New 1.5-Liter Engine

Mazda Motor Corporation has developed a new 1.5-liter DOHC engine with a sequential valve timing (S-VT) mechanism that better achieves the requirements of improving output and torque while also lowering fuel consumption and CO2 and NOx emissions. This engine will be featured in the new Familia.

new 1.5-liter engine from Mazda

This S-VT engine continuously varies the open-close timing of the air intake valves and thereby optimizes valve timing under all driving conditions, whether in the city or on the freeway.

In order to transfer the rotation of the crankshaft to the camshaft, a pulley is attached to the front end of each shaft. These are linked by a timing belt. In most engines, the pulley is attached directly to the camshaft, which determines the valve timing.

In the S-VT engine, however, a vane actuator attached to the pulley part of the intake camshaft is used to facilitate continuous adjustment of the valve timing. The vane actuator comprises a housing fixed to the pulley and a vane fixed to the camshaft, with the hydraulic chambers of the advancing chamber and delaying chamber systems between the housing and the vane. The hydraulic pressure applied to these hydraulic chambers is controlled by an oil control valve (OCV), whereby the relative phases of the pulley and the camshaft can be varied and the intake valve timing controlled. The OCV also detects engine rpm, the amount of air taken in, and water temperature by means of a computer so that it can perform optimal control of valve timing under all driving conditions.

These functions enable S-VT to achieve the following:

1. When driving with a heavy load at moderate rpm, reverse flow of air intake is suppressed by closing the air intake valve early, thereby improving the volumetric efficiency (charging efficiency) of the air in the combustion chamber and in turn improving torque.
2. When driving with a heavy load at high rpm, closing the air intake valve late makes it possible to take full advantage of the inertia effect of the intake air, thereby improving charging efficiency and in turn improving maximum out put.
3. When driving with a moderate load, overlapping (a condition wherein the air intake valve and exhaust valve are open at the same time) can be expanded by speeding up the timing of the opening of the air intake valve. This increases the amount of exhaust gas circulation (internal EGR), thus reducing pumping loss, which in turn reduces fuel consumption and the amount of CO2 emitted ( diluted-burn effect ).
4. Internal EGR pulls inert gases back into the cylinder, lowering the combustion temperature and in turn lowering NOx emissions.

S-VT employs a simple system that does not require complicated mechanisms, so it is both reliable and low cost.

S-VT Engine Performance

Engine Type	Type ZL-DE 1.5-liter DOHC
Max. power (ps/rpm JIS net)	130/7,000
Max. torque (kg-m/rpm JIS net)	14.4/4,000

Increase of max. power	13%
Decrease of fuel consumption &. CO2	16%
Decrease of NOx	14%

(Comparison with the previous Familia
sedan model equipped with a B5-Z5
engine &. 4-speed automatic transaxle)

Find more news and information at www.mazda.com