≈80
% OF TORQUE FROM LOW REVS
The 605 shares with the Citroën XM the last PRVs of the PSA group: the 167-170 bhp 12-valve ZPJ, then — from 1990 — the 24-valve ZPJ4 and its ACAV variable-geometry intake, 200 bhp without any turbo, on the SV24.
The ZPJ — SFZ in the type approval — is the 12-valve 3.0-litre with Fenix 3B injection; the ZPJ4 — SKZ — is PSA's own 24-valve, with its heads, its sequential Fenix 4 injection and its ACAV intake, of a different spirit from Renault's Z7Xs. Same code on both sides of the group: the Citroën XM gets both.
ACAV — Admission à Caractéristiques Acoustiques Variables — changes the length of the intake runners with engine speed: nearly 80 % of peak torque from low revs on a naturally aspirated V6. Three configurations, driven by two solenoid valves according to revs and throttle position: at idle, the two intake half-volumes are separate, one per bank — gas speed is at its highest, the torque configuration; between 4,000 and 5,000 rpm the long-link solenoid connects them, the transition; above 5,000 rpm both solenoids are energised and the half-volumes become one, the power configuration.
Light-alloy heads with one overhead camshaft each, four valves per cylinder driven through hydraulic tappets, specific 62-link chains against 64 on the ZPJ: every detail is on the ZPJ4 file. At the 1988 Paris Motor Show, the Peugeot Oxia had shown what this 24-valve could dream of: twin-turbo by WM, 680 bhp.
The 605 and the Citroën XM share both engines, code for code — 12-valve ZPJ, 24-valve ZPJ4 — and their workshop sheets answer each other: the XM V6.24 also has Citroën Technical Note no. 23, which explains how the 24-valve and the ACAV work.
The production PRV is a 12-valve from 1974 to the end of its career — Safrane Biturbo included. Only three road cars are exceptions: the 605 SV24, the XM V6 24S and the Venturi 400 GT. Among concept cars and racers, the Peugeot Oxia (680 bhp) and the Venturi 600 LM (~600 bhp).
From 1997, a 60° « PR » V6 — ES9 at Peugeot, L7X at Renault — succeeds the PRV on the 605 and XM. That engine is not a PRV: only the ZPJ and « early » ZPJ4 versions belong here.
The lion's previous PRVs — 504 Coupé and Cabriolet, 604, 505 — each have their file. Between them and the 605 everything changes: in 1990 the ZPJ4 inaugurates the 24-valve heads and the variable acoustic intake.
The figures from the two workshop sheets — 605 SR/SV 3.0 V6 (5A89) and 605 SV 24 (1A90) —, readable page by page in the Library, and the FAQ answers on the 24-valve.
The 605's two workshop sheets, and the Citroën technical note on the same 24-valve: 605 SR/SV 3.0 V6 (ZPJ) — Pub et Trade sheet · 605 SV 24 (ZPJ4) — Pub et Trade sheet · Citroën Technical Note no. 23 — the 24-valve and the ACAV
The 605 has its own section on the forum — presentations, restorations, questions to members who drive one. Peugeot 605 section →
The 24-valve ZPJ4 and its ACAV intake, explained in detail — and the XM that shares everything.