In the department of engine design for the Volga Automobile Plant, we found out why the new unit is better than its predecessor and what modifications were required for this.
Two major events brought the modernization of the VAZ-21114 eight-valve engine: the launch of the Grants market and the transition of the entire model range to the next ecological step - Euro-4. And although the former 1.6-liter, despite its considerable age (its roots stretch towards the mid-80s of the last century), did not look like a weak old man, new standards and trends required extensive changes. At the same time, the ability to maneuver the minders, as often happens, narrowed the financial framework.
Therefore, we went along the already beaten track. Indeed, several years earlier, the update survived a 16-valve engine of the same volume (VAZ-21126), on which some technical solutions were tested. Moreover, not only the approach, but also many details, for example, a connecting rod with bushings, a piston pin and rings, could unify. The cylinder block, albeit with its own index, is exactly the same as the VAZ-21126 engine: with additional nozzles for cooling pistons with oil and plateauing of the cylinder walls, which reduces the break-in time.
However, it was not possible to copy exactly all the changes: it is more difficult to organize the working process in a motor with two valves per cylinder. Moreover, the requirements for the upgraded eight-valve turned out to be tougher. Take at least a resource - 160 thousand km for the VAZ-21126 and 200 thousand km for the VAZ-21116. What changed and why, tell photos with captions.
The new H-intake module was tested on an intermediate version - the VAZ-11183-50 engine (with a collector for Euro-4, but with a heavy connecting rod and piston group). Even without relief, it was only through optimization of the intake and exhaust that the basic characteristics were improved.
The upgraded unit received longer channels, which allowed to increase the torque, approaching the performance of the sixteen valve. Moreover, at VAZ-21116 its peak was reached 700-800 rpm lower. Another important feature: an electromechanical throttle module is now installed at the receiver’s inlet (common name is “e-gas”), and wires are not stretched from the accelerator pedal to the engine. Thus, the control unit was able to fully control the supply of not only gasoline, but also air to the cylinders. This is for the benefit of not only ecology, but also safety, because many electronic assistants (their list on VAZ models will soon be replenished) keep the car on the trajectory, including by dosing traction.
Masses of connecting rod and piston groups for VAZ-21114 engines (heavy ShPG, data in brackets) and VAZ-21116 (lightweight ShPG)
Masses of the connecting rod and piston groups for VAZ-21114 engines (heavy ShPG, data in brackets) and VAZ-21116 (lightweight ShPG)
In the former collector with a cylindrical block, four channels coming from the engine converged at almost one point - the exhaust gas flows collided, creating additional back pressure.
In the modernized one, the length of the pipes was increased, and the flattened shape of the block made it possible to change the pattern of their entry into the “barrel”: the streams were bred, respectively, reducing resistance and losses.
The layout and noise standards did not allow making the channels even longer: the longer the channels, the louder the sound. In addition, the farther the collector is moved away from the engine, the slower it warms up and takes longer to operate. Result: more harmful substances fly out of the exhaust pipe after start-up.
One of the most time-consuming processes was the selection of the piston. At first, they wanted to leave the motor “plug-free” (when the timing belt breaks, the valves do not bend), so the first pistons were with holes on the bottom. But they abandoned this idea: due to the increased thermal load in thinned places microcracks appeared, which affected the resource. Since the part of the combustion chamber of the eight-valve engine is located in the piston (this is the only way to ensure the normal combustion process), we selected the size of the so-called trough (German Mulde - hollow, trough) - recesses in the bottom.
Due to the critical temperature in the area of the first piston ring, an additional anodizing of the groove had to be introduced. By the way, 16-valve motors experience less thermal load in this area and therefore do without additional processing.
The new piston has another interesting and very important difference for our conditions. A graphite coating is applied to the skirt, which reduces the likelihood of scoring during cold start. It is possible that the VAZ-21116 will share graphitization with 16-valve units.
Indicators of power and torque of eight-valve VAZ engines: 21114 - with a relatively heavy ShPG; 11183–50 - with a heavy SHPG, but with a new inlet and outlet; 21116 - fully upgraded
Indicators of power and torque of eight-valve VAZ engines: 21114 - with a relatively heavy ShPG; 11183–50 - with a heavy SHPG, but with a new inlet and outlet; 21116 - fully upgraded.
Even more extensive are changes to the head of the block. Due to the modified combustion chamber, it grew 1.2 mm in height - such an adjustment can be made without serious readjustment of the equipment operating in the factory workshops.
Using computer simulation, we selected the optimal flow area of the gas channels, improving their throughput and reducing inlet losses. As the power was increased, the engine became more thermally loaded, so I had to include in the process an additional operation - heat treatment. By the way, all 16-valve heads pass it. In addition, for the sake of more efficient heat removal, the cross-section of the cooling channels was increased, but only for those that really need it.
They increased the reliability of the gas joint by introducing a two-layer metal gasket: it provides higher specific pressures and tightness with less tightening torque. This made it possible to reduce the diameter of the bolts tightening the head and cylinder block (from M12 to M10). The advantages are not only in reducing weight and saving metal: the lower the tightening force, the less the cylinders are deformed. Of course, the count goes to microns, but just such little things affect reliability and resource.
Since when the timing belt breaks on the VAZ-21116 engine, the pistons meet the valves, one of the important tasks was to develop a more reliable and durable drive.
A trusted partner, Gates, helped select the belt. The serial sample fully met the basic technical conditions: operate at a temperature of -40 to +45 ºС and not require replacement for the entire engine life. Yes, it will not have to be changed before 200 thousand km! And to tighten too - the automatic tensioner will take care of this.
It not only relieves of unnecessary operation, but also provides the correct tension, which affects the resource to no lesser extent than the quality of the belt itself. If you pull, the bearings of the rollers and the water pump suffer. The latter, by the way, is also modernized: they installed more reliable bearings and an oil seal, and also increased productivity (a unit from a sixteen-valve, only with a pulley under a narrow belt).
The drive is now protected from mechanical damage by a closed plastic casing with hermetic seals.