Dodge SRT-4 - Engine Details

Engine Details

The SRT-4 used the same basic engine block as the naturally aspired 2003+ 2.4L, and was different from the years previous used in the naturally aspirated Chrysler 2.4L mid-size cars such as the PT Cruiser and four-door Stratus. The SRT4 engine had many improvements, including: stronger crank case webbing, a thicker deck with 11 mm head bolts (vs 10 mm), a oil drain back for the turbo, a cast aluminum structural oil pan, a higher capacity oil pump, a crankshaft of higher hardness steel, improved machining of bearing journals, oil squirters (to cool underside of pistons), eutectic aluminum alloy pistons made specially by Mahle, and forged connecting rods with cracked caps and 9 mm bolts. The cylinder head was also different for turbo engines, from naturally aspirated. The turbo version (PT Cruiser GT Turbo and SRT-4) included: larger diameter valves and seats, exhaust valves made of Inconel, improved cooling and larger oil drain back passages, different camshafts. The PT Cruiser Turbo engine package differs from the SRT-4 because the intake manifold, turbocharger plumbing and intercooler are different. The SRT-4 intercooler was a front-mounted cast aluminum 8-row unit produced by Valeo, unique in its efficiency and computer designed end tanks for air flow. The turbocharger was a reverse rotation Mitsubishi TD04LR-15Gk with a 6 cm2 (0.93 sq in) turbine inlet. Tight packaging forced some creative thinking on the turbocharger. The TD04 compressor has a compressor bypass valve built right into the compressor housing. The exhaust manifold and turbine housing were cast in one piece by Mitsubishi from high-nickel Ni-Resist steel. The one-piece design improved flow, reduced size and reduced thermal mass for quicker cat light-off. The turbine discharge was also part of the manifold/turbine housing casting, and it looped back around and hit the manifold again on its way to the catalytic converter. Where they met, there was a wastegate valve; keeping the wastegate valve away from the turbine housing improved flow where it mattered most. Maximum boost in stock form was around 14 psi (97 kPa). Piston velocities and valve-train components force a rev limit of 6240 rpm although MOPAR upped the ante with their Stage 2 and 3 kits which have a rev limit of 6500 rpm.

The exhaust system for the vehicle consists of 2.25-inch (57.15 mm) steel tubing, which is run first through the catalytic converter, then through two resonators. The exhaust then splits into two separate sections of piping, exiting through two 3.75 in (95 mm) stainless steel tips at the rear of the vehicle. The exhaust system is unique in that it does not rely on a muffler for noise reduction, instead relying on the turbocharger and resonators to reduce the exhaust volume. The end result is a very distinctive and audible exhaust note, specific only to the SRT-4.