VAZ-2112 Engine

The VAZ-2112 engine is a petrol, four-stroke, four-cylinder, in-line, transversely mounted, sixteen-valve engine with two camshafts.

Firing order: 1–3–4–2, counted from the crankshaft pulley.

Fuel system — sequential multipoint fuel injection.

Engine management — control unit (Bosch, «Janvar» or GM).

Most engines are fitted with a catalytic converter.

The engine, gearbox and clutch form a power unit mounted in the engine bay on four flexible rubber-metal mountings.

The right and left mountings are the same as on the 2110 and 2111 engines.

The front and rear mountings are identical, in the form of tie rods.

One end of the tie rod is attached to a bracket on the engine, the other to a bracket on the body.

On the right-hand side of the engine (in the direction of travel) are: the camshaft and coolant pump drives (toothed belt) and the alternator drive (poly-V belt).

On the left-hand side are: the thermostat, coolant temperature sensors, oil pressure sensor, starter motor (on the clutch housing).

At the front: the intake manifold, fuel rail with injectors, knock sensor, oil dipstick, crankcase breather hose, alternator (lower right), phase sensor (upper right).

At the rear: the exhaust manifold, oil filter, crankshaft position sensor (lower right).

On top (under the plastic cover) are the receiver, spark plugs (in guide tubes sealed with rubber rings) and high-tension leads.

The cylinder block is cast in cast iron and bears the index «21083» — as on the 2110 and 2111 engines, but they are not interchangeable: the cylinder head bolt holes have M10×1.25 threads (unlike M12×1.25 for the 2110 and 2111 engine blocks) and are shallower.

Another difference is due to the more severe thermal conditions of the 2112 engine compared with the 2110 and 2111 engines.

To cool the pistons during engine operation, their crowns are washed from below with oil through special jets pressed into the second, third, fourth and fifth main bearing supports.

The cylinders are bored directly in the block. The nominal diameter of 82 mm may be increased by 0.4 or 0.8 mm during repair.

The cylinder class is marked on the lower face of the block with Latin letters according to the cylinder diameter in mm: A — 82.00–82.01, B — 82.01–82.02, C — 82.02–82.03, D — 82.03–82.04, E — 82.04–82.05.

The maximum permissible cylinder wear is 0.15 mm on diameter.

In the lower part of the cylinder block there are five main bearing supports with detachable caps secured to the block by special bolts.

The caps are not interchangeable (the bearing bores are machined together with the caps) and are marked with scores on the outer surface for identification.

The middle support has seats for the thrust half-rings, which prevent axial movement of the crankshaft.

At the front (on the crankshaft pulley side) a steel-aluminium half-ring is fitted; at the rear — a metal-ceramic one.

The rings are made in nominal thickness and in a thickness increased by 0.127 mm.

If the crankshaft axial clearance exceeds 0.35 mm, one or both half-rings are replaced (nominal clearance — 0.06–0.26 mm).

The main and connecting rod bearing shells are thin-walled steel-aluminium.

The upper main bearing shells of the first, second, fourth and fifth supports, installed in the cylinder block, have a groove on the inner surface.

The lower main bearing shells, the upper shell of the third support and the connecting rod shells have no groove.

Repair shells are produced for crankshaft journals reduced by 0.25, 0.50, 0.75 and 1.00 mm.

The crankshaft is made of high-strength cast iron.

It has five main and four connecting rod journals and is provided with eight counterweights cast integrally with the shaft.

The crankshaft of the 2112 engine differs from that of the 2110 and 2111 engines in the shape of the counterweights and in higher strength.

Therefore, fitting a crankshaft from the 2110 and 2111 engines to a 2112 engine is not permitted.

To supply oil from the main journals to the connecting rod journals, channels are drilled in the crankshaft, their outlet holes being closed by pressed-in plugs.

On the front end of the crankshaft, on a Woodruff key, the camshaft drive toothed pulley is mounted; the alternator drive pulley is attached to it, which also acts as a torsional vibration damper for the crankshaft.

