The VAZ-2123 engine is a petrol, four-stroke, four-cylinder, eight-valve, in-line engine with an overhead camshaft.
Firing order of the cylinders: 1—3—4—2, counting from the auxiliary drive pulley.
Fuel system type: distributed fuel injection.
The engine is controlled by the BOSCH-M7.9.7 controller (Euro-4 emission standards).
A catalytic converter is installed in the exhaust system.
On the right of the engine (in the direction of vehicle travel) are located: the receiver with the throttle body, throttle position sensor and idle speed control valve; the intake pipe and exhaust manifold; the fuel rail with injectors; the knock and coolant temperature sensors of the control system; the thermostat; the coolant pump; the starter motor (secured to the clutch housing); the air conditioning compressor (on vehicles with air conditioning).
On the left of the engine are located: the alternator, the power steering pump, the spark plugs and high-tension leads, the ignition coil, the oil level dipstick, the oil filter, the coolant temperature gauge sensors (in the instrument cluster) and the low oil pressure sensor.
The air filter with the mass air flow sensor is secured in the engine compartment to the left of the engine.
At the front — the auxiliary drive (poly-V belt), the crankshaft position sensor and the phase sensor.
The engine, gearbox and clutch form the power unit, secured on three elastic rubber-metal mountings.
Cylinder block: the engine cylinder block is cast from special low-alloy cast iron, the cylinders are bored directly in the block.
Nominal cylinder diameter — 82.00 mm, machining tolerance +0.05 mm.
The calculated minimum clearance between piston and cylinder (for new parts) must be 0.025–0.045 mm.
It is determined as the difference between the minimum cylinder diameter and the maximum piston diameter and is ensured by fitting a piston of the same class as the cylinder into the cylinder.
For this purpose, the cylinders and pistons, depending on the dimensions obtained during machining, are divided into five classes every 0.01 mm.
The cylinder class, according to its diameter, is marked with Latin letters on the lower plane of the cylinder block: 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 mm.
During repair, the cylinder diameter can be increased by boring by 0.4 or 0.8 mm for oversize pistons.
Maximum permissible cylinder wear — 0.15 mm on diameter.
In the lower part of the cylinder block are five main bearing supports of the crankshaft with removable caps, secured to the block by special bolts.
The holes in the cylinder block for the bearings are machined with the caps fitted, so the caps are not interchangeable and are marked with score lines on their outer surface for identification.
On the end faces of the rear support there are recesses for the thrust half-washers, which prevent axial movement of the crankshaft.
At the front a steel-aluminium half-washer (white) is fitted, and at the rear a metal-ceramic one (yellow). The grooves on them must face the crankshaft.
The half-washers are supplied in nominal size and in a size increased by 0.127 mm.
If the crankshaft end float exceeds 0.06–0.26 mm, one or both half-washers must be replaced (maximum permissible crankshaft end float in service — 0.35 mm).
Bearing shells of the main and big-end bearings of the crankshaft — thin-walled steel-aluminium.
The upper main bearing shells of the first, second, fourth and fifth supports have a groove on the inner surface, while the upper shell of the third support and the lower shells fitted in the caps are without a groove.
Repair shells of the main and big-end bearings are produced for crankshaft journals reduced by 0.25, 0.5, 0.75 and 1.00 mm.
The nominal calculated diametral clearance between the crankshaft journals and the bearing shells must be:
- for the main bearings — 0.026–0.073 mm (maximum permissible clearance — 0.15 mm);
- for the big-end bearings — 0.02–0.07 mm (maximum permissible clearance — 0.1 mm).
Crankshaft — of high-strength cast iron, with five main and four big-end journals.
The shaft is provided with eight counterweights cast integrally with the shaft (fully counterweighted).
To supply oil from the main journals to the big-end journals, channels are drilled in it, closed by pressed-in and staked plugs.
These channels also serve to clean the oil: under the action of centrifugal force, solid particles and resins that have passed through the filter are thrown towards the plugs.
