I'm thinking about going with gapless rings, I don't see a reason to run a gapless 2nd ring, only the top, as it is the main pressure boundary. I have seen a couple of "tests" that didn't show much other than a supposed back to back test. does anyone have any scientific data to back up whether or not gapless rings are worth a damn?
These are the rings I was considering, it's a set for a V8, so I may be able to get them cheaper if I call total seal and order 6.
https://www.summitracing.com/int/parts/tsr-ms0394/all
Gapless rings
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ericjon262
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Gapless rings
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The Dark Side of Will
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Re: Gapless rings
Gapless 2nd rings are dumb. Never use them.
Gapless top rings are awesome. Always use them.
William's opinion is that gapless 2nd rings are just a bad idea that TS markets so that they can "upsell" to gapless top rings.
That being said, there are factors.
In a fresh build, there's little difference in performance between well fit conventional rings and gapless top rings. There are two factors that make the case for gapless rings:
1. Safety: The two components of a gapless ring can be gapped significantly wider than conventional rings with no loss of performance. This makes the engine much safer from ring butting in the less controlled environment of the real world, which includes bad gas, hot days, road trips and sitting in traffic.
2. Wear: As the bore wears, conventional rings open up, but gapless rings don't, preserving the engine's performance over a longer service life. This in turn lets less combustion gas into the crank case, which prolongs oil life, which keeps the engine running cleaner, longer.
Another factor is technology. In the Pro-Stock world of 500 cid naturally aspirated engines turning 10,000+ RPM with higher BMEP than F1 engines, a well-optimized ring pack can be worth 40 HP over a poorly optimized ring pack.
A higher tech conventional ring will out perform a lower tech gapless ring. Higher tech = thinner, lighter, steel (vice cast iron), tighter side clearance, gas ports. The way a high tech ring pack makes power is by having low tension to minimize frictional losses during the exhaust, intake and compression strokes, while utilizing gas ports to provide an excellent seal during the power stroke. A lighter ring with tighter side clearance will do this better at high RPM than a heavier ring with a looser fit.
1.5mm rings are old tech... basically the first step out of the stone age world of olde Chevy 5/64 rings.
That being said, my Northstar has a 1.5,1.5,4.0 ring pack. The 4.0 oil ring is an artifact of my thinking that I would dry sump the engine. The top ring is gapless steel, the 2nd ring is Napier profile iron. I wanted thinner top rings, but Total Seal's availability in my bore size (3.670) was poor at the time I bought mine. TS also did not make its own rings for that bore size. They bought rings and modified them to be gapless. That put me at the mercy of TS's supplier for dimensional accuracy. My first set of gapless rings with no special prep varied in thickness by 0.001 across most rings and ~0.0015 across the set. There's no way to run 0.001 side clearance on those rings. TS has a couple of optional treatments that involve fixturing the rings in the desired bore size and lapping them flat. The lower level "gold finish" was only available in bore sizes >4.000, so I had to spend more for the "diamond finish" on my rings. This made them essentially perfect within the limits of my capabilities to measure... <0.0001 thickness variation across any ring, 0.0001 across the set. I sent the rings to CP, who cut the grooves in my pistons to match the rings. Side clearance is around 0.001 and the combo makes great power.
I'm probably going to have lateral gas ports cut in my pistons when I have the engine apart to replace the low tension dry-sump oil rings with high tension wet sump oil rings. Gas ports may not actually do much because I have comparatively thick, high tension rings, but I'll give it a shot.
All of this is kind of moot if you're shopping for shelf rings because you're keeping stock pistons.
Gapless top rings are awesome. Always use them.
William's opinion is that gapless 2nd rings are just a bad idea that TS markets so that they can "upsell" to gapless top rings.
That being said, there are factors.
In a fresh build, there's little difference in performance between well fit conventional rings and gapless top rings. There are two factors that make the case for gapless rings:
1. Safety: The two components of a gapless ring can be gapped significantly wider than conventional rings with no loss of performance. This makes the engine much safer from ring butting in the less controlled environment of the real world, which includes bad gas, hot days, road trips and sitting in traffic.
2. Wear: As the bore wears, conventional rings open up, but gapless rings don't, preserving the engine's performance over a longer service life. This in turn lets less combustion gas into the crank case, which prolongs oil life, which keeps the engine running cleaner, longer.
Another factor is technology. In the Pro-Stock world of 500 cid naturally aspirated engines turning 10,000+ RPM with higher BMEP than F1 engines, a well-optimized ring pack can be worth 40 HP over a poorly optimized ring pack.
A higher tech conventional ring will out perform a lower tech gapless ring. Higher tech = thinner, lighter, steel (vice cast iron), tighter side clearance, gas ports. The way a high tech ring pack makes power is by having low tension to minimize frictional losses during the exhaust, intake and compression strokes, while utilizing gas ports to provide an excellent seal during the power stroke. A lighter ring with tighter side clearance will do this better at high RPM than a heavier ring with a looser fit.
1.5mm rings are old tech... basically the first step out of the stone age world of olde Chevy 5/64 rings.
That being said, my Northstar has a 1.5,1.5,4.0 ring pack. The 4.0 oil ring is an artifact of my thinking that I would dry sump the engine. The top ring is gapless steel, the 2nd ring is Napier profile iron. I wanted thinner top rings, but Total Seal's availability in my bore size (3.670) was poor at the time I bought mine. TS also did not make its own rings for that bore size. They bought rings and modified them to be gapless. That put me at the mercy of TS's supplier for dimensional accuracy. My first set of gapless rings with no special prep varied in thickness by 0.001 across most rings and ~0.0015 across the set. There's no way to run 0.001 side clearance on those rings. TS has a couple of optional treatments that involve fixturing the rings in the desired bore size and lapping them flat. The lower level "gold finish" was only available in bore sizes >4.000, so I had to spend more for the "diamond finish" on my rings. This made them essentially perfect within the limits of my capabilities to measure... <0.0001 thickness variation across any ring, 0.0001 across the set. I sent the rings to CP, who cut the grooves in my pistons to match the rings. Side clearance is around 0.001 and the combo makes great power.
I'm probably going to have lateral gas ports cut in my pistons when I have the engine apart to replace the low tension dry-sump oil rings with high tension wet sump oil rings. Gas ports may not actually do much because I have comparatively thick, high tension rings, but I'll give it a shot.
All of this is kind of moot if you're shopping for shelf rings because you're keeping stock pistons.
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ericjon262
- Posts: 2824
- Joined: Mon May 24, 2010 5:34 pm
- Location: Aiken, SC
Re: Gapless rings
TS offers a 1mm top ring in my bore size, but I'm not really interested in swapping pistons at the moment, and the current ring pack is 1.5/1.5/3.0
I like the idea of the longer service life, and more importantly, a larger safety margin, which is really the main reason why I am considering them. I'll have the engine apart enough that it won't be a burden to swap the rings, I may just leave the stockers in there though.
I like the idea of the longer service life, and more importantly, a larger safety margin, which is really the main reason why I am considering them. I'll have the engine apart enough that it won't be a burden to swap the rings, I may just leave the stockers in there though.
"I am not what you so glibly call to be a civilized man. I have broken with society for reasons which I alone am able to appreciate. I am therefore not subject to it's stupid laws, and I ask you to never allude to them in my presence again."