LPG on Toyota Landcruiser 1FZ-FE / Nissan TB42e and Nissan TB45e Engines
LPG on 1FZ-FE’s and TB42/45E’s
Some LPG systems are suitable for turbocharging straight away, but most require at least some minor changes to the converter and possibly mixer. Injected systems may require additional injectors and changes to the pressure regulator.
With many LPG installations, installers may purposefully install an “undersized” system, in the attempt to gain the client better economy ( or the installer used a cheaper alternative…) This can create a significant issue with tuning a turbo application, as the LPG system will never be able to support the appropriate flow rates or pressures required to suit boost. In some of these cases, even the lock-off valves and pipes are undersized and will need to be replaced with the correct units for the vehicle.
Blow Thru Vs Draw Thru:
Many people consider setting the LPG system up as a draw-thru system, where the gas mixer is installed before the turbocharger. This is extremely dangerous, as it allows a large amount of optimum mixture air and LPG, under pressure, through the whole intake system. All that is needed is a slight misfire or worn valve seat to start the combustion.
There can be enough LPG mixed to create a significant explosion – enough to cause a large car fire or at least significantly damage the bonnet and bodywork. Basically, draw-thru is a big no-no.
Blow Thru Set-ups are just as flammable in the right circumstances, however, the mixer is normally located next to the throttle, so there is usually less than 10% of the volume that a draw-thru system would have, so the bang is much smaller. This is why poorly running vehicles may pop a hose or damage the airbox, but otherwise, very little damage will occur.
Throttle Body Draw thru:
This is most commonly the Gas Research type set-up. This is actually a proper LPG carburettor designed to flow the LPG through special venturi after the throttle plate. In all the ”vapour draw” type systems, this is the safest, as the LPG mixture is only in the intake manifold, and has the throttle plate to stop any backfire path. Being a full carburettor it also allows for much more accurate tuning potential, allowing for excellent power tuning and economy. These type of systems are a lot more resistant to the “waxing” build-up found in most LPG system, as the design allows for a lot more clearance that typical vacuum differential type mixers. ( The much larger venturi allows for a much more consistent vacuum differential, and due to the airspeeds, it “self-cleans” to a much greater degree ).
All systems require a suitably sized LPG converter. This is actually a pressure and flow regulator, which converts the liquid LPGin the tank to a vapour, suitable for combustion. Many converters utilise plastic components for economic reasons. These plastics are not suitable for boosted applications, as they can deform over time and this will dramatically affect the vehicle tuning. Some of the plastics are also known to crack with any sort of pressure, so these must be replaced with the correct alloy equivalents. Internally, adjustments and alterations may be needed, to ensure that the LPG outlet pressures remain correct. In a naturally aspirated engine, the LPG outlet pressures may be as low as 3-4PSI. If a turbocharger is pushing out 5-6 PSI, then instead of the LPG flowing out, the boost pressure will be trying to push it back into the converter.
This could result in dangerously lean air/LPG mixtures, or even no flow at all. A pressure Balance pipe is run to the converter, to allow the regulator to maintain the correct pressure differential, so when you have 6PSI boost, your tuner may set the regulated LPG pressures to peak at 10PSI, keeping a positive 4PSI pressure difference. These modifications are quite straightforward but must be quite precise to ensure correct operation.
The mixer itself may also require better materials and upgrades to ensure reliability. Many mixers use rubber diaphragms, which perish over time. With the additional flow of a turbocharger and possibly additional heat, these can rapidly fail. Rectifying this prior to turbo installation is imperative for safe long-term operation.
LPG Injection systems – Vapour Vs Liquid
Most commonly available Injected LPG systems are very similar to earlier vapour systems, with a couple of main differences. Firstly they use computer controlled LPG “injectors” which are basically just a solenoid that allows gas to flow. Secondly, they run at much higher pressure ( 30-50PSI ) as to be able to flow enough LPG through a much smaller entry, directly into the airflow. Many early LPG injection systems require special venturi style nozzles to be fitted to the intake manifold. These need to be sized and orientated perfectly, to allow the LPG to flow in line with the airflow. These nozzles are not designed with turbocharging in mind, as the additional airflow and speed will easily exceed the design parameters. Specialised nozzles may need to be fitted, along with other modifications, such as regulatory adjustments ( for the pressure differential issues) and possibly additional injectors to handle the extra flow required. Some later systems use a much more improved non-directional venturi port, which has a much greater range of flow capability, but this does need to be checked and tested to ensure tuning will be correct.
Liquid Injection systems,
Usually quite expensive comparatively but do offer significant tuning potential, combined with “natural” intake cooling. These systems reduce tank pressure but retain the LPG liquid form until it is injected into the intake tract. This keeps the fuel mixtures extremely consistent, resulting in a much more efficient fuel burn. As the LPG is still very cold, the air intake charge is actually cooled, resulting in a denser air-fuel mixture, which is very good is helping reduce the risk of detonation. As the LPG is also atomising in the air mixture, fuel is much more evenly dispersed in the cylinder, resulting in a much more even fuel burn, which adds to efficiency and power. These systems are rarely fitted to these vehicles, due to the cost, and overall benefit. While the process is much more efficient, the base engine itself still uses 20year old design, so cannot truly take advantage of these types of systems.
What systems do AXT Turbo recommend?