Therefore, when repairing the shaft and when balancing, the channels must be cleaned of accumulated deposits.
The plugs must not be reused — they are replaced with new ones.
On the front end (nose) of the crankshaft, on a segment key, are mounted: the sprocket driving the timing gear and the auxiliary drive pulley (alternator, power steering pump and coolant pump), which is also a torsional vibration damper of the crankshaft.
On vehicles with air conditioning, the air conditioning compressor pulley is pulled against the auxiliary drive pulley by the crankshaft nut.
On the auxiliary drive pulley a toothed ring is made for reading information by the crankshaft position sensor.
The ring has 58 teeth (the ring circumference is divided into 60 teeth, but two are missing, forming a gap — this is necessary to obtain a synchronisation pulse at each revolution of the crankshaft).
On the outer cylindrical surface of the pulley runs the front crankshaft oil seal, fitted in the timing drive cover cast from aluminium alloy.
The timing drive cover has a lug with a hole for the crankshaft position sensor.
The rear oil seal is pressed into a holder cast from aluminium alloy, which is secured to the rear end face of the cylinder block.
The seal runs on the surface of the crankshaft flange.
Into the rear end face of the crankshaft is pressed the front bearing of the gearbox input shaft.
The flywheel is secured to the crankshaft flange by six bolts through a common washer.
It is cast from cast iron and has a pressed-on steel toothed ring for starting the engine with the starter.
The flywheel is fitted so that the conical recess near its ring is opposite the big-end journal of the 4th cylinder — this is necessary for determining TDC after engine assembly.
Connecting rods — steel, of I-section, machined together with their caps.
To avoid mixing up the caps during assembly, the cylinder number is stamped on them, as on the connecting rods (it must be on the same side of the connecting rod and cap).
Into the holes of the connecting rod lower eye special bolts are pressed; during dismantling they must not be driven out of the eye.
Into the connecting rod upper eye a steel-bronze bush is pressed.
By the diameter of its bore for the piston pin, the connecting rods are divided into three classes with a pitch of 0.004 mm (just like the pistons).
The class number is stamped on the connecting rod upper eye.
The connecting rods are also divided into 9 classes by mass, which are marked with paint of different colours on the connecting rod shanks.
All connecting rods of the engine must be of the same mass class, i.e. marked with paint of the same colour.
The piston pin — steel, of tubular section, of the floating type (rotates freely in the piston bosses and in the connecting rod eye), retained against falling out by two spring circlips located in the grooves of the piston bosses.
By outer diameter three classes of pins are distinguished (every 0.004 mm), which are marked with paint:
- 1 — blue (21.970–21.974 mm);
- 2 — green (21.974–21.978 mm);
- 3 — red (21.978–21.982 mm).
Piston — cast from aluminium alloy.
The piston skirt has a complex shape: in longitudinal section it is barrel-shaped, and in cross-section — oval.
In the upper part of the piston three grooves for the piston rings are machined.
The oil control ring groove has drillings for supplying the oil collected by the ring from the cylinder walls to the piston pin.
The piston pin hole is offset by 1.2 mm from the diametral plane of the piston, therefore when fitting the piston one must be guided by the arrow stamped on its crown: it must point towards the crankshaft pulley.
By outer diameter (nominal size) the pistons are divided into 5 classes: 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 mm. The piston class is stamped with a letter on its crown.
On pistons of repair sizes a triangle (diameter increase by 0.4 mm) or a square (diameter increase by 0.8 mm) is stamped on the crown.
As spare parts pistons of three classes are supplied — A, C and E (nominal and repair sizes), which is quite sufficient for matching the piston to the cylinder.
At the same time, it is not recommended to fit a new piston into a worn cylinder without boring the cylinder.
The groove for the upper compression ring in the new piston may be slightly higher than in the old one, and the ring will break against the «step» formed in the upper part of the cylinder during its wear.
By the diameter of the piston pin hole the pistons are divided into 3 classes: 1 — 21.982–21.986, 2 — 21.986–21.990, 3 — 21.990–21.994 mm.
