V8DualFuel: LPG / Autogas Conversions and kits

LPG / Autogas conversions and Kits from the experts

V8DualFuel from RPi Engineering: LPG / Autogas Conversions and kits for the Rover V8 Engine
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All about LPG

LPG shut off solenoids and vaporisers

(Ultimate system safety is ensured by defaulting to the system being shut down as installed default, with the LPG solenoids shut unless all three are supplied with voltage. Only available with ignition on, with engine running and with input - both electrical and engine vacuum - required).

Tank solenoid

Electronic and default is closed. If required allows simple disconnection of feed and fill pipes (to engine bay and LPG filler) without Fuel escape and is only open when engine is running and switched fuel mode is LPG.

LPG Filter Solenoid

Electronic and default is closed. If required allows simple disconnection of LPG pipe from tank to filter in the engine bay and is only open when engine is running and switched fuel mode is LPG.

Vaporiser Solenoid

Electronic and default is closed. If required allows simple disconnection of LPG pipe from filter to vaporiser in the engine bay and is only open when the engine is running and switched fuel mode is LPG.


 (Simply the demand valve part of the system)

The vaporiser/regulator has two basic functions:
  • Vaporiser. This is achieved by being plumbed into the carís water system, thus simply controlling its working temperature to ensure the liquid LPG wonít freeze as it becomes a vapour. This is done by making the appropriate twin connections via supplied T-pieces for connecting into the carís water cooling circuit.
  • Regulator The second function is to regulate the amount of LPG supplied to the engine. Just like a carburettor it tries to keep the mixture of LPG and air at the optimum proportion. This is achieved by default as engine vacuum and fuel demand is very much linked. Therefore the vaporiser/regulator delivers LPG pressure to the engine at a rate, controlled mostly by engine demand. This can be further regulated by means of Lambda, throttle position and stepper motor control, an issue covered later in this document.

Vaporisers come in 3 types
  • Single-stage Vaporisers (suitable for smaller capacity engines)
  • Two-stage Vaporisers (suitable for engines with big demand but essentially passive use)
  • Direct line (suitable for injection)

Single-stage vaporisers (mostly suited to smaller engines)

The relationship between vaporiser and mixer size/type is an issue often disregarded. The fact is that with bigger single-stage vaporisers which have to be big to supply the higher fuel demands of a V8 engine, they create unwelcome inefficiency at low- to mid-range torque, when considering most V8 applications, which also demand good cruise, passive and economy. Also, when employing a big single-stage vaporiser, there is a need for a restrictive size mixer, thus causing poor engine performance both at the upper end of petrol and LPG power expectations. Two-stage vaporisers (essential for all V8's and larger engines) Itís probably the most essential part that makes our system the best for Rover V8 applications. The two-stage vaporisers are just what the V8 Rover Engine needs, with improved and controlled fuelling at low engine demand, and big fuelling ability for those V8 moments.

Direct line
 (Suitable for EFI Gems and Thor)
Direct injection suitable for direct draw K&N filters and non re-circulating plenum breathing. Essential for Thor with over-run spark. My 5.2 Range Rover has no problem keeping up with the fastest of street cars, but also offers superb controlled torque and economy at lower speeds and passive driving. (as well as BMW-beating attitude).

The two-stage, tandem vaporiserís basic functioning is almost the same as all vaporisers except it is further and more accurately controlled by engine demand

The primary stage is operating when smaller quantities of LPG are required by the engine. Because of the small internal size of the valve the LPG release pressure is very stable. at this level.

The Secondary Stage (high power stage) will be actuated when the required amount of fuel has reached the maximum capacity of the primary stage (generally when you have just put your foot down). Best suited to larger capacity engines

Two main LPG mixture adjustment types (fine tuning)

Appropriation The main LPG adjuster is installed between the vaporiser and the mixer. Its basic function is to adjust the LPG fuel flow appropriate to engine demand. The LPG system in return must create an LPG/Air mixture of a constant ratio. While this issue is mainly taken care of by demand (simply actuated by engine vacuum), additional control is often advantageous/needed to compensate for varying engine demands.

We offer 2 different types of main LPG mixture adjusters:
  • An electronic controlled main flow adjuster (basically Lambda and actuator controlled).
  • A fixed main flow adjuster (mainly for carb. and early injection types).

Electronic controlled main flow adjusters (exclusively for later Efi type applications)

With input from the lamda probe in the exhaust providing a voltage signal output relevant to weak or rich emissions, and throttle potentiometer (throttle positon information) relating to full throttle power requirement or part throttle cruise (plus all variants between) combine to activate a stepper moter that enables futher control of LPG delivery between the vaporizor and LPG mixer for optimum economy. This system is supplied with all Hot-wire and Gems type Rover Efi sytems included. An additional supply of separate lambda probes if required is available and recommended. The Software system we use (Millennium/Leonardo) also offers unique advantages with the ability of self-learning, and can further minimise fuel consumption and power losses compared with other manual, fixed main-flow adjusters (see below) or lesser lambda-controlled systems.

The LPG peak flow controller/solenoid (stepper) receives its information from the Lambda sensor and throttle position sensor to compensate for and adust to relevant fuel flow requiments, both for cruise passsive driving and the more demanding load pulling or hurried accelaration times.

Manual controlled main flow adjusters

Appropriate for Carb. and early injection (flapper type) models. And for non Efi and early injection engines

Because the engine you have will provide its fuel demand (by vacuum) requirements as accurately as a deep sea diverís regulated and appropriate oxygen suppy, LPG is also demand-regulated via engine demand, indeed very accurately, without always having the need of additional electronic devices. So donít feel left out, as the right combination of mixer, size, vaporizor and filter can gain all the requred results without the more expensive EFI issues and upgrades of later engines.