tisdag 16 september 2014

What if… The 1958 VW Karmann Ghia S

What if the VW marketing department had manage to convince the rigid VW CEO Heinrich Nordhoff to start making a Karmann Ghia with performance on par with the competition?

Of course, it couldn't be too fast to not upset the co-operation with Porsche. At the time the Ghia was launched the entry level Porsche was a 44 DIN hp 1300 cc (type 506). Thus, with the lower weight of the Ghia all attempts to increase horsepower would have given it similar performance to the Porsche 1300.

But during spring 1957 Porsche did drop the 1300 cc and the entry level was now the 1600N at 60 DIN hp. This would have opened up a possibility for VW to slide a model in-between the standard Ghia and the Porsche.

Looking at competition in Europe at the time 45-50 DIN hp would be needed to get performance in level with the middle class cars at the time. By aiming at the lower figure VW could keep a safe distance to the 1600N.

Sporty European Coupés anno 1957

With this power requirement a VW based engine similar to the Porsche type 506 would be suitable. VW would even have looked at what Okrasa did with the TSV1300, a VW based engine with the same power. Let's take a look component by component:

For simplicity I guess VW would have stuck with the standard one to avoid creating a new partnumber. The case of the Porsche pre-A was similar, but had larger bore to accommodate the 80 mm cylinders.

Cylinder volume
Both engines we use as reference have a 1300cc displacement, it make sense for the S-Ghia to go the same route. To be able to use the same case, and avoid expansive Nicasil cylinders, I guess VW would have chosen a longer stroke crank to arrive at 1300 cc. Looking in the future, that's exactly what VW did eight years later when introducing the 40 DIN hp 1300 cc.

Both the Porsche 506 and the Okrasa TSV1300 did use the standard VW camshaft. It seems as if you are only looking at revs up to 4500 rpm the standard one is a good choice as you retain the good low to mid rpm properties of the VW engine. Thus it would have been a natural choice for the S-Ghia.

A Porsche 506 engine installed in a 1953 Type 1

As mentioned before in this blog the stock 30 DIN hp engine is dead above 3400 rpm due to the restrictive intake system. Both Porsche and Okrasa did make the extra effort to develop their own heads with improved flow, as well as going for dual ports instead of siamese as the original. Porsche did complicate things by tilting the exhaust valves. For the S-Ghia I guess VW would have chosen the Okrasa path with valves sitting in-line. Eight years later that's exactly what they did when dual port heads were introduced on the type 3 engine.

Also on this point the 506 and the TSV1300 have a common solution: the Solex 32 PBIC carbutator. However if VW was to introduce a new model late 1957 this solution was already a bit old fashioned. That autumn Porsche did replace the PBIC with the Zenith 32 NDIX and it's possible that VW would have followed the same route to benefit from a more modern design. The smaller version of the NDIX did use 24 mm venturies, which puts it in the same size range as the 32 PBIC used in the 506 and the TSV1300.

Ignition system
Porsche did use the Zeniths without vacuum outlet. Thus the S-Ghia would need an all centrifugal distributor. Perhaps they would have used the one they had, the VJ4BR8 (019), from the transporter. Or, they could have spiced the curve up a bit to arrive at something like its 1959 replacement, the VJ4BR25 (010). The coil would probably have been a unit better suited for high compression engines, as the one Porsche did use at the time. Finally we could expect a change in heat range of the spark plugs from the standard 175 to the 225 Porsche was running.

As the observant blog reader probably already has noticed this is the route I am taking for my own Karmann Ghia. To build a replica of a car that never existed, The 1958 Karmann Ghia S. It will not be a sporty car by todays standard, but I hope it will drive, and feel like, a typical mid-class sporty coupé of its time.

The bulk of the content in this post has already been published earlier in this blog, but as I now have more international readers I thought it would be good to make a summary in English.

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