The class number is also stamped on the piston crown.
On new parts the class of the pin holes in the connecting rod and piston must be identical to the pin class.
The engine pistons are produced in one mass class, therefore separate matching is not required.
Piston rings — located in the piston grooves.
The two upper rings are compression rings. They prevent gas blow-by into the engine crankcase and conduct heat from the piston to the cylinder.
The lower piston ring is the oil control ring.
The nominal height clearance between the piston rings and the grooves in the piston (measured with a set of feeler gauges) must be:
- for the upper compression ring — 0.04–0.07 mm;
- for the lower compression ring — 0.03–0.06 mm;
- for the oil control ring — 0.02–0.05 mm.
Maximum permissible clearances due to wear — 0.15 mm.
The ring gap for all piston rings must be 0.25–0.45 mm.
The clearance is measured with a set of feeler gauges, after inserting the ring into a special gauge or into the engine cylinder and aligning it with the piston crown.
Cylinder head — of aluminium alloy, common to all four cylinders.
It is centred on the cylinder block by two bushes and secured by 11 bolts.
If the bolt shank length exceeds 117 mm, it must be replaced with a new one.
A non-settling metal-reinforced gasket is fitted between the block and the head.
Reuse of the gasket is not permitted.
In the upper part of the cylinder head, an aluminium camshaft bearing housing is secured on nine studs.
It is centred on two bushes fitted on the outer studs.
The clearance between the camshaft journals and the housing supports must not exceed 0.2 mm.
Camshaft — cast iron with chilled cams, five-bearing; driven by a single-row roller chain from the crankshaft sprocket.
Axial movement is limited by a thrust flange which enters the groove of the front support journal of the shaft.
For correct setting of the valve timing, marks are provided on the sprockets.
The mark on the crankshaft sprocket must coincide with the lug on the cylinder block, and the mark on the camshaft sprocket — with the lug on the bearing housing.
The camshaft sprocket is mounted on the shaft in only one position and is tightened by a bolt with support and locking washers.
The tab of the latter enters the hole in the sprocket, and the side part is bent onto the face of the bolt head.
A metal element is riveted to the sprocket — the phase sensor pulse generator.
The valve seats and guides — cast iron, pressed into the cylinder head.
As spare parts, repair guides with an outer diameter increased by 0.2 mm are supplied.
The holes in the guides are finished with a reamer after pressing in.
The bore diameter of the inlet valve guides — 8.022–8.040 mm, of the exhaust — 8.029–8.047 mm.
On the inner surface of the guide lubrication grooves are cut: for the inlet valve guide — over the full length, for the exhaust — up to half the bore length.
On top of the guides metal-rubber valve stem seals with a bracelet steel spring are fitted.
The clearances between new guides and valve stems must be within 0.022–0.055 mm for inlet valves and 0.029–0.062 mm for exhaust valves (the limit clearance due to wear in service is 0.3 mm).
Valves — steel; the exhaust valves — with heads of heat-resistant steel, with deposited chamfers.
The valves are arranged in a row, inclined to the plane passing through the cylinder axes.
The inlet valve head diameter (37 mm) is larger than that of the exhaust (31.5 mm).
The valves are operated from the camshaft cams through valve rocker arms («rockers»).
The clearances in the valve train are not adjusted.
At one end the rocker arm rests on the spherical head of the hydraulic tappet (hydraulic clearance compensator), and with the other acts on the end of the valve stem.
The engine is fitted with INA hydraulic tappets, which differ in construction from the hydraulic tappets used previously.
Into the cylinder head a steel bush (body) is first screwed in, and only then is the tappet inserted into it with a sliding fit.
This assembly method eliminates the possibility of deformation of the precision pair of the hydraulic tappet.
To supply engine oil under pressure to the hydraulic tappets, four aluminium spacers are fitted between the hydraulic tappet bodies and the cylinder head — one spacer for the hydraulic tappets of two valves of each cylinder.