On the toothed rim of the pulley two teeth out of 60 are missing — the gaps serve the crankshaft position sensor.

To the rear end of the crankshaft the flywheel (index 2110), cast in cast iron, with a pressed-on steel toothed ring for starting the engine by the starter motor, is secured by six self-locking bolts through a common washer.

The conical recess near the flywheel ring must be opposite the connecting rod journal of the fourth cylinder (this is necessary for determining TDC after engine assembly).

The connecting rods are steel, of I-section, and are machined together with their caps.

On the caps, as on the connecting rods, the cylinder number is stamped (it must be on the same side of the rod and cap).

The connecting rods are divided into three classes according to the diameter of the steel-bronze bush pressed into the upper eye, with a step of 0.004 mm.

The class number is stamped on the connecting rod cap. The connecting rods are also divided into classes by mass — they are marked with paint or a letter on the connecting rod cap.

The piston pin is steel, of tubular section, of the floating type (rotates freely in the upper connecting rod eye and in the piston bosses).

It is secured against falling out by two spring circlips located in grooves in the piston bosses.

There are three classes of pins by outside diameter (at 0.004 mm intervals): 1 — with a blue mark, 2 — green, 3 — red (smallest diameter).

The piston is of aluminium alloy. The piston skirt is conical in longitudinal section and oval in cross-section.

Three grooves for the piston rings are machined in the upper part of the piston.

The oil control ring groove has drillings opening into the bosses, through which oil collected by the ring from the cylinder walls reaches the piston pin.

The piston pin bore is offset by 1 mm from the diametral plane of the piston.

When fitting the piston, note the arrow stamped on the crown (it must point towards the crankshaft pulley).

The pistons of the 2112 engine have a flat crown with four recesses for the valves (the pistons of the 2110 and 2111 engines have an oval recess in the crown).

The pistons, by outside diameter (measured in the plane perpendicular to the piston pin, at a distance of 51.5 mm from the piston crown), like the cylinders, are divided into five classes (marking on the crown).

Piston diameter (for nominal size, mm): A — 81.965–81.975; B — 81.975–81.985; C — 81.985–81.995; D — 81.995–82.005; E — 82.005–82.015.

Pistons of classes A, C and E (nominal and repair sizes) are available for sale: the calculated clearance between them is 0.025–0.045 mm, and the maximum permissible clearance when worn is 0.15 mm.

It is not recommended to fit a new piston into a worn cylinder without reboring it: the top ring groove in the new piston may be slightly higher than in the old one, and the ring may break on the «step» formed in the upper part of the cylinder as it wears.

On repair-size pistons a triangle (+ 0.4 mm) or a square (+ 0.8 mm) is stamped on the crown.

By the diameter of the piston pin bore, the pistons are divided into three classes: 1 — 21.978–21.982; 2 — 21.982–21.986; 3 — 21.986–21.990.

The piston class is also stamped on its crown.

The piston and pin must be of the same class.

The pistons of one engine are selected by mass (the spread must not exceed 5 g) — this is done to reduce the imbalance of the crank mechanism.

The upper two piston rings are compression rings, preventing blow-by of gases into the engine crankcase.

They also help to transfer heat from the piston to the cylinder. The lower ring is the oil control ring.

The cylinder head — common to all four cylinders — is of aluminium alloy.

It is centred on the block by two dowels and secured by ten bolts.

Between the block and the head (their surfaces must be dry) a non-settling metal-reinforced gasket is fitted (its reuse is not permitted).

The sequence and torque for tightening the cylinder head bolts are given in the appendix.

In the upper part of the cylinder head are the camshaft bearings — five on each side of the head.

The bores in the split bearings are machined together with the bearing housing.

The housing must be replaced together with the cylinder head.

On the surfaces of the cylinder head that mate with the bearing housing, Loctite No. 574 sealant is applied.

The sequence and torque for tightening the bearing housing nuts are given in the appendix.

