Volvo Owners Club Forum - View Single Post - Volvo V70 CNG bifuel 2004., engine shutting down randomly

mickey21 · Jul 17th, 2023, 16:35

I have replaced my tanks half a year ago, and it included taking 2 smaller cylinders out and replacing the big one. The only option I had at that time was getting new Type 1 steel cylinder from Vitkovice Cylinders, Czech Republic, 13.5kg CNG (although I can never take more than 13kg or even less, dependent on the pressure at the gas station/their main compressor). It is a bit wider and quite heavier so it barely fits the place of the previous tank and car has lost some clearance down. It was a pain getting back the plastic protective cover, as well, I needed to drill new holes in the plastic etc. I also had to change the cars registration license since car is now heavier than it was and different weight had to be added.

In the meantime I heard that there are now more options available with Type 3 composite cylinders of the same size (probably made in China) but those can hold only around 10 kg of CNG which would not be enough for me since I need at least 200km of range for my intercity travels without the need to top up during the trip.

I wrote this in a separate subject but once again, in brief: Since new cylinders, unlike original Volvo's have only one inlet for the gas valve instead of two for the valve and for the pressure sensor, I had to take the old CNG pressure sensor out from the old main cylinder (used VW diesel injector socket to unscrew it) and relocate it to the steel gas line from the tank to the engine. Without this modification the system will not work because ECU needs to read pressure level before opening the valve on the cylinder and switching to CNG. So this was working great with the factory gas regulator and distributor until recently when I realized that is pointless to repair the factory system. As much as I was stubborn to keep everything stock, new third party CNG systems have come a long way since NECAM KOLTEC system in Volvo was designed and are way superior in terms of efficiency, engine management and consumption.

So yes, I can confirm that there are options to replace the rear tank only and that it can work with the factory system. There are no options for the front tanks, theoretically, there are but they are extremely expensive and Faber who makes them, will not negotiate for the individual orders.

Nevertheless, with 13kg single large cylinder I am content.

Jul 17th, 2023, 16:35	#8
mickey21 New Member Last Online: Jul 17th, 2023 17:13 Join Date: Jan 2019 Location: Belgrade	I have replaced my tanks half a year ago, and it included taking 2 smaller cylinders out and replacing the big one. The only option I had at that time was getting new Type 1 steel cylinder from Vitkovice Cylinders, Czech Republic, 13.5kg CNG (although I can never take more than 13kg or even less, dependent on the pressure at the gas station/their main compressor). It is a bit wider and quite heavier so it barely fits the place of the previous tank and car has lost some clearance down. It was a pain getting back the plastic protective cover, as well, I needed to drill new holes in the plastic etc. I also had to change the cars registration license since car is now heavier than it was and different weight had to be added. In the meantime I heard that there are now more options available with Type 3 composite cylinders of the same size (probably made in China) but those can hold only around 10 kg of CNG which would not be enough for me since I need at least 200km of range for my intercity travels without the need to top up during the trip. I wrote this in a separate subject but once again, in brief: Since new cylinders, unlike original Volvo's have only one inlet for the gas valve instead of two for the valve and for the pressure sensor, I had to take the old CNG pressure sensor out from the old main cylinder (used VW diesel injector socket to unscrew it) and relocate it to the steel gas line from the tank to the engine. Without this modification the system will not work because ECU needs to read pressure level before opening the valve on the cylinder and switching to CNG. So this was working great with the factory gas regulator and distributor until recently when I realized that is pointless to repair the factory system. As much as I was stubborn to keep everything stock, new third party CNG systems have come a long way since NECAM KOLTEC system in Volvo was designed and are way superior in terms of efficiency, engine management and consumption. So yes, I can confirm that there are options to replace the rear tank only and that it can work with the factory system. There are no options for the front tanks, theoretically, there are but they are extremely expensive and Faber who makes them, will not negotiate for the individual orders. Nevertheless, with 13kg single large cylinder I am content. Last edited by mickey21; Jul 17th, 2023 at 16:44.