It seems very odd, but Nissan’s 2.8-litre turbo-diesel six-cylinder as seen in Australian-delivered Patrols, actually began its development journey as a petrol engine. What’s strange about that is that petrol and diesel engines usually have vastly different design parameters to account for their differing characteristics.
A diesel engine’s bottom end (crankshaft, con-rods and pistons) for instance, are usually much stronger (and, therefore, heavier) to account for the huge forces inside any engine with a compression ratio between about 17:1 and 20:1 (typical for a diesel). This rotating mass is one of the reasons diesel engines don’t rev as fast as petrol units, but it also means that a lot of petrol engines won’t stand up to the internal pressures and forces trying to tear such an engine apart.
But there has been at least one Nissanpetrol engine that was stout enough to take on this challenge, and that engine was the RB series of inline six-cylinder petrol engines with capacities anywhere from two to three litres. And, if you talk to people in the know, that’s precisely what the 2.8-litre turbo-diesel, the RD28 was spun off. The RD28 will bolt up to the same bell-housing bolt-pattern as an RB and even the engine mounts are interchangeable. There are even rumours that the cylinder heads can be interchanged with minor modifications.
Obviously, there were still differences internally, but the basic cast-iron block and alloy cylinder head were retained, as were the bore centres, the belt-driven overhead camshaft and seven main-bearing crankshaft which, in RD28 form, was a steel forging. Obviously, that design heritage made the RD28 a light-duty diesel engine, but Nissan buyers knew that and, if they required a vehicle to tow bigger loads, there was always the 4.2-litre diesel option in local Patrols.
Speaking of which, the RD28 arrived down under in the engine bay of the 1995 GQ Patrol, selling alongside the 4.2 and the two petrol engine options (one of which was a carburetted version of the RB30 engine, meaning that both petrol and diesel derivatives of the one engine were available from the same showroom at the same time.
In GQ Patrol tune, the RD28 was good for 85kW of power and 235Nm of torque or about the same as the non-turbo 4.2-litre diesel was offering in the same vehicle. Again, though, buyers understood the strong points of each engine and made their choices according to how the Patrol would be used (not to mention that the 2.8 turbo-diesel was around $8500 cheaper than a 4.2). By the time the GU replaced the GQ, Nissan had improved the output of the RD28 to 96kW and 252Nm, but it was always a five-speed manual-transmission only deal.
Driving an RD28-powered Patrol was a bit of an acquired taste. The turbocharger seemed pretty slow to build boost which meant that there was a considerable delay between putting your foot down and the vehicle responding with an increase in velocity. Drivers who could be bothered soon learned that they had to make good (and frequent) use of the gearshift if they wanted anything like decent progress, but even once the boost had arrived, it could be a bit underwhelming in the 2.3-tonne Patrol. In Australia, where lazy driving is the norm, the RD28 has a distinct reputation for being gutless.
But there are other facets of its reputation that aren’t great, also. The most common issue owners come up against is a front crankshaft pulley (that drives the alternator and water pump) that comes loose on the snout of the crankshaft. When that happens, it begins to fret and damages the crankshaft to the point where it’s a throw-away. Experts reckon owners need to use a torque-wrench to check the tension on the crank-pulley nut regularly, and to always assemble it with a thread-locking compound, and lots of it.
The RD28 arrived down under in the engine bay of the 1995 GQ Patrol.
Cracked cylinder heads can be another problem with the RB28 and a weeping head gasket can be the first sign of trouble with the head. Fuel-injection pumps are also known to be troublesome and expensive to replace. Actually, replacement part supply seems to be another of the down-sides to RD28 ownership. Because the engine was only sold here for a handful of years, getting hold of spare parts can be a tough battle.
Overall, the RD28-powered Patrol is destined to be seen as the poor relation when it comes to Nissan Patrols, and the only thing that saves its reputation even a little is that the engine that replaced it, the four-cylinder diesel ZD30 engine, was even worse when it came to reliability.