Auto Case Study

Mitsubishi Pajero VO500 Case Study

The VO500 was proven in automotive service after various installations using the same core technology were successful in heavy power applications including marine propulsion where the largest engines exceeded 10,000shp.  The technology was also successfully used on 1,000kW Caterpillar generating sets.

With this experience behind us, we then chose to use the technology on automotive applications.  The automotive application has its own specific issues, so we decided to take a common SUV and operate it on vegetable oil and vegetable oil blends to compare.

We knew, from our marine experience, that there were some potential changes to the engine’s performance profile, so we installed a boost pressure controller, so that we did not put the engine at any risk.

The selected Mitsubishi Pajero 4M40T engine is a pre-combustion chamber engine, and that permits the use of oils with polyunsaturated oils, specifically cottonseed oil.  Direct injection engines work with saturated oils, or mono-unsaturated oils, but tend to form deposits with polyunsaturated oils.  Not having had experience with indirect engines to that point, we felt that it would broaden our knowledge base to use the 4M40T.  It was also the smallest engine that we had trialled to that point.

We had an Australian made auxiliary tank installed using a common filler neck.  Design rules required that the installation was certified and the vehicle plated, and this was done, although a small plug was provided that permitted the oil or diesel to be filled without cross-contamination.

A Facet Posi-Flow fuel pump was fitted to the chassis under the left front door where it was protected by a cross member.

Installation of the VO500 itself was simple, as there was a convenient position on the left hand side of the engine compartment where there was provision for mounting a second battery.  By selecting a short fuel filter element, we were clear of the wheel arch. 

We first coupled up the water connections.

The waste heat was taken from the engine by redirecting the cabin heater hose to the VO500, and the return from the VO500 went to the cabin heater bulkhead fitting using a new hose.  The existing hose was kept, undamaged.

Next the fuel supplies were connected.  The diesel and oil supply hoses were connected to a barb on the right hand side of the VO500 and the opposite side ports were closed by transferring the blanks.  On the left side, the delivery to the pump was connected and the returns to the appropriate tanks connected to barbs.  The 4M40 fuel pump has a closed loop spill return so the spill return was blanked off on the VO500.

As the trials were being undertaken in a sub-tropical environment and that the melting point of Cottonseed Oil is at or close to 0°C, no hose heating nor tank heating was fitted.  Had the oil been Coconut or Palm, then trace heating and a tank immersion heater would have been essential. 

This installation was instrumented with thermocouples to provide data on the oil temperature the water temperature and the exhaust temperature.  To remove the clutter of wires from the interior, arising from the monitoring equipment, a small ISO radio sized display was assembled with a rotary switch.  A turbo-timer was also fitted and controlled from the same display.

Start up was accomplished on diesel using glow plugs, and engine heat - 0.97 bar up was swift – a matter of only 5kms or so.  The system was left permanently on “Automatic”, so the engine switched over to oil when the oil reached the desired temperature, which on this installation was 80°C.  The temperature difference across the heating water was only 5°C when the engine settled down, and the water/oil outlet temperature difference was also 5°C.  This corresponded with generating set installations, where the engine was fully established on vegetable/plant oil within 7 minutes of start.

Shut down was achieved using the turbo timer, that permitted the oil to be purged over five minutes before shut down.  In daily operation, though, the timer was not used, as the engine fired first time on the cottonseed oil whilst the engine was still warm.

The main surprise was the general improvement in performance – notably in mid-range.  We had known from the marine propulsion installations that the boost pressure was enhanced when running on palm oil, and this was entirely because of the greater mass flow across the turbine of the turbo.  The secondary effect of this greater mass flow was increased air volume and pressure to the cylinder, which provided more scavenging and more oxygen leading to far better combustion, and fuel consumption, on oil, much better than theoretical calculations would suggest based on density and energy value.

The maximum boost pressure of the 4M40T is 14psi (0.97 bar).  Previous Pajero performance enhancements had demonstrated that the 4M40 is not too happy with increased boost unless the air plumbing is totally revised, so it was decided to keep the installation as close to stock as was possible.  The boost controller was therefore adjusted to open the waste gate at 14 psi.  Measurement showed that on diesel, the waste gate usually never opened and that the normal operating boost was up to 8 psi.

The first surprise came after a steady highway run of 200kms, and the fuel consumption using oil was within 1% of the same journey using diesel.  The second surprise was the pulling power in mid-range.  Instead of dropping from fifth gear to fourth to overtake or on an incline, the engine pulled happily in fifth.  Cruise control never seemed to be working hard, as speed stayed pretty constant.  The big shock came when accelerating hard, when the boost could readily cause the waste gate to blow off in third or fourth gear.  A slightly more moderate driving style was adopted that made the vehicle much more agile in traffic, and so much more comfortable to drive.

The conclusion was therefore that the cottonseed operation actually improved the vehicle on all counts, comfort, economy and fun.  There was no more smoke on acceleration.

As a final experiment prior to removing the monitoring kit and just using the vehicle as a daily driver, we tried a diesel/oil blend.  This turned out not to be a good idea.  Starting was temperamental, smoke was reduced, but performance was also reduced.  We ran the tank down and refilled it with diesel and the starting problem disappeared.  Blended fuel did not work in this installation.

We were sufficiently confident in the performance of the vehicle, that we ran the old Pajero until she had done well over 200,000 miles (320,000kms) and sold her on.

Since the Pajero, the VO500 has been installed on a number of different types of engines, and where the common rail injection system is fitted to the engine, we modify the oil circulation to provide cooling to the injectors, and, also pick up additional heat that would otherwise have gone to waste.

The biggest puzzle remains: Why do more people not recognise the advantages of plant and vegetable oils as a fuel?