Multi-valve heads are in fashion these days. Turbocharging is passé and supercharging has not yet been taken up by enough manufacturers. No, the way to increased horsepower and torque, according to current trends, is more valves per cylinder.
Volkswagen-Audi has followed the dictum of most engineers that head design is the most important part of an engine as far as power output is concerned, with the result that a number of its models have the 16v tag. New on the scene, however, is an Audi bearing the 20v insignia, a new dohc head having been developed from the Sport quattro to accommodate the extra valves.
Congestion in the engine compartment has been avoided by restricting the size of the exhaust valves to 28mm diameter and the inlet valves to 32mm. Altogether there is a 35 per cent increase in the valve area and 25 per cent extra gas flow.
Maintenance-free hydraulic tappets, sequential injection, three-way catalytic converter and Lambda control, which dramatically reduce exhaust emissions, a high 10.3:1 compression ratio, a bore increased to 82.5mm, a lighter crankshaft, sophisticated knock sensors and a newly developed management system all contribute to a sturdier engine. The 2309cc unit is capable of 170 bhp at 6000 rpm with a top speed of 137 mph. However it was not the quest for greater sPeed that led Audi engineers down this route, but the lure of increased torque. The figures testify to success here, for the 20valve is a great improvement over the 10valve, developing a good 162 lb ft at 4500 rpm compared with 137 lb ft at 4000 rpm. Even at 3300 revs the new engine develops 1411b ft, proving that it has pulling power all the way up to the red line at 7100 rpm.
On a quick visit to the west coast of Scotland and a drive through Glen Coe, a 90 20v was quick off the mark, revved willingly and was a pleasure to drive, although there was neither the time nor the place to substantiate the claim of a 137 mph top speed and 0-62 acceleration figures of 8.4 seconds. Although it has been decided that the engine will be available in both the 90 and Coupe, in quattro and front-wheel drive versions, prices and specifications have yet to be decided by the British importer. It has already been introduced in mainland Europe in many guises. In Germany the 20valve is just another option, while for tax reasons a 160 bhp 20-valve 2.0-litre is offered in France and Italy, but that unit is unlikely to find its way to these shores. WPK