Pre-installation check
Confirm the piston, cylinder and ring grooves are clean and free of debris, and check the ring size and specification against the engine model.
Seven installation steps each for petrol and diesel engines, with an animated diagram and the C.T.I. ring section reference.
Petrol and diesel ring sets are designed differently, so the procedures differ. Pick an engine type and scroll — the diagram follows each step.
Step 01 / 07
Confirm the piston, cylinder and ring grooves are clean and free of debris, and check the ring size and specification against the engine model.
Identify the top ring, second ring and oil ring in the set. Where a ring face carries a TOP mark, lettering, a dot or any other orientation mark, fit it towards the piston crown as the specification requires.
Fit the expander first, then the top and bottom side rails. Check that the two ends of the expander butt together correctly and do not overlap.
Use a proper piston ring expander tool. Opening the ring further than necessary will distort or break it.
Check which face goes up, fit the ring into the first groove, and confirm it moves freely in the groove.
Stagger the end gaps as the engine manufacturer specifies. Never leave every gap on the same line.
Apply the specified engine oil to the rings, the piston and the cylinder wall, compress the set evenly with a ring compressor, and fit the piston into the cylinder.
Clean the ring grooves and cylinder thoroughly, inspect the condition of the grooves and the cylinder bore, and confirm the rings match that diesel engine.
Locate the top ring, second/intermediate ring and oil control ring for that set. Diesel sets vary in ring count and type with engine design, so fit the set specified for the engine.
Check the TOP mark, lettering, dot marks and the shape of the ring face. A ring with a special section, an inner or outer chamfer or a special surface treatment must not be fitted upside down.
Work upwards from the lowest groove: the oil ring first, then the intermediate/second ring, and the top ring last. Use the proper tool and do not over-expand the ring.
With the set fitted, confirm every ring sits correctly in its groove with no binding, twist or other abnormality.
Set each end gap at the angle the engine manufacturer specifies. Do not group the gaps together or line them up.
Apply the specified engine oil, compress the set with a suitable ring compressor, and fit the piston smoothly into the cylinder — never drive it in by force.
The sections C.T.I. manufactures, for reference. Enquiries and orders are placed by engine model, OEM number or C.T.I. catalogue number — you do not need to pick a section yourself. If you do need a particular one, just note it with your enquiry.
Barrel-shaped running face: quick to bed in and wears evenly. The standard top-ring section for petrol and light-duty diesel engines.
Plain rectangular section — the most basic shape, widely used in small and general-purpose engines.
Bevelled on one face. Used where groove carbon build-up is a concern; common in heavy-duty diesel.
Bevelled on both faces, with still better resistance to carbon sticking.
A very slight taper on the outer face gives line contact with the bore: it scrapes oil on the down stroke and spreads it on the up stroke.
A section with a taper outer face and an inside bevel; the bevel on the top face (IF) or the bottom one (IFL) sets the direction of twist.
A taper face undercut at the back: a lighter section and higher face pressure for scraping.
A hook on the bottom edge that scrapes oil down on the return stroke. The most common second-ring choice.
A section with an under-hook bottom edge and an inside bevel; again the position of the bevel sets the direction of twist.
Bevelled on the top inside edge; once in the bore the asymmetric section produces positive twist.
Bevelled on the bottom inside edge; the section is asymmetric the other way, producing negative twist.
A square step cut into the top inside edge, giving a more definite twist than a bevel.
A square step cut into the bottom inside edge, twisting the opposite way to the top.
One piece: a single ring body that scrapes with its running face, the oil returning through slots or past the bevel. Mainly diesel.
Slotted Oil Control Ring — a one-piece slotted ring; the running face scrapes surplus oil, which returns through the slots.
Bevelled Edge Oil Control Ring — a single bevel narrows the contact face and raises face pressure for stronger scraping.
Double Bevelled Edge Oil Control Ring — bevelled on both edges of the running face for tighter oil control.
Two pieces: a one-piece ring body with a coil spring behind it, the spring adding radial tension. Mainly diesel and heavy-duty diesel.
Bevelled Edge + Coil Spring — a single bevel with a coil spring, for closer conformability to the bore.
Bevelled Edge + Coil Spring — a steel body with a coil spring, nitrided (NIT) for wear resistance and stable tension.
Double Bevelled Edge + Coil Spring — bevelled on both edges with a coil spring, balancing scraping against conformability.
Three pieces: two steel side rails around an expander — the rails scrape, the expander supports them and supplies tension. Mainly petrol. The four below are different expander types.
R-Type Expander Oil Control Ring.
N-Type Expander Oil Control Ring — three-piece like the R, differing in the expander. N here is an oil-ring expander code and is not the N used above for a taper-face compression ring.
PC-Type Expander Oil Control Ring — good scraping and bore conformability.
U-Flex Oil Ring — a U-shaped flexible section with good bore conformability and oil control.
How the ends are cut. The codes and sections C.T.I. can produce, again for reference only — just note it with your enquiry if you need a particular one.
Joint with side notch — a lateral notch at the joint, for groove location or a special design requirement. Common in diesel, commercial-vehicle and industrial engines.
Side notch + Keystone — the wedge section lowers the risk of ring sticking from carbon build-up, suiting high temperatures and heavy loads. Common in heavy-duty diesel, trucks, buses and construction machinery.
Joint with internal notch — an inner notch matching a particular groove or locating design, keeping the ring correctly fitted and working. Common in diesel and in special industrial and commercial engines.
Overlapped Joint (Angle) — the ends overlap on an angle, cutting the direct path for gas or oil through the gap compared with a plain butt joint. Used in large diesel engines, compressors, and industrial and marine engines.
Hook Joint — the ends hook into one another, lengthening the sealing path and reducing direct leakage at the gap. Used in large diesel, marine and industrial engines and in compressors.
Send us the engine model, the OEM number or the C.T.I. catalogue number and we can confirm the product and price quickly.
For a special size or specification, attach a drawing, PDF, Excel file or photo and we will work from that.
© C.T.I. Traffic Industries Co., Ltd. Original content by C.T.I. — reproduction, copying or commercial use without permission is prohibited.
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