V6 PRV engine

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The PRV engine is an automobile petrol V6 engine that was developed jointly by Peugeot, Renault and Volvo Cars and sold from 1974 to 1998. It was gradually replaced after 1994 by another joint PSA-Renault design known as the ES engine at PSA and the L engine at Renault.

Corporate history

The PRV story begins in 1966 when Peugeot and Renault entered a cooperative agreement to manufacture common components. The first joint subsidiary, La Française de Mécanique (also called Compagnie Française de Mécanique or simply FM) was launched in 1969. The FM factory was built in Douvrin near Lens in northern France. The PRV engines are sometimes referred to as "Douvrin" engines, though that name is more-commonly applied to a family of straight-4s produced at the same time.

In 1971, Volvo joined Peugeot and Renault in the creation of the PRV company, a PLC in which each of the three manufacturers owned an equal portion. The company originally planned to build V8 engines, although these were later scrapped in favor of a smaller and more fuel efficient V6.

The PRV engine could be seen as a V8 with two missing cylinders, having a 90 degree angle between cylinder banks, rather than the customary 60, but with crankpins being 120 degrees apart. The Maserati V6 of the Citroën SM followed a remarkably similar pattern of development.

The 1973 energy crisis and taxes levied against engine displacement greater than 2.8 L made large V8 engines somewhat undesirable and expanded the market for smaller engines.

Additionally, Renault needed a V6 engine to fit in its new model, the Renault 30.

Machinery for assembling the engines arrived at Douvrin in early June of 1973 and buildings for producing the engines were finished in January of 1974. The first PRV engines were officially introduced on October 3, 1974 in the Volvo 264. Adoption was swift, and the PRV V6 had been sold in at least five different models by the end of 1975.

In 1984, the first commercially available turbocharged PRV V6 was sold in the Renault 25 V6 Turbo. This was the first to be even-fire with split crankpins and was the first of the second generation, and indeed EFI engine of any sort. Turbocharged versions went on to be used in the Renault Alpine GTA V6 Turbo (essentially the same engine as the 25 Turbo at 2458 cm³), Renault Alpine A610 and Renault Safrane Bi-turbo - both with 2963cc low compression. Naturally aspirated 2963cc and 2975cc versions of both low and high compresson 3 litre engines appeared in a number of Peugeot, Citroen and Renault cars until 1997.

While Renault were working forced induction into the PRV, Peugeot and Citroen developed their own 24v engines as an option in the 605 and XM respectively. The compression remained the same as the Renault 12v but the pistons differed, as did some of the timing gear, and the heads were re-engineered to allow easier maintenance (the cam being fitted from the opposite end for example). This engine was however extremely expensive and suffered cam wear problems. This was down to the exhaust valves sharing a single lobe, while inlet valves had a lobe each. This was at least partially solved by the use of ceramic followers as one of a succession of recalls.

Meanwhile, French supercar manufacturer Venturi had been developing their own versions of the PRV. The most powerful versions they built were in the Atlantique 300 at 281 PS (207 kW) from a single turbocharged 3 litre 12v, and they successfully raced at the 24 Hours of Le Mans with the 600LM with a twin turbocharged 24v 3.0 L pushing out over 600 hp (over 450 kW) in race spec, and the road-going spin-off, the 400GT managed 408 PS (300 kW). This used the low compression bottom end common to the Renault turbo engines, coupled to 24 valve cylinder heads with bespoke rockers and tappets.

Peugeot too allowed a small group of engineers to create a team for endurance racing and after a few years the team grew to be called WM Peugeot. The ultimate version of the car used a low compression 3.0 L bottom end coupled to bespoke twin-cam heads. It is the only DOHC PRV. This car still holds the top speed record at 24 Hours of Le Mans, but this was achieved only as a short-lived PR stunt, done by taping up the cooling intakes and sacrificing the engine after a very short time.

Volvo began to withdraw from the PRV consortium in the late 1980s, shifting its powerplant reliance onto in-house inline engines. Peugeot, Renault and Citroën continued using the PRV until 1997.

After producing 970,315 units, production of the PRV V6 was stopped on June 15, 1998.

Engineering

Ignition timing

The original engineering work done on the V8 can still be seen in the resulting V6: its cylinder banks are arranged at 90° instead of the much more common 60°. V8 engines nearly universally feature 90° configurations because this allows for a natural firing order. V6 engines, on the other hand, are generally arranged at 60° (again because of timing) but can be built as 90° engines with either staggered timing or split crankshaft journals.

First-generation PRV engines (1974-1985) featured uneven ignition timing. Second generation PRV engines (introduced in 1984 in the Renault 25 Turbo) featured split crankshaft journals and even ignition timing all electronically controlled. [1] Other similar design examples are the odd-fire and even-fire Buick V6 and the Maserati V6 seen in the Citroën SM.


The ignition timing has nothing to do with the bank of the cylinders; V8s run smoothest with a 90º bank, while V6s run smoothest with a 60º bank. I do believe, however, that changing the cylinder firing order can result in a better idle quality and less vibrations. That is why the modern chevy small block v8 changed its firing order with the introduction of the LS series of engines in 1997.

Specifications

  • Power (DIN): 100 kW at 92 r/s (136 hp at 5,500 rpm) [2]
  • Power (SAE): 97 kW at 92 r/s (130 hp at 5,500 rpm)
  • Torque (DIN): 215 Nm at 48 r/s
  • Torque (SAE): 208 Nm at 48 r/s (153 ft.lbf at 2,750 rpm)
  • Compression ratio: 8.8:1
  • Bore: 91 mm
  • Stroke: 73 mm
  • Displacement: 2,849 cm³
  • Firing order: 1-6-3-5-2-4
  • Weight: ~150 kg

PRV powered automobiles

PRV engine in a De Lorean

The dates following each entry denote the introduction of a PRV V6-equipped model

PRV engines in racing

  • Alpine A310 V6
  • Fouquet buggies
  • Peugeot 504 V6 Coupé
  • Schlesser Original
  • Venturi 400GTR and 600LM
  • WM Peugeot

External links

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