to assist in getting the engine to breathe better. Top Right: The old intercooler (left) as compared to the new Safari unit (right). |
| Improving
the spool-up ability of the turbo led to the exhaust. The standard
system worked fine within standard, compromised factory parameters, but obviously
wasn’t going to be up to the task of dealing with the extra efficiency contributed
by the larger intercooler at the upstream end. From 1700 rpm, the standard
system is able to produce useful power but below that, it tends to fall
into a hole – partly explaining the step-off tardiness. APS found
this could be noticeably improved via a better balance of backpressure and
designed a new, three-inch exhaust system to give just that. Clearly these revisions to the turbo-diesel’s breathing meant that the engine management system would also need to be addressed and this is where APS looked to its expertise in optimizing standard factory systems. The company believes that accurate control of fuel and timing is central to any engine enhancement, yet is an area often overlooked by those seeking to extract more power from a modern engine. Addressing these areas is both made easier and more difficult by the widening use of electronics in engine management systems, but harnessing this potential is an area that is largely misunderstood. Central to the enhanced engine’s operation is the ‘Unichip’ – an extruded aluminium box smaller than two cigarette packets that contains the electronic circuitry to manage the enhanced engine. The Unichip steps in above idle to precisely control things such as air-fuel ratio and injection timing, while the standard management system is left to look after regular parameters as cold start and idle speed. The programmable Unichip is claimed to be more durable than many factory components and is being used around Australia by car-owners keen to extract more efficiency from their engines, merely by tapping into the compromised potential that resides within. One of the main charms of the Unichip is that it allows all the original engine management system’s functions to be retained. This means that while important functions such as fuel supply and, in the case of a petrol engine, ignition can be modified to provide optimum individualized performance. All other parameters controlled by the regular ECU operate exactly as they did before the enhancement process. As far as the Toyota is concerned, none of this represents anything radical in terms of modifications of the standard 1HD-FTE engine, but does result in demonstrable across-the-board improvements in driveability. The official figures give a torque improvement of 18 per cent, as well as a lift in power of twelve per cent but these figures tell a less than complete story. On the road, the APS-enhanced LandCruiser undergoes a subtle but forceful transformation. Left to its own devices and upshifting (in automatic versions) at 3700 rpm, the Cruiser provides a steady, seamless surge of acceleration. It feels somehow lighter on its feet, eager to surge forward even with the merest tickle of the accelerator pedal and seemingly more ready to kick down. Perhaps the most impressive aspect is that the optimized Cruiser drives as quietly and easily as a regular, off-the-shelf model. Nothing is compromised in the extraction of the extra urge. We didn’t get to drive in towing mode, but we believe the claim that the much more useable torque curve will accelerate the Cruiser off the mark quickly enough to match regular traffic, even with a fully laden tandem trailer. Of course, for heavy-duty applications the Cruiser’s manual five-speed gearbox is the recommended option, as it copes with a big load better than the automatic. APS says the enhancements also mean the 1HD-FTE engine runs more economically than in standard form – which makes sense considering the turbo and fuel delivery systems are all essentially standard items. They are merely working in a more efficient environment. Of course all this is only chipping away at the edges of what would be possible with the turbo-diesel. There’s not doubt that attention to the exhaust manifold, or further work on the turbo system, would unleash considerably more power. But there’s a point at which the edges of the engine’s reliability are being nudged. The optimized Cruiser feels more refined in many ways than the standard turbo-diesel, yet will snarl away with real gusto if asked. Importantly, that initial off-the-mark lag familiar to many 1HD-FTE drivers is no longer an issue. Because the engine is more readily producing low-rpm torque, there is a tendency to use fewer rpm during acceleration, meaning quieter, more fuel-efficient operation. APS Engineering will have the turbo-diesel conversion on the market about the time this issue goes to press and is anticipating a price of around $3,500. Installation takes one day and is carried out through a specialized network of workshops covering all major population centres throughout Australia. For any turbo-diesel owner, this is a well-considered investment that should save money at the fuel pump, while also taking the strain off any of the heavy-duty chores to which the big 4WD naturally lends itself.  Above: The Unichip module handles the engine tuning parameters. |
Click here to return to page 1
