Engine performance improves supercharger performance ...
I am compiling a guide for information on how to select the exact engine parts to suit your power requirements. Basically, I want to eliminate all assumptions about tuning and save you from having to do something over and over.
While I was doing research for buying the right intercooler. Honestly, I'm lost. There are two types of information that you will find there:
1-One class of articles is written by engineers talking about pressure drops, thermal efficiency, enthalpy, and many variable equations that are very remotely related to flow, power, torque, blower circulation, or other things that we KNOW that we can use as input to our equations. (In principle, this science should be translated to non-professional terms)
2-Another class is a group of random trial and error recommended by enthusiasts, press releases and other materials that you find on the Internet.
Here is what we know:
First, let's talk about how intercoolers work. There are several disputes about how an intercooler looks like a heat sink, whose function is to absorb thermal energy from the incoming air to prevent heat from the engine from heating, or an intercooler like a radiator, where the air flow over the intercooler is equal to the one responsible for extracting heat from the air inlet charge.
The true answer is correct.
The air passing through the intercooler spends very little time in the intercooler and slows it down for more heat exchange (for example, we cooled in the radiator) would mean that the air does not reach the engine, which is a power limit. Since air spends little time in the intercooler, the intercooler usually has several passes, internal fins and fins inside it to maximize surface contact between the aluminum of the intercooler and the compressed air molecules. In this sense, the total volume of the intercooler and the total area of its internal surfaces are similar to a radiator, which absorbs thermal energy from compressed air. In this aspect, it makes sense that the larger our intercooler, the better. In addition, it makes sense that the more complex and complicated the internal passages of our core, the more heat we can extract from the charge air. Of course, this means that very complex internal passages can create turbulence and limit air flow, so there is a very good balance between internal complexity and throughput.
When we start, the intercooler is cold, and with our first start-up, when the hot compressed air passes through the intercooler, heat is transferred to our radiator (which is an intercooler), and good cool air remains to enter the engine. After the first start, the intercooler heats up; and if we had made the second power flow back, the intercooler would not be able to go through a lot of heat, because this is already something heated. Here, the intercooler is switched on as a radiator, the heat that was transferred from the air to the intercooler core must be taken either by a transverse air flow in the intercooler to the air, or by cooling the liquid in the air to water with an intercooler or even ice water for use in racing Without collecting the heat that the intercooler absorbed from the compressed air, the aftercooler heats up after running until its temperature is the same as the heating of the compressed air. At this moment, there is no temperature difference between the air and the core of the intercooler, and we can no longer turn OFF the heat.
On some cars, intercoolers are located under the hood of the car (for example, Mazda Sentia / 626). With this installation, the intercooler is basically a radiator and will be used for several passes until it is absorbed, so it absorbs it to return to the temperature under the hood before it becomes effective as an intercooler again. From this we collect that any intercooler, however small or poorly placed, is better than the intercooler, because at least for this first power start-up this will potentially increase power.
Now I would like you to remember this information while we are talking about the size of the intercooler ...
There are three main sizes in the intercooler: height (H), width (W) and (D), and based on this there are some physical concepts that we want to think about:
Cross-sectional area:
Height x Depth = cross-section of the intercooler and is related to how well the intercooler will go, and regardless of whether it represents a restriction on the inlet flow. This is the surface area facing the compressed air as it passes through the intercooler. Like free flowing air intakes, throttles and exhaust gases, if this area is small, it will limit flow and reduce performance.
Width:
Width = length of the intercooler, and if you have the same inlet / outlet side intercooler, then the length of the intercooler is 2 * W. This is the distance that air must travel through the turbulent and complex core of the intercooler. The longer this length, the more pressure drops occur in the intercooler, so it is not recommended to have a too wide intercooler, because we will use compression of the turbocharger with an intercooler pressure drop, although it is desirable to have the same inlet / outlet intercooler where the air must travel a long distance in the core.
Frontal area:
Width x Height = front intercooler area facing the incoming ambient air, a good sized frontal area is required to ensure that the intercooler does not heat up and that the airflow is able to cool the intercooler efficiently (for example, a radiator) so that you can reverse power supply. As we increase this area, we expect the intercooler to better control the peak operating temperature and to have better repeatability no matter how long we stay in the up state (good for a standing mile race, for example, or on all road racing events).
Depth:
Depth = intercooler depth, usually the front intercooler is installed in front of the radiator ... if you increase the depth too much (and especially without a proper duct to the intercooler and aerodynamic profiles between the intercooler and radiator), you can slow down the incoming ambient air to your radiator started to overheat. Thus, an increase in D gives us better intercooler performance and greater throughput (H * D is the cross-sectional area mentioned above), but this reduces the efficiency of engine cooling, so it also needs to be controlled.
Last but not least:
Overall volume:
Height x Width x Depth = total volume of intercooler, which is an indirect measure of the internal surface of the intercooler. The larger the volume, the larger the heat exchange surface area, the more heat we can remove from the air in a very short period of time (100 milliseconds or so that the air remains inside the core). Obviously, the larger the volume, the better the cooling and the worse for the pressure drop. Again this number needs to be controlled.
