Get To Know An Engine: Mercedes M102 16v Cosworth


The Mercedes W201 190 was one of Europe’s best selling cars.  It had great utility for its small stature with 4 doors and a proper trunk.  The chassis was strong, and the 5-link independent rear suspension make the 190 feel light on its feet.  At its heart beat a four cylinder non turbo engine that, let’s be honest, didn’t impress anyone.  The Mercedes M102 was your basic German 4cyl, and it was configured a million ways throughout the lifetime of the powerplant.  Well, actually closer to 20 separate variations, but still.  You could get a car with an 8v 1.8l M102 engine equipped with a 175 CDT Carb that made around 84hp on a nice day.  You could also get a car equipped with a 2.5l Mercedes M102 that made well over 200hp, with the help of electronic injection and some extra valves.  Because the latter would obviously be a better story, let’s dive in.

The Mercedes M102 Cosworth

Mercedes 450 SLCAlright, I said the magic word a little early.  The 16v M102 2.5 liter variant was particularly special.  In the 70s, the Mercedes factory race team was enjoying themselves rallying.  Their car of choice was the very suave 450SLC, a sports coupe for the discerning European car owner.  Even though it had a big V8, the heavy use of aluminum replacement everything and compact size lent itself to a relatively competitive racing version (SLC meaning super light coupe, or in German Superleichtes Coupé).  Hilariously, the SLC rally cars had a production based 3 speed 722.x automatic transmission.  That car is a story for another day.

When the Mercedes performance squad became interested in replacing the aging beast, the 190 looked to be a great car to fill the position of Mercedes Benz’s next rally car.  The production version would be much closer to the racing counterpart, and would finally feature a manual transmission. There was a problem though that the V8 didn’t have.  The basic Mercedes M102 needed some major help to get power up to where it needed to be for racing, especially since Mercedes execs were looking to cut spending in the motorsports program in favor of other endeavors.

On the down-low they gave Cosworth (world renowned racing engine maker) a ring, and commissioned them to turn the basic 4cyl into a racing engine.  This was before the AMG relationship started up. Cosworth responded with a new 16v high flow head in 1986, around 6 years after the engine had made its original debut.  Mercedes is still reluctant to mention Cosworth as part of this process.

Unfortunately for them, by that time Audi had just changed the landscape of rally racing completely with their Quattro and the silver star realized that it wouldn’t be worth it to try and compete.  Instead of inventing their own AWD system and turbocharged engine, they set their sights on the German road racing scene.  DTM was quickly gaining popularity throughout the mid 80s afterall.

2.3l Of Pretty Good Engine

 

Cosworth used the top of the range 2.3l m102 variant as their starting point.  Described as oversquare, the cylinder bore was larger in diameter (95.5mm) than the piston stroke (80.25mm).  The result was a high revving unit with a surprisingly flat power curve and nearly equal power and torque numbers.  To get this formula to work right, the cylinder head was very specifically designed to maximize airflow and increase compression (which topped out around 10.5:1 for the racing engine).  Pistons were upgraded and lightened, and the rings were slightly changed to accommodate the higher RPM range.  The bottom end on the new engine was left relatively unchanged.

The cylinder block on the M102 is cast iron, and has a closed deck.  In general the engine was great for Mercedes Benz’s first ‘peoples car’.  Fairly reliable, basic, affordable and never getting too crazy.  It even had solid lifters up to around the introduction of this new 16v head.  One of the only shortcomings was a single row chain that was known to fail.  It was replaced with a dual row timing chain in 1987, but we’re not there yet.

In order to compete under the homologated DTM Racing series rule book, this new engine had to be put into actual production.  In 1983, the Mercedes 190e 2.3-16 was unveiled to the world, having freshly broken a few endurance speed records at the Nardo Ring with the new 16v engine producing in the neighborhood of 185hp.  Here’s a very cool video documenting that historic time for MB.  In YouTube you can select closed captioning and then use the settings to auto-translate to English if you so choose.

Those records earned by the new 16v engine were quickly overshadowed when the new Nurburgring circuit opened for duty with a very interesting spectacle, the 1984 Nürburgring Eröffnungsrennen.  The principle of the event was to precede the first F1 race on the new course.

Nicki Lauda, being a chief proponent of safety at the time, participated alongside several international racing superstars in identical Mercedes 190e 2.3-16’s on the new track, designed to be safer than the outgoing “Green Hell” that had nearly claimed the life Lauda in August 1976 (and successfully has claimed the lives of nearly 70 people since opening).

The then up-and-coming Ayrton Senna de Silva displayed the driving skill that would ultimately earn him a place in history, but the new Mercedes 190e 2.3-16v would be the real winner here, displaying excellent performance and helping rocket German 190e sales (16v or not) from around 65,000 in 1983 to 120,000 in 1985.  Worldwide, W201 sales would finish above 1.8 million by the time it was retired in 1993.  The road going cars would unfortunately feature somewhat dumbed down versions of the touring car M102 16v engine, with wet sumps, mainstream Jetronic fuel injection, smaller ports, less aggressive cams, and a lowered compression ratio.  I assume that was to cope with the possibility of lesser quality gasoline in America and other non-German foreign markets.

Time to finally race!

In 1985 the 190e 2.3 16v passed the requirements for homologation production, and in 1986 the race car would finally make it to real competition in the Group A German Touring Car series at the hands of experience privateer teams.  Mercedes was testing the waters before making their factory effort public, and the test went well with a runner up in the championship going to driver Volker Weidler.  In 1988 5 privateer teams with factory support finally got to sink their teeth into the DTM series, which would ultimately bring home another 2nd place at the hands of Roland Asch.

Mercedes M102 2.5l 16v Evolution

The series was getting faster and more powerful, and The Mercedes M102 Cosworth would go through a significant upgrade in 1988 for the 1989 season, with an engine blog bored out to 2.5l.  Called the Evolution I, this new 16v M102 could produce upwards of 340hp, and the rules allowed Mercedes to drop a massive amount of weight through means of interior trim removal and body panel replacement with aramid composites.  The final weight would be allowed to bottom out at 1,040kg.  In order to compete under the rules to be a production car, 500 road going Evolution’s had to be manufactured.  Mercedes-Benz made 501.

Mercedes M102 2.5l 16v Evolution II

Mercedes 190e Evolution II

That wasn’t it, however.  They kept working on that little engine until eventually the real legend was born.  You’ve heard of this car.  You’ve probably read about it in magazines, or driven it in video games.  The 190e Evolution II would push the limits of what was achievable at the time, capitalizing on steady and predictable development throughout the 80s.  MB was letting go of the horses reigns, and the result was impressive.  On June 16th 1990, 373 of those horses would stretch their legs on the Nurburgring north course, the virtual motorsports birthplace of the 190e.  The best part? Once again, MB made 501 road going versions.  Out of all the Mercedes street cars out there, this rare Evo II model is one of the most sought after.

The M102 2.5l 16v Cosworth engine would ultimately rack up 52 victories and a number of championships by 1993, when it was replaced by the new C-Class.  In many ways, this engine is one of the most German ever made.  Starting out as an economical compromise, the Mercedes M102 slowly and steadily climbed the ladder to the top against major rivals.  When it eventually got there, it brushed the dust off, placed a small rigid flag, took a picture, and moved on to the next one.  I like that about Mercedes.  Never over the top, even when they are.

 

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