Through a channel of the cylinder block and head, the oil reaches the camshaft bearing housing, and then through a tubular steel rail — to the spacers of the valve hydraulic tappets.
The connections of the rail tubes with the spacers are sealed with rubber bushes.
The use of INA hydraulic tappets led to the use of new valve rocker arms, in which the diameter of the support sphere was reduced — from 12 mm (on the previous rocker arms) to 11 mm.
The valve closes under the action of two springs with opposite winding, mounted coaxially.
At their lower ends they rest on support washers, and at their upper ends — on a retainer which is fixed by two conical collets entering the groove at the end of the valve stem.
To reduce the oscillations of the timing chain, on its left run between the oil pump drive shaft sprocket and the camshaft sprocket, a plastic damper is mounted on two bolts.
The right run of the chain is tensioned by a spring-hydraulic tensioner installed in the cylinder head.
The pre-tension of the chain (with the engine not running) is provided by the spring, the working tension (after starting the engine) — by oil pressure.
The oil is supplied to the hydraulic tensioner through a seamless steel tube of 6 mm diameter with end fittings.
This line starts from a threaded hole on the left wall of the cylinder block, into which the union of the emergency oil pressure sensor is screwed.
The correctly selected bending stiffness of the tube made it possible to attenuate its oscillations; moreover, metal holders with rubber inserts suppressing vibration are used.
The tube end fitting is secured to the tensioner body by means of a union bolt which is used for securing the front brake hose of the rear- and all-wheel-drive VAZ family vehicles.
The tensioner plunger presses on the shoe, made, like the chain damper, of wear-resistant plastic.
The tensioner shoe turns on an axis located in the lower part of the cylinder block, to the right of the crankshaft sprocket.
The oil pump drive shaft is also driven from the timing chain.
The securing of its sprocket (30 teeth) is similar to the securing of the camshaft sprocket (38 teeth).
The shaft rotates in bushes located in the cylinder block and is retained against axial movements by a thrust flange entering the groove on its front journal.
The toothed ring of the shaft meshes with the oil pump drive gear mounted vertically in a bush of the cylinder block.
In the gear a longitudinal splined hole is made, into which the splined shank of the oil pump shaft enters from below.
Oil pump — gear type, single-stage, with a relief valve; mounted in a body secured in the lower part of the cylinder block.
The intake pipe is cast integrally with the lower part of the body and closed by a stamped mesh for coarse cleaning of the oil from mechanical impurities.
The nominal clearances in the oil pump must be:
- between the gear teeth — 0.15 mm (maximum permissible value — 0.25 mm);
- between the gears (by outer diameter) and the walls of the pump body — 0.11–0.18 mm (maximum permissible value — 0.25 mm);
- between the gear ends and the plane of the body — 0.066–0.161 mm (maximum permissible value — 0.20 mm);
- between the driven gear and its axis — 0.017–0.057 mm (maximum permissible value — 0.10 mm);
- between the pump shaft and the hole in the body — 0.016–0.055 mm (maximum permissible value — 0.10 mm).
Engine lubrication — combined.
Under pressure, oil is supplied through the filter to the main and big-end bearings of the crankshaft, the hydraulic tappets of the valve rocker arms, the hydraulic chain tensioner, the camshaft bearings and the bush of the oil pump drive shaft.
By splashing, oil is supplied to the cylinder walls (then to the piston rings and pins), to the «camshaft cam — rocker arm» pairs, chains and valve stems.
The oil filter — full-flow, non-demountable, with bypass and anti-drain valves.
Crankcase ventilation system — closed, forced. Under the action of the vacuum in the intake pipe of the running engine, gases from its crankcase pass through the oil separator into the intake tract through the hoses of two circuits.
Through the hose (of larger diameter) of the main circuit, crankcase gases are discharged, at partial and full load conditions of the engine, into the space in front of the throttle valve.
Through the hose of the idle circuit, crankcase gases are discharged into the space behind the throttle valve both at partial and full load conditions of the engine and at idle.
