Keith Jones from Total Seal Piston Rings recently introduced the new Mitutoyo SJ-220 profilometer, and for engine builders who care about cylinder bore finish, this is a significant update. The SJ-220 replaces the recently discontinued SJ-210 and brings a new chassis, updated controls, a color touchscreen, USB-C connectivity, and optional Bluetooth wireless capability. For anyone who measures cylinder wall finish, deck surfaces, or other critical machined surfaces, the new SJ-220 looks like a major step forward.
Keith has spent decades working with profilometers and cylinder bore surface finish, going back to older analog machines, large SJ301 units, paper printouts, and earlier portable Mitutoyo models. Over time, the portable Mitutoyo units evolved through models such as the SP211, SJ201, and SJ210. Those earlier units shared a similar physical platform, with each generation adding more capability. The SJ-220, however, is not just another feature update. Keith describes it as an all-new handheld unit and calls it a “game changer.”
Why a Profilometer Matters in the First Place
Cylinder bore finish is one of the most important details in building a reliable, powerful engine. It is also one of the most misunderstood. Many people look at a fresh hone pattern and assume that if the crosshatch looks right, the cylinder finish must be right. The problem is that appearance alone is not enough.
A profilometer measures the surface finish so the engine builder can verify what the cylinder wall actually looks like at a microscopic level. That matters because piston rings are lubricated parts. They need a controlled oil film between the ring face and the cylinder wall. That oil film does two jobs at the same time: it lubricates the ring and also helps seal the ring against the cylinder wall.
Lake Speed Jr. (The Motor Oil Geek) has explained this concept well in previous Total Seal educational content. The oil on the cylinder wall acts like a moving gasket. Since oil is not a fixed gasket, the cylinder wall must have the right surface texture to retain it. The valleys in the cylinder wall hold oil, while the peaks and plateaued areas help support the rings. If the surface is too rough, it can wear the rings. If it is too smooth or lacks enough valley depth, it may not retain enough oil. Either condition can hurt ring seal, increase wear, reduce horsepower, and shorten engine life.
It's even worse with Nikasil - if it's not honed perfectly - you'll know almost immediately. Engines will burn oil, smoke, and ultimately fail in hundreds, not thousands, of miles. That's why LN Engineering uses their SJ-210 and SJ-220 along with Digital Metrology's TraceBoss+ to make sure every cylinder that leaves their shop has passed their quality control checks.
That is why a profilometer is not just a fancy measuring tool. It is the only practical way to confirm that the hone finish matches the piston ring package, cylinder material, fuel type, and application.
Not checking your cylinders and assuming they are honed correctly is like playing Russian roulette.
The SJ-220: A New Handheld Profilometer from Mitutoyo
In Keith’s SJ-220 video, the first thing that stands out is that this is not simply an SJ-210 with a new label. The SJ-220 has a new case, new body design, updated ports, and a color touchscreen interface. Keith highlights the unit’s USB-C connection for charging and computer communication, along with an optional Bluetooth module that allows wireless operation when paired with the proper software.
The kit includes the main SJ-220 unit, the detector or stylus assembly, a calibration reference, a calibration stand, the extension cable for the detector, charging hardware, multiple international plug adapters, a printed manual, and digital documentation. The extension cable is especially important for engine builders because it allows the detector to be separated from the main unit and positioned down inside a cylinder bore.
That detail matters. Measuring a flat coupon or deck surface is one thing. Measuring a cylinder wall requires getting the stylus into the bore, holding it steady, and allowing the motorized detector to trace the surface properly. The extension cable makes that possible.
The Color Touchscreen Is a Major Usability Upgrade
One of the most noticeable changes on the SJ-220 is the touchscreen interface. Earlier SJ-series units were menu-driven through buttons. They worked well, but setup and navigation could feel less intuitive, especially for users who did not use the tool every day.
The SJ-220’s color touchscreen makes it easier to move through menus, check traces, change settings, access calibration, and configure wireless features. For shops that use a profilometer regularly, this can save time. For users who are newer to surface finish measurement, the interface may also make the unit less intimidating.
Keith calls the SJ-220 the best handheld unit on the market, largely because it combines portability, capability, and modern usability in a compact tool. Although a skid-less profilometer is better, it's hard to argue with the price tag for the skidded SJ-220 that comes in 60-70% less than a skid-less.
Setup Still Matters
Even with a newer unit like the SJ-220, the fundamentals of setup still apply. The prior SJ-210 setup guidance remains useful because the same basic measuring principles carry over: the unit must be charged, calibrated, configured for the correct surface parameters, and used carefully.
In the earlier SJ-210 setup video, Keith emphasized that the battery should be kept charged because the unit stores customized settings. He also explained that the detector, or stylus, is a delicate and expensive part that should be handled carefully. The stylus should not be dropped, dragged through dirt, or used on an oily or contaminated surface. The cylinder should be clean before measurement, using a suitable cleaner and wipe-down procedure so the stylus is reading the surface finish rather than debris, oil, or honing residue.
That guidance applies just as much to the SJ-220. A profilometer is a precision instrument. If the stylus is damaged, contaminated, or used incorrectly, the readings will not be trustworthy.
