Caterham CSR200 Cosworth Seven in the Pyrenees

The Caterham 7 (or Caterham Seven) is a super-lightweight sports car produced by Caterham Cars in the United Kingdom. It is based on the Lotus Seven, a lightweight sports car sold in kit and factory-built form by Lotus Cars, from 1957 to 1972.

The Caterham Seven CSR is the latest model from sports car manufacturer Caterham Cars. The CSR is the most heavily modified Caterham, though it still retains the basic look of the Super Seven. The CSR has two engine options based on the same Duratec block, though modifications and power output differ. The entry level engine produces 200 bhp (149 kW), with a 0–60 mph (0–97 km/h) time of 3.7 seconds. The upgraded engine produces 260 bhp (194 kW), with a 0–60 mph (0–97 km/h) time of 3.1 seconds and a top speed of 155 mph (249 km/h).

Performance

The CSR represents the most radical redesign of the car since the introduction of the Seven in its 48-year history. The CSR is the subject of numerous improvements over previous models (see below), though it still retains the main aesthetics of Caterhams.

While slightly heavier than other Caterhams the CSR still upholds Colin Chapman’s philosophy of “add lightness.” Weighing only 575 kg (1,268 lb), the CSR has excellent handling, making it extremely agile. On the skidpad, the Caterham outperforms many supercars. Its 1.05 lateral g-force beats the 2007 Porsche 997 Turbo’s 0.94 G, the Ferrari F50’s 1.03 G, and the Ferrari Enzo’s 1.01 G.

In braking tests, the CSR performs well. From 70 mph (113 km/h) to a complete stop, the CSR took 140 feet (43 m). The 997 Turbo, stopping from 60 mph took 99 feet (30 m). The Ferrari F50 performed well, stopping from 60 mph (97 km/h) in 119 feet (36 m).

For comparison, an average 2011 road car (2011 Chevrolet Cruze LS) takes 167 feet (51 m) to completely stop from 70 mph (110 km/h) and Formula One cars can stop in 56 feet (17 m) from 62 mph (100 km/h).

The CSR has excellent low-end acceleration because of its high power-to-weight ratio of 410 bhp (310 kW) per ton (260 model). It can accelerate from a stop to 60 mph (97 km/h) in 3.1 seconds (estimated), though during trials, Car and Driver magazine could only achieve 3.6 seconds. This discrepancy is due to the close gear ratios of the transmission and the rev limiter. The CSR that they tested could not reach 60 mph (97 km/h) in first gear, and required the extra 0.5 seconds to shift.

Car and Driver explains:

It’s also wickedly quick, blowing past 60 mph (97 km/h) in 3.6 seconds… The Caterham had an improperly set rev limiter that cut fuel at 7,700 rpm, 300 rpm short of the redline and 2 mph (3.2 km/h) short of 60 mph (97 km/h). At 7,700 rpm, the Caterham is going 58 mph (93 km/h), so we had to do a time-consuming shift before hitting 60 mph… With the correct fuel cutoff, at 8,000 rpm… it would likely hit 60 mph (97 km/h) in the low threes.

For comparison the Porsche 997 Turbo, which has AWD and weighs over twice as much as the CSR, has a power-to-weight ratio of only 269 bhp (201 kW) per ton, but has a 0–60 mph (0–97 km/h) time of 3.4 seconds.

The 260 bhp (194 kW) Cosworth-tuned engine is heavily modified from the stock 2.3 litre Duratec. The cylinder head, block, crankshaft, connecting rods and pistons are upgraded by Cosworth.

Cosworth also integrates an advanced dry-sump with an extra internal scavenge pump to distribute the oil. While a dry-sump system requires more oil (more weight), a dry-sump will keep the engine lubricated under hard cornering unlike a wet-sump system. Cosworth also radicalizes the cam shafts and upgrades the exhaust system. This may cause the engine to run a little more “rough” at low RPMs, but it drastically increases performance. The inlet system is also replaced with an advanced, custom roller-barrel system. This increases airflow at full throttle compared to a butterfly inlet, boosting performance. The engine also has a custom chip designed by Cosworth for a further increase in performance.

The 200 bhp (150 kW) model uses the same Duratec block, but is not as heavily modified. The connecting rods and pistons are not upgraded significantly, though it does have the dry-sump system. The cam shafts are slightly radicalized, and the exhaust system is upgraded. The inlet system is enlarged, but not replaced with the roller-barrel system. The computer chip is upgraded, but not to the extent of the 260 model. Generally speaking, the 200 model is upgraded, albeit not as heavily.

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