The origin of VW tuning – Type 170, part 2

The first version of the type 170 featured a top mounted Roots supercharger, the photo was taken in March 1943.

This blogpost was supposed to be about Sturmboot prototypes type 174/174A, but when asking my source some follow up questions I received some more very interesting information. So until this new information is digested I will wait with the174/174A post, but until then I have some new findings related to type 170 I want to share.

As it turns out, type 170 were built in two versions: One with the Roots supercharger on top of the engine and one were it's axial mounted in line with the crankshaft. The first one is labelled version one and the photo is dated March 1943. The latter does only say type 170 and 1943, with no further details.

The new photo material of Sturmboot prototypes I got show different versions of prototypes and even complete units that appear ready for the sea. This put my statement in earlier blogposts in a new light. Probably no one knows for sure anymore how many prototypes were made.

The second version had an axial mounted Roots supercharger. Could this have been the engine that ended up in Ferry's kdf cabrio? To me it seems like the earlier version above would have been more practical...

The origin of VW tuning – Type 171, 1942-1943

A prototype of the type 171 Sturmboot engine dated 1943

Next in line for the air-cooled Sturmboot project was project 171. This time a normally aspirated 1131cc pushrod engine with hemisphearical combustion chambers. The inspiration of the heads seems to origin from the pre-war SOHC type 115, but this time a bit more conventional using pushrods from a centrally placed camshaft.

To me it's a mystery why they did chose to go to this rather complicated design instead of increasing the cylinder volume, a solution that would have required less amount of new parts. Somehow I have the feeling Porsche took this military order as an opportunity to make designs that could be useful in future projects after the war. According to my source document this rather novel design was scrapped due to the cost (and probably time) it would take to put it into production. Not many details remained unchanged from the original kdf-design.

As can be seen not many parts are interchangeable with the original kdf-engine. A fact that was to be the fall of this concept.

But how far did the development of this engine go before it got stopped? Both the document I have access to and Chris Barbers book "Birth of the Beetle" indicates that of the different air-cooled Sturmboot designs only type 174 was ever tested in a the real application. However, from the picture above we can assume that a prototype of the 171 was made. According to one of the worlds leading kdf-experts only one prototype of each (170, 171, 174) were made and they were all later scrapped in Linz/Donau in 1960. 

Some believe that 171 heads were used by Kurt Khunke in his VLK (Vollstromlinien-Leichtbau-Konstruktion) in which he won the 1947 Braunschweig Autobahnrennen (first ever victory for a kdf/VW based vehicle). This has not been confirmed and if only one prototype of a complete 171 was ever made this seems highly unlikely. From the design it is obvious that these heads can not be used on a kdf engine as the case is very different. My conclusion is that we can probably rule out that the 171heads were ever used in racing applications (I welcome any fact that can strengthen my theory, or destroy it).

In some current litterature the V-heads in Peter Max Mullers race car, displayed at the Prototyp museum in Hamburg, are referred to as Sturmboot heads. Looking at this picture, showing one single valve cover for two cylinders, I think we can safely rule out that connection.

If anyone has more information, please contact me! If new information surfaces I will share it on this very blog.

The origin of VW tuning – Type 170, 1942-1943

Basic data for the type 170 engine dated 1943. As can be seen the original compression ratio of 5.8 was retained despite the use of a supercharger (Gebl.).

In 1942 three new project numbers aimed for the same purpose saw the light of day at the Porsche Designbureau: 170, 171 and 174. The background was a problem with the Sturmboots (a kind of simple motor boat with a very long propeller shaft) in which dirty water did clog the cooling system. The idea was to replace it with an air-cooled engine, but the only one in production, the kdf, was not powerful enough. Thus, Porsche  Designbureau was consulted to fix the power issue.

In this blogpost I will focus on the first one, type 170. It was a pretty normal 1131cc kdf engine, but with a Roots type supercharger mounted axially behind the crankshaft. Remember my reference in the last blogpost to Barbers book "Birth of the Beetle"? What he claims to be a type 115 engine looks very much like a type 170 mounted in a car. Also looking at the timeline it makes sense. According to Barber, the first version of a kdf engine with axial Roots compressor was completed in September 1942 which is more in line with project number 170 than 115 that is dated to 1939.

This is the only picture I have found on the type 170, I have chosen to zoom in on the axial mounted Roots type super charger (the rest of the picture was of poor quality anyway)

From a business point of view my belief is that the type 170 should have been killed already before the drawing stage. The engine was far to heavy for its purpose due to all the parts surrounding the supercharger. But, perhaps Porsche did proceed with the project just so he could put the high power engine in Ferry Porsches private kdf-cabrio? Who knows…