Wagenwerks® · Historic Technology & Registrations
Riechert, TDE, Oettinger, OKRASA, Willibald & Co. – historic VW Beetle modifications and what is still legal today
Classic Volkswagens were never just simple everyday cars. Soon after their widespread use, a vibrant scene of technicians, motorsport enthusiasts, and developers emerged around the Beetle, Karmann Ghia, Type 3, and VW Bus – all aiming to get more out of the air-cooled VW technology.
Back then, it was often called "pimping." Today, we call it classic VW tuning, contemporary modification, or technical optimization. At Wagenwerks®, we don't just superficially address this historical technology – we examine such modifications professionally, inspect them on the specific vehicle, and combine historical documents, craftsmanship, and preparation for technical registration.
Important Notice
- Registrations only at Wagenwerks® on-site
- No loose expert opinions issued
- No remote registrations
- Every vehicle is inspected directly
- No sale of third-party archive documents
- Modification and preparation from a single source
01 — The Pioneers: Oettinger, OKRASA and the Beginnings
The history of high-performance air-cooled VWs doesn't start in the 1970s. An AMAL dual carburetor system is considered a very early attempt to give a VW engine more power with two motorcycle carburetors – dating back to around 1949/1950.
A key name is Gerhard Oettinger. Oettinger started an engineering office as early as 1946, was involved with VW engines early on, and founded the tuning company OKRASA in 1951 – "Oettinger's Kraftfahrttechnische Spezialanstalt" (Oettinger's Automotive Technology Special Institute). This was not an accessory company: it was about genuine engine technology.
Machined cylinder heads with modified compression
Intake optimization and dual carburetor systems
Modified crankshafts and systematic performance enhancement
Early power stages of 38 hp, 42 hp, 50 hp, and up to 70 hp
1964: Five Beetles with Oettinger engines in the Spa–Sofia–Liège long-distance rally
02 — TDE / Theo Decker Essen: Dual Carburetors, COMET and METEOR
Another major name is TDE – Theo Decker Essen. Theo Decker founded his company in Essen-Borbeck in 1958 with his wife Isolde. By 1968, TDE is said to have produced over 7,000 carburetor systems. Solex even manufactured a variant of the 34-PCI carburetor according to Decker's specifications.
| Program | Engine / Basis | Carburetor | Power |
|---|---|---|---|
| TDE 1.2 l | 1.2-liter engines | 2 × Solex 28 PCI | up to approx. 52 hp |
| TDE COMET | 1300 and 1500 cm³ | 2 × Solex 34 PCI | up to approx. 56–65 hp |
| TDE METEOR | 1600 cm³ | 2 × Solex 34 PCI | up to approx. 70–75 hp |
In addition to carburetors, the TDE program also included modified cylinder heads, special camshafts, special distributors, bypass oil filters, and partly reinforced oil pumps. For Wagenwerks®, this is crucial: such modifications follow a technical concept. Engine, carburetor, ignition, exhaust, brakes, and vehicle type must match.
03 — Riechert: Speed Rex, Solex, and over 60 years of carburetor technology
Riechert Motorentechnik stands for over 60 years of expertise in carburetor technology. Historic Riechert expert opinions and documents are documented for various engines with 2 × Solex 34 PCI – from 1.2 l over 1.3 l and 1.5 l to the 1.6 l engine, including Speed-Rex versions.
Riechert
Carburetor technology since the 1960s
Classic dual carburetor systems, Speed-Rex systems, Solex 34 PCI, historical expert opinions and test documents for all engine sizes.
Oettinger / OKRASA
Engine manufacturing from 1951
Systematic performance increase, ABE engines, motorsport use, machined heads, modified crankshafts, camshafts.
TDE / Theo Decker
Essen-Borbeck, from 1958
COMET and METEOR programs, Solex dual carburetor systems, camshafts, distributors, over 7,000 systems by 1968.
Willibald
Type-4, VW-Porsche technology
Larger engine conversions, Type-4 concepts, VW-Porsche-related technology, K-Jetronic expertise, most technically demanding category.
Wagenwerks® Note
Just because a Riechert or TDE system is historically known does not mean that every arbitrary combination can be registered today. Crucial factors are always the vehicle type, year of manufacture, engine base, exhaust system, noise level, braking system, tire size, and professional installation.
04 — Porsche Salzburg and MAHAG: The Beetle in Rally Sport
The history of fast Beetles would be incomplete without Porsche Salzburg. The motorsport department of the Austrian VW and Porsche importer successfully prepared VW Beetles for rally sport from 1966 to 1973. Initially, VW 1300 and 1500 were used, later 1302 and 1303.
The well-known 1302 and 1303 rally Beetles were described as having approximately 118 to 125 hp with 1,584 to 1,599 cm³. The individual approval reportedly listed 105 hp. Only slightly over twenty 1302/1303s were built in Salzburg.
Wagenwerks® Assessment
The VW Beetle was not only improved on the road but also seriously developed in motorsport. Brakes, suspension, engine, tires, and bodywork had to function – not just look good. This is the attitude we share at Wagenwerks®.
