Cylinder Bore Scoring - Part 2: Does My Engine Have It? - with Lake Speed Jr.

In part one of our three part series on bore scoring, Lake Speed Jr. from Total Seal Piston Rings and Charles Navarro of LN Engineering discussed hypereutectic cylinder technologies such as Alusil and Lokasil, how exposed silicon particles and oil film formation support the cylinder/piston/ring system, and how to use a profilometer to evaluate surface finishes.

Now that we know how hypereutectic cylinder technologies function and why scoring can occur, determining if an engine has cylinder bore scoring is the next step.

The most common method to evaluate cylinders for scoring is to bore scope them. Although traditionally you would do this through the spark plug with the piston at BDC (bottom dead center), scoring usually starts at the bottom of the cylinder bore and the piston position can hide this wear.

Although more difficult, by placing the cylinder at TDC (top dead center), you can scope the cylinders through the sump area using a bore scope and inspect the bottom of the cylinder bore. Typically bore scoring in the M96 or M97 engine occurs in cylinder bank two, so that would be cylinders 4, 5, and/or 6.

If your engine already has symptoms such as excessive oil consumption, one tail pipe sootier than the other, misfires, or piston slap, inspecting cylinders 4, 5, and 6 will likely find scoring throughout the full length of the cylinder.

The other tool that can be used to detect cylinder bore scoring well in advance of symptoms is used oil analysis. LN Engineering uses and recommends SPEEDiagnostix (SDX) exclusively. Where other labs use the ICP method that can see particles up to 5 microns, SPEEDiagnostix uses the RDE method that can see particles up to 10 microns. With twice the resolution, you’re going to get the most accurate results. Although a spike in aluminum and silicon from the cylinder bores and iron from the piston skirt coating and piston rings are a good indication of cylinder bore scoring in progress on engines with Alusil or Lokasil bores, more important is having multiple samples from your engine to determine trend data for your engine. That way you know what is normal and when there is a jump, that you have a problem and can monitor it.

Beware some of the other labs out there that don’t know engines with hypereutectic cylinders - they commonly will tell owners that high silicon levels are because of a dirty oil filter, which couldn’t be further from the case!

SDX also uses gas chromatography to provide accurate fuel dilution measurement which is also another contributor to cylinder wear. Fuel is not a lubricant, so if your cylinders are being washed down with fuel, you’re losing the oil film required to lubricate and protect the rings, piston, and cylinder bores. More on this in part 3.

So when do you need to bore scope your engine? Ideally, you want to do this before you have a problem or symptoms, followed up with carrying out used oil analysis. These steps are very important if you are planning on buying a Porsche or any other vehicle with a hypereutectic engine block or cylinders and should be carried out as part of a pre-purchase inspection, or PPI.

Likewise, before you change your Porsche’s intermediate shaft bearing, scoping the cylinders is a must. This is part of LN Engineering’s pre-qualification procedure that should be carried out before installation of an IMS Retrofit or IMS Solution bearing in your Porsche Boxster or 911.

If there is bore scoring, the IMS bearing should not be replaced at that time until time when the engine can be torn down to address the cylinder bore scoring.

So if you find that your engine has bore scoring, what can you do? Is it terminal? Watch and learn.