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The SVIS (Sequential Vapour Injection System) is Technocarb's main alternative fuel system product for gasoline vehicles.  The SVIS is a complete digitally-controlled, sequential vapor injection underhood conversion kit with versions available for both port and direct-injected engines. The closed loop LPG or CNG digital controller is an advanced computerized device factory pre-programmed for each specific application.

The main problem with converting fuel-injected vehicles is the high internal volume tuned intake manifold. While this intake manifold is great for improving torque, it also causes a fuel signal transport delay with mixer-style propane conversions. This delay can lead to costly repairs from lean fuel-mixture backfires. The solution of course is to keep the fuel out of the intake manifold with vapour injectors at the intake ports. Besides eliminating lean mixture backfires, port vapour injection also makes the engine more responsive. While the old Impco fumigation systems generally have propane fuel economy around 75% to 80% of the car's gasoline economy, Technocarb's SVIS (Sequential Vapour Injection System) result in a propane fuel economy of about 90% of the car's gasoline economy. Power only drops by about 10% too.

While not a DIY project for a novice mechanic, Sequential Vapour Injection is quite straightforward and relatively easy to do. Technocarb has very kindly supplied us with the following documents for their Sequential Vapour Injection System:

SVIS Installation Manual

SVIS Owner's Manual


Order Technocarb SVIS conversion kits from our e-store.

SVIS LPG Components


Digital signals gathered from the engine operation, such as the exhaust gas oxygen content, RPM, TPS, fuel pressure, vacuum pressure, fuel temperature, and gasoline injector actuation pulses.  In many late model applications the SVIS can connect directly to the OBDII system. This digital system controls and adjusts the LPG or CNG ratio by precisely pulsing measured vapor fuel (measured in milliseconds) to each separate cylinder injector.

Vapor injectors are installed directly into the intake manifold as close as possible to the OEM gasoline injectors virtually eliminating “lag” found in other systems.

The digital controller keeps the onboard gasoline computer active in its monitoring, diagnostics and controlling functions even while the vehicle operates on the alternative fuel.

Technocarb CNG or LPG digital controllers allow for full on road diagnostics, calibration and configuration utilizing user-friendly Windows based platform software which will run on a laptop or desktop computer. Many vehicle applications allow for direct connection to the OBDII diagnostic port (CAN Bus) allow unequalled performance and enabling fuel trim data to be read on your laptop.  This eliminates the need to use a separate OBDII scan tool.

The SVIS digital controller uses sophisticated software developed to compute the most efficient alternate fuel injection ratio to achieve low fuel consumption and low emissions, yet providing the best possible drivability and power.  Many SVIS kits have EPA certifications.

The Technocarb SVIS digital controller does not interfere in any way with the OEM onboard controller, meeting compliance regulations for all current international alternate fuel regulations.

State of the art injectors SPECIFICALLY designed for vapor fuels (unlike re-worked gasoline injectors) give superior performance and durability while also being more forgiving of contaminated fuel.

All components meet US/Canadian and International safety standards.

All LPG and CNG regulators are specifically designed and tested to ensure excellent performance, service life and durability on high demand North American engines as well as all import applications.

Many SVIS systems are now supplied with fuel injector “interface harnesses” these harnesses allow the installer to just “plug & play” the injector wiring portion of an installation, cutting hours of work (and the potential for wiring errors) greatly.