Can you convert a petrol automatic to CNG or LPG?

Those of you who are tempted with the idea of buying a big car like a Honda Accord automatic or even a Honda Civic automatic, but can’t deal with the running costs, here’s an idea: You can convert your luxury automatic petrol sedan to run on the cheapest fuel available – compressed natural gas, and reduce your running costs by over 70%.

The Pros

Consider this. You get the best package all-around: A comfortable car, a high-powered car, an automatic transmission that takes the stress out of city bumper-to-bumper traffic and most of all gives you pretty low running cost. And it gives you the option of running on petrol only, when out on the highway.

But is this possible?

The Cons

Let’s take a look at the downsides of a CNG conversion first, before looking at its feasibility in an automatic car. CNG powered vehicles lose about 15% of their peak power compared to when they are run on petrol. Also CNG powered vehicles are about 100-150Kg heavier than their petrol-only counterparts.

In a normal manual transmission car, this loss in power and additional weight can be compensated for by shifting gears earlier or revving to a higher rpm for better peak power. But in an automatic, it has pre-defined shift points in the transmission – where the gearbox will shift into the next gear only when certain speed-rpm conditions are met.

The other downside to CNG conversion is that the life of certain engine components such as the valves, and seals is reduced, owing to the higher heat build-up in a CNG powered engine. And parts like the fuel pump too can fail prematurely if the car is not run often enough on petrol.

Can you convert an automatic?

So is it worth converting an automatic car like the Honda Accord or Honda Civic to CNG? Approved CNG kits are available from companies such as Landi Renzo, BRC and Zavoli for the Civic and Accord. These are closed-loop sequential injection kits that come with their own ECU to separately monitor gas injection. These kits costs between Rs. 55,000 to Rs. 65,000 for the Civic and Accord. A CNG installer in the NCR region confirmed that these kits can be installed on manual or automatic variants. Once you convert the car to CNG, you will get a claimed 15 km per Kg of CNG on the Civic and about 13 Km per Kg of CNG on the Accord 2.4. Also see: Different types of CNG kits – Advantages and Disadvantages

This results in a per km running cost of just Rs. 2.96 per km on CNG as compared to Rs. 7.70 per km on petrol, which are substantial savings in the long term and equivalent to running a diesel car. Wear and tear on the engine can be offset to some extent by using a high-quality synthetic engine oil and a good engine coolant brand.

CarToq experts concur that even with the additional wear and tear that the engine may incur, it is worth converting the car to run on CNG. Also read: Pros and Cons of installing a CNG kit in a Honda City automatic

The automatic transmission in the Civic has a tiptronic mode which will allow you to shift gears earlier or later if you find the car not shifting exactly when you want it to in CNG mode. This gives you the benefit of an automatic with CNG, with the choice of shifting like a manual when you need to (like sudden overtaking maneuvers for instance).

Overall, yes, it makes sense to convert a luxury petrol automatic to run on CNG.