Piston Rings
 

Few weeks ago, was at a trade show, where Mahle had a seminar on piston rings. Started talking with the rep from Mahle, in regards to piston rings and what not. I asked him about "gapless" rings. His general opinion, was that they aren't all they are hyped up to be. Years ago, with alcohol engines, they did help keep fuel out of the crankcase. Modern gasoline engines, he felt they aren't warranted. He did say, if you like low "leakdown" numbers on a gauge, they are the ring for you. I mentioned to him, that dan (icdedppl) and I, have supercharged bbc pump gas marine engines, 800-900hp, and are running Plasma moly file fit rings, he said "perfect, thats exactly what I would recommend for that) so it wasn't like he was trying to promote his product to us.

Mahle supplies many of the OEM's with pistons and ring packages. He had a time chart, that showed how piston ring technology has evolved over the years, from a durability standpoint. Where in 1970, it was typical to burn 1qt of oil per 1500-3000 miles. By 1985, 1qt per 4000-5000 miles, and 2010, 1 qt per 7500-10,000 miles in engines. These evolutions, had nothing to do with ring gap, but instead with ring tension, radial wall/thickness, and so on.

They supply pistons and rings to the factory race cars, like the hemi and copo camaro, etc. Considering the amount of money that General motors, Daimler chrysler, Ford Moco, BMW, Honda, and all of them have behind them, I would like to think that if the gapless patented total seal piston ring design, worked so great, that they would easily cut a check to the owner of total seal, and send him off into retirement, along with his great grandchildren. Mahle's aftermarket division, has 22 locations world wide, and did 836 million in sales in 2014, with 1600 employees.

Does anyone know of an OEM vehicle, that is using total seal gapless rings in their engines?

i have used a lot of the total seal gapless rings with good results BUT i also have used their ap file fit rings with the same results so for me i am kind of getting away from the gapless rings because i am not seing a gain from spending the extra 200 bucks,plus it is more work with the gapless ring and you really need to take your time when installing the piston.jmo.

joe,i will also add that i have seen the equipment that gm&ford are using to bore&hone the cylinders and unless you are made of money no shop could afford to buy that equipment.almost all the gm engines are built by robots&million dollar machines these days.i remember when in the 60s&70s the factory rings were junk before 100 thousand miles,today the cylinder finish and ring material they they put out will last damn near forever.hell i have a 2003 gmc 2500 with a 6L in it with over 150 thousand miles on it and i beat the snot out of it,i change the oil every 5000 miles and it is not even a half quart low at 5000 miles.

crazy isn't it mike. My last two ford 4.6 engines, one had 240k , other 170k. Neither of them consumed oil. Of course far cry from a high perf marine engine, but still cool .

Something I noticed about the 2008 Hemi I have. First engine lasted to 192k miles, before it dropped a valve seat. Weird thing, for like the first 50k miles or so, it would burn at least a quart between oil changes. Sometimes even more. At some point, I don't recall when, I switched from 5w20, to 5w30. I noticed it had stopped using oil between changes.

Anyhow, after the engine expired, I got a new (not reman) engine for it. It now has 30k miles on it. Changed the oil yesterday, and it was down almost 2 qts. Had about 5-6k miles on it. I had used synthetic 5w20 since the new engine went in. I am thinking of trying the 5w30 again, and see if the oil consumption decreases like it did on the first engine.

i can tell you that my 2012 honda accord calls for 0w20.i noticed it would use a quart or so in 5000 miles,for chits&giggles i tried 5w30 and it used no oil.the car stays in the heated garage most of the time so i am going to stick with the 5w30.with the 0w20 it would blow a puff of smoke upon startup,i don,t see that with the 5w30,i forgot to mention i use mobil one in all my late model cars.i am thinking honda calls for the 0w20 to help gas mileage numbers,idk.

Good info guys. Doesn't get discussed much and valuable information for everyone. Btw joe 240k pretty good for a ford. Lol... John Sr would disagree but he's a Ford guy.

I think one of the problems with recommended oil is that the manufacturer is forced to meet fuel mileage and EPA standards so that helps get them there. my '96 GMC 3500 7.4 gas motor has had 15-50 mobile 1 synthetic since it was new and now with 280,000 hard miles it still holds the same oil pressure as new and uses less than a quart every 5000 or so. as for the gapless rings, if they were that great an improvement then, as said above, the OEM's would be all over them to help meet the mileage and exhaust standards.

I think your all on the right track. For a short time Audi ran a loose piston to wall clearance with low tension rings to meet carb standards, they where using a lot oil, customers that barked the loudest got new pistons and rings. They have to be making a killing on those cars to cover such a bold move. Mike tKach post, it fits cheap way to free up an engine thin oil.

