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Advantages, disadvantages, decision

The result of the conversion decision: yes <> no, there can only be two types.

The two types of engines, however, show many differences from a physical and material point of view.

After considering these, the result of the decision is given. We summarize the advantages and disadvantages of the Diesel engine and the Miller cycle LPG engine, referring to explanations in several places:

Fuel consumption, range, refueling

The energy efficiency (efficiency) of both engines is almost the same, but the calorific value and density of the fuel are different. 1 liter of LPG = 69% diesel (1 liter of diesel = 1.45 LPG).
Consumption is highly dependent on speed, so the proportions are illustrated here.
The fuel cost savings are:


  • With 40 tonnes, an average of 34 litres/100km.

  • If the fuel tank is 700 liters, the range is ~2,000 km.

  • Refueling normal speed 35 liters/minute,   fast charger 60 liters/minute. 

  • The well network is dense.

  • THErdifference +/-2% (not on motorways).


  • With 40 tonnes, an average of 50 litres/100km.

  • Equipped with 2×180 liter tanks (can be filled up to 80%), the range is ~570km.

  • Refueling 20 liters/minute.

  • The well network is adequate.

  • THErdifference +/-7% (not on the highway).


The two engines operate in completely different ways, the differences are significant.
Fuel cost savings can be found in detail in:


  • The most complicated engine.

  • Biturbo common rail, expensive parts.

  • Complex flue gas treatment system.


  • Special workshop, dgum repair.

  • Renovation is complicated and expensive


  • Essentially a simple Otto engine.

  • Average cheap parts.

  • There is no flue gas treatment system.

  • Simple, inexpensive repair.

  • Designed for diesel use, but operating under less than half load.

  • Long life.

  • It can be renovated easily and cheaply.

Environmental issues

Environmental protection is becoming more and more central. The transformation of the vehicle fleet shifts towards clean vehicles: 397/2022. (X. 20.) Government decree. This only affects public procurement, but it will have direct consequences in the competitive sector as well.
which will appear in the road toll, other forms of support and probably in the tightening of controls.  

Only LPG corresponds to this.




  • The combustion of diesel fuel is imperfect.

  • A lot of NOx is produced.

  • A lot of harmful particles are produced.


  • it has many components and is very complicated

  • Particle filter regeneration is a  most polluting process.

  • The manufacturers guarantee the reliable operation of the system for only 7 years.

  • The exhaust gas treatment system costs more than the rest of the engine.


  • LPG burns almost perfectly

  • Little NOx is produced.

  • There are practically no particle emissions. Flue gas treatment is at most a simple  catalyst.

  • No particle filter, nothing to regenerate.

  • The price of the catalyst is a fraction of the price of the engine, its replacement is simple and cheap.

Nyomatek and tperformance

The power is the product of the torque and the speed (angular speed), i.e. by dividing the power (gearbox = gearbox) we can provide more and more torque, i.e. power to the wheel. The gearbox of a diesel heavy vehicle typically has 16 gears, the lower 3 gears of which are almost never used. Therefore, even the LPG engine with a much smaller torque can deliver enough power to the wheels when starting off with extremely high power.
So the power transmission system does not need to be modified.


  • High torque (2,100 Nm).

  • High power (310 kW at which point the engine is at the limit of its load).


  • Narrow speed range (diesel combustion deteriorates above 1,800 rpm rpm), therefore more frequent gear changes.

  • Significant power reserve when accelerating and going uphill.


  • Ttypical travel time:

240km = 3 hours


  • Smaller torque (8500 Nm).

  • Less power (220 kW, the engine remains well below the maximum load limit).

  • Wide speed range (LPG burns well even at 2,500 rpm), so it is rarer,  gear change is enough.

  • During acceleration and uphills, there is less power reserve, therefore a time loss of 5-15 sec/km).

  • Typical travel time:

240km = 3 hours + 10 minutes


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