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Technical Details / GlossaryLambda sensor with Lambda boss// BACK Even though your engines exhaust system may not already have Lambda sensors, this kit is still the best suited for you as detailed in our Millennium with Lambda loop control explanation. Adding lambda to your LPG system monitors the exhaust gases and looks at your throttle position and trims the fuel flow to the engine accordingly thus for full power a rich mix is available and in cruise and deceleration the mixture is weakened off to keep emissions low and economy high. It also keeps your engine in great shape to offering crisper fuel burn and all the advantages it brings. If you already have lambda sensors fitted (normally 1992 onwards) we still prefer to fit the lambda sensor supplied here to keep the LPG and petrol management separate, especially as the original ones are very expensive so its best not to disturb them. LPG EFi Change over switch with LPG level gauge// TOP // BACKThe basic LPG switch for a fuel injected engines has two positions/modes. The LPG switch has two operating modes. Petrol, as the name suggests this mode is to run the engine on petrol and the LPG system is inactive. LPG, this activates the LPG solenoids and allows the engine to run on LPG, with the petrol system inactive. There is a level gauge using LED's on the switch which is controlled by the float in the LPG tank. LPG Change over switch with LPG level gauge// TOP // BACKThe LPG switch for a carburetted engine has three positions/modes. The LPG switch supplied is a digital switch as has the following three modes, Petrol, petrol run out and LPG. The modes petrol and LPG are self explanatory, the reason for the petrol run out mode is that when changing from petrol to LPG you have to run your float bowls out of petrol before switch to LPG. When on LPG though you leave the switch in the LPG position so that the engine starts and runs on LPG. There is a level gauge using LED's on the switch which is controlled by the float in the LPG tank. OMVL Vapouriser// TOP // BACKA Vapouriser is the component located under the bonnet and linked directly to the LPG tank with a copper pipe via a fuel solenoid/filter. The copper pipe from the tank supplies liquid LPG to the vapouriser, and then, as the name suggests, the vapouriser changes this liquid to a vapour ready for the engine to burn. The vapouriser is also a demand and supply valve, sucked at from the mixer ring located in the induction pipe. The harder the engine works, the higher the vacuum from the mixer ring, therefore, the diaphragm inside the vapouriser is moved further and more vapour is let through to the engine. The V8 engine is a large engine in comparison to most everyday cars (fuel injected 2.0 litre engines for example), and therefore needs a large vapouriser to supply it with the correct amount of fuel at the higher end of the rev range. So most would think of fitting a larger vapouriser. Yes, this is what is needed, however, at low rpm there is not much vacuum in the induction pipe and this means it is very difficult to move a large diaphragm to let vapour through. So, in this instance, when the V8 is at lower rpm, a smaller vapouriser is required. The OMVL unit is a tandem vapouriser, and therefore works just like a 2 stage carburetor. It has a small diaphragm at the front which is easy for the vacuum to pull at and open, and then, as the vacuum from the mixer ring increases, the larger diaphragm at the rear is opened to allow more vapour through so that the engine does not run lean. OMVL Dream Vapouriser// TOP // BACKA vapouriser is the component located under the bonnet and linked directly to the LPG tank with a copper pipe via a fuel solenoid/filter. The copper pipe from the tank supplies liquid LPG to the vapouriser, and then, as the name suggests, the vapouriser changes this liquid to a vapour ready for the engine to burn. This vapouriser is set to supply a constant vapour LPG pressure for the supply to the LPG injectors. Romano Major Vapouriser// TOP // BACKA vapouriser is the component located under the bonnet and linked directly to the LPG tank with a copper pipe via a fuel solenoid/filter. The copper pipe from the tank supplies liquid LPG to the vapouriser, and then, as the name suggests, the vapouriser changes this liquid to a vapour ready for the engine to burn. The vapouriser is also a demand and supply valve, sucked at from the mixer ring located in the induction pipe. The harder the engine works, the higher the vacuum from the mixer ring, therefore, the diaphragm inside the vapouriser is moved further and more vapour is let through to the engine. Pair of SU LPG Mixer Plates// TOP // BACKThe mixer rings are placed in the induction pipes (they bolt between the carb. and the elbow) and this is where the LPG vapour is mixed with air being drawn into the engine. It works on a very simple to understand principle very similar to that of a diver with second stage breathing apparatus. As the air travels through the induction pipe it passes through this mixer rings, which have a venturi inside it to create low pressure on the exit side of the ring. This creates the vacuum required to suck on the vaporizer and draw the vapour through into the engine. Fuel filter with shut off solenoid// TOP // BACKOnce you have the LPG system fitted, there should be three electrical shut-off solenoids in total. One will be located on the LPG tank, there is another on the OMVL vapouriser supplied with this kit, and the third is a separate solenoid which is mounted in the supply line under the bonnet just before