How do i know if the intercooler is sufficient?
The effectiveness of the intercooler can be tested in two ways:
1-Thermal characteristic
a. Measure the temperature difference between the intercooler intake air and the intercooler exhaust air and use this delta T for comparison between you intercoolers. The best intercoolers there can lower the air temperature by more than 100 * F and get within 20 * of the ambient temperature. If your factory intercooler can already perform similar results, then there is no need to upgrade.
b.Make sure that the temperature of the intercooler will be increased over a long time, or when re-feeding. The design and placement of the intercooler should be sufficient for the temperature to rise over time (say, 60+ mph air entering the intercooler), if the temperature control is too steep, then you may need a better radiating effect; a core with a larger frontal area, better air ducts and an air film, as well as better placement with high pressure air in front and low pressure air behind it ... more on this later.
2-flow performance
a. Measure the flow through the intercooler core at 28 ° water (standard for most flow meters) or measure the total intercooler pressure drop at the flow rate required by your target power. If the intercooler is on the vehicle, measure the differential pressure through your intercooler at peak hp values.
The best intercoolers will have less than 1 psi pressure drop (usually from 0.5 to 0.9 psi) with peak load and power. If your intercooler is within these power ratings, you may not need to upgrade.
Now, returning to choosing the best-fit intercooler for your application, it would be very difficult for me to determine the exact math on how to optimize the size of the intercooler, and then I would have to translate this mathematics into terms power, inlet air temperature, blower outlet temperature, pressure and discharge pressure ratios ... etc.
Here is another solution; One thing engineers love to do in order to cope with such a problem is by creating statistics on a chart and distorting some trends ...
I found about 30 different intercoolers online using flow tests (CFM) or Dyno tests (HP) or both, and since we know that about 1.5 CFM of air is required to produce 1 HP (depending on density), then I combined both datasets for both stream-tested OEM intercoolers and for the secondary market. intercoolers for obtaining the following graphs:
The flow in CFM against Cross section:
Consumption (CFM) = 11.63 * Cross-sectional area (square inches) - 12.84
This is a graph of flux in CFM (vertical) and cross-sectional area (square inches) for 30 cores for which I had data. As you can see, there is a linear relationship between the flow and the area that is expected. Therefore, we can use this as a guideline to determine (for a given depth D) the available cores, what the minimum height of our intercooler should be a good flow performance.
It should be noted here that these flow measurements were made at 28 ° water pressure or 1 psi. As is known from the supercharger theory, the greater the pressure of the boost (and the higher the pressure ratio), the greater the compressed air. half its volume compared to 0psi (or 1 psi). Thus, the production of 700 hp (1050 CFM) @ 15psi (for example, on a 3.5-liter 6-cylinder) may require as little as 42 square inches of cross-sectional area (since the air is half its original size), while making 700 hp. (1050 CFM) @ 3psi (for example, on a 7-liter 8-cylinder) may require a large cross-sectional area in the square.
Here is my second trend:
Horsepower (hp) = 0.533 * The volume of the intercooler (cubic inch) + 50.17
This is a graph of power (vertical) compared to the total volume of the core (cubic inches) for the 30 cores for which I had data. As you can see, there is a linear relationship between power and volume expected. The more horsepower we want to do, the more air we need to swallow. The greater the air mass; the more energy that mass can carry (at the same temperature as compared to a smaller mass), and thus, the more intercooler we have to absorb this energy in our intercooler.
I think that between these two graphs you can now return to my “dual charging” Toyota Celica and say:
I wanted to make a peak of 320hp @ 20 psi. This corresponds to 480 CFM @ 2.36 Pressure ratio.
Starting with the standard 3-inch intercooler core, let me figure out my other 2 dimensions:
The minimum cross-sectional area = ((480 / 2.36) + 12.84) / 11.63 = 18 square meters. Inches = D * H
Intercooler height = 18/3 = 6 "
Total volume = (320 - 50,17) / 0,533 = 506 cubic inches.
Intercooler width = 506/18 = 28 "
So my ideal kernel size looks like 28 "X 6" X 3 ", which is a fairly convenient size of an intermediate intercooler.
Now 28 "is a reasonable width of the intercooler for the pressure drop. If this figure was too big, I would go back and use, for example, a 3.5-inch core. Similarly, if my 6-inch intercooler would not fit my bumper, I could go back and increase the depth a little and repeat the calculation.
The intercooler pressure drop is really important for tracking a supercharged car, because, unlike a turbocharger, we cannot simply increase the supercharging pressure using a tow controller, we are limited to the superchargers for the gears we have in our supercharger pulley. So waste any of these pulses is very bad for performance. That is why it is really important in order to reduce the intercooler, to strangle the engine, and not to increase it in order to create a large pressure drop.
