JZ Type Engines

"The large-bore, short-stroke design and the 45° valve included angle allow maximum valve area, thus offering increased volumetric and thermal efficiency. Turbo lag has been significantly reduced by making the ratio of intake valve area to exhaust valve area larger than in conventional engines, and by making the exhaust duct extending from the cylinder head exhaust port to the exhaust manifold more compact to allow effective turbocharging at low engine speeds.

In addition, twin exhaust ports for the turbo system reduce exhaust interference and give improved output at maximum engine speed.

Engine efficiency has been improved by utilizing a large intercooler. Also, for the first time, a distributorless ignition system, Toyota Direct Ignition (TDI), has been adopted to boost spark energy."

"Low and medium torque are improved by about 10% using the newly developed VVT-i engine technology, which provides optimum operation-oriented intake valve timing by continuously changing the air intake valve opening and closing timing, the use of an air intake cooling duct, and optimization of the intake/exhaust manifold system. Besides substantially improving fuel efficiency through the VVT-i, raising the compression ratio, and reducing friction loss, noise levels have been improved through the increased rigidity of its parts."