Track impressions: Mercedes 190E 2.5 Evolution II
My experience of the most recent Mercedes weapon in the evolution homologation warfare against BMW, a 2463cc shorter stroke version of the Cosworth 190E power unit and radical aerodynamics, packaged under the unbecoming Evolution II label was as concentrated as the BMW assessment was extended (MOTOR SPORT, Sept. 1990, pp976,977). This was understandable as only six of 500 Evolution II Mercedes 190E come to Britain, their £55,200 cost met by private owners and the Patrick Museum Collection.
On arrival in the blazing sunshine of race week Goodwood, a cheerful Kenny Acheson (Sauber Mercedes team member in their 1989 World Champion season) quipped, “Who is the first victim?” Since he was walking purposefully toward a metallic rendition of the latest in Evolution 190E models, I fell in step quickly and learned that it was also to be Acheson’s first outing in such a saloon, although he has raced the M3 in Japan. To act as the homologation base to face the 2.5 BMW M3 Sport Evolution in the German touring car championship, the second generation Evolution Mercedes carries extensive modifications beyond the familiar 2.5/16, an example of which was available in automatic form for comparison purposes. The second Evolution model carries modified panels to effect just about every competitive facet of its aerodynamic performance. The result is ugly, but it is necessary. Although it does not look to be the case, Mercedes have been more subtle than BMW, and those swollen side panels and comprehensive rear wing set are part of a plan that sees the upper half of the rear glass covered by dark plastics to direct airflow down to the rear wing. The effect is to block out following cars in motorway conditions, but Acheson was completely at home with such a set up as — like the majority of racing drivers outside the saloon car set — he relies on exterior mirrors only. Such detail work, including a reshaped front bumper keeps drag factor low (0.31Cd) whilst using generous 8.25 x 17 inch Speedline wheels and (for Goodwood) Goodyear Eagle 245/40 ZR tyres.
The engine changes centre on the quest for high rpm, shortening the standard 2.5 litre stroke from 87.25mm to 82.8mm and enlarging the bore to 97.3mm from the production 95.5mm. All major reciprocating components have been revised or replaced, compression now 10.5:1 in association with new inlet camshaft profiles, revised intake and exhaust systems. The latter emerging as a rather startling perforated oval of the kind that you might associate more with dirt track bikes than a Mercedes.
The engine work yields a gain in road car rpm from 7000 to 7700; maximum power is now recorded at 235 bhp on 7200 rpm instead of the usual 194 bhp at 1000 rpm less on the £32,940 Mercedes 2.5/16. That represents a bhp per litre figure of 95.4 bhp per litre, a fine normally aspirated figure whilst retaining road car flexibility and catalytic convertor exhaust emission standards. The racing variant would achieve over 340 bhp and reach the 9000 rpm marked at the end of the scale on the road car. Peak torque is maintained at 180 lb ft between 5000 and 6000 rpm, whilst the unmodified 2.5/16 yields 173 lb ft at 4500 rpm. An Evolution II, despite its screaming sporting messages is easy to drive, with a generous power spread that is easily accessible, particularly around a fast 2.42 miles like that of Goodwood.
Mercedes engineering pride will not allow them to turn out a traditional British “homologation special” that is full of groans, rattles and reverberations and served by a restive chassis. Thus the car tested came with a steel catalytic convertor, leather seats, electric memory adjustment of the front seats, electric tilt-and-slide sunroof, central locking and so on. The BMW M3 Evolution road car that sits outside my house as this is written pleasantly surprised by sporting air conditioning. Thus the Germans have gone about as far from those early British specials — such as the Mini Cooper S. and Lotus Cortina — as possible.
Former triple Formula Ford Championship winner Acheson took the largish leather rim wheel first, and confirmed that his winning record outside Grands Prix is the result of a smooth style that “takes the least out of me. I am not particularly strong for endurance racing and so I always let the car tell me where it wants to go.” This technique of running slightly wide at an initial apex to provide a smooth arc and exit to a second apex is particularly effective at Goodwood. This meant that the Mercedes was not always turned in from the coned positions marked by Peter Gethin at the home of his extremely successful road and circuit driving courses, but both men (the Monza Grand Prix winner in a superbly refrigerated and chauffeured 500 SL) were pleasantly informative.
. Neither had the arrogant “this is the only way, my way” that customers often have to suffer from instructors of lesser pedigree. Driving road cars at race circuits makes it very difficult to draw relevant impressions for the potential road customer, but there are some strong memories that are worth recalling. Kenneth Acheson confirmed that he was pleased with the handling of the car, “much more precise than I expected of a road car.” This reflects engineering changes that include a 45mm drop (1.77 inches) in ride height, tauter damping, “reinforced” front and rear axle hub carriers and wheel bearings. I was unofficially told that the five link system at the rear now had rose joint solid mounts incorporated and it is worth noting, that as for the Evolution 2.5 M3, front and rear spoiler adjustments can be made that will significantly change characteristics. So will the facility to adjust ride height back up to the standard level to cope with realities of street life.
For myself I liked the way that the Mercedes turned into corners with the assurance of generous grip and positive feedbacks, but I was not so thrilled with the behaviour of the automatic limited slip differential. I would prefer to be able to switch this electro-mechanical device off for circuit and similar work, finding that its action promotes a restless “wriggle,” particularly at speeds beyond the overall UK limit, or in really tight and slow corners. It is not dangerous, and the extra traction is welcome in reducing wheelspin to negligible proportions, yet it demands the allowance of a little more run-off space than is strictly necessary. Recirculating ball power steering is geared at three turns lock to lock and is sensitively rapid enough to adjust cornering angles even when the Evolution II is on the edge of adhesion at 100 mph, and the same facility (at lower speeds) is evident in the well balanced production 2.5/16. The engine was a delight, especially by 2.5-litre four cylinder standards. It revved exceptionally well between 4000 and 7000 rpm, urging the bulk of 2948 lb kerb weight to 110 mph with suave speed. Manners that belie its 155 mph claimed maximum and the ability to encompass 0-62 mph in 7.1 seconds. The gearbox, with the traditional competition isolation of first, wanted care initially, but can supply rapid fire ratio exchanges.
Braking was fully up to the weight and speeds Mercedes must tackle in a road car. A quartet of pistons are used in substantial front calipers, clamping 300mm/11.8 inch ventilated fronts. These backed by ABS only when really necessary, and 278mm/10.9 in rears that have two piston callipers. I feel that an Evolution ll Mercedes 190E is a supreme example of making the homologation special a bearable everyday companion. My personal preference is for the racier, rougher and simpler Evolution 2.5 BMW at £34,700. You gain over £20,700 in small change between BMW and Mercedes Evolution II, or £22,260 between the Evolution 190E and a 2.5/16. JW