Alternate Radiator Locations
 

Since the radiator is connected via hoses I was thinking one could in theory locate a cooling heat exchanger in other locations (and with other configurations). I'm not seriously planning this (although I DO have some surplus truck A/C condensors kicking around...), but was curious if it might spark some ideas in any of you folks.

Yes, it is very common when dealing with project truck where the engine is mounted behind the cab in the bed. You wouldn't really gain anything by doing it though for a standard vehicle.

We used to race in an Enduro.

In some of the races we would overheat. So we routed the heater hoses to the trunk, and installed an additional radiator in the trunk (complete with electric fan)- never even came close to overheating again.

-BC

I knew someone with a DeLorean, and it had hoses to hook the radiator up to the rear mounted engine. He had some trouble with it, I seem to recall. That car was a money pit.

I know several ambulance manufacturers place additional A/C condensers underneath the truck, and put electric fans on them to boost the A/C output. I'm sure you could just as easily do the same with a radiator.

They have a shield to prevent rocks and such from damaging them I assume?

NASCAR stock cars have rear axle oil coolers that are just mini radiators for rear oil instead of engine coolant. Those radiators are located under the car with a small electric fan for cooling.

There are really only 2 factors that are impoprtant in the location of the engine coolant radiator: air flow and protection. As long as the radiator is getting enough air flow and is protected from damage, the location isn't important.

Blowing air into a big box (the engine compartment) just seems less efficient than other options, especially if some sort of damper could be used in to close it off when not needed.

Now that's an idea...what about a servo motor hooked to some sort of shutter than opens when the radiator fans kick on? The electronics are simple for that, so it's really about the shutter design. That has possible retrofit applications.

A servo motor? That's a wicked-expensive way to do something very simple. A much cheaper thing might be a vacuum-operated solenoid, or even just a DC motor.

Don't forget, though, that warm air generally helps MPG so it is beneficial to pre-heat the air going into the engine compartment...

-BC

RC car servos aren't so bad, depending on how big. This would basically be a retractable grille block, right? What's the jury's verdict on those?

He's talking about air used to cool the engine, not air for the engine to intake.

Also, warm air is not more efficient. You want a warm engine (coolant and oil) but not warm intake air. Cool air is more dense and makes more power.

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I think a better option would be to better route the air out of the engine compartment. The most efficient way to cool the engine would be to use the wind and not the fan. Blocking the grille area would just cause the fan to come on sooner. I think if the air was able to freely excape the engine compartment you would lower the drag on the car.

The idea is used on racecars, the Ford GT and even the Mitsu EVO.

Below is the Ford GT. Air enters the radiator below the bumper and then exits through the hood and over the car.
https://www.auto-focus.us/autofocusga...2/P1010132.JPG

Below is a similar (less effective) design used on the Mitsu EVO. Air is allowed to excape the engine compartment just behind the radiator.
https://www.autobytel.com/images/carP...ution_hood.jpg

That makes a lot of sense. Cutting the back out of the box. The weather going right in there doesn't matter?

Exactly.

Cooler, more dense air makes more power by allowing you to move more air and inject more fuel.

A warm-air intake is commonly observed to be effective for increasing fuel economy. On some vehicles it works, and on others it doesn't have any effect, but I don't think I've heard of anyone whose fuel economy went down when their intake air temperature went up.

The grille block is another modification that has proven effective. It does seem like it would cause the fan to run more (and it surely does), but the end result is an improvement. It seems to work by reducing aerodynamic drag from air entering the engine bay as well as keeping the engine bay temperatures warmer.

Allowing air to freely escape may provide a similar aerodynamic benefit, but it will cool the engine bay.

There are some things that are done for speed that help fuel economy, and there are some that hurt it.

I did notice all the cars with that hood vent were pretty powerful. This is turning out to be a very informative topic.

Thinking about the shutter grille block some more and a more sophisticated control system than just opening it all the way when the fan comes on wouldn't be too hard. It being partially open in response to temperature. The microcontroller work needed for that wouldn't be terrible. Still need a good design for the shutters, though. I will think some more.

I find a lot of early car developments fascinating. Such a variety of different techniques. Microcars had a lot of variety like that too.

The WAI helping fuel economy is a myth. While it doesn't hurt economy, it can hurt performance and if too warm, cause detonation.
https://www.metrompg.com/posts/wai-test.htm

I made this statement before and the thread went south. The most important part of better mileage is the temperature of the coolant entering the engine.
In colder weather the cooling system has too much heat removing capacity.
This could be addressed by an additional thermostat that worked with a bypass hose. The thermostat would only allow coolant to enter the engine at 120 degrees, which is about the temperature of inlet coolant in hot summer weather.

