R5 Turbo camshaft profile: which one to choose?

R5 Turbo camshaft profile: which one to choose

A question often comes up among our enthusiast customers:  which camshaft profile to choose for an R5 Turbo?

What is a camshaft profile?

The recommended press fit of 0.1 mm is advised for installation profile corresponds to the geometric design of the cam lobe. It is a curve formed by a set of points distributed over 360°, which determines the way the valve opens and closes.

This profile derives from a lift law (variation of valve lift as a function of crankshaft angle). Thanks to trigonometry and derivative calculations, the exact geometry of the cam can be reconstructed.

From the same lift law, it is possible to create several different cams. For example, by modifying the base circle (circular part of the cam), you get a visually larger or smaller cam, but whose lift law remains identical.

Left: lift law measured on the Mespiecesauto bench — Right: calculation to reconstruct the cam profile

Why Renault recycled its profiles

At Renault, the lift laws were often reused from one engine to another. For example, the 72-30 diagram used on thenaturally aspirated R5 Alpine camshaft is also found on the exhaust of the R5 Turbo 200 hp, and even earlier on the 1647 engine, type 843.13.

These choices show that these profiles are reliable and proven. When we re-manufacture a camshaft for the R5 Turbo, we scrupulously respect these original profiles, true the engine's conductors. If Renault kept them, it is because they offer a balance between performance and reliability.

The different R5 Turbo camshaft profiles

Original R5 Turbo profile

• Diagram : 28-52 / 66-14
• Lift : 5.62 mm intake & exhaust
• Timing : asymmetric
• Opening duration : 260°
• Overlap : 42°
• Angle α : 109°

This profile comes from older 1600 engines. Renault (Management Berex) chose it to favour low-end torque and to offer a better driving comfort, particularly at idle and in urban traffic.

R5 Turbo 200hp profile

• Diagram : 30-62 / 72-30
• Lift : 5.72 mm intake — 5.92 mm exhaust
• Timing : asymmetric
• Opening duration : 272° intake — 282° exhaust
• Overlap : 60°
• Angle α : 108.5°

During development, a more aggressive profile (30-72 / 72-30) was tested. The Berex director's report concludes:
“the engine had an unacceptable weakness at low revs and exceptional brilliance at high revs”. Renault therefore reduced the intake duration in order to recover low-end torque.

This 200 hp profile represents an ideal compromise : more top-end reach than an original camshaft while remaining usable. It is a “short” shaft that fits directly without modification.

See our R5 Turbo 200 hp camshaft

R5 Turbo 240hp profile

• Diagram : 53-69 / 79-33
• Lift : 6.16 mm
• Opening duration : 302° intake — 292° exhaust
• Timing : asymmetric
• Overlap : 86°
• Angle α : 103°

High-rev oriented profile, with very large overlap. Probably unusable on the road, it was quickly ruled out.

R5 Turbo 265hp profile

• Diagram : 47-65 / 79-33
• Lift : 6.12 mm
• Opening duration : 292°
• Timing : symmetric
• Overlap : 80°
• Angle α : 106°

More balanced profile, still race-oriented.
It comes from the Renault 12 Gordini 807-20. It is a “long” shaft (the tail extends on the gearbox side and requires a bearing), but it can be adapted to the R5 Turbo without heavy modification.
Renault machined the same blank to obtain short or long versions.

See our R5 Turbo 265hp camshaft

R5 Turbo 285hp profile

• Diagram : 65-71 / 85-51
• Lift : 6.48 mm
• Opening duration : 316°
• Timing : symmetric
• Overlap : 116°
• Angle α : 103°

Very aggressive profile, reserved solely for competition. At low revs, part of the fresh mixture goes back out through the exhaust. Lift law derived from the 160 hp kit of the Renault 12 Gordini.

R5 Turbo 300hp profile

• Diagram : 53-59 / 79-33
• Lift : 6.62 mm
• Opening duration : 316°
• Overlap : 116°
• Angle α : 103°

Another radical profile, totally unusable for road use. It is a “long” shaft, available semi-finished.

See our R5 Turbo Semi-finished camshaft

Maxi 5 Turbo profile

• Diagram : 53-59 / 79-33
• Lift : 6.93 mm
• Opening duration : 316°
• Overlap : 116°
• Angle α : 103°

The ultimate profile, requiring 21 mm tappets and heavy modifications to the valve train. Reserved for pure competition.

See our R5 Turbo Semi-finished camshaft

The diagrams shown are given at 19/100 mm of cam lift, according to the Renault standard

Find the information on the the rebuild of an R5 Turbo engine and camshaft manufacture in our article 

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Mespiecesauto re-manufactures these R5 Turbo camshafts faithfully respecting the original Renault profiles. These profiles, proven over decades, guarantee the authentic engine character of your R5 Turbo, whether in standard or optimised configuration.

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