Gapless top piston rings
Introduction
This modification is about almost completely removing compression and combustion blow by caused by standard piston rings.
Contents
Instructions for mod
This modification can be done to any widely used piston engine, carburated or fuel injected, past or present. The best time to preform this modification is during an engine rebuild. Any one attempting to do this will need to have a brand new engine block or have there old engine block bored and honed by a machine shop to an "over size" or "over bore" normally used on that engine type. Common SAE over sizes are +0.02, +0.03 and +0.04. The most common Metric over sizes are +0.5mm, +0.75mm and +1mm.
Over sized pistons will be required too.
Contact a "Total Seal Piston Rings" dealer for sizes and application.
User experiences
| User Name | Car Make, Model, Year | Cost of Mod | Time to Perform Mod | MPG Before Mod | MPG After Mod | MPG improvement guess | Instruction Link |
|---|---|---|---|---|---|---|---|
| oil pan 4 | none | between $10 and $30 per cylinder | 4 to 16 hours | N/A | N/A | The 3% dyno proven boost could mean a 1 to 2 mpg boost depending on base FE | User mod detail or measurement detailed data |
Problems / Consequences of mod
The side effect of any over sized cylinder bore will cause a slight increase in compression ratio. This coupled with the slight increase in dynamic compression ratio from reduced cylinder leak down during the compression stroke may require a small ignition timing adjustment to be made.
After running on the street for many hours and miles engines with gapless rings tend to see these ring gaps realign. Engine builders do not recommend gapless rings for street use. People who ignore this advice tend to end up with engines that burn oil. Most street drivers using gapless rings claim they will not use them again. Instead opting for standard file fitted rings, where piston ring gaps are custom filed to the minimum recommended gap for each cylinder.