When the coolant enters the engine in cold weather, it is so cold it causes the combustion chambers to loose heat energy. It also causes the thermostat to close some which increases the resistance of the coolant flow through the water pump.

By specifically controlling the inlet coolant temperature, the regular thermostat would be open more, reducing the restriction at the water pump and increasing the flow through the radiator and bypass hose.

The conceptual part of this is to allow a certain percentage of the coolant to bypass the radiator, with a 120 degree thermostat in the connection point where the bypass and radiator flow inlet meet.

This would allow the inlet coolant temperature to be the same regardless of the outside temperature. The colder the outside temp the greater the bypass volume. The greater load placed on the engine, such as sustained hill climbing the more coolant flows through the radiator.

Remember two crucial points;
67% of the energy loss in auto engines is heat
Cooling systems are designed to provide sufficient capacity for the worst case scenario.

There is no control whatsoever of the inlet coolant temperature which can vary by close to 80 degrees depending on outside temperatures. It also will vary depending on the condition of the radiator, with a old almost plugged radiator giving you better mileage in the winter when it does not have the cooling capacity for summer heat.

Maintining inlet air temperature at summer levels as well as coolant inlet temperatures would virtually eliminate winter fuel economy losses.

Anyone who thinks cold engines with cold intake air are more economical does not understand the correlation between winter and summer fuel economy differences which can easily exceed 10 %. Warmer intake air allows greater throttle opening and higher compression with less fuel. Most modern fuel delivery systems regulate fuel delivery based on mass and temperature of the incoming air. Cold air allows more peak horsepower but also requires more fuel than hot air. Since all modern engines are way overpowered for their application they run at small throttle openings with relatively high manifold vacuum. This basically means your effective compression is much lower than it would be if the throttle position wa high enough to have atmospheric pressure available to the engine. So your super high performance engine is cruising at normal speeds with effective compression ratios of less than 5 to 1.

Take a manifold vacuum reading while cruising. If it is 15 inches you are only working with half of your atmospheric pressure. Your effective compression is half of your engines capability. This is much more inefficient than any "pumping losses".


Engines produce power by expansion of the mix of air and fuel during combustion. That expansion capability is reduced by 50 % when you only allow half of the available atmospheric pressure to enter the combustion chamber.

A typical 4 cylinder engine on a dyno producing 20 HP, will produce 50 HP with a 50% increase in fuel with the throttle wide open. That is the reason why real hypermilers can get so much better mileage. They pulse with 50 no vacuum HP and glide with the engine off. They extract 50 HP with 1.5 units of fuel instead of 20 with 1 unit of fuel. This means they get the 30 extra pulse horsepower with only half again as much fuel as the 20 sustained low effective compression horsepower of the person who is not hypermiling.

regards
gary

No myth, I managed 68.5 MPG in my Civic VX with WAI, and have averaged 60.3 in my Insight beginning December 5th 08 in the coldest part of the year in Virginia.

More air and fuel=more power

Warm air and less fuel + higher effective compression, due to WAI give you better mileage. Proven over and over.

I have never seen any proof that colder intake air and or colder engine operating temps produce better mileage.

NEVER IN 42 YEARS DRIVING.

regards
gary

Not really, and we never had problems with them either... I think there was some plastic shielding, but nothing substantial...

Gary,

I inadvertently came up with a way to test your theory for the radiator temps in the winter. Block part of the radiator along a few cooling tubes. I did that on the tracker and my return temps shot up like crazy. I was attempting to see if I was right about the return temps re-closing the thermostat in the winter causing an overheating issue and while that was what i had happening it caused my mechanical fan to work so hard I had to figure out another way to fix it(never did). But, I'd actually blocked half of the radiator tubes so it was essentially bypassing on those and then re-blending on the other end.

I'd slowly block them and watch temps as it doesn't take much for the return. I suppose you could block across the tubes but i found along them to be more effective.

On a side note: If anyone decides to try that you'll want to block the tubes closest to the return line to the engine to avoid having untouched coolant passing over your transmission cooler.

I've started looking into WAI in my Accent. Seems cheap and pretty easy to try out (and reversable).

Really, it's the engine compartment getting too cold from an additional hood vent that impacts this thread, right? If the radiator were in its own separate compartment that'd be less of a concern. Also, a setup that can use all the cooling it can get wouldn't care either.

