Filled in old Inter cooler hole in bumper.

[Sam Powell]

At the urging of at least one member on another thread and after reading several threads on the forum about this, I decided to go ahead and fill in the hole in the bumper for the now-gone inter-cooler. It was about the simplest thing I have done so far. I just cut a rectangle of aluminum sheet and sandwiched it between the mesh and the license plate. This is how it looks now. Based on my reading here, I am sure this is a more efficient design than what was there before.

I am sorry I cannot report any actual numbers for mileage. I change this car too often to get a good baseline. But, it is going up continually. A year ago it was getting as low as 12 MPG in local driving. I think this last tank of local driving is going to yield around 20 based on the gas gauge. This has been extremely local, with trips as short as 5 miles to car cruises often. Today I took it on my job and drove it 50 miles total. I will begin to get better numbers here as I use it more. I am going to look into the MPG display that is possible with my fuel injection so I can have better data available.

[AndrzejM]

Good job! But you can go much further and cover most of the grill, just go for a stealth modd, to not spoil the clasic look of your car.

[euromodder]

Originally Posted by Sam Powell

I am sorry I cannot report any actual numbers for mileage. I change this car too often to get a good baseline. But, it is going up continually. A year ago it was getting as low as 12 MPG in local driving. I think this last tank of local driving is going to yield around 20 based on the gas gauge.

Well, the testing that these mods work has been done over and over again.
I couldn't be bothered less about testing
What counts is your mpg going up.

[Sam Powell]

Thanks for the nice comments and the advice. I have been thinking about how to handle the grill effectively and tastefully for some time, but need to learn more. Since the air cannot get around this grill if I block it off because of the big frame around it it seems I must direct the air behind the grill in the best way possible. Am I right about that? If I block off this grill isn't the air just going to build up on the frontal area and force the car to push the air down the road. Or is that not what happens? Can the air still get around that big lip around the grill area if I block the grill from behind. The guys who race these cars build a front cap for the grill that sticks out further and curves in a way that allows the air to move over the top and under the car easily. And I agree with you, I do not want to change the look that much.

As it is now there are no partitions behind the grill as are found in my other cars. These partitions in those cars divide the space into three areas. There is a the area right in front of the radiator, the space to the right of it,and the space to the left of it. All the air that gets through the grill in the grill opening in my 328 for instance must go through the radiator. Air that comes through the bottom openings and into the side areas is channeled into the intake air filter or the brakes. This is all done with rather flimsy, light weight polyethylene., but it is effective.

The challenge with the Dart is that if I build this same kind of partitioning, there is currently no place for the air to go that enters the grill on the side areas. So I must create a place for it to go, or block the grill off completely and force it to stay outside of the car and go around,which seems very awkward with the front end design. I could funnel the air on the driver's side into a pickup for the engine air cleaner. It sits right behind the radiator core support on that side. It currently picks up air from the fender well. I could open up the space behind the grill in the core supports on either side of the radiator, and funnel it into the wheel well and out that way. Or I could also create sloped blocks behind the side portions that direct the air through the radiator. None of these options seems real good.

So if I simply blocked off the entire grill on this design, where would the air go? How would it behave? This is key to figuring out a design here. Would it just ram its way through the air, or does the air still split and get around, over and under the car? I know from my reading that 55 mph is the speed at which the air no longer wants to separate easily. So it seems this concern gets more important as speed increases.

It boils down to this: Should I block it off, or manage the flow behind the grill?

Thanks for thinking about this as always. This is not as easy as dealing with a modern, slick front end design.

Sam

[aerohead]

Originally Posted by Sam Powell

Thanks for the nice comments and the advice. I have been thinking about how to handle the grill effectively and tastefully for some time, but need to learn more. Since the air cannot get around this grill if I block it off because of the big frame around it it seems I must direct the air behind the grill in the best way possible. Am I right about that? If I block off this grill isn't the air just going to build up on the frontal area and force the car to push the air down the road. Or is that not what happens? Can the air still get around that big lip around the grill area if I block the grill from behind. The guys who race these cars build a front cap for the grill that sticks out further and curves in a way that allows the air to move over the top and under the car easily. And I agree with you, I do not want to change the look that much.

As it is now there are no partitions behind the grill as are found in my other cars. These partitions in those cars divide the space into three areas. There is a the area right in front of the radiator, the space to the right of it,and the space to the left of it. All the air that gets through the grill in the grill opening in my 328 for instance must go through the radiator. Air that comes through the bottom openings and into the side areas is channeled into the intake air filter or the brakes. This is all done with rather flimsy, light weight polyethylene., but it is effective.

The challenge with the Dart is that if I build this same kind of partitioning, there is currently no place for the air to go that enters the grill on the side areas. So I must create a place for it to go, or block the grill off completely and force it to stay outside of the car and go around,which seems very awkward with the front end design. I could funnel the air on the driver's side into a pickup for the engine air cleaner. It sits right behind the radiator core support on that side. It currently picks up air from the fender well. I could open up the space behind the grill in the core supports on either side of the radiator, and funnel it into the wheel well and out that way. Or I could also create sloped blocks behind the side portions that direct the air through the radiator. None of these options seems real good.

