Daf unveils marathon runner
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It took more than two years of hard engineering work and 190-million Dutch Gilders before Daf's latest premium tractor was ready for its Brussels Show debut. It's more powerful, frugal and comfortable—so is the 95XF going in the right direction for long-haul operators?
by Brian Weatherley • It's been a long time coming. But at last Dal has its own "big" engine, and not just in terms of cubic capacity. The 12.6-litre six which powers the Dutch manufacturer's latest 95XF range offers more power and greater economy: it also meets the Euro2 emission limit without any electronics, thanks to the further development of Dafs tried and tested engine technology.
However, about the only thing it has in common with the old 11.6-litre 95 Series engine is its bore. According to Leyland Dafs marketing manager Tony Pain: "You could say we've stroked it—but actually it's an all-new engine."
Reduces noise
The XF block is certainly different, with an improved, stiffer design that reduces noise. On top there's a diamond-configuration four-valve head with central injector, as proved in Dafs racing trucks, featuring a crossflow design with siamesed air intake ports.
The XF engine's conventional Bosch fuel pumps are mechanically controlled with fuel injected through eight-hole injectors at a pressure of around 1,250bar. All three XF engines have charge-cooling: on the most powerful (480hp) version a waste-gate is fitted to the Garrett turbocharger.
While other manufacturers have opted for unit injectors and an overhead camshaft, Daf has stuck to a conventional low mounted cam but with redesigned hollow pushrods featuring roller cam followers.
Engineering guru Hans Staals says that by keeping to "a very simple design" Daf has been able to keep the engine height down, allowing it to fit a compression engine brake; either its own DEB or, on the 14-litre Cummins, a Jake Brake. The new crankshaft has been developed for smoother running, as have the extremely rigid bridge piece for the fuel pump mounting, the vibration damper on the fuel pump driving gear and the new rubberdamped valve covers.
Daf has opted for dry liners, which suffer less distortion than wet liners. As a result, says Pain, piston and liner tolerances can be reduced, resulting in even lower oil blow-by to reduce particulate emissions. The downside is the need for greater cooling, and Daf now fits a larger radiator which has led to the XF tractor's distinctive new grille.
The changes have not been at the expense of weight: the XF engine weighs only 30kg more than the old WS diesel. More importantly, Daf is claiming significant reductions in fuel economy (4%) and base engine noise (4%); with a life expectancy of at least a million kilometres, The XF is currently rated at a maximum of 480hp but Staals says there is "scope for further performance as the demand for power goes up". In the meantime operators who want more than 500hp can still spec a 14litre Cummins in electronically controlled Euro-2 guise.
Matching the 95's new drive. line is a revised cab. The XF cabin is 203mm longer than its predecessor and mounted 102mm higher on the chassis, which has been tidied up. To improve handling Daf has developed what's effectively a subframe for the cab-mountings—the Space cab sits on a mixture of rear coil springs and front metalastic bushings; the Super Space cab has a fourpoint air suspension.
The new interior features a smoother, less intrusive dash, improved heating and ventilation and a new steering column which adjusts via a push-button for height and rake before locki n g itself in the required position after seven seconds. Other detail changes include the sensible relocation of the radio from the headliner to the dash.
Extended warranties
Leyland Daf says delivery of right-hand-drive models will start around the middle of April. The XF will be sold with a two-year full-vehicle and fiveyear cab paint warranty as standard, with the option of extended warranties according to operator needs.
71 More details on the latest 95XF family will appear in next week's issue.