A CNG conversion is one of the highest-return automotive investments available to Bangladeshi car owners today. With petrol at ৳125/litre and CNG at ৳43/kg, the per-km cost difference is substantial enough that most conversions pay for themselves within 5–7 months for an average driver. But not all CNG kits are equal — the wrong kit on the wrong engine can cause long-term damage that costs far more than the fuel savings. This guide helps you choose the right kit and calculate your personal break-even point.
Types of CNG Conversion Kits Available in Bangladesh
CNG Kit Types Comparison
| Kit Type | How It Works | Best For | Cost Range |
|---|---|---|---|
| Venturi / Mixer Kit | Mixes CNG with air in the intake manifold — simple, no ECU interaction | Carbureted engines, older cars (pre-1995) | ৳25,000–৳40,000 |
| Open-Loop Sequential Kit | Injects CNG into each cylinder separately, follows original injector timing | Modern EFI cars up to 1.6L | ৳45,000–৳65,000 |
| Closed-Loop Sequential Kit | Reads engine sensors (lambda/O₂ sensor) and adjusts fuel trim in real time | Modern EFI cars with OBDII, best choice for Euro-4+ engines | ৳60,000–৳85,000 |
| OEM Bi-fuel | Factory-installed CNG/petrol system (some new Suzuki, Toyota models) | New vehicle purchase | Built into vehicle price |
Note
For cars manufactured after 2010 with OBDII diagnostics, always choose a closed-loop sequential kit. Open-loop and venturi kits on modern engines can trigger engine fault codes, run lean/rich, and cause premature valve seat wear. The extra ৳15,000–৳20,000 cost is recovered quickly through better fuel economy and reduced engine maintenance.
CNG Cylinder Sizes and Costs
CNG Cylinder Options in Bangladesh
| Cylinder Size | Usable CNG | Range (18 km/kg) | Cylinder Cost | Installation Location |
|---|---|---|---|---|
| 40-litre | 6.6 kg | ~119 km | ৳18,000–৳25,000 | Boot (small cars) |
| 60-litre | 9.9 kg | ~178 km | ৳22,000–৳32,000 | Boot (most sedans) |
| 80-litre | 13.2 kg | ~238 km | ৳28,000–৳40,000 | Boot or rooftop rack |
Total Installation Cost Breakdown
Total CNG Conversion Cost Breakdown: Item | Low Range | High Range ----------------------------------|-----------|---------- Sequential injection kit | ৳35,000 | ৳55,000 CNG cylinder (60-litre) | ৳22,000 | ৳32,000 BRTA inspection + certification | ৳5,000 | ৳8,000 Installation labour | ৳3,000 | ৳5,000 Piping, fittings, accessories | ৳2,000 | ৳4,000 ----------------------------------|-----------|---------- TOTAL (approximate) | ৳67,000 | ৳1,04,000 Budget estimate for most mid-size sedans: ৳70,000–৳85,000 complete.
Break-Even Calculation — Your Personal Payback Period
Monthly Fuel Saving = (Petrol cost/km − CNG cost/km) × Monthly km Petrol cost/km = ৳125 ÷ 14 km/L = ৳8.93/km CNG cost/km = ৳43 ÷ 18 km/kg = ৳2.39/km Saving per km = ৳8.93 − ৳2.39 = ৳6.54/km Driver A: 1,500 km/month Monthly saving = ৳6.54 × 1,500 = ৳9,810 Break-even (৳75,000 kit) = 75,000 ÷ 9,810 = 7.6 months Driver B: 2,500 km/month Monthly saving = ৳6.54 × 2,500 = ৳16,350 Break-even (৳75,000 kit) = 75,000 ÷ 16,350 = 4.6 months Driver C: 4,000 km/month (professional) Monthly saving = ৳6.54 × 4,000 = ৳26,160 Break-even (৳85,000 kit) = 85,000 ÷ 26,160 = 3.3 months
5-Year Savings Projection
5-Year Net Savings After Kit Cost (at 2,000 km/month)
| Year | Annual Saving | Cumulative Saving | Net (after ৳75,000 kit) |
|---|---|---|---|
| Year 1 | ৳1,56,960 | ৳1,56,960 | ৳81,960 |
| Year 2 | ৳1,56,960 | ৳3,13,920 | ৳2,38,920 |
| Year 3 | ৳1,56,960 | ৳4,70,880 | ৳3,95,880 |
| Year 4 | ৳1,56,960 | ৳6,27,840 | ৳5,52,840 |
| Year 5 | ৳1,56,960 | ৳7,84,800 | ৳7,09,800 |
BRTA Regulations You Must Follow
- Only BRTA-approved CNG kits and installers are legal — verify the workshop's authorisation certificate before work begins.
- The CNG cylinder must carry a BSTI certification mark and a hydrostatic test date (must be within 5 years).
- Your vehicle registration (blue book) must be updated to show 'Bi-fuel (Petrol/CNG)' — failure to do so means running an unregistered modification.
- Cylinder must be re-tested every 5 years under BRTA rules. Budget ৳3,000–৳5,000 for each 5-year re-test.
- CNG cylinder must be installed by a certified technician; DIY installation is illegal and voids insurance.
Tip
Use the CostNest CNG & LPG Conversion Cost Calculator to enter your actual conversion cost, monthly km, and fuel economy — it calculates your exact payback month and generates a monthly savings projection so you can present the ROI case clearly to a spouse, employer, or fleet manager.