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190E 2.3-16 valve & 2.5-16 valve "Cosworth"
The Story
Back in the late 1970s, Mercedes competed in rallying with the big
V8-powered Coupés of the R107 Series, mainly the light-weight Mercedes 450 SLC 5.0.
Mercedes wished to take the 190E rallying, and asked British race car
engineering company Cosworth to develop an engine with 320 bhp for the
rally car. This project was known as project "WAA" by Cosworth". During this time, the Audi Quattro with its all wheel drive and turbocharger
was launched and made it apparent that the 2.3-16v would not be
competitive. With a continued desire to compete in high-profile
motorsport with the 190, and also now an engine to do it with, Mercedes
turned to the Deutsche Tourenwagen Meisterschaft
(DTM) motorsport series instead. Cars racing in this championship,
however, had to be based on a roadgoing model. Mercedes therefore had
to put into series production a 190 fitted with a detuned version of
the Cosworth engine. This high performance model was known as the 190E
2.3-16, and debuted at the Frankfurt Auto Show
in September 1983, after its reputation had already been established.
Three cars, only slightly cosmetically altered, had previously set
three world records in August at Nardo, Italy, recording a combined average speed of 154.06 mph over the 50,000 km endurance test, and establishing twelve international class endurance records.
The Engine
The Cosworth engine was based on the 2.3-liter 8-valve 136-hp unit already fitted to the 190- and E-class series cars. Cosworth developed the cylinder head, "applying knowledge we've learnt from the DFC and BDA". It was made from light alloy using Coscast's unique casting process and brought with it dual overhead camshafts and four valves per cylinder, meaning 16 valves total which were developed to be the "largest that could practically be fitted into the combustion chamber".
In roadgoing trim the 190E 2.3-16 produced 49 hp (36 kW) and
41 ft·lbf (55 N·m) of torque over the basic single overhead cam 2.3
engine on which it was based. The 2.3 L 16 valve engine made "185 hp
(137 kW) at 6,200 rpm and 174 ft·lbf (235 N·m) at 4,500 rpm, the
oversquare 95.50 x 80.25 mm bore and stroke dimensions ensuring that it
revs easily up to the 7000 rpm redline". Acceleration from 0-100 km/h (62 mph) was 8.0 seconds, and the top speed was 230 km/h (143 mph).
US-Specification cars had a slightly reduced compression ratio
(9.7:1 instead of 10.5:1), and were rated at 167 hp @ 5800 rpm and 162
lb-ft @ 4750.
The roadgoing version of the engine was reconfigured with reduced
inlet and exhaust port sizes, different camshaft profiles, no dry sump
configuration and Bosch K-jetronic replacing the specialised
Kugelfischer fuel injection. These changes helped bring power down to
the required 185 bhp specification, but still resulted in a "remarkably
flexible engine, with a very flat torque curve and a wide power band".
The heads for the engines were cast at Cosworth's Coscast foundry in
Worcester and sent to Germany to be fitted to the rest of the engine,
parts of which were different from the standard 2.3 including light
pressed alloy pistons, and rings designed to withstand higher engine
speeds, whilst con-rods, bearings and bearing caps were found to be
strong enough as standard and left unaltered.
The 2.5 model
An enlarged 2.5 L engine replaced the 2.3 L in 1988 and increased
output by 17 hp (12.5 kW) with a slight increase in torque. For the
European market without catalyst the car delivered 202 bhp (150 kW).
The catalytic converter was becoming prevalent at this time, and
catalyst equipped 2.5-16s produced a slightly reduced 197 bhp. It is a
subject of debate whether the 2.5 L engine was developed and built by
Mercedes or Cosworth. Mercedes were not keen to broadcast the fact that
their most sporting saloon car has an engine developed by a British
company. However some cylinder heads from 2.5 L cars are stamped with
the Coscast logo indicating they were cast at Cosworth's foundry just
like the 2.3s. Cosworth also list a Project code "WAB" for the
development of the 2.5-16 cylinder head just as they do for the 2.3-16
cylinder head.
16v Differences
Due to their performance status, the 16 valve cars were in some areas
very different from the other 190 models. The body kit on the 2.3 16
and 2.5 16 reduced the drag coefficient to 0.32, one of the lowest cd
values on a four door saloon of the time, whilst also reducing lift at
speed. The steering ratio was quicker and the steering wheel smaller
than that on other 190s, whilst the fuel tank was enlarged from 55 to
70 L. The getrag 5-speed gearbox was unique to the 16 valve and
featured a "GT" gear pattern with 'dog-leg' first gear, left and down
from neutral. This meant that the remaining 2nd, 3rd, 4th and 5th gears
were in a simple H pattern allowing fast and easy selection. The
gearchange quality was, however, noted as "notchy, baulky", criticisms also levelled at the E30 BMW M3
which shared the same gearbox. An oil cooler was fitted to ensure
efficient oil cooling for the inevitable track use many of these cars
were destined for.
The strictly four-seater interior had Recaro sports seats with
strong side bolsters for front and rear passengers. 3 extra dials - an
oil temperature gauge, stopwatch and voltmeter - were included in the
centre console. The, 190E 2.3-16 was available in only two colours,
Blue-Black metallic, and Smoke Silver (which looks gold). The
introduction of the 2.5-16 brought along two extra colours, Almandine
Red and Astral Silver.
All 2.3-16 valve 190 models are fitted with a Limited Slip Differential
(LSD) as standard. They were also available with Mercedes' ASD system
which was standard equipment on the 2.5-16v. The ASD is an
electronically controlled, hydraulically locking differential which
activates automatically when required. The electronic control allows
varied amounts of differential lock from the standard 15% right up to
100%. It is not a traction control
system however, and can only maximize traction rather than prevent
wheel spin. Activation of the ASD system is indicated by an
illuminating amber triangle in the speedometer.
The suspension on 16 valve models is very different to the standard
190 (w201). As well as being lower and stiffer, it has quicker dampers,
larger anti-roll bars, harder bushings and hydraulic Self-Levelling
Suspension (SLS) on the rear. This allows the rear ride height to
remain constant even when the car is fully loaded.
At the inauguration of the new, shorter Nürburgring
in 1984, a race with identical cars was held, with former and current
F1 pilots at the wheel. A rather unknown young driver named Ayrton Senna took First place in that race.
Private Teams such as AMG later entered the 2.3-16 in touring cars races, especially the DTM. In the late 1980s, the 2.5-16 (never released in the United States) raced many times, against the similar BMW M3 and even the turbocharged Ford Sierra Cosworth
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