The camshafts are cast, of cast iron, five-bearing, each with eight cams (a pair of adjacent cams opens two valves in the cylinder simultaneously).

The camshafts are driven in rotation by a toothed belt from the crankshaft.

Owing to the increased loads on the toothed belt, its width in the 2112 engine, compared with the 2110 and 2111, has been increased from 19.0 to 25.4 mm (correspondingly, the width of the toothed pulleys and rollers has been increased).

Under the intake camshaft pulley there is a support roller, under the exhaust one — the tensioner.

For the phase sensor to operate, a disc is welded to the toothed pulley of the intake camshaft.

The drive sprockets have setting marks: if the mark on the crankshaft pulley coincides with the mark on the oil pump housing (the mark on the flywheel is opposite the middle division of the scale on the clutch housing), then the marks on the camshaft pulleys must coincide with the marks on the rear cover of the camshaft drive.

The valve seats (made of metal-ceramic) and valve guides (brass) are pressed into the cylinder head.

The bores in the guides are machined after pressing in. The internal diameter of the guides has been reduced, compared with the 2110 and 2111 engines, from 8 to 7 mm.

Repair guides with an outside diameter of 12.279–12.290 mm (increased by 0.2 mm compared with nominal) are also supplied in the spare parts range.

On the inner surface of the guides, lubrication grooves resembling a thread are made: in the intake valve guides — over the full length, in the exhaust ones — up to half the bore length.

Oil-deflecting caps made of oil-resistant rubber are fitted over the guides.

The valves are steel, the exhaust valve having a head of heat-resistant steel with a deposited chamfer.

The area of the intake valve head is larger than that of the exhaust valve.

In size they are smaller than the valves of the 2110 and 2111 engines.

The valves are arranged in two rows, in a V formation.

They are actuated from the camshaft cams through hydraulic tappets.

The cam axis is offset by 1 mm relative to the tappet axis.

Owing to this, during engine operation the tappet body rotates about its axis, which promotes more uniform wear.

The hydraulic tappets take up the clearance between the cam and the tappet body during engine operation, which reduces the noise of the valve train and also eliminates its maintenance (no clearance adjustment is required).

The hydraulic tappets require a constant supply of oil under pressure.

For this purpose the cylinder head has a channel with a ball check valve (it prevents oil from draining from the channels after the engine stops), as well as channels on the lower face of the bearing housing (they also supply oil to the camshaft journals).

The hydraulic tappets are very sensitive to oil quality and cleanliness.

If mechanical impurities are present in the oil, rapid failure of the hydraulic tappet plunger pair is possible, accompanied by increased noise in the valve train and intensive wear of the camshaft cams.

A faulty hydraulic tappet cannot be repaired and must be replaced. The valve closes under the action of a single spring.

Its lower end rests on a washer, and its upper end on a retainer held by two split cotters.

The assembled cotters are externally in the form of a truncated cone, and on their inner surface have three thrust collars engaging in grooves on the valve stem.

Engine lubrication is of the combined type.

Under pressure the main and connecting rod bearings, the «bearing — camshaft journal» pairs and the hydraulic tappets are lubricated.

By splash, oil is supplied to the cylinder walls (and thence to the piston rings and pins), to the piston crowns, to the «camshaft cam — tappet» pair and to the valve stems.

The remaining components are lubricated by gravity.

The oil pump — with internal gear rotors and a relief valve — is mounted on the front wall of the cylinder block.

The driving gear is mounted on two flats at the front end of the crankshaft.

The limiting diameter of the bore for the driven (large) gear when worn must not exceed 75.10 mm, the minimum width of the segment on the housing separating the driving and driven gears is 3.40 mm.

The axial clearance for the driving gear must not exceed 0.12 mm, for the driven gear — 0.15 mm.

The oil pick-up is bolted to the second main bearing cap and to the pump housing.

The oil filter — full-flow, non-detachable, provided with a bypass valve and an anti-drain valve.

The crankcase ventilation system is closed, forced, by extraction of gases through an oil separator located in the cylinder head cover.