05 — Willibald: Type-4 engines and VW-Porsche technology
The name Willibald stands for larger engine conversions, Type-4 technology, and concepts close to VW-Porsche. Especially Type-4 engines are a sensitive topic for classic Beetles and convertibles. They can be technically very appealing, but require a thorough overall assessment:
Engine mounting, engine compartment and end plates
Air guidance, cooling, and exhaust system
Heating and gear ratio
Braking system and axle loads
Noise behavior, tires, and speed rating
Wagenwerks® Principle
A major engine conversion is never just an engine conversion. It is always a vehicle concept.
06 — Solex, Weber, Zenith: Carburetors as the Heart
Many historical VW conversions revolve around carburetor technology. Solex 28 PCI, Solex 34 PCI, Zenith 32 NDIX, Weber IDF – terms still sought after today. Solex dual carburetor systems are particularly well-documented for TDE and Riechert.
For Wagenwerks®, however, the carburetor is never just a beautiful historical component. Crucial for a functioning system are:
- Engine base, displacement and jetting
- Intake manifolds, cylinder heads and camshaft
- Ignition, exhaust and noise behavior
- Idle and driving behavior, consumption
- Everyday usability and technical documents
Wagenwerks® Assessment
An old dual carburetor conversion can work fantastically – or run poorly if the tuning isn't right. That's precisely why we inspect and build such systems with technical expertise.
07 — Abarth, Sebring and classic exhaust systems
Exhaust systems are among the most popular and at the same time most sensitive modifications. They influence sound, appearance, performance, exhaust gas routing, heating, and noise levels. Abarth presented the "Abarth Exhaust" at the Turin Motor Show as early as 1950 – the exhaust system became a central element of classic VW tuning kits.
Sebring is also a well-known name in the Beetle scene. NOS Sebring sports exhaust systems were listed with ABE (General Operating Permit), including versions with double preheating for engine types AS, AR, and AJ.
At Wagenwerks®, we always check exhaust systems for the following:
Does the system match the engine type and is an ABE available?
Is the preheating correct and is the heating affected?
Are noise levels plausible and was it installed correctly?
Does the system fit the H-plate concept?
08 — Kamei, Heigo and classic accessories
Kamei: Front spoiler with history
Kamei is one of the best-known accessory names in the Beetle scene. Karl Meier / Kamei presented the Beetle spoiler "Tiefensteuer" at the Geneva Motor Show as early as 1953. The VdTÜV leaflet explicitly addresses front spoilers: only front spoilers approved by VW or assigned by an expert opinion from a Technical Inspection Body may be used.
Heigo: Roll bars and safety
Heigo is still present today in the field of safety technology and roll bars. Crucial for a registration process are: vehicle model, material (steel or aluminum), mounting points, installation quality, seating system, belts, relevance for H-plate, and usage. A roll bar must fit the vehicle, its use, and the overall inspection.
09 — Borrani, Hegglin, ATS, Lemmerz, Kronprinz: Wheels with History
The VdTÜV leaflet lists the following wheel manufacturers and wheel types for VW models among others in its wheel/tire combinations: ATS, Kronprinz, Lemmerz, Südrad, Borrani, Decker TDE/02 and Hegglin HDK 890. This is not just about aesthetics, but about rim size, bolt pattern, offset, wheel load, clearance, and operating permit.
For non-standard wheels, the leaflet requires a visual inspection of the clearance in the wheel arch as well as to chassis and brake components – in doubtful cases, even driving tests under full load, full steering lock, and cornering. At Wagenwerks®, we don't just check if a wheel looks good. We check if it is technically suitable for the vehicle.
What Wagenwerks® offers for classic VW conversions
Why remote registration is not possible
Two Beetles of the same year of manufacture can be technically completely different if axles, brakes, engines, wheels or body parts have been changed over the decades. We need to see, measure and inspect the vehicle. Only in this way can we reliably assess what is technically feasible.
Brand and Legal Notice
The mentioned brands, names and designations such as Volkswagen, VW, Porsche, Riechert, TDE, Theo Decker Essen, Oettinger, OKRASA, Sauer, Willibald, MAHAG, Kamei, Heigo, Abarth, Sebring, Solex, Weber, Zenith, Borrani, Hegglin, ATS, Lemmerz, Kronprinz and Südrad are used exclusively for historical classification and to describe classic vehicles, parts and modifications. There is no automatic business connection, representation, authorization or brand partnership with the mentioned manufacturers or rights holders, unless explicitly stated otherwise. Every approval remains an individual decision of the respective inspection body.
Wagenwerks® Conclusion
The pioneers of yesterday, the craftsmanship of today
Riechert, TDE, Oettinger, OKRASA, Sauer, Willibald, Porsche Salzburg, MAHAG, Kamei, Heigo, Abarth, Sebring and many other names represent a special era of VW history. They showed that classic Volkswagens can do more than stock performance. But they also showed: Good conversions require technical understanding.
At Wagenwerks®, we combine exactly this history with today's diligence. We do not copy third-party archives, do not sell third-party documents and do not issue loose expert opinions. We use historical technical knowledge, our own documents, vehicle inspection and professional conversions.
Classic Volkswagens. Historic technology. Professional conversions. Registration preparation exclusively on-site with us.