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 mixers/injectors

The LPG mixer has two main functions
  • Generating a vacuum signal to the vaporiser instigating movement and subsequent LPG supply (achieved by the creation of unequalled atmospheric pressure (reduced) to supply side of the vaporiser diaphragm working on the principal of atmospheric pressure being on both sides of vaporiser diaphragm when non supply is relevant.
  • Offer efficient supply of appropriate amount of LPG fuel with regards to peak efficiency and performance. Normally positioned close to the throttle butterfly on both Efi intakes and between Carb and air filter. Components, of carburettor application as with our new Weber Active Mixer, discreetly contained within the air filter of 4-Barrel carb. systems.

The vacuum signal must be as constant as possible compared with the amount of air that is going through the venturi of the mixer. To achieve this the mixer must be carefully designed and one of the most important components is the venturi.

The LPG/air exit of the venturi must have an ± 8 degrees angle to achieve a constant ratio of LPG with air. One of the problems of this mixer will be its length (± 30 CM) which makes it almost impossible to install.

Rail Injectors

The electro-injectors are situated on a common (RAIL). When alimentated they, provide fuel (L.P.G) to the manifold situated before the inlet valves. The actual injection happens individually according to the order of the strock of the engine and is controlled by the C.P.U.

Not only is the shape of the mixer important, but also the size of the venturi. The smaller the diameter, the higher the vacuum signal to the vaporiser and the more accurate the LPG flow. The disadvantage is that the engine gets less mixture because of the smaller diameter. This is why for V8 application we supply the most appropriate mixer up top, 50mm and suited to our V8s from 3.5 to 5.2 ltr.

Therefore we supply and recommend that:
  • The venturis must be at least 75% of the superficial measure of the carburettor’s venturi or butterfly valve if it’s an EFI engine.
  • The venturi’s superficial measure must be 7.5mm and if possible 10mm for every 1HP.
  • It is important to have a mixer that has suitable diameter to create the vacuum needed for the vaporiser to work (hence we only use the ‘Tandem’ vaporiser on V8's) but of a big enough diameter to offer minimum air-flow restriction for the occasional higher rpm use. Our mixers are available from 40mm to 50mm and have no plastic insert/parts (unlike some systems where these can perish and be drawn into the engine).

Other Mixer types

The Rover V8 is often fitted with the Holly, or more recently the Weber/Edelbrook 4-barrel carburettor. This type of large bore carburettor creates big problems for LPG dual fuel use as the air flow is far too free to create a worthwhile vacuum signal to the vaporiser. So although mixers are available for this type of carburettor, petrol use becomes impossible due to the need to restrict nearly 80% of air flow for the LPG to work (until now, that is) To overcome this problem, we have designed what we call an ‘Active Mixer’ which, whilst on LPG, closes off 80% of air flow by means of an internal plate which is neatly hidden inside the filter housing. When switched back to petrol, the plate rises automatically (vacuum controlled) and restores the 80% of air flow to allow petrol performance without power loss.