Engine cooling optimization

Shift518 Automotive
1

I have constantly been working to improve the cooling on my car especially since my first engine went due to the oil boiling and loosing its viscosity.

I decided to make this thread to state what I think I know and to get input from other people with more knowledge.

There are a few things that I have read about optimizing the radiator.

1. Size: Size can be broken down into thickness, and width. A thicker radiator with the same density of air flowing through it will shed more heat than a longer radiator. A longer radiator can offer more airflow opportunity and therefore shed more heat than a radiator of the same thickness but less width.

Thick, full width core:

http://img.photobucket.com/albums/v638/Mafdark/Tech/fluidyne_aluminum.jpg
fluidyne_aluminum.jpg800×600

2. Material: Common materials used for radiator construction include plastic, copper, brass, and aluminum, The better the conductivity, the quicker the radiator will shed heat. Some products exist which increase the conductivity of heat such as Swaintech’s “heat emitting” BBE coating: http://www.swaintech.com/store.asp?pid=10968

  1. Airflow: airflow can be broken down into two parts, moving and parked. For both it is important to note that air like nearly anything in nature takes the path of least resistance.

With the car moving the radiator will naturally have airflow through it. The closer in the bumper opening size to the radiator size the greater amount of radiator surface area used. If the radiator is centered on the car, the pressure will be higher than if on the side of the car (think side mount intercoolers and oil coolers). To optimize moving airflow, you want high pressure in front of the radiator, and low pressure behind it. To lower the pressure behind the radiator you want to pull air out of the engine bay. There are three ways that this is commonly done.

1. by venting the hood. This method is quite tricky and requires testing to insure that the high pressure air above the hood and in front of the windshield doesn’t get pushed into the engine bay.

2. By creating vents behind the wheels and ducting the air out through them. This method is not possible for many cars without heavy fabrication due to the unibody. and

3. Below the car. From the factory the airflow through the radiator and enginebay continue below your car and is pulled by the fast moving air below. To insure air is forced through the radiator and not redirected around it shrouding or sealing/blocking ducting should be used.

Example of ducting forward of the radiator:
http://img.photobucket.com/albums/v638/Mafdark/Tech/airflowducting.jpg

[FONT=Book Antiqua]Example of ducting behind radiator to vents:
http://img.photobucket.com/albums/v638/Mafdark/Tech/radiatorducting.jpg

Example of a vented hood:[/FONT]
http://img.photobucket.com/albums/v638/Mafdark/Tech/hoodvents.jpg

example of fender vents:
http://img.photobucket.com/albums/v638/Mafdark/Tech/wheelvents.jpg

When parked the airflow is forced by a mechanical/belt driven or electric fan. With a mechanical/belt driven fan the fan is moving at its slowest speed while at idle and at its quickest speed when it is unneeded at higher RPM and the car is moving. Replacing a belt driven fan for an electrical one can decrease the load on your engine and improve cooling at idle. Electrical fans can aid in cooling even after you turn the car off. These fans are set to thermostats and relays so that they turn on when your car is above a certain temp and so they can remain on for a few seconds after you turn off your car to afford it additional cooling. For any fan, the airflow is again a matter of concern. If a fan does not have appropiate shroud to seal the fan to the radiator then the fan can pull the air from the engine bay itself so air from the front of the radiator will not be pulled through the radiator. The fan if wired appropiately with a reversible motor can be placed on the front side of the radiator but still requires the appropiate shrouding to insure the air is forced through.

Belt driven fan:
http://img.photobucket.com/albums/v638/Mafdark/Tech/enginefan.jpg

fal fan with shroud:
http://img.photobucket.com/albums/v638/Mafdark/Tech/falfan.jpg

4. Fluids: Water is the best in terms of cooling, however the drawbacks include damaging rust which may go unnoticed inside your block and freezing in sub 32* temps. A 50/50 mixture of coolant and water will offer sufficenit cooling properties but will save your steel/iron parts. Additives such as water wetter increase the adhesive properties of water which improves heat transfer from inside of the radiators walls.

5. Insulate heat: This should go without saying, but by insulating heat emitting componants in your engine bay will reduce heat soak back into your radiator. Especially if your airflow out of the engine bay is not optimized. Simple modifications such as underdrive pullys can create much more heat in the engine bay which can soak back into your radiator and even intake. By skipping the underdrive pullys and by insulating hot headers, turbos, and exhausts engine bay and therefore engine and coolant temps can be reduced dramatically. A good way to do this is with turbo blankets or ceramic heat insulating coatings such as swaintechs “white lighting” http://www.swaintech.com/store.asp?pid=10969

turbo blanket
http://img.photobucket.com/albums/v638/Mafdark/Tech/turboblanket.jpg

Work in progress, more to come.

