ACE moves for Renault
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• Renault has begun supplying Magnum and Major trucks fitted with its new ACE (Advanced Combustion Engine) engine (CM 2-8 April 1992). And this is the first UK publication to get to grips with the smoother, more responsive 12-litre unit, for which greater economy is claimed.
ACE replaces the existing MIDR 06.35.40H engine. Renault engineers have combined a number of updates with changes necessary to prepare the vehicles for Euro 1 emissions certification in October 1993. The modifications also pave the way for future upgrades to Euro 2 and beyond.
Filtration
Bore and stroke dimensions are unchanged, as are the rocker cover, sump and oil filtration system. Valve timing also remains unchanged. But everything else is new, including the injector nozzles and their position. Also modified are the inlet and exhaust breathing characteristics. An uprated compressor delivers 30% more air than before.
The result is a more durable and cleaner unit with fewer moving parts, says Renault. It claims fuel consumption improved by 5% (specific fuel consumption is down two points to 197g/kWh) with longevity improved by 30%.
CM tried out an ACE in an AE Magnum 4x2 chassis pulling a triaxle curtainsider at 37 tonnes. Outwardly there is no change to the vehicle, except for the 385ti door badge. Power and torque have both been increased by 3% in the redesign.
As the engine's name sug gests the new aspect of this engine is how the charge air is drawn in, how the fuel is injected and how the result is exhausted. On the road that translates into a deeper, throatier tone drivers will enjoy.
We've driven a large number of old 380 AEs in a selection of axle configurations since the launch in mid-1990. We've driven them throughout Europe at weights between empty and 50 tonnes. On the whole they are flexible to drive; the engine's torque characteristics giving speedy performance in most conditions, aided by the installation of the B18 gearbox under the new cab.
The ACE engine isn't that different — the overall package being purposefully similar — though the extra torque does allow the driver to hang on to gears that little bit longer.
Roundabouts
This is particularly noticeable with the mid-speed ratios, as we discovered when manoeuvring the laden artic around the small, sometimes undulating, roundabouts that make up Birmingham's city centre. Braking and feeding into one particular concrete circle at little more than walking pace, saw a drop to 5th low and accelerate away, rather than going down to low range. When we did drop to 4th it was never necessary to go lower except, of course, if we came to a full stop.
All that mid-gear, mid-speed torque should translate into improved mid-range economy, as long as the driver thinks with his brain, not with his right foot.
Like every new engine launched since the early 1980s, ACE requires a degree of new thinking from the driver, if not full training if its full potential is to be extracted otherwise.
Roadtests
Repeated roadtests have shown Renault's engines are some of the most fuel efficient of all the big diesels, but they must be driven correctly.
Another interesting aspect of the ACE engine is its exhaust brake. While the basic mechanism, like the engine's swept volume, hasn't changed, depressing the floor switch starts a deep booming retardation which, if it isn't actually absorbing more energy than before, certainly gives that impression. The redesigned exhaust ports
and retuned manifold play a part here.
Combustion
The ACE 12-litre will almost certainly power Renault's AE 420 model due for launch at the Hanover Motor Show in May. Renault says a considerably stiffer block design is now used to withstand higher combustion pressures. The same strengthening will, we're sure, be put to good use in the 420. This engine will no doubt be significantly cleaner, not to say lighter, than the old MIVR 08.35.30G vee-eight engine of the R420.
The switch to a 313kW (420hp) straight six will also make way for the first righthand-drive Renault 420.
The earlier vee-eight model was never offered in right-hand drive form due to the position of the steering box relative to the bulky engine.