How the A/C of the Dodge SRT Demon Creates Horsepower
Using horsepower to make more horsepower? We’ve heard of spending money to make money, but this is just mind boggling. When you think about it though, isn’t that how everything works? After all, a supercharged engine gets more horsepower via the supercharger, and that system is actually run by 90 units of the horsepower initially generated by the engine itself. How does the Dodge Challenger SRT Demon use power for more horsepower?
A Stack of Systems
The Dodge SRT Demon gets all of its power from a circuit of systems that, when put together, form a sort of totem pole or pyramid. Starting from the bottom, it would go – air vent, supercharger, intercooler, engine.
In a nutshell, it goes like this:
- Ambient air comes through the air filter into the supercharger
- Supercharger compresses that air
- Intercooler then cools that air and sends it into the engine
In essence, superchargers compress the air, effectively making the air dense, and the more there is to burn the more horsepower is generated by the engine. But wait, if the supercharger compresses the air, doesn’t it also make the air a little hotter? Each component has its own cooling system to combat that result.
The engine is kept cool via a radiator like most vehicles today. The engine expels hot liquid coolant that is then sent into the engine radiator where it is cooled by ambient air. An engine driven water pump then pulls the now cooled coolant back into the engine.
The intercooler is run by an electric pump and essentially drains power from the car itself. Following the supercharger compressing the air, the intercooler cools it off before sending it into the engine. After it does this, it then expels its own hot liquid coolant. That hot liquid coolant passes through a heat exchanger behind the radiator, cooling it down a bit. It is then further cooled when the electric pump sends it through a power chiller and then back into the intercooler.
During all of this, an A/C compressor is driven by the engine and expels hot, compressed gas refrigerant that travels through an A/C condenser. The A/C condenser turns the hot gas into a hot liquid refrigerant that travels into an expansion valve where the liquid “expands” and cools. Here, the cooled liquid refrigerant can go through the cabin evaporator for the a/c system or through the power chiller.
Remember, the hot coolant from the intercooler has been chilled and is sent into the power chiller via the electric pump. So, while the expanded refrigerant turns into a gas and is then sent into the engine through the power chiller, the coolant from the intercooler is being sent into the power chiller via the electric pump, effectively turning it into cold coolant before sending it into the intercooler. This process where the expanded refrigerant gas and cooled intercooler coolant meet also help cools down the air from the supercharger in the intercooler. So effectively, two components are sending cool air into the engine.
Both, the a/c system and power chiller can’t run at the same time though. It’s one or the other, so either the driver runs the A/C and drives casually, or shuts off A/C and runs down the drag strip via the launch button. Either way though, the power chiller only runs as long as the engine RPM is below 4500.
During this entire process, air is pulled through all three systems via the engine fan. So, as mentioned, we have a stack of systems as well as a circuit. The circuit is the expulsion of hot coolant/refrigerant and how it is cooled before being reintroduced into its proper, respective component. The stack is air vent, engine radiator, heat exchanger, a/c condenser, supercharger, intercooler, engine. In addition, although not mentioned, variable valve timing (VVT) technology has most likely been implemented into the SRT Demon engine to accelerate the timing of the lift valve events because everything is being cooled down a lot faster.
All of this results in air that is 45 degrees F cooler before it is introduced into the engine.
And just for the fun of it, we have the after-run cooler. Via the engine cooling fan and electric pump, the intercooler cooling circuit continues to run, so that when the engine starts back up, cool air is introduced into the combustion chamber.
Phew, wow that’s crazy. Discus it with us on social media, and we’ll see if we can get Jason Fenske, the brains behind this explanation, to join.