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ZPJ4 —
the 24-valve

The ZPJ4 is PSA's reading of the PRV V6: four valves per cylinder, an ACAV variable-geometry intake, 200 naturally-aspirated bhp at 6,000 rpm — a different spirit from Renault's Z7X, and the base of the most powerful road PRV ever built, the 408 bhp Venturi 400 GT.

200
BHP (NATURALLY ASPIRATED)
24
VALVES
408
BHP (EIA TWIN-TURBO)
The ACAV intake

An intake that changes shape with engine speed

ACAV stands for “Admission à Caractéristiques Acoustiques Variables” — variable acoustic intake. Instead of a fixed manifold, a plenum and flaps alter the effective length of the runners with engine speed: below about 5,200 rpm the long runners use pressure-wave resonance to swell the torque; above it the geometry opens up and releases the power. Three configurations, driven by two solenoid valves according to speed and throttle position.

The result: nearly 80 % of the torque available from low revs — flexibility and reach, on a naturally-aspirated V6. The early days were difficult though: camshaft problems and a chaotic development, the context is in History. The production 24-valve remains an exception: only three road cars — 605 SV24, XM V6.24 and Venturi 400 GT —, the PRV being a 12-valve from 1974 to the end of its career, Safrane Biturbo included.

ZPJ4
PSA CODE · 2,975 CC · 24 VALVES · ACAV INTAKE · FENIX 4
2975
CC
~80 %
OF TORQUE FROM LOW REVS
5200
RPM SWITCHOVER
Identity

What makes a ZPJ4 a ZPJ4

Figures read in the constructor's documents held in our Library — repair manuals, Pub et Trade data sheets, period bulletins. Nothing here comes from a web fact sheet.

ZPJ4 2,975 cc · 24 valves · ACAV intake · Fenix 4 Technical Note no. 23 →
93 × 73
The ZPJ4 (SKZ): six cylinders, 93 mm bore, 73 mm stroke, 2,975 cc, 9.4:1 compression ratio. 147 kW — 200 bhp — at 6,000 rpm, peak torque 26 mdaN at 3,600 rpm, maximum speed 6,500 rpm. 16 fiscal hp, RON 95 unleaded.
Culasses
Light alloy, four bearings, one overhead camshaft per head driven by chain with a mechanically-resetting hydraulic tensioner; four valves per cylinder operated through hydraulic tappets housed in the rockers — six separate rockers on the inlet side, three one-piece on the exhaust, per head. The front head also carries the balancer shaft.
62 maillons
Specific 62-link timing chains — 64 on the 12-valve ZPJ — and a guide arrangement of its own; timed to the marks, at one turn plus 240°. The central tappets are not all identical: the Technical Note says so in capitals.
Fenix 4
An SBAE Fenix 4 ECU, housed in the electronics box on the right front wheel arch, manages injection, ignition and the two ACAV intake solenoid valves.
408 ch
At EIA, the same 24-valve block receives two turbos for the Venturi 400 GT — “the French F40” — and 408 bhp: the highest output the Douvrin V6 ever reached in a road car.
Known variants

From the big saloons to the “French F40”

The production 24-valve and EIA's twin-turbo preparation — the full code table is on the Engines page.

ZPJ4 200 to 408 bhp Every known code →
ZPJ4200 bhp
Fenix 4 injection24-valveACAV intake
Peugeot 605 SV24 · Citroën XM V6.24 (from 1990) — 200 bhp: a PSA-specific 24-valve, with its own heads and intake.
ZPJ4 · EIAjusqu'à 408 bhp
Twin-turbo24-valveEIA-prepared
Venturi 400 GT — 408 bhp, the most powerful road PRV.
On the road

The cars of the ZPJ4

Peugeot 605 SV24 → · Citroën XM V6.24 →

The first 24-valve PRVs, from 1990: 200 bhp, a workshop sheet each in the Library, and Citroën Technical Note no. 23 explaining the engine.

Venturi 400 GT →

EIA's 408 bhp twin-turbo ZPJ4 — the “French F40”, and the peak of the PRV's road career.

Peugeot Oxia et WM P88 →

Off the road: the twin-turbo 24-valve of the Peugeot Oxia (680 bhp) and the ZNS5 of the WM P88 at Le Mans (about 910 bhp) — the prototypes.

In the workshop

What the documents say about the ZPJ4

Answers taken from our FAQ, each one read in the Library. The full FAQ holds several hundred more, engine code by engine code.

The ZPJ4, in the documents The full FAQ →
SKZ
What exactly does the 24-valve PRV V6 of the XM deliver?
The ZPJ4 (SKZ): six cylinders, 93 mm bore, 73 mm stroke, 2,975 cc, compression ratio 9.4:1. 147 kW — 200 bhp — at 6,000 rpm, maximum torque 26 mdaN at 3,600 rpm, maximum engine speed 6,500 rpm. Unleaded RON 95. Citroën Technical Note no. 23, XM V6.24, page 3.
Culasses
How are the 24-valve cylinder heads built?
Light alloy, four bearings, one overhead camshaft per head driven by a chain with a mechanically reset hydraulic tensioner. Four valves per cylinder, operated through intermediate followers by hydraulic tappets housed in the rockers. A support plate carries two rocker shafts: one for the intake, with separate rockers — six per head —, one for the exhaust, with one-piece rockers — three per head. The front head also carries the balance shaft. Citroën Technical Note no. 23, XM V6.24, page 5.
ACAV
How does the ACAV variable intake actually work?
Through three configurations, commanded by two solenoids according to engine speed and throttle position. Engine stopped or idling, neither solenoid is energised: the two half-plenums are separate, one per bank — gas speed is at its highest, this is the torque configuration. Between 4,000 and 5,000 rpm, the long-link solenoid is energised: the volumes communicate, the transition stage. Above 5,000 rpm, both solenoids are energised: the half-plenums are joined into one, the power configuration. Citroën Technical Note no. 23, XM V6.24, pages 12, 13 and 19.
400 GT
What is the most powerful PRV-powered road car?
The Venturi 400 GT, nicknamed “the French F40”: its 2,975 cc 24-valve PRV, twin-turbocharged by EIA, delivers 408 bhp — the highest output ever reached by the Douvrin V6 in a road car. 400 GT file →

In the Library

The 24-valve's documents, searchable page by page: ZPJ4/SKZ workshop sheet — Peugeot 605 SV 24, 200 bhp · ZPJ4/SKZ workshop sheet — Citroën XM V6.24, 200 bhp · Citroën Technical Note no. 23 — XM V6.24

The rest of the family

Architecture, generations and every known engine code of the PRV V6 — on the main Engines page.

ZPJ — the 12-valve →Z7X — the 3.0 at Renault → All PRV engines →