stays on until 23 degrees if i do stop and go. And 27 degrees when i do lots of highway

The upper grill block may stay there all the time, if the air is properly ducted through radiator core.

The logic of ducting is like this:

1. Most of the drag at the front of the car is due to the airflow through engine bay, not the shape of the car's front;

2. The airflow through radiator is mostly due to pressure differential at the front and rear sides of the radiator.

So, if the intake grill is left open at the highest pressure point on the car's nose and the exit of the air from the engine bay is at the lowest pressure point, the grill opening may be very small and still achieve good cooling.

Drag improvement is not due to smaller opening, but due to leaving more air to flow over the nose of the car.

[MeteorGray]

I live in Louisiana, a semi-tropical state that is hard on people and equipment due to the heat. Ambient summertime temperatures in the 32C/90F to 38C/100F range are the norm.

Temperatures in the engine bay can run much hotter than ambient, of course. Batteries often fail in this heat. To help alleviate the pressure on engine bay components, I put louvers in the hood of my Mazda3. Some of them are located directly above the heat-sensitive battery. This venting of excessive heat helps.

I installed a digital temperature probe in the engine bay to keep tract of things. The gauge shows that on the highway, engine bay temperatures are exactly the same as ambient temperatures: if it's 95F ambient, it's 95F under the hood; so that's about as good as it can get. Of course, in town at slower speeds, temperatures rise a few degrees warmer than ambient; how much so depends on traffic. After engine shut-down, the engine block heat takes over for a while, causing temperatures to rise to 65C/150F or more, depending on ambient temperatures.

Even with the louvers in place, the battery and other engine bay components take a beating after engine shut-down, but having the louvers to allow it to dissipate faster helps a lot. I even installed a six-inch-diameter radiator-type fan under one of the louvers to help discharge the heat faster after parking in really hot weather. I have a timer to run the fan for 10 minutes after engine shut-down. This helps too.

Because of the heat in my area, I wouldn't consider blocking the grill. On my 2015 Mazda3, a lot of the grill is actually already blocked from the factory. Any further obstruction would aggravate the detrimental effects on heat-sensitive stuff under the hood. My car also has almost a full tray installed under the car from the factory to help the aerodynamics, but this covering actually works against heat dissipation. Fortunately, Mazda provided an opening in the tray immediately behind the engine to allow for engine bay heat to escape under the car at speed. Of course, this opening does relatively little to remove hot air after parking, since heated air rises. That's one of the reasons for my hood louvers: they provide an escape route for the rising hot air.

About fuel economy: I have noticed no effect on my miles-per-gallon with the louvers. So, they have proven to be all-win and no-lose for me.

[mpg_numbers_guy]

Do you have pictures of your louvers somewhere?

Driving style definitely has an effect on the amount of grille you can block; when driving more aggressively, faster, and with no EOC I ended up having to reduce my lower grille block down to 80%, whereas if I drive efficiently and EOC when I can I can run a full lower grille block up to close to 100 degrees *F outside temp.