I built a couple of 509's for a friends Campion chase. I hate to say this, I have never done this before and will never do it again, long story. Both engines were built exactly the same except for rings. I had Plasma moly file to fit in one engine and total seals file to fit gapless rings in the other. After we broke them in, we gave them a wide open run. He said what's up? I have to throttle back the port engine to keep them in sink. I didn't have the heart to tell him that I had put the gapless rings in the port engine and not the other. I had built the engines the first go around with molly rings and they didn't have this issue. That is the only real test I have.

file to fit gapless?? boy am I behind the times, tonight is the first time I have heard of a gap less ring. Gonna give my Mech friends a poke. That sounds intreging except for the file fit, I'm frigen sick of fileling rings.

i doubt the gapless rings had any thing to do with one engine not keeping up with the other.something else has to be wrong.

file fitting the rings is a piece of cake if you buy one of the fancy 800 dollar ring filers.if trying to do it with the old hand operated deals it sucks.

I stopped using gapless rings about 10 years ago. I wasn't happy with the way they sealed on my engines. They consumed about a quart of oil every couple of hours and would pop the dipstick under boost. I was told the wrong cylinder wall finish was probably the cause but every engine I've torn apart since then that had oil consumption issues, either had GM Metric rings or Gapless rings with glazed cylinder walls. I'm not a believer in the gapless, not my cup of tea.

I have never tried the gapless, so no comment there, but after doing 3 different BBC drag race builds my machinist got a new very expensive honing machine. I will have to say that this last build with a hone from this new machine seemed rougher than normal but this motor sealed up fast and has no blowby. I have used the same ring pack on all 3 motors. The motor I just buillt for my boat also has this diamond hone but I cannot comment yet as it only has dyno time. All of them have file fit rings and really is not a big deal if you have time and pay attention. I use the summit hand filer screwed to a bench.

The total seal rings still need to be file fit...it's double the work

all my parts will be here by tomorrow this is my first marine build, ring gap? is marine different from standard automotive, I run in lake Michigan cold water? never seen water temp above 160 seems low to me, do I tighten the gap or did some idiot put the wrong thermostat in her. The later seems more likely bought it cheap cheap, timing was retarded 12 degree, junk carb I got two good seasons out of it before the fuel pump filled the crank case with fuel and washed the bearings. not a hint of ridge on the bores, this boat spent most of its time tied to the dock with leaky risers.

No need for less than 5-30 synthetic, unless you want to use oil. Done this 'experiment' on 100's of cars for 100's of thousand of miles.

5w-30 was invented for better fuel economy also ,,, way back when but does well with modern engines.

The lighterweight oils are all about fuel economy. Read about C.A.R.B. and you will really realize what the manufacturers are up against with fuel mileage...especially Ford.

Thickness and tension of the rings seems to be the biggest + or - horsepower 'effecter' with rings.

I went to gapless in the street car and pan vacuum went down significantly and blow by from the vacuum pump did too. So I put them in the boat, 8 hours so far so good..

I dont necessarily think they are bad by any means. I know lots of guys like them and use them. On the flip side, i know lots of guys who use them, and have blowby issues at high rpm, even though leakdown gauge shows 5% or less.

Yeah we will see how they hold up to the nitrous this season, :party-smiley-004:

I agree. The whole gapless thing sounds great, and at first thought, would lead you to believe that not having a top ring gap, can only help reduce psi loss, compared to whats lost , thru a conventional ring gap.

But how big of a gap are we talking about. Lets say a 540ci, with a 4.500 bore. Even in a blown application, and say .027 gap cold. We know the gap gets smaller as the piston warms up. How much, idk, lets say it shrinks to .010. Then , you only have a small portion of this gap, between the bore and the piston exposed. Depending on the piston width and bore clearance.

Point being, this gap under running conditions, is very minimal. Probably why like you said, the power gains have been proven to come from ring tension, thickness, cylinder honing procedure, and block/cylinder rigidity . If ring sealing for max power was my goal, id be looking at a nice solid merlin , dart style block with thick cylinders that wont distort , good machine work and assembly. Seems like those things,, are more important than whether the ring has a gap, or doesnt. Both designs seem to work well, if all those things are considered, and both wont work well if they arent.

I do have to agree on blocks. I just got my big m back from my friend who is a machinist and he said that with the deck plates on it only took .0003 to clean up. That is impressive being a gen 5 I had him do before was close to .002 out with deck plates on.

Maybe I'm old school but I'm not quite sold on the thin metric rings just yet. I know they're supposed to free up HP but on some of the big bore engines I've torn down with metric rings, the sealing wasn't the greatest and they were oil burners. Could have been the skirt design on those engines (very short) as well but I'm not sold just yet.

My machinist also had similar feedback and they told me that they burn through a lot more stones with the Dart blocks as the metal is harder to cut and it takes a lot longer to machine.

