FIVE OR six years ago, Jeremy Fearn fitted an uprated intercooler to our 200Tdi 90. The performance improvement was immediate and quite an eye opener. The traditional notion of the diesel Land Rover as smokey old plodder, was consigned to the dustbin of history. No hot hatch driver was safe in the belief that the 90 posed no threat at the traffic lights grand prix, and many a sheepish Max Power reader was left in a dust cloud to contemplate the money he’d wasted on his new aerodynamic spoiler kit.
Today, being a more respectable Discovery driver, my performance requirements are somewhat different. The Discovery is near perfect as a comfortable load carrier taking us, as it does, to events and venues all around the country loaded down with magazines, t-shirts and assorted other paraphernalia. However, and it had become a serious ‘however’, the 300Tdi coupled with its automatic gearbox is a woefully turgid combination.
Load it to the rooflining, couple up a trailer and even the most modest of uphill gradients takes on all the qualities of the Himalayan foothills. Gutsy is not a term that could be realistically used to describe the 300Tdi Auto Discovery with any degree of honesty.
So, what to do? Live with it or do something about it?
The obvious solution appeared to be the uprated intercooler route. It worked on the 90 so there seemed to be no reason why it shouldn’t work just as well on the Discovery.
“Do you think it will make a difference?” I asked Jeremy.
“No”, he replied. “I know it will”.
And he wasn’t wrong.

big is best
The principle of the intercooler is simple enough. Gas expands as it heats up and contracts as it cools down. An engine needs huge gulp fulls of air to combine with the fuel to combust effectively. Hence, logically, the cooler the air entering the inlet manifold, the more dense it will be and, therefore, the more oxygen the engine can breath in in one gulp.
The turbocharger forces air under pressure into the inlet manifold. This is a good thing as ‘forced induction’ ensures an increase in air flow thereby increasing an engine’s performance parameters.
However, the turbo isn’t all good news. Because the fan blades that force the air through the turbo are themselves driven by the action of the engine’s exhaust gases, the entire turbo charger reaches extremely high temperatures. This in turn heats the air passing through the turbo.

The task of the intercooler is to reduce the temperature of the air between the turbo charger and the inlet manifold. This is done by passing the air along tubes through a radiator where it is cooled before passing into the engine.
Land Rover’s turbo charged diesel engines are all intercooled to give satisfactory performance across a huge range of operating conditions. They manufacturer to create power units that will satisfy as many customer requirement as possible which can leave the high performance seeker wanting.
In a nutshell, Land Rover fit intercoolers of a modest size. Jeremy Fearn replaces them with whopping great big ones.
Typically, says Jeremy, one of his intercoolers can reduced the air temperature from as much as 1301⁄4C at the turbo to just 301⁄4C at the inlet manifold. The advantages of that are fairly obvious – the cooler, dense air allows the engine to operate at much improved efficiency producing increased horsepower and torque.
Both the 200 and 300Tdi engines will see increases in power output of some 35bhp over standard to a total 145bhp. Torque is increased to 250lbs/ft. Turbo boost pressure is increased by 3psi on 200 engines, but not on the 300.

But that’s not quite the end of the story on the 300 Tdi Discovery automatic. The huge increase in engine power is also achieved by resetting the fueling. For this, the engine control unit is ‘rechipped’ – a specially reprogrammed microchip is installed which alters fuel delivery to the engine allowing the auto set up to make the most use of the extra power.
Fitting both intercooler and new chip are no more than a day’s work at Jeremy’s Derbyshire workshop at a cost, in the case of our Discovery 300 Tdi auto with air conditioning of some £650. Which leaves only one question. Is it worth it?
To that there can be only one answer. A most definite yes.
Two things are immediately noticeable, Firstly, the vehicle goes faster. Obvious perhaps, but that’s not the whole story. Should you actually not wish to go any faster than usual, you find that speeds can be reached and maintained with considerably less engine effort than with Land Rover’s standard intercooler set up.
For example when pulling out from a junction into a line of traffic the Discovery now has an urgency completely lacking previously – the ability to get up to speed safely and easily is immediately noticeable. A initial test with the stop watch saw us instantly shave five seconds off the 0-60mph time – it may not be racing car stuff, but that five seconds can mean a lot when you’re pulling onto the motorway and there’s and Eddie Stobart truck filling your review mirror.

Having the additional horsepower available means that it’s possible to make more rapid progress along A and B roads and cruise with much greater comfort on dual carriageways and motorways. Overtaking slower vehicles on ordinary roads is no longer impossible – and trust me, there are times in a standard Discovery 300 Tdi auto, when ‘impossible’ is no exaggeration.
The increase in engine power allows the driver to use the automatic box to hold on to each gear longer allowing faster getaway times and more responsive and usable performance at any speed.
With improved acceleration throughout the speed range, fast moving motorway traffic can with negotiated with ease and confidence. Give the accelerator an extra squeeze at 70, 80, 85 and the Discovery responds in a way that it never did before. Long uphill gradients no longer see the automatic shifting down – high gear is held and the Discovery just keeps on cruising. Wonderful.
The Fearn intercooler has transformed the Discovery from a vehicle that was good up to a point into one that is excellent in every way.

boosting the Td5
Drivers of Td5-powered Land Rovers and Discoverys can enjoy the thrills of a Fearn intercooler, too. We took the opportunity to put Jeremy’s Td5 Discovery to the test through the Derbyshire hills and dales and I have to say, it’s just awesome.
The Td5 is a far superior engine to the 200/300 range anyway, but coupled with improved intercooling and rechipping, the vehicle wiped the grin off the face of more that one Mondeo driver as we ripped across the open countryside. To say that it drives like a car is, truly, the only way to describe the engine’s new found responsiveness and flexibility.
To prove the point, and in pitch darkness, Jeremy took LRM’s publisher for a white knuckle ride high speed across the hillside fields of his Derbyshire farm in the BMW-powered racer in which he and Brent Taylor had finished second in this year’s hillrally.
“An unbelievably exciting ride”, said Cathie. “I don’t know what you mean,” replied Jeremy, “it’s only a diesel”.