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…

The origin of VW tuning – Type 115, 1939

Cut-away of the cylinder and head of the type 115. As can be seen it has a single overhead camshaft with a 74 mm bore and 40 mm intake valves. The bore size, with a 64 mm kdf crank makes 1101 cc. A rather odd displacement for a conpetition engine.

In the list of Porsche design numbers we can read that type 115 was a kdf based 1,1 litre engine with overhead cams, hemispherical combustion chambers and supercharger. Thus, a pretty advanced engine for its time, and as such a very interesting one for this blog! Perhaps it can also be seen as the grandfather of the Carrera engine?

Cut away drawing in which we can see the bevel gears and the shafts driving the over head cams. Even though the Carrera engine has twin cams per head the drive principle of the type 115 is not too far off.

But what was the background? Was it even intended for a kdf type car? Did it ever really exist?

Reading Chris Barber’s excellent book “The Birth of the Beetle” it is easy to believe it was a running prototype as a picture of what is supposed to be a type 115 engine in a kdf-wagen is published. However, looking closer at the picture we see a supercharged kdf engine with normal cylinder tin and what appears to be a standard case. For once the otherwise very correct Mr Barber seems to be wrong. What we see on the picture is a "normal" kdf-engine with a Roots type supercharger. As far as I know there are no known pictures of a completed type 115 engine.

The background why the project 115 was started I know very little about. My source has been able to measure the original engine block (yes it still exist) and confirms that if fits on a kdf-type transmission. He further claims that the case is very similar to its kdf sibling aside from the rear of the engine where the cam drive is. Thus it seems reasonable to believe that the type 115 was somehow connected to the kdf (race car) program rather than Porsches private sports car project (As the kdf-program was state owned Porsche was not allowed to use such parts in his own endeavors).

The supercharger is of a centrifugal type throwing out air in one pipe for each cylinder bank.

Another view of the rather unusual supercharger

The assembly drawings I have access to are dated 28.8.1939 and 1.9.1939, only weeks before the Berlin-Rome event. My immediate conclusion was that the engine must have been aimed for a future race after the famous one. But, my source who has interviewed mr. Kaes, cousin of Ferry Porsche, claims that the documentation sometimes were made afterwards, thus the date doesn't mean that much. In any case my guess is that the Type 64 needed a more "normal" kdf-engine for Berlin-Rome due to propaganda reasons and that type 115 was aimed for a future race.

If there ever was a running engine, or even a complete one, I don’t know. But, it seems that most of the parts were manufactured at least. According to my source, Otto Mathé saved the parts when he emptied Porsche’s shelves of old prototype stuff in the 40’s. It would be a thrill to see those parts come alive one day!

The first page of the drawing lot that this blogpost was based upon.

The origin of VW tuning – Introduction

 Together for the first time in a long-long while! In 2015 the Berlin-Rome car IIIA0701 (ex. Mathé) was finally re-united with its original engine 38/43, a mildly tuned E60 kdf engine.

A little over a year ago I did write about the origin of the ”V-heads”, that is the very special cylinder heads used on the type 367 Porsche prototype as well as on one of Peter Max Müllers race cars. Since then I have come in contact with a long time kdf-collector based in Central Europe who have provided me with very interesting information.

As it seems, my expression “V-heads” was not a good one. What I thought was basically versions of the same head proved to be three very different designs. But my guess that the design principles of a V-headed VW/kdf-engine stems from the time of the Berlin-Rome Wagen seems to be correct though.

Reading in books and articles there are a lot of confusing and sometimes contradictive information related to this mythic car and the race that never happened. Some state very detailed information that, upon a closer investigation, turns out to be totally wrong.  However, I will focus on the engines only and try my best to avoid using unreliable sources.

All VW/Porsche history writers tends to agree that the engine that in the end made it to the sleek Berlin-Rome car was a tuned version of the normal kdf engine using dual carbs. A qualified guess is that the engine needed to be recognized as a kdf-one for propaganda/marketing purposes. The Berlin-Rome Wagen needed to be perceived as a sports version of the peoples car rather than an exotica.

A teaser for the next blog post in which the technical specifications of the Type 115 will be revealed.

But, it's doubtful if this whole race car program was started for just one single race. Most likely they had future events in mind. In parallel with the preparation for the September 1939 Berlin-Rome race Porsche did develop a far more exotic engine based on the kdf platform. This project, type 115, will be the topic for my next blog post. Stay tuned.

*Images courtesy of my anonymous Central European contact

The blog will soon re-open!

Thanks to a generous blog-reader in Central Europe I have come across some very interesting material related to the early attempts of making high performance versions of the kdf/VW engine. Thus I find it's now time for me to re-open the blog!

Above is a teaser. It's a part of an engine drawing from Porsche dated 1 September 1939, the very same day as German did invade Poland. In upcoming blog posts I will tell you the story behind this drawing and how the off-springs of this design did affect the post-war racing scene.

To be continued