While we do not have “specific” brands we would actively promote, we have found the Gas Research system to be one of the most reliable and tunable systems around. This system does need modifications to suit boosted applications, and is not usable “out of the box”. In fact, Gas Research specifically does not endorse use in turbo vehicles, however, the aftermarket has shown it to be a very good base to work from.
Impco branded systems will also require modifications, but even then we have found they are really only suitable for lower boost applications. Some customers have had boost pressures set as high as 10 PSI, however, we have found the flow rates drop sharply after 7PSI. This can be compensated by lifting pressures, but it doesn’t leave much room for normal wear and tear. Again, Impco does not specifically rate their units for boosted applications.
With the many varieties of Injected LPG systems, with many just being rebranded other units, we will not mention any branding here, however when looking at any of these systems, simply check to see what packages are available for a Ford XR6 turbo. These packages will suit most normal turbo installs, and they many even have higher performance packages. If you already have one of “their” systems, don’t be tricked into immediately thinking you can just upgrade “some” of the components, as they may use completely different systems for naturally aspirated and boosted applications, just under the one logo…Some systems can be upgraded with components only, but you will need to check exactly what needs to be done.
A bit about Upper Cylinder Lubrication and LPG:
There are many products available claiming benefits by providing an extra liquid type additive that is drawn into the intake, with the purpose of providing additional upper cylinder lubrication, and acting as a valve seat recession preventative. Only some of these products actually do work. Many cheaper systems simply use lightweight engine oil, which in some cases can actually do more damage than good. Modern LPG mixtures include additional agents designed to reduce valve seat recession, and provide upper cylinder lubrication, however on these engines, there was never any specific design scope for running LPG. Ring to bore clearances and materials, valve seat materials and even spark plug heat ranges are not typically suitable for long-term LPG use.
People expect that “valve preventatives” products and other minor modifications will allow the standard reliability to be retained. In naturally aspirated form, some of these liquids may assist, however, even the ACCC has independently tested some of the claims to find little to no benefit for a lot of these products. When considering a turbocharged application, some of these systems are simply not compatible, whether they actually work or not. Most require vacuum from the intake manifold to draw in small amounts of liquid into the intake tract. Under boost, this same port will become pressurised, effectively pumping out the fluid. Typically, these systems also use plastic bottle type containers mounted in the engine bay, which can potentially pop or explode under pressure. This is a significant fire risk, and we have seen the end results first hand.
There are other alternatives to these products also. Many engine oils are rated for LPG and contain compounds that are specifically designed to aid with upper cylinder lubrication, and also provide valve lubrication through PCV fuming. Most of these type of oils do require increased service intervals over the factory schedule, however, for performance applications, the factory schedule is not really appropriate regardless.
Luckily, to actually convert the engines to be suitable for LPG and Turbo to start with is not as comparatively expensive as many may expect. Typically, a new set of piston rings and valve inserts is all that is needed. While apart, a set of bearings and seals ( all usually provided in the kit ) will mean your engine is as good as new. As long as the engine is in a good state of health to start with, then this is quite cost effective for your engine builder, and will probably result in a much better overall job once done. Of course, if during disassembly issues are noted, then you’ll still be better off. If you turbo an already damaged motor, you can expect much more damage to occur a lot sooner. A good example of this is a crank and conrod damage. This sort of failure can be quite costly to repair compared to a minor rebuild.
Ideally, we do suggest LPG is only fitted with an appropriate engine build, especially when considering turbocharging. We do recommend the Gas Research system but remember it must be modified to suit boost pressure. With all LPG options, except for dedicated LPG vehicles, we do recommend running Petrol for initial start and warm-up periods, and at least 10-15% of the time on trips. If the vehicle has been working hard, running on petrol for a reasonable cool down period may also help with engine longevity.
Dedicated LPG running vehicles:
Many people consider running LPG only, particularly if they need emissions compliance, or have had a major fuel system failure. With these vehicles, there are all sorts of Gas tank options, with the substantial range available, through the fitting of multiple tanks and types. We have seen vehicles with 2 rear mounted tanks in place of the OEM petrol tank and spare tyre, triple scuba tanks under the body, and shipboard tanks in the outer chassis rails. These tanks are heavy, and suspension upgrades will be needed. With multiple LPG tanks, you will have a “cobweb” of high-pressure LPG lines under the vehicle. These need to be appropriately protected for off-road type conditions.
Normal installation standards should NOT apply with these type of installations, as it only takes 1 branch to dislodge a pipe and cause all sorts of problems. When done right, these installations are not only impressive but also provide excellent performance potential. Being a dedicated fuel, optimum tuning can be done, ensuring the best performance from the fuel. LPG is considered to be the equivalent of 100 Octane petrol, so it is ideal for performance.
The biggest problem with dedicated LPG is actually running out of fuel. Jerry Cans won’t help, so it is always best to plan to maintain some reserve fuel. While it may be illegal to use BBQ gas to power an LPG vehicle (because of the taxation), it does work very well. In fact, BBQ gas is usually pure propane, whereas AutoLPG is a mixture of propane, butane and other compounds. Obviously, being illegal, (and also somewhat dangerous if not done correctly), getting fuel from a BBQ bottle to your vehicle may initially seem difficult, however, most forklift repairers may have replacement nozzles and a good “hose” specialist may be able to make a custom line, that just so happens to fit… A 9KG bottle might provide about 100km additional range if driven very conservatively.Of course, this is definitely not suitable for public roads, and if it is illegal where you are, don’t even consider it.