Dismantling the Cg300b Gasoline Trimmer Engine

Dismantling the Cg300b Gasoline Trimmer Engine

  • Engines
  • Nissan
  • VG30ET

The 3.0-liter Nissan VG30ET engine was produced from 1983 to 1991 at a Japanese plant and was placed both on sports models of the 300ZX family, and on civilian Zedric and Gloria. This unit was produced with two different turbines and accordingly different power.

The 12-valve engine of the VG series includes: VG20E, VG20ET, VG30i, VG30E and VG33E.

  • Characteristics
  • Consumption
  • Application
  • Breakage

Technical specifications of the Nissan VG30ET 3.0 liter engine

Exact volume2960 cm³
Supply systemdistributed injection
Engine power195.230 h.p.
Torque295.345 Nm
Cylinder blockcast iron v6
Block headaluminum 12v
Bore87 mm
Piston stroke83 mm
Compression ratio7.8. 8.3
ICE Featuresno
Hydraulic compensatorsYes
Timing Drivebelt
TurbochargingGarrett T3 or T25
What kind of oil to pour3.9 liter 5W-30
Fuel typeAI-92
Environmental classEURO 1/2
Approximate resource360,000 km

Fuel consumption VG30ET

For example, the 1986 Nissan Cedric with automatic transmission:

City16.7 liters
Track12.3 liters
Mixed14.5 liters

Similar engines from other manufacturers:

What vehicles was the VG30ET engine used for


300ZX Z311983. 1989
Leopard f301983. 1986
Cedric y301983. 1987
Cedric y311987.1991

Disadvantages, breakdowns and problems Nissan VG30 ET

The most dangerous thing is a breakdown of the shank of the crankshaft, which often leads to bending of valves

The exhaust manifold burns out, and when it is removed, the studs break

Replacing thicker studs carries the risk of future cracking of the manifold

The resource of the timing belt is about 70 thousand km, and when it breaks the valve almost always bends

After 100 thousand km, leaks of the pump and knocking of hydraulic lifters are often found

Complete rebuild of the VG30ET

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In new designs of combustion chambers designed to burn lean mixtures, the requirements for mixture formation, which are characteristic for both gasoline engines and diesel engines, are manifested. These designs often use gasoline injection directly into the cylinder or into a small chamber with a spark plug placed in it. If reliable ignition of the mixture is ensured in the area of ​​the spark plug, clean air can be supplied to the cylinder without throttling. The engine power is regulated by the amount of fuel injected. In this case, the actual compression ratio at an incomplete engine load does not change, and the engine efficiency increases.

Fig. 1
Schematic diagram of the organization of the working process in the engine “Ford PROKO”:
1. nozzle; 2. spark plug; 3. a burning charge; 4. air rotation direction.

Video: Dismantling the Cg300b Gasoline Trimmer Engine

The engine of this “transitional” type is the experimental Ford PROKO engine, which has direct fuel injection into the cylinder and spark ignition. Intensive rotation is given to the air in the cylinder at the intake and compression strokes, in the 4 direction of which the fuel nozzle 1 and the spark plug 2 are placed close to each other (see Fig. 1).

Fuel injection begins immediately before sparking. In this way, the mixture is enriched in the zone of the spark plug by the time of the spark discharge; further, the fuel supply can continue even with a burning charge 3. Detonation does not occur, since the fuel is contained mainly in a small volume between the nozzle and the spark plug. Air supplied to the cylinder is not throttled.

This method has not found application in practice due to the high cost of fuel equipment, the ignition system, as well as the insufficient specific power of the engine (about 22 kW / l).

According to tests conducted by the Swiss magazine Automobile Revue, the average fuel consumption of a Volkswagen Passat TS car with an engine having a combustion chamber of the same design was reduced from 8.5 l / 100 km to 4.96 l / 100 km.

The carburetor engine of the Porsche 924 has been specially upgraded for the use of lean mixtures. The compression ratio was increased to ε = 12.5, and at a partial engine load the mixture could be leaner to α = 1.2. The combustion chamber is formed eccentrically in the piston crown to achieve a better charge swirl required to burn lean mixtures.

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Regulation of the mixture from α = 0.9 at full load to α = 1.2 at partial load and ensuring optimal ignition timing allowed us to achieve a significant reduction in fuel consumption when driving in the urban cycle. At speeds of 90 and 120 km / h, the increase in fuel economy ranged from 6 to 12%. The results achieved can be seen from a comparison of the curves of real engine compression ratios with a geometric compression ratio ε = 8.5 and the same modernized engine with a geometric compression ratio increased to ε = 12.5 (see Fig. 4 in the article “Effect of compression ratio on the indicator Engine efficiency “). The minimum specific fuel consumption of this engine decreased from 280 to 260 g / kW · h, and the reduction in fuel consumption was achieved over the entire range of loads and engine speeds. Even better results can be obtained if electronic devices are used to control the ignition and composition of the mixture.

Fig. 5
Honda Engine Combustion Chamber:
1. main combustion chamber; 2. inlet valve; 3. inlet of the prechamber; 4. pre-chamber valve; 5. spark plug; 6. prechamber; 7. the hole of the connecting channel of the prechamber with the main combustion chamber.

Significant success in the combustion of lean mixtures in gasoline engines was achieved by Honda, which used the so-called small blown prechamber with an independent inlet and a valve for supplying the enriched mixture. The spark plug is located on the side of the prechamber. In fig. 5 shows a section through the cylinder head of such an engine. The mixture ignited in the prechamber is ejected under pressure through a narrow hole into the main combustion chamber, where it ignites a heavily depleted, intensely rotating charge received through the main inlet valve.

Despite the difficulties associated with ensuring the reliable operation of the prechamber valve, the creation of an auxiliary channel in the head, a complex carburetor and a thermoreactor for burning CO and CHx, Significant successes have been achieved in eliminating harmful substances from exhaust gases.

Good results were achieved by the Japanese company Nissan on cars of the NASP Z510 model with a carburetor engine and on the 200 SK model with an engine equipped with gasoline injection. In both cases, a hemispherical combustion chamber was used. NO formation reductionx 17% of the exhaust gas was recirculated, which allowed to maintain a high indicator power of the engine and low specific fuel consumption. The achievement of good results was facilitated by the ignition of two candles located opposite each other in the combustion chamber, which significantly reduced the path of the flame. A special insert placed in the inlet channel created an intensive rotation of the mixture in the cylinder, which increased the combustion rate.

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Fig. 6
The location of the windproof prechamber and spark plugs in the Toyota gasoline engine.

Cross-flow cylinder heads (with inlet and outlet channels located on opposite sides of the longitudinal axis of the engine) have an inlet valve slightly offset from the cylinder axis in order to make room for the spark plug. To ensure a good fill factor, the valve diameter can be increased by 10%. Figure 6 shows a part of such a cylinder head of a Toyota engine (Japan) with a small windproof, that is, without a special valve, prechamber. The rich mixture enters the pre-chamber by a beak-shaped turbulent protrusion at the entrance to it, partially protruding into the main combustion chamber. At the end of the compression stroke, the air entering the prechamber draws the fuel collected through centrifugal forces into it.

The spark plug is installed at the entrance to the prechamber, since tests have shown that this place is optimal for its placement. All the above structural measures allow the use of highly depleted mixtures with a mass air / fuel ratio of 19 (α ≈ 1.27. 1.28). The exhaust pipe is insulated from the cylinder head, and a heat-insulating liner is installed in the exhaust channel of the head. To eliminate CO and CH from the exhaustx thermal reactor used.

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