The wiki article on WAI suggests that the primary gain comes from the reduced air intake resistance caused by the computer opening the intake diaphragm more to keep the oxygen level the same. FYI.

https://en.wikipedia.org/wiki/Warm_air_intake

Thinking some more, a ventilated engine compartment wouldn't matter if one had the bypass valve / thermostat arrangement to keep the coolant inlet temperature from declining too much. That should be able to mitigate the increased engine heat losses sustained from the cooler ambient engine compartment temps, right?

I ran the WAI on my VX until I could feel the lack of power at greater throttle openings.

In the old carburetor days, without WAI the fuel atomization was so bad the fuel would not atomize and you got serious hesitation as well as black spark plugs. My 37 Ford ran like crap until I figured out that the exhaust crossover passageway under the carburetor was plugged up.

Nissan had a wire screen under the carburetor in the early NAP-Z engines to help with fuel atomization. The screen was heated.

With the advent of fuel injection and the end of high velocity air over a venturi, poor atomization became a thing of the past, but that does not mean that atomization is not improved by hot air coming into the engine.

Restricting air flow through the radiator area also has the effect of increasing the temperature of the air coming into the engine. Air density at 200 degrees is 80% of the density at 32 degrees. All turbo cars run better in cold temperatures, but without an intercooler any turbo has much higher intale air temps. In fact any surpercharged car has higher intake air temperatures due to the simple fact that increasing air density also increases temperatures.

Thats the reason your air compressor tank gets hot. Leave it overnight and let it cool off and all the moisture condenses in the bottom of the tank. I used to do this when I painted cars, let the tank cool off overnight and you din't have to worry about water in the lines in the morning when you painted the car. It also helped to let the paint flow in the summer because the air was cold whent came out of the lines.

Think of the heat content of air in degrees Kelvin, not farenheit or centigrade and its easy to understand the increased heat under compression.

WAI and higher coolant intake temperatures are reutilizing the heat normally lost to the atmosphere. Considering you only get an average of 18% of the heat energy in useful work, you should easily understand the significance of reusing even as small as 3 % of that normally lost heat energy. That amounts to a 14 % increase in efficiency of your engine.

The best way to control the coolant inlet temperature would be to have a system that read the incoming coolant temperature and adjusted the bypass to radiator outlet volumes to maintain the desired (approx 120 degree) incoming coolant temperature.

regards
gary

The possibility of damaging the transmission by blocking flow to the cooler lines is certainly a significant point dkjones.

I am assuming your tracker had a fan clutch (viscous coupling) that was hooking up more as a result of the increases temperatures over the bimetallic spring that controls the valving in the coupling?

I think in light of your added information it may also be a good idea to monitor the intlet coolant temperatures to preclude damage to an auto tranny if your car is so equipped.

In most cases, in winter temperatures the tranny coolant would probably not rise as much as it does in summer temps even if you blocked a significant part of the radiator. I remember the old early 70's Plymouth state police cars in Va had the cooler lines blocked off. Didn't seem to kill the trannys.

I AM NOT ADVISING ANYONE HERE TO MESS WITH THEIR TRANSMISSION COOLER SYSTEMS, THE RESULTS COULD BE VERY EXPENSIVE.

They say an ounce of prevention is worth a pound of cure. Best bet would be to install remote temperature sensors to minitor temps of both engine coolant intake and transmission fluid temperatures if you choose to block off a significant portion of your radiator surface area.

regards
gary

Then you could have the hood vents and try to reduce drag or,
alternately, there could be a separate system controlling louvers over the radiator, reducing excess radiator capacity and reducing drag.

This started as an aero question, so I wanted to tie it back in.

OK, had a chance to think more on the implementation details.

For a totally new design, the shutters seem superior.

For a retrofit, the design of the shutters get very tough, so a hood vent coupled with the radiator bypass control system seems easier. The control system should probably monitor not only cooling temp in, but also cooling temp out.

The third option is a remote radiator location, of course. That gives you more freedom to explore other options, bringing shutters back into consideration.

This all assumes that a grille cover can't be at a fixed position all the time with good results. Then that is the way to go, clearly. Many factors in that one.

Does all that seem to sum things up properly?

I totally agree and I go one step further: oil temps. Keeping the engine warm (coolant and oil) is the most efficient.


Yes, a warm engine, but not warm intake air.
Yes, more air means more fuel for more power but that also means less throttle opening to produce the same power. Smaller throttle openings means less air flow means less fuel added. Also, the cooler the intake air, the more ignition advance you get. The earlier you ignite the fuel the more complete burn you get. Warm air means risk of detonation so the ignition is retarded. Retarded ignition means less burn time and more fuel wasted.