Some of gm and hondas short skirt , low tension designs had some issues with piston slap and oil consumption for sure but alot of the engine guys swear thats where the internal friction gains are made or lost. Finding that balance . I remember hearing some of Lingenfelters stroker motors on cold start, make some alarming amounts of piston slap. But they made huge power and stayed together.
Honda is back to thinner low friction rings , and there have been some problems with them having gaps line up and the rings not seating properly , then what happens is the oil comes up and cokes up in the ring lands and really causes sealing issues. Wouldnt anticipate that in marine enviroment with more frequent oil changes most see.
I would trade some oil consumption , minor of course , for a handful of free horsepower personally.

Subaru uses low tension rings as well and has had problems with oil consumption, especially with their 2.5L boxer that calls for 0W20 synthetic. My wife has one in her '15 Legacy. The oil consumption problem was supposed to be fixed for her model year but dealerships are performing oil consumption tests and putting long-blocks in '15's and up as well as the older models. Wife's car uses 1 qt. 0W20 M1 every 5K. I've not owned a new car that touched a drop of oil since my '94 Bonneville that had bad valve guide seals from new. I run 5W30 instead of 5W20 in my Ford trucks (5.4L and now 5.0L) but not sure how the Subaru boxer engine would take the heavier oil. Wife's old '10 Accord didn't use oil running 5W20 and neither does my son's '16 Wrangler JK.

An aside about Mahle-

Another forum I visit has a frequent poster that works for Mahle. I'm not sure of his exact title, but the way he discusses how they build and gauge pistons is incredible. Holding 0.0001" dims on huge production runs, designing pistons with a profile such that the piston's deflection works in their favor, all sorts of extremely intricate stuff. Most of the info is relatively sanitized but reading through all of it gets you a clear message- Mahle runs one hell of a production facility.

Post #6
http://www.practicalmachinist.com/vb...istons-167754/

If you talk to good ring guys at Total Seal, they will tell you not to use gapless rings in anything other than a race car that sees just WOT. Any engine vacuum/part throttle they will oil pretty damn good

Plasma moly rings are ok, but the application of the moly has changed and is subject to breaking off. I use a moly ring from CP I believe comes from total seal. This I use on a NA application. This may include a Napier 2 nd and low tension low control.
Supercharged I use a Hell Fire on lower HP builds and a Gas Nitrided steel top ring on the higher HP. This will include a Napier and low tension oil control. Cylinder finish changes with each change of ring pack. Long ago I used a gapless 2 nd ring, I was steered away from that, by CP engineer, he explained what happened and how important opening up the 2 nd ring end gap was. We talked about gapless top rings, there is a very critical fit with those two rings, if one thing goes wrong with the fit or the tune, it's all over with. The 2 nd ring doesn't seal compression, nor is it a back up. The Napier 2 nd is actually wiping the oil from the cylinder wall.
If the combustions pressures build between top and second ring, both rings become pissed off and ring seal is lost.
Gas porting aids in ring seal, but in endurance applications, prematurely wears rings and cylinders.

99% of Blowby and Oil consumption issues are due to Incorrect Honing Procedures . Piston Ring design has less to due with sealing than most think, just with oil control and friction. If you find a ring pack that fits your particular cylinder wall finish specs , it will stand out amongst the other designs. I know about all the napcar builders use Mahle pistons ,
and about half of them use either Rikken or Total Seal rings and not the gapless ones over the Mahle rings. Ive participated in dozens of piston - ring - cyl wall finish tests.
The biggest common denominator is Cyl Wall Finish , AKA honing procedures. Every ring wants a uniform cross hatch , nice flat plateau , and very little burr in the crosshatch. We tried the smooth as hell finish on some of the production race engines , to cut down on friction , all they did was eat oil and smoke! Ring faces were burnished and so were the bores. The rings just slid across the bore and never sealed up.
The only honing stones capable of this are diamond , and believe it or not you need an automated hone . The old crown wheel hones do an excellent job also , but
your finish will not be quite as accurate and your ring seating cycles will take longer . Also your honing oil needs to be clean,clean, clean! Ive seen microscopic shots
of cylinder walls with broken down abrasive and cast iron stuck in the plateaus! The engine would not seal up , it just destroyed the ring faces. What it boils down to is , an old cast ring will seal up on about anything , for alittle while . But the newer metric , and tool steel rings need a very specific honing procedure to make them work.

I sold a '04 Ford Mustang Cobra prior to buying my boat. They are blown (supercharged) 4.6's from the factory and the engines are hand assembled using Mahle pistons and file fit rings. The OE engines were are good into the 750 hp realm without issue. When built most of the big wig's were using Total Seal file fit rings over gapless to well over 1300 hp, ring material varied by builder.............for reference.

a $1200 ring filer makes the job go well