Series 1 Land Rover Project EFI

Australian petrol hovers around $1 per litre while LPG sells at less than 40c per litre making it the most viable fuel for vehicle users who do a lot of kilometers. All of the vehicles I have owned over the past 20 years have been dual fuel or LPG powered. The easiest way to increase power is to boost the compression ratio but unleaded fuel has a low octane rating causing detonation if the compression ratio is above 8.5-9 to 1.

LPG has a very high octane rating and will work with compression ratio's over 10.5 to 1 allowing good horsepower to be produced without the risk of burning holes in your pistons. The only problem with LPG is using a jerry can to top up when you fall a bit short of the petrol station. For this project the other problem is the lack of a suitable gas tank location that doesn't interfere with the load area.

I have never heard of an inlet over exhaust motor running on LPG and do not know how good it would be with such a low compression engine. With a flat head it would take extensive block machining to increase the 2 litre motors compression ratio so EFI will be used to keep running costs as low as possible on PULP.

The components to be used were left from a project on my son's JD Holden Camira that provided some good experience with injection systems.

Two different injection systems were used on the JD model the change taking effect in Jan 1996 according to my research. The pre 1986 JD used a Bosch MPI system tuned for leaded fuel while post 1986 unleaded models and the Nissan pulsar used the Delco TBI system while later 2 litre family II engines use a MPI Delco system.

A compression ratio of 9.5 to 1 makes the early TBI motors ping when run on unleaded. Retarding the base timing stops the pinging at the cost of power and results in engines that blow head gaskets.The later 1.8 TBI motor produces 63Kw compared with 83Kw for the MPI running leaded petrol.

Camira tank

Series 1 Land Rover

Mating the earlier MPI components to the later 8.8 to 1 compression ratio motor has allowed the base timing to revert to the original specifications without a hint of ping. The exercise had many trying moments but the result is one little ball tearer. When released the MPI 1.8 accelerated from rest to 100km/hr in 9.9 seconds.
	Many argue that MPI systems do not produce significant power improvements over TBI systems. You cannot compare ECU's physically like jets and venturi's and the same ECU will not operate both systems so this is very hard to prove either way. The graph to the left shows a definite power improvment on Camira's with MPI compared to the TBI systems meager 63Kw. It is hard to project how much power will be gained from the 2 litre Rover motor with either type of EFI system but it would seem the MPI would be the better choice for a 2.25 litre Rover motor. The main area of improvment expected from EFI is better driveability over a carbureted engine. No more flat spots, lumpy idles or faulty needle and seats dribbling fuel everywhere but into the motor. The effort has to be worth never fiddling inside a float bowl again.
Like mechanical fuel systems EFI systems vary considerably but all work on the same set of principles and use sensors to monitor the operating conditions. The signal strength, measurement device, resistance and type can vary but the fundamental operation is the same for all ECU's. Common problems with EFI can be divided into 2 areas fuel and air like all carburetor problems albeit with some subtle twists. Engine flooding and loading up - check the water temperature sensor connection. Open circuit will cause most systems to open the injector/s for the longest possible duration. Putting a resistor in series with the temperature sensor is a cheap way to richen the mixture over the entire rev range. The factory alter the value of resistors on the computer board to alter the basic unit specs as required by each car manufacturer/model. Engine idles (often poorly) but won't rev - check the airflow measurement device is attached correctly. Map sensors connect to a vacume port adjusting the fuel flow according to manifold pressure. When an air flow meter is used any air leaks or a disconnected air pipe will stop fuel supply from increasing when the throttle is opened. The Bosch LE Jetronic system uses a flap type air sensor that can be adjusted to provide different fuel rates without changing the ECU memory. To alter fuel delivery with an EFI system 3 variables can be altered, fuel pressure, injector flow rate or the injector open time. All 3 have physical limits but give EFI amazing flexibility to adapt to a wide range of requirements easily. I have compiled more technical information on EFI systems here for those who are interested.