Racing Turbo Porsche 911 / 934 / 935 in scale

1974 Porsche 911 Carrera RSR Turbo

The first turbocharged race version of the 911, racing in the prototype class, mainly to gain experience with a turbocharged 911 for the upcoming Groups 4 and 5 (expected to start in 1975, but delayed until 1976). Engine capacity reduced to 2.14 liter, to stay below the 3 liter prototype limit with the 1.4 turbo multiplication factor. One KKK turbocharger, with air-air intercooler in a body extension under the wing. Because it was raced in the prototype class, Porsche could perform almost unlimited modifications to the car. Nearly all exterior panels were replaced with fiberglass parts. The rear window was raised to improve air flow to the rear wing. An aluminium frame replaced part of the rear chassis. Aluminium roll cage. Rear wheels sprung by coil springs instead of torsion bars. The fuel tank was moved from the nose to the rear right seat area, boxed in with sheet metal; possibly this only applies to the later version, like the #22 at Le Mans. The early version had normal side-rear windows, like the #21 at Le Mans. A later version had closed side-rear windows with NACA ducts, the air being dumped in the engine bay.

1976 Porsche 934 and 934/5

Version developed for Group 4 racing. 3.0 liter turbo engine, with a complex intercooler system: each cilinder bank had its own water-air intercooler, and two radiators were mounted in the nose, since no radiator openings were allowed in the rear fenders. The rules imposed a minimum weight of 1120 kg, and subsequently series bodywork was used, and little was removed from the interior (rear seat, sound proofing material) and for example the electric window openers were retained. Aluminium roll cage and stiffening bars in the tank area. 14 inch wide tires allowed by rules, hence 12.5" wide wheels for the rear. To increase tire surface, 16" diameter wheels were used, which Porsche didn't have, hence the choice for BBS modular wheels. Rear suspension torsion bar springs supported by coil springs. Approximately 30 built for customers, there was no works race team.

In 1977 ten more 934s were built. The European Group 4 lost much of its appeal in 1977, and therefore nine out of ten went to the USA, for use in Trans-Am and IMSA. They were called '934/5' since they included some 935 components. Modifications included with wider wheels (16" rear, front unclear), a bigger turbo for more power, and a 935-76 style rear wing. For IMSA use the 935 wing had to be swapped for an RSR-type wing. Previously, the Gunze '934/5' model was thought to represent this version, but that model was actually a Kremer K1. Reji Model makes a 'Porsche 934/5 rear spoiler' (SP969).

1976 Porsche 935-76 (works)

Version developed for Group 5 racing, with much more freedom than Group 4. 2.86 liter turbo engine to stay in the under 4 liter class (1.4 turbo multiplication factor) with 970 kg minimum weight. 590 hp output. Basic chassis of the series 930 retained, but doors, engine and boot covers, fenders and front spoiler were made of glassfiber/foam. Bare interior. Side and rear windows of Plexiglass. Aluminium roll cage and fuel tank bracing. Rear wing was based on the original 930 wing, with side plates and horizontal wing element added. Car was 90 kg under the weight limit, so lead balast was placed in the nose and passenger foot well area. 114 liter tank in the nose. Front and rear torsion springs deleted in favor of coil springs. Maximum tire width 16", hence 15" wheels at the rear. Brake system as used in 917. Two cars were built.

Four body styles can be distinguished. The car's first race was at Mugello, where it had the flat front fenders with headlights in the front spoiler. Among others, this nose shape was disputed by the organisers, but became standard later on. The flat nose was combined with with rounded rear fenders like the RSR Turbo. This will be called the first body style in the kit list below. Due to the disputes, the nose was replaced by 911-style front fenders/headlights in the second and third races (Vallelunga and Silverstone) and possibly during the Le Mans test, at least on car #40. This will be called the second body style. The third body style (remaining races) had square headlight covers and square rear fenders that extended to the rear of the car. The larger rear fenders were required to make room for intercooler radiators, after CSI banned the air-air intercooler that didn't fit under the original bonnet. It seems that the 934 radiator lay-out was used as an interim solution for one race. The fourth body style is a combination between the second and third: square rear fenders combined with the round headlights of the second body style (still looking where this combination was used).

1976 Porsche 935-K1

In the 1976 season, no customer version of the 935 was available. The Kremer brothers got the specifications and some 935 parts from Porsche, and built their own car. The car was retrospectively called K1. Only one was built. It retained the headlights in the fenders, like the road-going 911 / 930, but had a 935-style front dam. A 935 wing was used. Initially it had rear fenders that resembled those of the RSR Turbo, but later they were changed to larger units with an ugly cut-off rear side. The car appears to have used 16" and 19" rear wheels. Technical data taken from 'Rallye Racing Motormagazin', January 1977 issue.

1977 Porsche 935-77 (works)

The Group 5 rules were changed for the 1977 season. To allow more room for turbos, coolers and exhaust systems, the floor could be raised to door sill level, the bulkhead between engine bay and cockpit could be moved 20 centimeters, and the car structure (that should be retained) was defined as the part between the front and rear bulkheads. This allowed Porsche to install a better water-air intercooler in an enlarged engine bay. The front suspension geometry was improved. Instead of a single large turbo, the engine received two smaller turbos, but supposedly it didn't gain power, just more flexibility and less turbo lag. Improved roll cage adding some stiffness.

The bodywork was restyled: a new nose section with slightly raised front fenders with rear view mirror fairings, more square rear fenders, air inlets behind rear side windows (likely feeding the turbos), narrower rear wing, wing supports integral with engine cover, running boards, and a second rear view window placed over the original window (the rules merely required that the original window to be retained), to improve airflow to the wing. The original 930 rear wing was no longer used, but could be fitted (as required) inside the new body with some persuasion. Three works cars were built.

