Forged connecting rods Citroën / Peugeot - 1.6L 16V Turbo - EP6 for forged pistons

The Citroën / Peugeot EP6 engine

The Citroën / Peugeot EP6 is a 1.6L 16V inline four-cylinder with double overhead camshafts, jointly developed by BMW and the PSA group and unveiled in 2006. It shares its architecture with the Prince engine fitted to the Mini (N12/N14). In its forced-induction versions (EP6DT, EP6CDT and EP6DTS), it combines a turbocharger with direct petrol injection, for a displacement of 1,598 cc (bore 77 mm × stroke 85.8 mm). Depending on the version, output ranges from about 150 hp to 207 hp, with torque markedly raised by forced induction.

Widely used in the Peugeot 207 RC, 308, 3008 and 5008, as well as the Citroën DS3 (up to the 207 hp DS3 Racing), DS4 and DS5, the turbocharged EP6 is a popular tuning base. As soon as boost pressure or engine speed rises, the original connecting rod becomes one of the first parts to reinforce: that is exactly the role of these forged rods, designed to withstand the stresses of built engines over the long term.

Forged connecting rods

A forged connecting rod is machined from a hot-forged steel billet: the metal grain follows the shape of the part, giving it far higher mechanical strength and fatigue resistance than an original sintered-metal rod. On an EP6 with raised boost, engine speed or displacement, this guarantees a bottom end able to handle the power increase reliably; they become essential when fitting forged pistons.

Designed for built engines (turbocharged as well as highly tuned naturally aspirated), these forged rods cover every discipline, from rally to drift through drag, circuit, hillclimb and time attack, and support Stage 2, Stage 3 and Stage 4+ builds, all the way to a competition engine.

Technical specifications of the EP6 forged connecting rods

Torque and bolt stretch

Everything starts before the torque wrench comes out: on the EP6, a dirty thread, a bore marked by the previous bolts or even a trace of degreaser will distort the result far more than a misread scale. Bolt and cap threads must be brushed, blown out and dried, mating faces free of burrs, before the ARP assembly lubricant goes on. Only then do the values in the table above, defined by the bolt manufacturer, deliver the stated preload: they apply with no rounding and no adaptation, whether the rod carries ARP 2000 or ARP L19 bolts. And because torque never reports the installed tension directly, checking stretch with a dial gauge remains the reference method across the engine’s eight bolts, with load applied progressively rather than in a single pull. The instruction sheet supplied with the kit is authoritative.

Technical guide

4340 forged steel: what is it?

Connecting rod profiles

I-Beam profile. With a slimmer central web, framed by two flanges that give it its « I » shape, this rod combines high rigidity with a controlled mass. On modern turbocharged engines such as the EP6, it is the profile of choice, supporting both the reinforcement of the bottom end and the increase in boost pressure.

How to choose your rod bolts?

On the turbocharged EP6, rod bolt preload has to cope with high combustion pressure at low and medium engine speed: a properly tensioned bolt no longer moves, whereas a bolt torqued onto dirty threads can lose tension within a few sessions. Before assembly, clean the threads of the cap and of the rod, blow out the holes, check that the seats are free of burrs, then apply the recommended assembly lubricant along the whole thread and under the head. Tightening is carried out in several passes and preload is validated through stretch measured with a dial gauge, a reading taken bolt by bolt. The two grades available, ARP 2000 and ARP L19 in 3/8"-38 mm, are chosen according to the power per cylinder targeted and the operating engine speed, keeping a margin for repeated sessions.

	ARP 2000 (tensile strength around 220,000 psi, i.e. ~1,517 MPa). Versatile high-performance hardware with no storage constraints: it handles up to 200 hp/cylinder in 3/8", at speeds up to 8,500 rpm. The robust, reliable choice for circuit, track day, drift, rally, drag and hillclimb.
	ARP L19 (tensile strength around 260,000 psi, i.e. ~1,793 MPa). Designed for engines pushed to the extreme, high boost pressure and sustained high revs: up to 250 hp/cylinder in 3/8", up to 10,000 rpm. Sensitive to corrosion and hydrogen embrittlement, it is stored and fitted oiled. The choice for big-power builds in drag, drift, rally and circuit.

Measuring bolt stretch

Buy the ARP stretch gauge →

The brands offered

ZRP, a Greek forged connecting rod brand created by Alex Drakos (Drakos Engineering, Athens). A recognised specialist in forged engine parts, ZRP machines its rods from high-strength 4340 steel and balances them to ±1 g to stay reliable at high rpm. Offered here in I-Beam profile with ARP 2000 or ARP L19 hardware, they are designed and inspected in Greece, and proven in rally, 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 EP6 engine

These forged connecting rods are compatible with all vehicles fitted with the Citroën / Peugeot EP6 turbo engine (1.6L 16V THP):

OEM reference:

Why it’s the most cost-effective solution?

When an original bottom end fails (a broken, bent or scored rod), returning to the factory configuration means replacing both the connecting rods and the pistons, which are often damaged at the same time. The bill rises quickly for a mere restoration. For a comparable budget, sometimes less, fitting forged rods brings far greater reliability and safety margin, and opens up genuine potential for more power. It has been the choice of European tuners for over fifteen years: for the same budget, more reliability, more potential and more longevity.