Closer Look at All 3 SRT Engines on the Dodge Challenger

December 26th, 2017 by

The lineup of Dodge’s SRT-powered vehicles has been strengthening over the years, and Dodge’s lineup of SRT-powered muscle cars for the 2018 model year is the most powerful lineup the brand has ever had. Over the years, Dodge has developed more and more ways to make engines more powerful, and for the 2018 there are three SRT engines available, and they all have a unique engine design that gives them the ability to produce a great amount of power. Here’s a closer look at how all three engines are different from information provided by FCA.

Availability

The three SRT-powered engines offered by Dodge for the 2018 model year are the 475-horsepower, 470 lb-ft of torque 6.4-liter HEMI V8 engine (also called the SRT 392 engine); the 707-horsepower, 650 lb-ft of torque supercharged 6.2-liter HEMI SRT Hellcat V8 engine; and the 840-horsepower 770 lb-ft of torque supercharged 6.2-liter HEMI Demon V8 engine.

For the 2018 model year, the 6.4L SRT engine is available on the Challenger R/T Scat Pack, Challenger 392 HEMI Scat Pack Shaker, Challenger T/A 392 and SRT 392 models. The supercharged 6.2-liter HEMI SRT Hellcat V8 engine is available on the Challenger SRT Hellcat and the new 2018 Challenger SRT Hellcat Widebody. The supercharged 6.2-liter HEMI Demon V8 engine is new to the 2018 lineup and it is only available on the Challenger SRT Demon.

Engine Displacement

People tend to think of engine displacement as the size of an engine, but actually engine displacement is the volume of the engine’s cylinders and/or the volume of air displaced by the action of the pistons. More cylinder volume means there is more room for air, and more air makes bigger combustions, and bigger combustions create more power.

The engine displacement of all three SRT engines isn’t very different from one another (392 cubic inches, and two engines are 376 cubic inches), however, the amount of horsepower (reminder: 6.4L engine produces 475 horsepower, the 6.2L SRT Hellcat engine produces 707 horsepower, the 6.2L SRT Demon engine produces 840 horsepower) produced by each SRT engine varies quite a bit and that’s due to some of the other engine qualities below.

Take Note: Engine displacement used to be expressed as cubic inches, but now it is expressed in liters, however, both units are equivalent to each other.

Bore:Stroke Ratio

All three SRT engines have eight cylinders, but there are two different sized (6.4L and 6.2L) engines, and the reason for that is the bore-to-stroke ratio of the cylinders.

Bore is the diameter of a cylinder and stroke is the length or distance traveled by piston from 0-180 degrees. There are three types of bore-to-stroke ratios, an oversquare ratio (bore bigger than the stroke), an undersquare ratio (bore bigger smaller than the stroke) or a square ratio (bore and stroke have an equal ratio). An oversquare bore-to-stroke ratio allows for a higher RPM without excessive piston speed, and that is why many performance engines have an oversquare ratio.

All three SRT engines have an oversquare bore-to-stroke ratio, however, the 6.4L engine has a smaller bore-to-stroke ratio than the 6.2L engines. The 6.4L engine has a bore-to-stroke ratio of 4.09:3.72 (or 1.1:1), and the SRT Hellcat and SRT Demon engines both have a bore-to-stroke ratio of 4.09: 3.58 (or 1.15:1), and that is one source where the engine can produce more power.

Compression Ratio

Another source for engine power is compression ratio. The only thing that creates engine power is the size of the explosion of fuel and air in the combustion chambers and more compression creates a bigger the explosion. The 6.4L engine has a compression ratio of 10.9:1. Because both of the 6.2L engines are supercharged, which increases the pressure of air being forced into the engine, there compression rate doesn’t need be as high and can even cause a problem, so both of the 6.2L engines have a compression ratio of 9.5:1.

Valves

All three SRT engines have the same number and type of valves. Each engine has 16 valves with sodium filled exhausts, 16 hollow stem intakes and 16 hydraulic roller lifters.

Induction System

An induction system are parts that meter and direct the flow of air into the engine. Since oxygen plays a big role in how big explosions are, which affects the amount of power an engine produces, air flow is a big component in performance cars.

The 6.4L SRT engine and the Challenger SRT Hellcat engine both feature Air Catcher headlamps, which allows air to flow into the engine from an missing headlamp, but the Challenger SRT Demon has quite a few components that make up the vehicle’s induction system. The Challenger SRT Demon is equipped with an Air-Grabber hood – 45.2 square inches, an air catcher headlamp as well as an air box opening near wheel liner.

Intercooler System

Intercoolers are commonly used on vehicles that have a supercharger or a turbocharger, so that explains why the 6.4L engine doesn’t have a special intercooler system and the SRT Hellcat engine and the SRT Demon engine do. The SRT Hellcat’s intercooler system is composed of a

separate low-temp cooling system with dual water-to-air intercoolers and a high-flow variable-speed electric water pump.

The SRT Demon engine is equipped with a separate low-temp cooling system with dual water-to-air intercoolers and a high-flow variable-speed electric water pump. In Drag Mode, the SRT Power Chiller™ liquid-to-air intercooler chiller system is activated and redirects air conditioning refrigerant to chill the intercooler coolant. When engine is shut down a radio-selectable After-Run Chiller system turns on radiator fan and intercooler water pump to reduce intercooler coolant temperature.


Want to see what an SRT performance engine is like for yourself? Come by Kendall Dodge to test drive all of our available Dodge Challenger models today!