How I retrofitted a CNG kit on my 12-year-old Santro Xing

The Santro now runs on both, petrol & CNG and returns a mileage of 22 km in mixed conditions with AC on.

BHPian justadiz recently shared this with other enthusiasts.

Hello Everyone

First of all, I'm dedicating this post to every other TeamBHPians who made their posts on this specific matter before which immensely helped me, hopefully, this post will provide insight to someone who may stumble upon it in the far future.

The Car:

The car in question is a 2012 Santro Xing GLS, it has been in our family ever since we bought it in the spring of 2012 and has clocked 94,000km on the odometer, running purely on Petrol. On petrol, it returns a measly 9km/Litre running with full AC in City conditions and goes up to 12km/Litre on the Highway.

Why CNG:

As you might know, thanks to all sorts of things, the Post Covid era witnessed a sharp increase in fuel prices, climbing from the mid-70s to hitting over 100 rupees per litre for Petrol, combined with economic conditions, inflation all (combined with my cars already low fuel efficiency) meant that we couldn't drive as much as we used to do in the pre-2020 time period. Thankfully, over the past few years, there has been an upsurge of CNG adoption here in the southern part of India, with CNG filling stations being built and LPG retrofitters adopting CNG retrofitment, which opened up the possibility of having a choice that didnt involve getting a new car. (Petrol costs 109/litre, CNG costs 88/kg in my area)

The Research Begins:

In the pursuit of educating myself on this new alternative fuel option and its viability, I stumbled upon this website, which has been helpful.

I need to have my sources backed up with strong user feedback since I had to convince my father who was against the idea of retrofitting CNG.

Sequential or Open Loop:

The retrofitters in my area dealt with either Open Loop or Sequential Injection Kits, however, considering the age of my car and the fact that we might use it for the next 5 or so years before selling it off meant it didn't make much sense to invest in a 50,000 rupees Sequential Kit, besides I thought to myself- "If Open Loop system is good enough for the Kaali Peeli Santro Xing running the Taxi Infrastructure of Mumbai, its good enough for my use", however, this decision would come back to bite me in the future.

Biting the Bullet:

Finally, we settled on an installer near our house with reasonable reviews on Google, who gave me a quote of 38k for a Lovato Open Loop Kit, Timing advancer and a 10kg cylinder. The other best installer in my city quoted 63k for a sequential kit and he said he doesn't do an open loop, he had a very rude attitude and a huge ego that turned me away. In any case, before the day of retrofittment, I gave the car to HASS and serviced it put in a new set of spark plugs and spark plug wires, cleaned out the throttle body and got a new air filter.

On the 10th of February, I gave the car to the CNG Fitting guys in the morning, I got the car back at 9:30 PM, and they took me on a test drive and everything seemed good, so I paid them 38k and I thought to myself, "that's a job well done".

Trouble Begins:

Usually here on teamBHP and generally, I've seen people reporting issues 5000, 10,000km after retrofitting. However, I had the luck to get issues a lot earlier, as in literally 5 kilometres after getting off the compound of the fitment centre. After driving for a couple of kilometres, I stopped to take a phone call and shut down the engine, when I restarted the engine after a couple of minutes, it wouldn't idle correctly on petrol and the engine shook violently, and the only way the engine stays works is if I'm on full throttle, if I let it go, the engine shudders, accelerate irregularly, the time was almost 10 PM, I called the guy who fitted it and I sent him the location, he came to where I stalled and tweaked around under the hood and got it started it again. But after some time, it stalled again, and I was stuck in a bad part of the town, in a stalled car. It wouldn't start no matter what I did, I begged the car and it finally started after multiple attempts, and I had to drive the 4 or 5km home at full throttle eating through 1/2 of my clutch's life and burning lots of petrol. The next day was Sunday, and I was stuck at home, on Monday, the CNG guys came to my home tweaked around, and replaced the Emulator, yet the issue didn't go away.

At this time, I got in touch with TeamBHPian @HimanshuKenshin who has posts regarding CNG conversion and his own experiences with CNG, and we came to the conclusion it was either the wiring issue or the reducer was faulty and leaking gas while the engine was running and messing up the AFR.

Now, the engine runs smoothly on CNG. Still, on Petrol, it was acting really bad, always stalling, with long cranks to start, and refusing to stay working unless I was on full throttle, and the CNG guys started coming up with an absurd diagnosis to shuttle me between the petrol mechanic and CNG mechanics like the Fuel Pump is faulty. I needed to replace it, and that made me lose my cool. I demanded them to fix my car which was running fine on Petrol before they laid their hands on the car. They told me to bring the car on the next working day, I had to take the entire day off and lost my college attendance, however, they managed to fix the issue and tried to blame the engine was overheating and I needed to clean my radiator and flush out the cooling system. Although I knew that wasn't the issue, I was tired of all this running around and the coolant system was already due for a cleaning, got it cleaned by our family mechanic and started driving around.

Now, on CNG, I found the car was quiet and had sufficient power, but when you applied full throttle suddenly, the car seemed to bog down a bit, and I was getting a measly 10km/kg. I took it to the CNG guys to get it tuned, and they just adjusted the gas flow to a point that it was running way too lean and the engine was shuddering and felt like it was about to fall apart, I asked them if that was supposed to be normal and they told me they can't do anything about it since its an open loop and its normal. I realized it was pointless to talk to them, so I followed guides from Team-BHP to tune the CNG system myself to a point where I thought it was acceptable.

500 KM on CNG:

At the moment, the car is running fine on both petrol and CNG, I procured a cheap Bluetooth OBD2 scanner to scan the ECU since I had an engine warning light, it was a P0130 code for a Faulty Oxygen Sensor, and after checking the real-time data, I realized on CNG, the o2 sensor gets cut off and on Petrol, it's back online, this causes the cars ecu to think that the O2 sensor is faulty and throws the code, I cleared it and it comes back often, it doesn't affect the car's performance in any way.

As for Performance, I tuned the CNG System to a leaner setting, it idles ok with/without AC on, the pickup is slower than petrol, but it is acceptable, and you need to downshift a lot more often unlike in Petrol


20-22km on mixed driving conditions with AC always on


So far, it's alright, yeah, if I went for a Sequential kit, but I've noticed a trend between CNG installers that one vendor won't touch the kit installed by another vendor. If your vendor is bad and you have a sequential kit, you are stuck with him since you need the specific software to tune the CNG system on sequential. Still, since I had a manual system, but if fitted by a reputed good quality installer who knows what he is doing, Sequential Kit is the way to go, also most cars these days use a Drive-By-Wire throttle, so sequential is the only choice you have, either way, ill update my experience on this thread. I'll post the pics below.


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