Liner & Piston Update for ISX Engines
Cummins has been producing the ISX engine since it replaced the N14 in 2001. In those years, many improvements have been made to the designs of both the pistons and the cylinder liners. Below are summaries of the updates to the designs of those two parts.
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ISX Piston Revolution
Piston types cannot be mixed within the same engine. Another important note concerning pistons is that all of the one-piece pistons must be used with drilled connecting rods and drilled bearings. If you forget these, don't worry too much—all of our sales people know these facts and will make sure you don't run into these issues.
1. Early Two-Piece Piston with a High-Top Ring
Okay, so we're going to be pretty explicit with the titles for these. The earliest piston was two-piece, with a crown and a skirt that fit together, but are separate. The top piston ring is up high on the piston, with a bit of distance between it and the middle ring.
2. Open Window, One-Piece Piston with a High Top Ring and Large/Reduced Diameter
The piston was condensed into a single piece. It has an open window, meaning there is a large-ish gap on the side of the piston, and the crown and skirt are 35mm apart. This is the only iteration of the piston that has an open window. This design still has a high top ring, meaning there is 8mm between the combustion face of the piston and the top ring groove. The diameter of the piston top is either 135.3mm or 134.86.
3. Closed Window, One-Piece Piston with a High Top Ring and Large Diameter
The window got closed up, and the distance between the skirt and crown shrank to only 25mm. The high top ring is still in place, with the same 8mm between the top piston ring and the combustion face. The diameter of the piston top is large, at 135.3mm.
4. Closed Window, One-Piece Piston with a High Top Ring and Reduced Diameter
This is the same as the above, still with the top piston ring near the top and the smaller gap between crown and skirt. The major difference between these is that the diameter of the piston is reduced, at 134.86mm.
5. Closed Window, One-Piece Piston with a Low Top Ring and Large Diameter
The diameter of the top of the piston is increased to 135.3mm again. The distance between the top ring groove and the combustion face of the piston also increased by 3mm to 11mm. The window remained closed at a 25mm gap between crown and skirt.
6. Closed Window, One-Piece Piston with a Low Top Ring and Reduced Diameter
As with the two changes before, the only difference between this and the previous piston design is that the piston top diameter has been reduced to 134.86. The window is still closed, and the distance between the top piston ring and the piston face is the same at 11mm.
ISX Cylinder Liner Revolution
Just like with the pistons, all six cylinder liners must be the same type, otherwise potentially catastrophic things could happen to your engine. Open skirt pistons and pistons with a high top ring cannot be used with APR cylinder liners.
1. 150MM Grooved Cylinder Liner Without Shim
The earliest cylinder liner is 150mm in diameter and has a deep groove at the top of the liner. This is the only design that has that groove. No other grooves exist on the cylinder liner.
2. 150MM / 152MM Flat Top Liner Without Shim
The liner is called flat top because there is no groove at the top of the liner. The diameter can be either 150mm or 152mm. There are no grooves anywhere on the liner, for any purpose.
3. 150MM Flat Top Liner With Integral Shim
This liner continues the flat top design. It goes back to a 150mm diameter, which is measured at the mid-stop band. There is an integral shim incorporated into the liner. A single groove also appears at the bottom of the outer liner.
4. 152MM Flat Top Liner with Loose Shim
Another liner with a flat top design, this one does not have a shim integrated into the liner. The diameter, measured at the mid-stop band, goes back up to 152mm. Another groove appears at the bottom edge of the outer liner, making it have two grooves total at the bottom.
5. 150MM Flat Top Liner with Integral Shim and Scraper Ring
The diameter comes back to 150mm, and we also see the integral shim return. There are still two grooves at the bottom of the piston. There is also a new feature, called a carbon scraper ring or an anti-polishing ring (APR). This is a ring that fits into a counter bore made on the inside of the top of the cylinder liner, and it helps to scrape carbon from the sides of the piston.
6. 152MM Flat Top Liner with Loose Shim and Scraper Ring
The shim is no longer integrated into the liner, and the diameter bounces back up to 152mm. The double groove still appears at the bottom of the liner. A carbon scraper ring is still present.
Are your liners the source of failure in your engine? Check out our liner failure analysis to find out more.