2

Race cars should run a 70/30 water/coolant mix. Better heat transfer. Use a GOOD coolant. I like using synthetic G12 in everthing(VAG/Porsche OEM) or even the synthetic BMW factory coolant.

Proper radiator core ducting is very important and done right will drastically increase the efficiency of the core on it’s own. I would avoid blowing the air under the car. Out the side of the car is the best(via vents of into wheel wells with proper extractors), above if not possible. Most race chassis will direct flow outwards,just an example here…this is actually my PS3 background :)…http://upload.wikimedia.org/wikipedia/commons/2/2d/McLaren_F1_GTR.jpg black vent on side forward of front wheels are rad extractors that fit regulations back then. Those also double as a turbulator(vortex generator) for the front wheels to reduce drag.

It’s difficult to coat a radiator completely with BBE where it’ll be of benefit. That coating is excellent for us on bloack/head exteriors. I use is extensively on my $10K+ porsche engine builds for the aircooled motors to pull heat from the cylinders, heads, and cam boxes. You’d see more benefit from using a ceramic coating on the manifold than using BBE on a majority of the parts under the hood, but it DOES works when all other options have been utilized and you’re looking for the last bit of efficiency out there.

Lot’s more to talk about, but I’ve got other stuff to attend to at the moment. If you got specific Q’s, do ask away :slight_smile:

3

What other awsome knowledge you got in that head :smiley:

4

Kinda weird you brought this up :rofl

5

You can run straight water with an additive in summer months… just be sure to change it out for the winter months.

6

thats what I said :wink:

7

Designing piston for 6.2L v12 in solidworks at the moment :wink:

One other small tip when considering radiator efficiency…it’s always better to increase the frontal surface area of the core vs going with a thicker core. On two cores of exact surface area, one just being thinner but larger in length/height will have better cooling efficiency than the smaller but thicker core. The air charge becomes temp saturated as it passes through the core and as such the rate of heat transfer is progressive(negative) and not linear. Obviously on an OEM fitment rad or in tight spaces it’s not always possibly to increase the frontal surface area, but when designing a chassis fitting the biggest possible length/height core is your best bet. Add thickness for thermal capacity thereafter.

8

Ah, see when I was reading about intercooler sizes some tuners had the opposite information, thickness rather than width. but they had no data to back up their claims.

9

good info.

http://www.t1raceparts.com/product_p/t1%20rad%20combo.htm

10

Intercoolers follow similar principles in fluid dynamics but are a little different, because you need to take in laminar flow of air and overall required CFM flow rate to supply the engine. In radiators where you want to reduce liquid cavitation caused by coolant exiting the core, intercoolers you want reductions in pressure drop. It’s more of a compromise between tube length and internal tube fin design that affects intercooler efficiency vs overall size, because the rate of transfer of heat through air vs a liquid are drastically different… (Overall longer core tubes tend to cool the air more but create a bigger PD than shorter tubes of a top-to-bottom style core, such as a Griffin.)

With intercoolers 99% of aftermarket manufactures/tuners will tell you a thicker core will yield more power, when in fact it’s really yielding more power POTENTIAL due to increased flow(CFM) capacity rather than increased cooling efficiency. Making an IC core thicker does increase it efficiency to a degree as it’s increasing it’s thermal capacity before 100% heatsoak, but its not nearly as effective as increasing frontal surface area.

The more surface area that air can initially get to on a core, the better the cooling can be. As air passes through the core it temperature increases progressively and it’s ability to transfer heat drops. The most efficient portion of your typical air/air core will be the leading face of the core directly in line with the air charge inlet. Increasing the surface area of that portion will gain the greatest results and the only way to do that is by increasing frontal area(internal mods excluded from this topic however). One thing to remember as well is that an air/air core’s efficiency is not rated across 100% of the cores front area. Think of it more like that of a turbocharger compressor map, but instead of islands of increased efficiency imagine elliptical bands. There are ways to alter/change/increase this effect across the entire core, to your benefit, but are internal and/or design related.

I know this was a bit off topic from the engine cooling discussion but still sorta fits in here. Delete as needed :slight_smile:

11

actually that is a future installment. :wink:

12

:smiley:

13

http://img.photobucket.com/albums/v225/bennyfizzle/badmonkeyradiatorshroud.jpg

(not my car)

14

i have to block off my grill for my cooling system to work right in the winter :slight_smile:

15

+14. Seal off your front bumper to the wheel well liners, get an underpanel, and force air through the rad, not around it. Welcome to BMWs.

16

What do you mean seal the bumper off to the liners?