Open-loop and Closed Loop sequential systems
My only concern now is to go with the open loop or closed loop thing.
Another thing to consider while choosing a CNG kit is whether you want an open-loop system or a closed-loop system. What this means is whether your CNG kit takes feedback from the oxygen sensor placed in the exhaust system and transfers that back to the ECU or not. There are advantages and disadvantages to both these systems. Closed-loop system
A closed loop system is one where the O2 sensor or lambda sensor in the exhaust gives feedback to the ECU controlling the CNG gas flow, and tells it whether exhaust emissions are within permissible limits or not. The ECU then regulates the gas flow accordingly to prevent too much pollution. Advantage
The advantage of a closed-loop system is that you get precise emission control and will be doing the environment a favor. You also get slightly better fuel efficiency because it keeps the gas injection at an optimum point. Disadvantage
However, not everyone is happy with a closed-loop system, especially if one is used to superior performance while driving on petrol. The reason is there is a marked drop in performance as the CNG ECU tries to inject only the optimum amount of gas to prevent excessive exhaust emissions. This means that you may not get the kind of acceleration you want, when you need it. Open-loop system
An open-loop system is one where there is no feedback taken from the O2 or lambda sensor in the exhaust, allowing the car to accelerate and inject more gas at will, without the lambda sensor acting as a nanny. Advantage
On older cars where there was no oxygen sensor in the exhaust system it results in cost saving, as one does not need to buy an O2 sensor (that costs about Rs. 4000). On newer cars, having a lambda system, installers often do not connect the sensor to the ECU, leaving it taped up, therefore remaining an open-loop system. Because it’s left this way, there is no restriction on the amount of CNG that can be injected into the engine at any given temperature, allowing for better performance and pick up. Disadvantage
However, an open-loop system has its inherent disadvantages. One is the higher exhaust gas emissions that occur as there’s nothing to monitor emissions in the system. And two, a more significant concern is the heat build up in the engine. Open-loop systems tend to run a lot hotter because of no monitoring of exhaust gases and this can damage exhaust valves of the engine.
Ideally, one should always choose a closed-loop system, even if it means a slight compromise in performance, as its better for the environment and for the engine.
Source: Sequential and Venturi CNG kit types, open loop and close loop CNG kits | Cartoq - Honest Car Advice Fyi
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