So if I simply blocked off the entire grill on this design, where would the air go? How would it behave? This is key to figuring out a design here. Would it just ram its way through the air, or does the air still split and get around, over and under the car? I know from my reading that 55 mph is the speed at which the air no longer wants to separate easily. So it seems this concern gets more important as speed increases.

It boils down to this: Should I block it off, or manage the flow behind the grill?

Thanks for thinking about this as always. This is not as easy as dealing with a modern, slick front end design.

Sam

Many of the modern cars have faux grille 'inlets.' Some elements of the grille are completely closed off.They're just there for aesthetics and the annual styling change.
Since the grille is so close to the radiator there's really no room for a diverging inlet duct and a smaller opening.
You might just block from behind with BBQ black material and leave an opening only as large as the fin and tube section of the radiator.
Also,if you've got a fender well-mounted ignition coil,provide some cooling air for it as you can cook the coil,or at least shorten its lifespan.
Ditto for ram-air to air cleaner.
This winter,when cooling efficiency is at its maximum,you could judiciously reduce the opening and let your temp gauge be your guide.
Hopefully you have a clutch-fan,or flex-fan,or electric cooling fan.All these reduce aerodynamic drag under the hood.

[elhigh]

The point of closing your grille, even in an older ride like yours that doesn't have such effective streamlining, is to eliminate the drag of air getting in and then having to get it back out from around the engine. With most/all of your grille blocked you'll create a sort of nose cone of high-pressure air in front of you as you drive, not as effective as an actual nose cone but still better than nothing, and that will direct more air around your car.

If you spend a lot of time in stop-and-go or at slow speeds, you'll want to leave more of your grille open until you've had more opportunity to monitor engine and underhood temperatures. Switching to an electric fan will eliminate a big drag on the engine while you're cruising; to the best of my knowledge virtually no vehicle needs the belt driven fan while at speed.

I bet you have a big opportunity under the car, too. Lots of potential for belly pans down there on older rides.

[Sam Powell]

Thanks all. These comments are helpful. I do have an electric fan. It is a two speed 16" with full shroud on the inside. Part of increasing the mileage involved wiring the fan with two different thermostats so it comes on the low speed only first, and then uses the high speed only when it gets really warm.

Given this feed back, I think I will plan on partitioning the inner cavity between the grill and radiator so the air that comes in through the open center section can only go through the radiator. The two outside sections I will simply block off from behind. What is barbecue black material? Is this a product I can buy that is already black, or is it paint? I usually fabricate my parts from aluminum or ABS and then paint. There is another thread that shows the front partial belly pan I have already built.

This will not actually be that simple as I might have to remove the bumper in addition to the grill. This means taking off the belly pan and airdam as well.

If you look at the photo carefully you will see that I sealed off the space between the hood and grill so no air can enter there. This si cooredinated with a pair of aluminum panels that keep the air which enters the grill from going over the radiator That was intended to force the air through the radiator for cooling, but I can see now it will make the grill block more effective. Here is a photo of those panels.



The coil is on the fender,but that is actually cooler than the engine block mount that was stock. The BMW M3 vents in the fenders are functional. They are there to try and cool the coil as well as the HEI module that is also on the fender. It is mounted to an aluminum sink.

There is another thread on the forum showing the partial bottom pan and air dam from below. I am eager to figure out how to design something more extensive that will not compromise the "look" and not complicate service too much. Thanks again. This is fun.

Sam

[Sam Powell]

At the advice of all here with a tip of the hat to AdrzejM I added more block off on the grill itself. I blocked off the right side from behind. I have included a photo here of the right side with the block and the left without. From normal viewing angles you cannot tell the right side is blocked off. I used .062 aluminum sheet stock and painted it black.

Here is the math. Counting the hole in the bumper, by the time I block off the left side of the grill I will have blocked off a total of 340 square inches of opening, and am leaving 112 open to the air. Do you think I have over done the block offs?. I have a large 16" electric fan with a full shroud, which has two speeds and a cross flow aluminum radiator. I am also running Evans coolant. Thanks for giving the information to know what to do here. The block on the right side was easier than I thought it would be. It took a fair amount of trimming and fitting, but did not require removing anything except the upper aluminum air flow panel.

Sam

[Sam Powell]

At the advice of all here with a tip of the hat to AdrzejM I added more block off on the grill itself. I blocked off the right side from behind. I have included a photo here of the right side with the block and the left without. From normal viewing angles you cannot tell the right side is blocked off. I used .062 aluminum sheet stock and painted it black.

Here is the math. Counting the hole in the bumper, by the time I block off the left side of the grill I will have blocked off a total of 340 square inches of opening, and am leaving 112 open to the air. Do you think I have over done the block offs?. I have a large 16" electric fan with a full shroud, which has two speeds and a cross flow aluminum radiator. I am also running Evans coolant. Thanks for giving the information to know what to do here. The block on the right side was easier than I thought it would be. It took a fair amount of trimming and fitting, but did not require removing anything except the upper aluminum air flow panel.


Right side with block off.

Here is the left side without the rear block added yet. Note the wires and such showing.

Sam

[elhigh]

Simplest thing to do now is to go for a ride and keep a weather eye on your temp gauge. If it goes north of your comfort zone, start opening the block until you aren't worried about it anymore. Drive it up some steep hills to load it heavier than you normally would, for a worst case scenario.