words by pablo deferrari
after reformulating itself as Auto Union GmbH on September 3, 1949, DKW remained as the sole survivor of the original merging which included Horch, Wanderer, and Audi. DKW went from producing affordable and reliable vans and motorbikes immediately following the reformation to a new compact front-wheel drive car in 1953 called the "Meisterklasse" (Master Class) two cylinder two-stroke F89 which essentially became their first passenger post-war car.
eventually, their persistence in producing two-stroke engines to power their cars led to a slump in sales, something Daimler needed to fix in order for their newly owned subsidiary to remain solvent. their solution? Mercedes-Benz decided to inject new life into the brand by designing a new four-cylinder, four-stroke engine for what would be the "new" DKW F102. the shedding of DKW's two-cycled skin called for a resurrection of the Audi name to showcase its new four-cycle dermis that would be known as the Audi F103.
this somewhat condensed chronology is necessary in order to understand how this engine would go on to define three very important models borne of this parent company; the Audi 100, VW's LT series, and Porsche's 924—one other model bears mention, but its existence is one many would like to wish away into the annals of lapses in judgement, the ridiculously unfashionable AMC Gremlin.
I must digress here for a bit and explain this so-called Heron design. named after it's inventor, Samuel Heron an engineer in the Royal Aircraft Establishment, this ingenious design allowed for turbulence to be created as the piston reached TDC thereby compressing the fuel/air mixture more intensely which reduced nitrogen oxide emission by some 30% more than the conventional "combustion-chamber-in-head" design could offer. aside from this, there was also a reduction in tooling costs should it be decided to change compression ratios since only the pistons with a revised "dish" in the crown needed to be produced and swapped out as opposed to machining the entire head. conversely, a flat-bottomed designed head afforded more precise tolerances during its machining.
although similar to its block design c. 1965, the next evolution of this lump would find itself in the legendary Audi 100, a car designed secretly by Audi Vehicle Development Director Ludwig Kraus in his spare time to protect the Auto Union heritage threatened under VW rule. putting out 99hp in 1,8 guise under the bonnet of Audi's C1 first generation 100LS until its production ended in 1976, a variation of this engine bored out to 1,9 liters with an output of 113hp was used in the Audi 100 Coupé.
Audi F103 engine in restoration
many stars aligned the moment decisions were made on both camps. Porsche would have complete freedom to romp through VW's parts bins to assemble their entry level car and VW would reap the benefits of keeping its industrial empire from crumbling under the hostility of the period's financial crisis specifically in keeping the NSU plant from closing its doors forever in 1975.
the 924, aside from being infused with Porsche's engineering pedigree, would become the beneficiary of Audi's new 2 liter four cylinder block it was producing for their second generation Audi 100 C2 (1976-1982) and VW LT vans (1975-1982). given the name EA831, this engine would do away with its predescessor's pushrod valve actuation in favor of a more economical overhead cam design driven by a toothed rubber belt. this design reigns superior since the engine can be spun at higher RPMs increasing power output for a given torque, inlet/exhaust ports are optimised in their design by the omission of intrusive pushrods allowing for a more fundamental "cross flow" design which increases the engine's ability to exchange induction and exhaust gases, overall valve train mass and complexity diminishes, and production is simplified. carried over from the previous design was the combustion chamber cast in the piston crowns (mentioned earlier).
care for more technical prose? ok then...
moving up to the head is where we begin to witness Porsche's engineering. the cam is held in by five bearing caps, the flat-topped cup-type tappets are similar to those used in the 908 and 917 engine, the inlet valves are 40mm for the Euro version and 38mm for the US market while the exhaust remains the same for both continents at 33mm and were seated on Rotocaps to rotate the valves prolonging their life—all valves are closed by a double coil spring design. rounding out the head, the spark plugs are on the exhaust side following Porsche tradition, the distributor is driven by the camshaft at the rear end, and fuel injector bosses were cast on the inlet side.
"one could sleep soundly knowing that scrap yards across this great land will have a dearth of Gremlins waiting for their engines to be pried out."
the LT28-31 got EA831 model CH with 75hp, Audi's Typ 43 100 (C2) model WF WA netted 113hp in carburetted form, and the silly Gremlin, the pinnacle of American automotive kitsch would only muster 80hp on a good day...quite sad when you come to the understanding that AMC apparently bought licensing rights and tooling to manufacture this engine themselves in Richmond, Indiana for a mere...wait for it...USD$60 million; in the future, if ever there were a shortage of EA831 blocks, one could sleep soundly knowing that scrap yards across this great land will have a dearth of Gremlins waiting for their engines to be pried out.
production of this engine at VW's Salzgitter plant is said to have ended around 1982. word has it that this left Porsche in a predicament necessitating them to use their newly minted but de-tuned 2,5 liter four used on the 944. clearly there must have been a 3 year surplus of these engines as production of the 2 liter 924 ceased in 1985 which remained basically unchanged since its inception in 1976.
it becomes quite clear how easy it is for one to begin the EA831's history with the LT van and the Audi 100, because that is of course when it drew first breath. but much the same as one who praises Mozart's work without a clear understanding of just how he arrived at such greatness misses out on the very foundation that made him so.
thanks to my man Jim Doerr of 928 Classics who's always ready to talk such intense history with me-
http://www.motor-talk.de, http://www.curbsideclassic.com, http://www.detailingworld.co.uk/, http://www.gopixpic.com,
Porsche: Excellence Was Expected: The Comprehensive History of the Company,its Cars and its Racing Heritage [Karl E. Ludvigsen]
http://www.autocar.co.uk/ Lewis Kingston