the vapouriser, this one contains a filter as well. All of these solenoids only become live when the vehicle is switched to, and active on, LPG, therefore, when the vehicle is running on petrol, or the ignition is switched off, the LPG system is effectively dead. Petrol Solenoid// TOP // BACKWhen running on LPG it is not only necessary to turn the petrol pump off (assuming you have an electronic fuel pump) but also to install a petrol solenoid in the fuel pipe just before the carburettor(s). The reason for this is that if you were to simply just turn the petrol pump off there is still fuel in the pipe that could surge forwards into the carb. when you stop/accelerate. With this solenoid installed this stops the fuel from being able to do this. 38 - 40mm Mixer Ring// TOP // BACKThe mixer ring is placed in the induction pipe (on the end of the plenum before the throttle butterfly) and this is where the LPG vapour is mixed with air being drawn into the engine. It works on a very simple to understand principle very similar to that of a diver with second stage breathing apparatus. As the air travels through the induction pipe it passes through this mixer ring, which has a venturi inside it to create low pressure on the exit side of the ring. This creates the vacuum required to suck on the vapouriser and draw the vapour through into the engine. As explained above, we use a tandem vapouriser so that the engine can fuel itself properly. Because of this we are also able to use a 38 - 40mm (internal diameter) mixer ring so that the engine is not restricted as it may be by some kits that use a smaller diameter mixer ring and a single stage vapouriser. Emulators// TOP // BACKThe emulators are what stop petrol from entering the engine when running on LPG. Unlike earlier carburetted engines where you could just turn off the fuel pump, later fuel injected engines require fuel pressure behind the injectors just in case you need to switch back to petrol at any point. The emulators plug between the petrol wiring harness and the fuel injectors, then when the system is switched to LPG they cut the feed to the petrol fuel injectors. But not only this, they also place a ‘dummy’ load on the petrol ECU so that it believes it is still firing all 8 injectors. In doing this it prevents the petrol ECU responding as if it has an injector fault, which can happen if cheaper emulators, or even simple relays are used. LPG Injectors// TOP // BACKThese injectors are fed from the fuel rails and are suitable for the Rover V8 engines in all of its capacities all the way up to the 400 bhp L322 Supercharged Range Rover. They are controlled by the LPG ECU which is explained on this page. Sequential LPG ECU// TOP // BACKThe sequential LPG ECU plugs in between the original petrol wiring loom and petrol injectors, then connects to the LPG fuel injectors. The LPG ECU picks up and interrupts the signal going to the petrol injectors and then converts the petrol injector pulse time to a suitable pulse time for the LPG injector and fires the LPG injector. Later 1999 onwards engine management systems are very complex and constantly adjusting there fuelling rate. They then checks back to there Lambda sensors to see what effect the changes made have had. If earlier draw through LPG systems are used on these engines, adjustments that the petrol ECU were making would not be transferred over to the LPG fuelling system. Therefore the petrol ECU would start to report fault codes. Millennium with Lambda Loop// TOP // BACKThe electronic ECU that controls the LPG system is very basic as there are no injectors to control, in fact the most complex process going on inside the LPG ECU is the Lambda loop. This works in just the same way as on the Petrol ECU controlling fuelling amounts. By having a Lambda sensor in the exhaust system (a Lambda sensor is capable of measuring emissions in the exhaust) the ECU is able to tell if the fuel to air mixture is either too lean or too rich, and will adjust itself accordingly. The ECU is also linked to the throttle potentiometer (throttle sensor) so that it is aware of when you want more from the engine, or are just cruising. On your petrol ECU the adjustment is made by altering the injector pulse timing, however, this is not possible on the LPG draw-through system, as the engine is drawing LPG vapour through with relation to the amount of air going through its venturi mixer. So, between the mixer and the vapouriser, the ECU has a stepper motor which it can control to alter the amount of LPG vapour which can pass through the LPG pipe. The stepper motor is an electronic equivalent of an adjustable valve, so the ECU can partially block the LPG vapour pipe when cruising to give better fuel economy, but can also move out of the way to allow the engine to have more fuel when you need to accelerate. Once you have the LPG system fitted, there should be three electrical shut-off solenoids in total. One will be located on the LPG tank, there is another on the OMVL vapouriser supplied with this kit, and the third is a separate solenoid which is mounted in the supply line under the bonnet just before the vapouriser, this one contains a filter as well. All of these solenoids only become live when the vehicle is switched to, and active on, LPG, therefore, when the vehicle is running on petrol, or the ignition is switched off, the LPG system is effectively dead. |
Home I All about LPG I LPG installation I LPG complete kits I LPG front end kits I LPG tanks only I Contact LPG / Autogas Conversions and Kits from the experts at RPi Engineering
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