Over the 928’s production life, various attempts were made at producing additional variants. Few were successful and fewer still went beyond the prototype stage. We look a few notable examples.
When the 928 was being schemed during the early 1970s it appeared as though several US states would outlaw convertibles. This led many European marques to abandon the format entirely, lest they wind up saddled with an expensively developed product they couldn’t sell. This explains the lack of a convertible 928 at launch, if not the fact that Porsche never quite got around to introducing one later.
However, this didn’t stop others from having a stab, perhaps the most successful, from a visual standpoint at least, being the German aftermarket firm of B+B Auto Exclusiv. Founded by Rainer Buchmann in 1974, bb produced a series of enhanced and restyled Porsche models, including one of the earliest of the so called ‘flatnose’ 911’s derived from the 935 racer. Buchmann’s conversions were of a high standard, seeing himself more as a carrozzeria than a mere embellisher.
First shown at the 1979 IAA motor show in Frankfurt, the bb 928 Targa was a convincing and rather attractive attempt at an open 928. With a re-profiled c-pillar-cum rollover member, fixed rear screen, conventional rear decklid and a removable ‘targa’ top, it looked coherent, broadly sympathetic to the original and professionally executed. It was also witheringly expensive, with a reputed five built.
It’s unclear as to whether Porsche themselves tried anything similar at their Weissach skunkworks, but in 1987 they finally did engineer a fully convertible 928. Naturally, removing the roof and rear structure did terrible things to the body’s structural rigidity, so a great deal of work would have been required to regain the requisite torsional stiffness. Whether this was achieved or not isn’t documented, but for whatever reason, Porsche management never sanctioned it – a decision which may have ultimately hobbled the model’s sales prospects in the US market.
Another strand of thought within Porsche was that the 928 wasn’t in fact too large; quite the contrary in fact and that a larger version would have a broader appeal.
In 1984, Ferry Porsche celebrated his 75th birthday and to mark the occasion, Porsche built a one off special edition stretched 928 for his personal use. Dubbed 942 or 928-4, it featured a lengthened wheelbase (by 254 mm) and a raised rear roofline, making it a full four-seater. It also had the revised nose and tail of the fourth series 928 in addition to the larger 5.0 litre engine. Given that Ferry Porsche was amongst the faction who seemingly opposed Dr Fuhrmann over the transaxle cars, this choice appears quixotic, but perhaps he his views had softened by then.
Another official attempt at a larger 928 dates from 1987. Dubbed H50 or 928 Studie, it also featured a lengthened wheelbase, but in this case a pair of hidden ‘coach’ doors were fitted and pillarless construction was employed – (a la Mazda RX8). However, it’s believed extensive testing demonstrated the body’s lack of torsional rigidity and the project was abandoned.
What is clear is that neither of Porsche’s attempts at producing a stretched 928 were in any way viable propositions, but then, getting the basic proportions as wrong as they did hardly aided matters. What both prototypes demonstrate is how difficult it is to significantly alter a car’s basic shape without making a bit of a hash of things. By comparison, chopping the roof off’s a doddle, wouldn’t you say? Doubtless, Rainer Buchmann would agree.
Driven To Write 
A far as 928 variants go am interested in the smaller engined models that never reached production such as the 180 hp 3.3 unit though there is some confusion as to whether the engine was a V8 let alone even a V6 (either being an unrelated design or a 90-degree unit derived from the V8).
Bob, I suspect the engine you refer to was a V6 derived from the 928’s V8. According to Car Magazine (Dec 1981), Zuffenhausen engineers experimented with a 90 degree V6 unit on a common crankcase to that of the V8. It was intended for the 924, but was rejected in favour of the slant four they developed instead, which also shared a good deal of its architecture with the 928 unit.
Given that the initial 928 was heavily criticised for it’s lack of outright urge as a 4.4 litre, it’s difficult to imagine how a smaller capacity unit would have coped, given that the car itself was rather portly.
But of course, there were all manner of skunk projects going on – some better known than others. It would require someone with a more in-depth knowledge and perhaps a greater immersion in the marque to answer your questions definitively however.
I see. Understand that Porsche sought to use a V6 or V8-based 90-degree V6 in a number of projects during the 80s and early 90s including the Porsche 989 and previous saloon projects, it would have been interesting seeing how the V6 ends up being enlarged in parallel with the V8.
I’d say that the 928’s original egg shape was so extremely coherent it can’t actually be bettered in any way. Either by taking off the roof or lengthening it, nothing can be gained from a stylistic point of view. It’s just so extremely just so as it is.