Calibration Is the First Step
Before using a profilometer to measure a cylinder, it needs to be calibrated against a known reference. In the SJ-210 setup video, Keith used the supplied calibration reference and stand, noting that many of the references are around 116 Ra, though the exact value can vary slightly depending on the reference included with the unit. The calibration value printed on the reference is the value the profilometer should be set against.
During calibration, the stylus traces the reference surface and the unit compares the measured value to the known value. If the unit reads slightly off, it can be updated so it matches the calibration standard. Keith also points out that profilometer readings will not always be exactly identical on every pass. Small variations are normal. Large differences, however, can indicate a problem with the setup, the surface, or the stylus.
That is important when measuring cylinder bores. Surface finish is not a single perfect number everywhere in the bore. The goal is to measure consistently, understand the normal range, and identify whether the finish is appropriate for the application.
Important Surface Finish Parameters
For cylinder bore work, Keith’s SJ-210 setup focused on turning on the parameters most useful for engine builders: Ra, Rk, Rpk, and Rvk. Although the SJ-220 uses a new interface, those same measurements remain central to understanding bore finish.
Ra is the arithmetic average roughness. It is the most familiar surface finish number, but it does not tell the whole story. Two surfaces can have similar Ra values and still behave very differently with piston rings.
Rk represents the core roughness depth. It gives a better picture of the main working surface that supports the rings after the initial peaks have been worn or plateaued.
Rpk represents reduced peak height. This helps describe the remaining peaks on the surface. Too much peak height can increase ring wear during break-in.
Rvk represents reduced valley depth. This is especially important for oil retention. The valleys hold oil on the cylinder wall so the rings remain lubricated and sealed.
This is why Keith and Total Seal place so much emphasis on profilometer readings rather than visual inspection alone. A cylinder that “looks good” may not have enough valley depth. Another may have excessive peaks that create unnecessary ring wear. Without measurement, it is guesswork.
Measuring Inside the Cylinder Bore
When measuring a cylinder bore, the detector can be removed from the main profilometer body and connected with the extension cable. This allows the stylus to be positioned inside the cylinder. Keith also shows the value of a holding fixture that stabilizes the detector inside the bore. A steady fixture helps prevent false readings caused by hand movement.
The stylus itself is motorized. The user does not slide the whole unit up and down the bore. Instead, the detector performs the trace. If the operator moves the detector during the measurement, the reading can be distorted.
This is one reason technique matters. Clean the bore, position the detector carefully, keep it stable, and let the profilometer do the work.
What the Readings Tell You
In the SJ-210 setup example, Keith measured a diesel cylinder and reviewed the results for Ra, Rk, Rpk, and Rvk. He described the example finish as having a reasonable plateau, good valley depth, and a useful core number. That kind of interpretation is the real value of using a profilometer. The tool does not just produce numbers; it gives the engine builder a way to evaluate whether the honing process produced the desired surface.
The correct finish depends on the application. A naturally aspirated gasoline engine, turbocharged engine, methanol engine, racing engine, and street engine may not all want the same cylinder wall profile. Ring material, ring tension, cylinder material, honing abrasive, and intended use all matter.
This is also where Total Seal’s application-specific recommendations become valuable. The profilometer tells the builder what the surface is. The ring manufacturer’s recommendations help determine what the surface should be.
The SJ-220’s Connectivity Advantages
The SJ-220’s updated connectivity is one of its biggest advantages over older handheld units. USB-C charging and computer communication make it more convenient than previous models. The optional Bluetooth capability is also a major improvement for shops that want to collect readings wirelessly with compatible software.
For professional engine builders, documentation is becoming increasingly important. Being able to save and transfer surface finish data helps create build records, verify machining quality, and support quality control. When an engine leaves the shop, having actual measurements is far better than relying on notes that say the finish “looked good.”
A Better Tool for a More Demanding Job
Modern engine building has become more precise. Piston ring packages are thinner, cylinder materials vary widely, and expectations for power, durability, and oil control are higher than ever. Surface finish is no longer something that should be left to feel, appearance, or habit.
The Mitutoyo SJ-220 gives engine builders a modern handheld profilometer with updated controls, better usability, USB-C connectivity, optional Bluetooth, and the same basic measurement capability that made earlier Mitutoyo units so useful in the engine world. For anyone honing cylinders, checking finished bores, documenting surface finish, or troubleshooting ring seal issues, it is a serious tool.
Final Thoughts
Keith’s enthusiasm for the SJ-220 makes sense. A good profilometer helps take the guesswork out of cylinder finish. It allows the engine builder to confirm that the bore has the right balance of peaks, valleys, plateau, and core roughness for the ring package and application.
The older SJ-210 setup lessons still apply: calibrate the unit, protect the stylus, keep the surface clean, use the correct parameters, stabilize the detector, and understand that the numbers need to be interpreted in context. The SJ-220 simply brings those same essential practices into a newer, more capable handheld platform.
For engine builders serious about ring seal, horsepower, oil control, and durability, a profilometer is not optional. It is the measuring tool that shows whether the cylinder wall is ready to do its job.
No comments:
Post a Comment