Road Tests: Scania R420

For this week’s Eurotest we snatch an exclusive drive in Scania’s latest Euro-4 spec R420 4x2 tractor around our northern France route. Scania is one of only two European heavy truck makers to have majored on EGR (Exhaust Gas Recirculation) for Euro-4 compliance, MAN is the other. One of EGR’s primary advantages is its self-contained packaging rules; unlike SCR systems there’s no need for added liquid or tanks, yet Scania will be the first to admit the limitations of EGR, including cooling issues and an unsuitability to stop-start urban duties. In order to reach Euro-4 on its nine-litre five-cylinder and 16-litre V8 models Scania too follows the SCR path, but is sticking with EGR for its straight six powerplants and hopes to apply it to its other motors before the arrival of Euro-5. Remove the Euro-4 decals from the cab and even the keenest Scania fan would struggle to discern that our R420 test truck is anything other than a regular Euro-3 vehicle. Tilt the cab and it’s more apparent as the EGR valve and associated pipes are in full view. The DC12-11 motor retains the same 127mm bore, 154mm stroke dimensions as the current Euro-3 incarnation, producing a final swept volume of 11.7 litres.

By virtue of its modular build strategy Scania’s straight six shares most of its components with other Scania engines, however the 17:1 compression ratio is unique to the Euro-4 motor. Maximum power of 420hp is developed at 1,900rpm, while peak torque of 2,100Nm is on tap from 1,100 to 1,350rpm. HPI injection, a joint development by Scania and Cummins, has been fitted to 420hp six-cylinder engines for the past three years, however the turbocompound unit located at the rear of the motor has previously been seen only on 470hp models in the UK. This is needed at Euro-4 to retain similar power/torque characteristics to the current R420 while overall emissions are reduced. A GRS900R gearbox is a 12-speed-plus-two-crawlers manual. Following Scania’s recent unveiling of a new gearbox series this range change and splitter box will be superseded next May, the new transmission boasting lighter weight and easier shifting. The spread of ratios on the GRS900R starts at a formidable 16.38 crawler through to the direct drive top gear. For users requiring an overdrive top the GRS0900 is available. The R420’s powertrain is rounded off by the R780 single reduction drive axle, in this instance housing a 2.92 ratio final drive. Braking duties are handled by electronically controlled discs front and back on this 3,700mm wheelbase chassis, aided by a retarder. Standard parabolic steel suspension takes care of the steer axle while the drive axle has been fitted with four-chamber air suspension since the arrival of the R series. The R series saw the unveiling of a new cab in Scania’s high datum cab range, the Highline, measuring 210mm higher than the regular height CR19 sleeper. This appears in single driver configuration, with a single bunk and Scania’s most expensive Interactor 600 fleet management computer and multi-media system. Ready to work with the test specification 300-litre alloy diesel tank brimmed to the top, the R420 weighs in at 7,335kg complete with the retarder, a 75kg driver and a full set of alloy rims. Coupled to a Scandinavian-spec 2.6m wide Nor Frig reefer trailer the Scania artic combination stands on the weighbridge of the current inter-European maximum of 40 tonnes GVW.

As the low NOx shadow of Euro-4 looms ever closer the first question on every operator’s lips will be “How much is it going to cost?” Accepting that adding new technology invariably translates into a higher purchase price – around 5%, according to the market – the chief productivity consideration here is how oftehn the diesel tank needs replenishing. Moreover, in the case of the EGR, will Scania’s diesel consumption work out more expensive than the diesel/AdBlue combination favoured by most of its rivals? If Scania’s spin can be believed the step to Euro-4 shouldn’t make much difference to your fuel bill. To many this sounds an interesting proposal, particularly compared to the extra involvement required by running an SCR supplied truck, but would it ring true out on the road? Our opening 82-mile motorway cruise gives the R420 a chance to warm up and monitor the Euro-4’s consumption for ourselves, tackling the A26 towards the Champagne region then picking up the A1 towards France’s capital. At our standard 85km/h cruising speed the 12-litre six hums away sweetly at 1,350rpm, right at the upper edge of the peak torque curve, while returning almost 9.5mpg. Scania’s Swedish-based press garage equipped its 315/70R22.5 shod Euro-4 contender with a 2.92 final drive which, according to some French Scania operators, is a fairly uncommon choice on Gallic roads. Admittedly, the high ratio diff gives the driver only 250rpm to exploit at 85km/h before the needle drops below the magic 1,100rpm peak torque threshold, yet one of the benefits of turbocompounding the Euro-4 420 lump is meaty torque delivery between 1,100 and 1,200 revs. Even when the time comes for a downshift, such as over the legendary Vimy Ridge, the R420 requires just a single split to get the job done, and the turbocompound unit whirring away like a mini jet engine it quickly recovers lost speed to resume its leisurely top gear cruise. Compared with the biggest V8 Scania’s performance up this 2km 8% hill the R420 is a little slower at 1min 35secs, some six seconds longer than the R580 required. On level roads the Scania’s six-cylinder lump doesn’t need to be thrashed to perform. We rarely took the needle beyond 1,500rpm in our progression through the gears, moving off from rest using 1-high and 3-low and then changing into high range and 4-high, followed by 5-low and a succession of half gears through to top. Choosing a full gear in the upper ratio costs a full 500rpm, leaving the motor too low in the rev range if the 1,500rpm ceiling is respected. Although our most recent pass of the route’s toughest section was made in Scania’s flagship R580 we were rarely left wanting more horses at the wheel of its little brother. True, climbing a steep bank like the nasty 9% ascent out of Moufflers village shows a distinct difference in pace, yet more tellingly the R420 makes the same ascent at 2.35mpg against 3.5mpg from Volvo’s superstar FH16 610. On this hill, beginning at 70km/h and then battling up a consistently stiff climb, the Euro-4 motor looks a bit thirsty, but on the two remaining climbs with their higher approach speeds, the R420’s consumption is at a more acceptable level. Overall, the R420 turns in 8.14mpg for the entire route, which compared with two high-power trucks we’ve put around this route previously would appear a very healthy return. As for journey times and average speeds, we’ve no complaints against the willing R420. Ultimately a modest 0.3mph difference separates the two Scanias through the tough stuff, but the overall closeness of the R420 to the supertrucks proves that for all but the stiffest mountain runs a 420 in full health will cope pretty well at 40 tonnes. As we’ve already mentioned, EGR avoids the need for an additional tank, offering a lighter unladen weight and making the installation of an AdBlue supply unnecessary. However, the installation of the EGR gear adds an extra 90kg to the Scania. Even so the R420, at 7,335kg including a light driver, weighs in as reasonably competitive for a Euro-4 high roof unit.