1977 Porsche 935-77 (customer)

1977 Porsche 935 Baby

The single 'Baby' had a 1.4 litre engine to compete in the under 2 litre class of the DRM during the 1977 season, where BMW and Ford had an interesting battle. Porsche wanted to show it could also be competitive in this class, which received more media attention in Germany. Entered in two races only: Norisring (DNF, cockpit heat) and Hockenheim (1st) as #40, then retired to museum with its goal achieved. Also referred to as '935 B2' and '935 TT'. The QV500 Porsche pages list this car as the converted third 935-77 (935/77-005) and racing in the 1978 season, which I doubt.

The Baby had 935-77 style bodywork, with the front radiator opening blanked off, and likely the rear fenders were made 128 mm narrower in total. The engine oil and gearbox oil coolers were moved from the nose to the rear fenders. Air for the air-air intercooler entered behind the rear side windows. Left side exhaust instead of rear exhaust, with an ingenious exhaust-blown intercooler system. Car weight was decreased from 970 to 725 kg, partly achieved by replacing the front and rear structures with aluminium frames. Engine had a single turbo, 370 hp. Narrower rear wheels, 14" maximum in the regulations, therefore the rear fenders were made less wide. In the first race (Norisring) 16" instead of 19" diameter rear wheels were used since the gearing was completely wrong.

1976 Porsche 935-K2

The 935 K2 was a Kremer modified 935-77 customer car, with bodywork by Design Plastic (DP). It has 1976 customer car specifics with K3-like vertical strips on the fenders. The 70 kg bodywork was designed for quick release, so the car could be disassembled in 5 minutes. Pneumatic jacks installed. Kremer built one 935-K2 on bare chassis # 007 00016. It was raced in the 1977 season in the green Vaillant scheme. In 1978 it had three other liveries, see Photos of Chassis 007 00016. It was destroyed on 18 Juni 1978 at Mainz-Finthen, driven by Louis Krages aka John Winter. A standard customer 935-77 delivered to Kremer was fitted halfway the 1977 season with K2 bodywork too, see Photos of Chassis 930 770 0903. Data listed below by Kremer.

1978 Porsche 935-78 (works)

The factory redesigned the 935 radically, using a loophole in the FIA rulebook, by lowering the complete car some 10 centimeters. Also called Moby Dick. The car initially had full width doors with NACA ducts and a full width and low-set rear wing, but these had to be redesigned before the first race (some models represent this pre-season design). Only one example was built, no customer cars were built in 1978, and it was raced only four times, all in 1978. Models with markings other than Martini are actually Joest-built replicas, usually designated 935-81, but still listed here.

1978 Porsche 935-78 (customer)

1979 Porsche 935-79 (customer)

There was no factory team in 1979, but a last batch of seven customer cars was built late 1978 for the 1979 season. They are therefore referred to as 935-79 customer cars. They were generally identical to the 935-78 customer cars, but had a single turbo 3.1L engine (specifically for IMSA rules) and an inverted gearbox like the works 935-78. Front fender louvres are seen on a few cars.

1979/1980 Kremer Porsche 935-K3

1980 Porsche 935-80

The factory had stopped producing customer cars, since they had no capacity, and because the Kremer K3 was superior. The factory did sell the latest parts such as the air-air intercooler, mechanical parts and body parts. A complete 935 to the latest specs could be bought in parts, and assembled by the customer. Joest and Loos tried various things to bring their cars up to speed with the Kremer K3, and therefore the situation with the '935-80' version is complex - there is no standard 935-80.

Some collected comments on the 935-80: "Similar bodied cars were entered in the 1980 DRM by Joest/Liqui Moly for Stommelen & Gelo/Kraus Hifi for Bob Wollek. The later also ran at Le Mans. Joest won 1980 24 Hours of Daytona with a 935 Baby. Such cars were entered at Le Mans in '81 (Joest/de Narvaez) & '82 (Joest/Vegla). The same (?) car won the '84 12 Hours of Sebring." and "The cars that resemble the "Baby" were the official Porsche 935/77 2.8 liter (over 2 liter) Group 5 versions. Many teams ran those. The factory even provided blueprints to Joest and they built authorized copies which Joest themselves ran before selling them to privateers like Moretti."

1981 Joest Porsche 935-81

Joest built two replicas of the 935-78. Both were right-hand drive as opposed to the factory car that had left-hand drive. These raced in Europe a couple of times in Momo (red, yellow trim) and Lui (white, black lettering). They then went to the USA, to the private teams of Fitzpatrick (J David) and Moretti (Momo/Penthouse) and raced in the 1981-83 time frame. Possibly '935-81' is not an official designation.

1981 Kremer Porsche 935-K4

Kremer built two K4's that were loosely based on the 935-78. The Barth/Dobronz book reports that the cabin was tilted backwards slightly, to improve the rear axle position. Data from 'Gruppe 5 Die Silhouetteformel 1976-1981'.

1983 Andial Porsche 935-L

Andial designed and built a single 935-L, that was raced in the 1982, 1983, 1984 and 1985 IMSA seasons. Again the design was based on the 935-78. It had filled-in doors with a large NACA-inlet on the top side, a long tail and a narrow rear wing. Andial built the chassis and suspension, A.I.R. built the body.

198x US Porsche 935s

A number of moderately to highly modified cars were built in the USA after Porsche stopped production. Apart from the 935-L listed above, no models exist of these replicas, as far as I know.