Why Do Factory-Fitted CNG Cars Lose Power When Switching from Petrol to Gas Mode?

Petrol enters the engine as a liquid, while CNG is supplied as a gas. Because the gas occupies part of the space inside the intake charge, less air can enter the cylinder under comparable conditions. This can reduce the amount of energy the engine can release in each combustion cycle and, so, it reduces maximum power.

Is the Power Loss Because CNG Has Less Energy?

Partly, but that explanation needs some context. CNG is a gaseous fuel, and its behaviour in the engine differs from that of liquid petrol. The reduction in power when using CNG fuel happens because the amount of combustible mixture that can be packed into the cylinder can limit power. CNG offers reduced volumetric efficiency, which makes engines produce less power than their petrol counterparts.

Also Read: What Happens If You Put Diesel in a Petrol Car? Here’s What You Should Do

However, CNG fuel can achieve higher thermal efficiency in some engine setups. In other words, the engine can use the fuel's energy efficiently even though the final power output is lower.

Petrol vs CNG: What Changes When You Switch Fuels?

Here’s what you may notice in power, efficiency and acceleration when switching between petrol and CNG.

Why Don't Manufacturers Simply Tune the CNG Mode for More Power?

A factory CNG engine has to balance performance, fuel economy, emissions, durability and drivability. Engine calibration changes how much fuel is supplied and when combustion occurs, while the intake and combustion system determine how effectively the fuel and air can be used.

Engine design and calibration can significantly reduce the performance gap. In fact, CNG could achieve performance comparable to a petrol engine under particular operating conditions. So the power difference is not an unavoidable fixed percentage for every CNG car.

When Is CNG Power Loss Not Normal?

A mild difference between petrol and CNG is expected, but a sudden or unusually large loss of power is not. If the car previously performed normally on CNG but suddenly becomes sluggish, struggles to climb, hesitates during acceleration or switches between fuels poorly, the issue should be investigated rather than blamed on CNG.

Possible areas for inspection include:

• CNG pressure and fuel delivery
• CNG injectors
• Ignition components such as spark plugs
• Air and fuel filters
• Sensors used by the engine management system
• Throttle and intake system
• Engine fault codes
• CNG-system calibration

CNG fuel-system components are covered by dedicated Indian standards, including requirements for pressure regulators, fuel lines, valves and other components.

Normal CNG Behaviour vs Possible Problem

A slight difference in performance is normal, but certain symptoms can point to a CNG-system issue. Use this table to tell the two apart.

Does Factory-Fitted CNG Damage the Engine Because It Has Less Power?

Lower power by itself does not mean the engine is being damaged. Factory-fitted CNG systems are engineered to operate the engine on CNG, with the fuel system and engine controls developed for that application. The more useful question is whether the car is behaving as it was designed.

If the difference between petrol and CNG has always been present and the car runs smoothly, there may be nothing wrong. If the car has suddenly lost performance, starts misfiring or develops hesitation, then you should get it serviced.

So, Why Do CNG Cars Lose Power on Gas?

Factory-fitted CNG cars can feel weaker on gas because CNG enters the engine as a gas and changes how much air-fuel mixture can be packed into the cylinder. That can reduce power compared with petrol, particularly when the engine is working hard.

CNG can deliver efficient operation and lower running costs, but it gives up some power output when compared to petrol. A small difference is therefore normal, but you shouldn’t dismiss a new or severe drop in CNG performance by simply assuming it’s “because it's CNG.”