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 190 E rallying, and asked British engineering company Cosworth to develop an engine with 320 bhp (239 kW) 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, making the 2.3-16v appear outclassed. With a continued desire to compete in high-profile motor sport with the 190, and also now an engine to do it with, Mercedes turned to the Deutsche Tourenwagen Meisterschaft (DTM) (German Touring Car Championship) motor sport 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 190 E 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 set three world records in August at the Nardo testing facility in Italy, recording a combined average speed of 154.06 mph (247.94 km/h) over the 50,000 km endurance test, and establishing twelve international endurance records. The Mercedes 190-E Cosworth was also featured on the second episode in series fifteen of the popular car show Top Gear.
The Cosworth engine was based on the M102 four cylinder 2.3-litre 8-valve 136 hp (101 kW) unit already fitted to the 190- and E-Class series. Cosworth developed the cylinder head, "applying knowledge we've learnt from the DFV 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 2.3 L 16-valve engine made "185 hp (138 kW) at 6,200 rpm and 174 lb·ft (236 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 less than eight 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 (125 kW) @ 5800 rpm and 162 lb·ft (220 N·m) @ 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 (138 kW) 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.
An enlarged 2.5 L engine replaced the 2.3 L in 1988. It offered double-row timing chains to fix the easily snapping single chains on early 2.3 engines, and increased peak output by 17 hp (12.5 kW) with a slight increase in torque. For the European market without catalyst (RÜF) the car delivered 204 bhp (150 kW). Catalyst equipped 2.5-16s produced a slightly reduced 197 bhp (147 kW). It is debated 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 had 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 the project code "WAB" for the development of the 2.5-16-valve head just as they do for the 2.3-16-valve head.
Due to their performance, the 16-valve cars were 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 manual gearbox was unique to the 16-valve and featured a 'racing' 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 which weren't levelled at the BMW M3 (E30) which shared the same gearbox. The pattern is also unusual in that the driver engages reverse by shifting left and up from neutral, as for first gear in a conventional pattern. This was demonstrated in a Top Gear episode (S15E02) where James May took a 190 E 2.3-16 Cosworth and repeatedly confused reverse and first gear. An oil cooler was fitted to ensure sufficient 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 190 E 2.3-16 was available in only two colours, Blue-Black metallic (Pearl Black in the US), and Smoke Silver. The 2.5-16 added 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 from 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 then unknown Ayrton Senna took first place.
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 RS Cosworth.
With the debut of the BMW M3 Sport Evolution, Mercedes' direct competitor, it became obvious that the 2.5-16 needed a boost for the circuit. In March 1989, the 190 E 2.5-16 Evolution debuted at the Geneva Auto Show. The Evo I, as it came to be called, had a new spoiler and wider wheel arches. Many changes were made to under-the-skin components such as brakes and suspension. There was a full SLS suspension allowing vehicle ride height to be adjusted from an interior switch. All were intended to allow the Evolution cars to be even more effective round a track.
The Evo I's output is similar to the 202 bhp (151 kW) of the "regular" 2.5-16. However this car had a redesigned engine of similar capacity but, most importantly, a shorter stroke and bigger bore which would allow for a higher rev limit and improved top-end power capabilities. Additional changes stretch to "rotating masses lightened, lubrication improved and cam timing altered". Cosworth also list a project code "WAC" for the development of the short-stroke Evolution engine.
Only 502 units of the Evolution model were produced for homologation in compliance with DTM rules. For those customers desiring even more performance, a PowerPack option engineered by AMG was available for DM 18,000. The PowerPack option included hotter camshafts, a larger diameter throttle body, more aggressive ignition and fuel management as well as optimization of the intake and exhaust systems. The net result was an additional 30 bhp (22 kW).
In March 1990, at the Geneva Auto Show, the 190 E 2.5-16 Evolution II was shown. With the success of the first Evolution model, this model's 502-unit production was already sold before it was unveiled. This car retailed in 1990 for USD $80,000.
The "Evo II" included the AMG PowerPack fitted to the same short-stroke 2.5 engine as the Evolution, as well as a full SLS suspension allowing vehicle ride height to be adjusted from an interior switch. An obvious modification to the Evolution II is a radical body kit (designed by Prof. Richard Eppler from the University of Stuttgart) with a large adjustable rear wing, rear window spoiler, and Evolution II 17-inch wheels. The kit served an aerodynamic purpose—it was wind tunnel tested to reduce drag to 0.29, while at the same time increasing downforce. Period anecdotes tell of BMW research and development chief, Wolfgang Reitzle, saying "the laws of aerodynamics must be different between Munich and Stuttgart; if that rear wing works, we'll have to redesign our wind tunnel." The anecdote claims that BMW did.
As mentioned 500 were made in "blauschwarz" blue/black metallic. But the last two, numbers 501 and 502 were made in astral silver.
16V AMG power pack
Available only to 2.5-16 and Evolution I models, optional AMG Power Pack increased power to 224 bhp (166 kW) at 7,200 rpm and torque to 181 lb·ft (245 N·m) at 5,000 rpm, while pushing the top speed up to 155 mph. In their final incarnations, these engines produced up to 350 bhp (260 kW) in racing tune.
AMG was not part of Mercedes-Benz when the 190 was first produced, but a separate racing and tuning company. As AMG had racing experience in the DTM, they were tuning all the factory petrol engines for the customers and 190 E was one of them. Engine tuning added 25 bhp (19 kW). They fitted aerodynamic features (spoilers) improving Cw and high speed stability, alloy wheels, leather interior and larger engines up to 6-litre V8's.
The 190 E 3.2 AMG was the first model sold through Mercedes-Benz dealerships with Mercedes-Benz new car warranty. About 200 complete cars were made, in black or silver: they were very expensive (about $90,000). Besides 200 complete 190 E 3.2 AMG's, Mercedes-Benz sold AMG body kits and 3.2l AMG engines separately, so there are 190's fitted with those features at the factory or retrofitted. Sporty 190 E 3.2 AMG straight-six 12-valve engines produced 234 bhp (174 kW), and reached 260 km/h (162 mph).