It would seem a sensible move to keep the moderately sporty variants of its range fresh, but the engine is also available in the Zafira MPV - not the sort of vehicle you would expect to be driven enthusiastically for enjoyment. The SRi cars were available to be driven around the historic Goodwood racetrack on a drizzly and blustery winter morning - the Zafira was not available for track testing.
Following a track briefing, I was allowed to take to the slippery 2.4-mile circuit in the new cars. The 145bhp 2.2-litre engine replaces the 134bhp 2.0-litre unit in both the Astra and Vectra, is 10% lighter, meets Euro IV emissions standards and offers improved torque at lower revs - with 90% of its peak available from 1,900rpm. My first experience of the 2.2-litre was in the Astra SRi - the lighter of the three cars to have the new engine. It isn't a particularly exciting car to look at. It's still beaten on looks by the Peugeot 306 and is not as striking as the Ford Focus. And when compared to the new Astra Coupe, the three-door hatchback can appear slab-sided.
With black fabric covering the seats and door, and plenty of black plastic elsewhere, the only form of 'light' relief is sporty black-on-white dials. However, there is easily enough room to accommodate a 6ft 1in driver wearing a crash helmet. The Astra 2.2 SRi (a 1.8-litre is also available) feels lively and responsive on the move, with crisp turn-in. The ride does feel firm - even on a circuit - but although you feel bumps and potholes, there is no harshness or jarring through the cabin.
Acceleration is smooth, with the Astra reaching 110mph on the back straight before the weather conditions made self preservation set in. Some areas of the Goodwood track have just a few metres of turf before wayward cars hit the wall. Although it would have been foolish to exploit levels of grip on such a wet day, the Astra was comfortable taking undulating bends at 80mph, with only a hint of a light rear end over crests.
On the whole, the engine feels and sounds refined, although there is a slight sporty edge to the exhaust note under harsh acceleration. The car is now the most powerful in the Astra hatchback range, with 0-60mph attainable in 8.2 seconds. It also performed well on the open road, with its firm suspension set up keeping things neat around fast bends, and smooth gearchange ensuring swift progress.
The Vectra feels more grown up than the Astra, despite sharing the same engine. Although its performance compared with the Astra loses its edge because of the extra weight, it is still surprisingly nimble when conditions demand. It was virtually the Astra SRi's equal around the circuit, and felt more comfortable on the open road. Twin balancer shafts ensure engine noise is never more intrusive than a distant purr, and Vectra drivers will have more choice with the 2.2-litre - it will be available in LS, SRi, CD and CDX guises. It reaches 60mph from rest in 8.5 seconds.
Although I was only able to drive the cars on the circuit and a 25-mile route on country roads, all the indications are that the Vectra will prove to be an effortless motorway cruiser. The car never felt stressed, and although, like the Astra has much of its pulling power on offer below 2,000 rpm, the Vectra felt the most relaxed of the trio. You can go higher than 2.2 litres in the Vectra range - there is a 2.6-litre V6 in the same trim as the 2.2-litre - but with V6s traditionally carrying heavier depreciation, and with the refinement and performance of this engine, there would seem to be little point.
The Zafira stands out in its compact MPV class with a 2.2-litre petrol engine option. Rivals like the Renault Scenic, Nissan Almera Tino and Daewoo Tacuma offer petrol engines up to 2.0 litres, while the Citroen Xsara Picasso only has a 1.6 or 1.8 and the Fiat Multipla offers a 1.6-litre petrol engine. This could be Vauxhall's way of muscling in on Ford Galaxy territory now that the larger Sintra MPV has been dropped.
Despite being revolutionary when it was introduced - offering seven seats in a compact body - the Zafira has dated surprisingly quickly compared with newer rivals from Citroen and Fiat. It still has a floor-mounted gearstick, causing unnecessary clutter, but apart from the lofty driving position it feels much like the Astra except with more body roll.
However, the Zafira is a strong seller, and Vauxhall plans to boost UK supplies with cars built in Thailand to keep up with demand. Of the 25,000 Zafiras Vauxhall expects to sell this year, up to 5,000 could come from General Motors' new factory in Thailand. The 2.2-litre will be available in Comfort and Elegance models, and boosts the two petrol and one diesel engine options already available.