The CTR (abbreviation of "Group C Turbo Ruf") was based on the 1987 911 Carrera 3.2 as opposed to the 930; Porsche's factory turbocharged version of the 911.
The decision to base the car on the Carrera 3.2 was made because of the 3.2's slightly lower curb weight and drag coefficient.
Factory body panels including the doors, hood and engine cover were replaced with aluminum pieces, helping to reduce an additional 200 kg (441 lb) of weight as compared to the vehicle's factory curb weight.
Efforts to reduce drag, the use of fiberglass front and rear bumpers and a pair of intake ducts on the rear flares to allow airflow to the intercoolers topped the list of body modifications.
The rear arches were also slightly increased in width to accommodate the larger Speedline wheels.

In addition to the lighter panels, considerable modifications were made to the engine, including boring the cylinders out to 98 mm (4 in) to increase displacement from 3.2 L (3,164 cc) to 3.4 L (3,367 cc), adding an uprated DME fuel injection system originally designed for the Porsche 962 race car.
A specifically designed turbo system featuring large twin-turbochargers and twin intercoolers were the main highlights of the modifications done to the engine, bringing total output to 469 PS (345 kW; 463 hp) at 5,950 rpm and 553 N⋅m (408 lbf⋅ft) of torque at 5,100 rpm.

At the time, Porsche offered the 911 3.2 with a 5-speed manual transmission, but the 930 featured only a 4-speed manual transmission, chosen because it was the only unit manufactured by the company that could handle the turbocharged engine's high power output.
Not content with only four forward gears and unable to satisfactorily modify the 5-speed unit, Ruf chose to use a new five-speed transmission of their own design on the CTR, which also gave them full freedom to customise gear ratios.
An upgraded suspension system, 17 inch Ruf Speedline alloy wheels, 330 mm (13.0 in) diameter Brembo braking system, and Dunlop's Denloc system performance tyres were used.

The company debuted the vehicle at the end of 1987 with pricing set at US$223,000 per unit, although that number could vary depending on whether a given customer ordered their car directly from Ruf or brought in a unit purchased via dealer for conversion.
Ruf manufactured only 29 cars from chassis bought from Porsche; about 20–30 cars were built from customers' Carreras.
The CTR (abbreviation of "Group C Turbo Ruf") was based on the 1987 911 Carrera 3.2 as opposed to the 930; Porsche's factory turbocharged version of the 911. The decision to base the car on the Carrera 3.2 was made because of the 3.2's slightly lower curb weight and drag coefficient. Factory body panels including the doors, hood and engine cover were replaced with aluminum pieces, helping to reduce an additional 200 kg (441 lb) of weight as compared to the vehicle's factory curb weight. Efforts to reduce drag, the use of fiberglass front and rear bumpers and a pair of intake ducts on the rear flares to allow airflow to the intercoolers topped the list of body modifications. The rear arches were also slightly increased in width to accommodate the larger Speedline wheels.
In addition to the lighter panels, considerable modifications were made to the engine, including boring the cylinders out to 98 mm (4 in) to increase displacement from 3.2 L (3,164 cc) to 3.4 L (3,367 cc), adding an uprated DME fuel injection system originally designed for the Porsche 962 race car. A specifically designed turbo system featuring large twin-turbochargers and twin intercoolers were the main highlights of the modifications done to the engine, bringing total output to 469 PS (345 kW; 463 hp) at 5,950 rpm and 553 N⋅m (408 lbf⋅ft) of torque at 5,100 rpm. 
At the time, Porsche offered the 911 3.2 with a 5-speed manual transmission, but the 930 featured only a 4-speed manual transmission, chosen because it was the only unit manufactured by the company that could handle the turbocharged engine's high power output. Not content with only four forward gears and unable to satisfactorily modify the 5-speed unit, Ruf chose to use a new five-speed transmission of their own design on the CTR, which also gave them full freedom to customise gear ratios. An upgraded suspension system, 17 inch Ruf Speedline alloy wheels, 330 mm (13.0 in) diameter Brembo braking system, and Dunlop's Denloc system performance tyres were used.
The company debuted the vehicle at the end of 1987 with pricing set at US$223,000 per unit, although that number could vary depending on whether a given customer ordered their car directly from Ruf or brought in a unit purchased via dealer for conversion. Ruf manufactured only 29 cars from chassis bought from Porsche; about 20–30 cars were built from customers' Carreras.
Ruf CTR