Warm Air Intakes do not create better mileage. Read the test proof:
https://www.metrompg.com/posts/wai-test.htm

That was one car. As I said, in my observations of data it varies from car to car. Some vehicles get significant increases, some record no change at all.

I've always thought that the reduced throttling/pumping loss is a large component of the savings.

The wiki entry lists that as the only source of improvement so I was curious what you thought.

So, more fuel means less fuel?

The throttle is an artificial restriction. It is purposeful waste whose job is to control engine speed. If engine speed can be controlled with less throttling (wider open throttle), the engine has to work less hard to pull air past the throttle.

Imagine the energy you would exert to drink a milkshake through a coffee stirrer, vs. the energy you would exert to drink a milshake through a jumbo straw. A closed throttle is a waste, an open throttle (as long as it's not causing excess power to be produced) reduces that waste. Operating on that concept has produced decent results for me.

Some days I theorize a lot, other days I merely observe results (which are really what matters). Ask again another day. :D

Well, we'll see what result I get as well. One more data point. The Accent sure does route its intake hose in a convoluted nature!

No, denser air does require more fuel but because it makes more power the intake doesn't have to open as much. That means the amount of fuel added is the same. You get the same ratio of fuel (14.7:1 stiochometric) with a smaller throttle opening.

You don't understand how an engine works. An engine does not PULL air past the throttle. Atmospheric air pressure PUSHES air into the engine.

Same as the example I said about sucking a milkshake through a straw. You don't pull it through, atmospheric pressure pushes it.

Air is not thick like a milkshake. You example is flawed.

Greater density means more fuel. Hot air is less dense, so you need to make sure you use the term density instead of more. I can feed 20% more volume of air into an engine if it is at 200 degrees as I can at 32 degrees and its the same mass (weight) of air.

We all should understand that the smaller engine working at a greater load is more efficient. If I could reduce the engine size by changing the displacement so it would operate at cruising speeds with no manifold vacuum, then I get the greatest effective compression and the highest efficiency.

The problem arises when I need more power to climb a hill or merge onto an interstate, but how many times in a 1000 mile trip do you actually floor the gas pedal. So we design cars for the extremes and lose any chance for real mileage. Now if you could add a supplemental power source for the extremes you could have twice the gas mileage.

WAI is a method of effectively reducing the displacement of a conventional engine, while increasing the effective compression and thus increasing the efficiency. For mr in thousands of miles off real world experience it is worth at least 10% in mileage. Whether it works or not in every car I certainly can't say, but in my case it has worked with every car I have driven that I could change the intake system. On my VX it was simple, I reversed the intak air snorkel so it was pulling air right at the top radiator hose and the top tank of the radiator.

The old Packards had the thermostatically operated louvres in the radiator that controlled air flow to the radiator. Tractor trailers have adjustable tarps with zippers that allow them to reduce the airlflow over the radiator, which also serves to increase the intake air temperature. they do this because it works, and reduces their fuel cost, guaranteed. Hot air allows the fuel to atomize better and results in more complete combustion. Perfect atomization of the fuel would increase engine efficiency by 25%. Check out homogenous charge compression ignition, which is when you can use compression only to ignite gasoline, like a diesel running on gasoline.

Honda designed a lean burn engine to run on regular gasoline at air-fuel ratios of 22 to 1 and higher. No preignition, just a very turbulent air intake strategy that allowed better atomization.

The old preheated carburetors gave way to injectors that sprayed a very fine mist of fuel directly on the head of the intake valve, which helped with atomization as well as cooling the valve.

New direct injection systems are now operating at pressures above 20,000 psi at the injectors which improves atomization, and the next step is HCCI (homogenous charge compression ignition) which is controlled detonation or "spark knock". There is no problem because the air-fuel mixture is truly perfectly distributed so the instant conbustion occurs it happens everywhere in the combustion chamber, instead of originating in separate points and colliding somewhere in the combustion chamber.

All of these things are coming, but no matter what they do they will not make an engine run better at 40 below than it does at 90 above. By better I mean more mileage, not more power.

In most cases more power does not mean more efficiency. Hondas most efficient gasoline engine is not a 4 valve per cylinder design. Instead it si a two valve twin plug design with a very high swirl in the combustion chamber to maximise the consistency of the mixture.

regards
gary

Ok, imagine going for a brisk run then breathing through a coffee stirrer vs. breathing through a jumbo straw.