Forged connecting rods Citroën / Peugeot - 1.6L 16V - TU5J4 / TU5JP4 19.46 mm pin for forged pistons

The Citroën / Peugeot TU5J4 / TU5JP4 engine

The TU5J4 and its TU5JP4 variant make up PSA’s family of sporting 1.6-litre 16-valve inline fours. Naturally aspirated, the engine combines a 78.5 mm bore with an 82 mm stroke for 1,587 cc, and was built from 1995 to 2007. Its multi-valve head and compact architecture made it a lively unit, particularly at home at high rpm, which explains its long competition career.

It powers the group’s sportiest versions: Peugeot 106 S16 and 206 S16, Citroën Saxo VTS and C2 VTS. These light hatchbacks built the reputation of the TU5 in rally, on circuit and in hillclimb, where the engine spends most of its time near the red line. Very responsive to tuning (intake, exhaust, camshafts, even forced induction), it quickly puts the standard rod at its limit as soon as power, rpm or cylinder pressure rise, all the more so as the piston pin measures only 19.46 mm.

Forged connecting rods

Forged from high-strength 4340 steel, these rods bring the bottom end of the TU5 up to the level of the rest of the build. They are called for as soon as forged pistons go in, as soon as the red line is raised, as soon as forced induction is added or displacement increased: all cases where the standard rod, with its 19.46 mm pin and its 133.6 mm centre-to-centre length, runs out of reserve.

Intended for built engines, highly tuned naturally aspirated as well as boosted, they serve every discipline: rally, drift, drag racing, circuit and track use, hillclimb, time attack. They follow Stage 2, Stage 3 and Stage 4+ builds, up to a fully rebuilt competition engine, without fearing long spells at high rpm.

Technical specifications of the TU5J4 / TU5JP4 forged connecting rods (19.46 mm pin)

ZRP: Lightweight design.

Torque and bolt stretch

Both bolts of the same cap must be tensioned in the same way: if one is left behind, the cap tilts slightly, the bearing bore loses its roundness on one side and the shell bears at an angle, with an uneven oil film across its width. That asymmetry is the most discreet form of under-tightening; the most common one is simply staying below the range: preload no longer covers the separating force, the cap lifts intermittently, the shell is hammered and clearance opens. At the other end, crossing the upper limit yields the bolt, which keeps a permanent elongation and loses its tension, while the bore distorts and the big end goes oval. The values in the table below are those the fastener manufacturer specifies for each ZRP rod of this TU5, in ARP 2000 as in ARP L19 in 3/8": they apply to every single bolt, without exception. Stretch measurement with a dial gauge remains the reference method, with ARP assembly lubricant and the kit instructions as the governing documents.

Technical guide

4340 forged steel: what is it?

Connecting rod profiles

	H-Beam H-Lite profile (lightened H). A lightened version of the H profile, it keeps the “H” section, with its two flat sides and central web, while reducing mass to ease the load on the rotating assembly. ZRP designed it to free up revving with proven reliability at high rpm, and recommends it for naturally aspirated engines such as the TU5.
	I-Beam I-HD profile (reinforced I). A “Heavy Duty” variant of the I profile, it keeps the same architecture with a thicker, reinforced beam, sized to withstand far higher loads. It is aimed at extreme loads, on high-power turbo, supercharger or nitrous builds running high boost pressure.

How to choose your rod bolts?

On a 1.6 16V that revs hard, the rod bolt takes a tension cycle on every revolution: it is what sets the real limit in rpm and in pressure. The grade is therefore chosen according to the intended use (rally and hillclimb with torque pick-up at low rpm, circuit with rpm held for tens of minutes, drag racing with very short but violent peaks) and to the target power per cylinder. The two grades offered here in 3/8"-38 mm are fitted to the stated torque and stretch, with no approximation.

ARP 2000, with a tensile strength of ~220,000 psi (~1,517 MPa), is the high-performance standard: up to 200 hp per cylinder in 3/8" and up to 8,500 rpm. On a 1,587 cc naturally aspirated engine used in rally, on circuit or in hillclimb, that leaves a very comfortable margin, including after a move to moderate forced induction. It is the most common grade in circuit racing, track days, drift, rally, drag racing and hillclimb, and it calls for no particular storage constraint.

L19 climbs to ~260,000 psi (~1,793 MPa), that is up to 250 hp per cylinder in 3/8" and up to 10,000 rpm. It is the choice for the most highly developed TU5 engines: very high boost pressure, sustained high rpm in hillclimb or circuit racing, high cylinder pressure, and more generally the big power levels in drag racing, drift, rally and circuit. Beware however of its sensitivity to corrosion and to hydrogen embrittlement: L19 bolts are stored and fitted oiled, away from moisture, and must never sit bare in a damp workshop.

Measuring bolt stretch

Buy the ARP stretch gauge →

The brands offered

ZRP is a Greek brand of high-performance forged connecting rods, designed by Alex Drakos in Athens. Each rod is forged from 4340 steel, precision-machined and balanced to ±1 g to stay reliable at high rpm. On this TU5 application they are offered in H-Lite (lightened H) or I-HD (reinforced I) profile with ARP 2000 or L19 hardware, designed and inspected in Greece, and proven in rallying, on circuit and in drift.

Glossary

1) Small end 2) Small-end diameter 3) Rod beam 4) Rod bolt 5) Big end 6) Rod nut / bolt 7) Rod cap 8) Big-end diameter 9) Center-to-center

Vehicle compatibility for the Citroën / Peugeot TU5J4 / TU5JP4 engine

These forged rods suit every vehicle fitted with the 1.6 16V TU5J4 or TU5JP4 in its 19.46 mm piston pin version. The table below details the Citroën and Peugeot models concerned.

OEM reference: 0603 86 (set of 4 rods).

Why it’s the most cost-effective solution?

When a TU5 breaks a rod, the repair never stops at the broken part: the matching piston nearly always has to be replaced, sometimes along with the liner. Going back to the original configuration therefore means buying standard rods and pistons again, for an engine that will remain exactly as fragile as before.

For a comparable, often lower budget, a set of 4340 forged rods fitted with forged pistons brings incomparable reliability and safety margin, and opens the door to a more ambitious build instead of a simple return to factory condition. European engine builders have worked this way for more than 15 years on competition PSA engines.

For the same budget the sum is quickly done: more reliability, more potential, more service life.