Reinforced exhaust valves Peugeot 106 S16 Citroën Saxo 16V TU5J4

Peugeot and Citroën engines covered

The TU5J4 is the 1.6 litre 16-valve engine of the Peugeot 106 S16, built from 1996 to 2004 as the NFX with 118 then 120 hp: a naturally aspirated four-cylinder that likes to rev.

The 16-valve Citroen Saxo, as the 120 hp 1.6 16V and then the 118 hp VTS, uses the TU5J4 from 1996 to 2004: a naturally aspirated twin-cam 1.6 litre known for its top-end pull on rally stages and on the road.

It has 8 exhaust valves, two per cylinder, with a 6 mm stem; in sporting use they spend long periods in contact with very hot burnt gases.

FERREA, SUPERTECH and CATCAMS reinforced exhaust valves

Each time it opens, the TU5J4 exhaust valve lets the burnt gases out towards the exhaust line: its head reaches 760 to 870 °C without boost; with a turbo it would go past 1,000 °C. About three quarters of this heat, 75 %, escapes via the seat and 20 % via the guide. Yet an EV8-family steel, the usual yardstick for the original valve, still resists 550 MPa around 600 °C but only 300 MPa around 800 °C. The higher the revs climb and the longer the load lasts, the hotter the head runs: it tires, distorts and ends up leaking at the seat.

The uprated parts on this page use materials designed for these temperatures. FERREA supplies two valves from its 6000 series in EV8 stainless steel, one in original size, the other with an enlarged head. SUPERTECH offers one in black nitrided stainless steel, whose hardened and smoother surface slows stem wear, and one in Inconel, a nickel-rich alloy retaining 860 MPa at 732 °C and 554 MPa at 816 °C, nearly 85 % more than EV8 around 800 °C. CATCAMS adds two valves with a 6 mm stem, at 24.5 mm and 26 mm.

Two enlarged-head versions exist: the F6760, which goes from 24.56 to 25.56 mm without changing stem or length, and the 26 mm 9249006M. A wider head lets the burnt gases out earlier, the cylinder breathes in more fresh mixture and power improves; the 8 exhaust seats are then machined to the chosen size.

Exhaust valve technical specifications

The FERREA and SUPERTECH valves have a 5.96 mm stem and a 104.4 mm length; the CATCAMS valves a 6 mm stem and a 104.2 mm length.

Valve fitting

Check the collets on reassembly: they must be sound and held firmly in the stem groove.

The stem slides in the guides: check their clearance and replace the valve stem seals during the rebuild.

The exhaust seats are reground with the new valves; with the 25.56 mm F6760 or the 26 mm 9249006M they are machined to the new size.

Technical guide

Our brands

	SUPERTECH Performance, located in California, has spent more than 30 years developing valves, guides, springs and titanium retainers for racing. In stainless, titanium or Inconel, every valve starts from a given engine and is then refined by well-known tuners in drag, rally and track racing.
	FERREA Racing Components dates back to 1978, when Horacio Ferrea set it up with Daniel Urrutia. Its two production sites, in Florida and Argentina, machine stainless steel, titanium and nickel superalloys, and its valves serve engine builders on every continent, in NASCAR as in drag racing.
	CATCAMS works in Belgium on valvetrain parts alone: cam profiles are calculated in house and every shaft is ground on CNC machinery. Tappets, retainers, shims and valve springs complete the offer, and its camshafts have competed in the BTCC as well as at Le Mans.

How to choose

For the TU5J4, three brands share the offer, in stainless steel or Inconel, all with a 6 mm stem. Pick the head size first, according to how worn the seats are, then the material, according to the intended use of the engine:

When reinforced valves become necessary

• Higher-lift cams or stiffer valve springs
• Rev cut raised by engine tuning or remapping
• Circuit, rally or hillclimb use
• Exhaust valves marked, leaking or already reground
• Full rebuild of the TU5J4 head of a 106 S16 or a Saxo

Vehicle compatibility

OEM part number (exhaust valve):

Don't forget the inlet valves

An open TU5J4 cylinder head is the right moment to renew inlet valves plus stem seals in one go, along with the exhaust side. The part suited to this engine: