low tension rings

There are some really informative post here and I always appreciate knowledgeable people sharing. I agree with PD on the gaps not being that important. The second ring should always be a larger gap. I agree with all that Brian offered up and find him to be a wealth of knowledge. I have not built a flathead but if I do, thanks Brian.

Going forward on the Circle Track article this is not a good comparison. When Randy Dorton was alive Nascar was allowing high compression ratios. They now limit the compression to 12 to 1 and Unleaded gas. The second ring is used primarily for oil control. Oil slipping by the rings causes detention. When the change away from the old 23 degree heads and very high compression ratios were possible I learned quickly that the cams had to be changed but equally, the oil control became critical. I added the second ring, valve seals, widened cam centerline and later a vacuum pumps to the crankcase. The time spent on these motors to keep the oil away from moving parts to reduce drag was considerable. We realized large hp gains from these things. Keep in mind that the Nascar engines are spraying their valve springs and the bottoms of their pistons for cooling purposes. The rings that they took out for the test was a back cut low tension rings and not the crude piece that we have to work with. I raced many years with only a top ring and ultra low oil tension rings. The added compression ratios changed everything! I do however agree that sealing up a motor is critical and there are other things to be done to accomplish this. My latest motors have some of these new innovations. Keep in mind I build open animals and just built my first UAS motor (Honda 450) and raced at my first UAS event at DVR. I am always trying to learn more.

When I was racing an animal limited I crudely took tension from the second ring. I just tried not to warp it so that it would not bind in the piston and yes it helps. If I could take it out I would.
 
jjchat said:
I believe ring prep is very important for a good performing motor. However, I believe seal is 10x more important than drag. I spend my time accordingly.
Click to expand...

In my opinion, I think that ring tension can be compared to what I did when I road-raced vintage motorcycles and sought out all the weight reduction possible. Using center drilled titanium or aluminum bolts doesn't hep much when you only use them on say, 4 locations on the bike. However, when you used them on every (safely) possible location, you could save a lot of weight. Machining out extra material from one component doesn't help, but "swiss cheesing" every possible part does. Now if you do all of these things you'll cut an incredible amount of weight and your power to weight ratio will go up. If you do a couple, it's not worth your time.

It all depends on the level that you want to achieve. If you have spent a lot of time and $ to build the best performing engine possible, then low tension rings are just one of dozens of things you've done that will add up to a significant benefit.
 
The amount of decrease in ring tension and increase in Hp is dependent on how much ring tension you had originally.
But if the total is only 1% i'll gladly take it.
I'd much rather have 606 HP than 600.
If i have 6 HP more than the competition i'm a real happy camper.
 
^ Which is why some engines have a rule on ring tension. If there were no advantage, there would be no reason for the rule. Well, for the most part anyhow. :)
 
Run 'em the way the manufacturer says to run 'em. Period.
Get what you want, from the manufacturer. Their engineers know more than you or I do about the subject. AND they engineer for the same things you want in a ring. That is, efficiency.
 
HMMMM Idon't think so

PD Power said:
Run 'em the way the manufacturer says to run 'em. Period.
Get what you want, from the manufacturer. Their engineers know more than you or I do about the subject. AND they engineer for the same things you want in a ring. That is, efficiency.
Click to expand...

Have not chimed in for a while as there has not been lots to input. But PD once again I have to totally disagree. I would definitely want you as my competition as far as an engine builder if you don't feel it is an advantage. I spend more time on ring seal and honing and tension than any other part of a competition build. If it is just a regular non competition rebuild I agree but you are way off on this one if we are talking performance.

Greg
 
But Jimbo, on a 12 HP motor, how much do you think .012 advantage is? Furthermore, according to Randy Dorton, that was not detensioning rings but rather the outright removal of the second ring. Would detensioning to rule specs gain you half that much? How much work and expense are you willing to go to for .006?

Not saying there is no gain, but wondering how much gain are people are actually getting via dyno-testing when detensioning the middle ring? How are you testing this?
 
Conspicuously absent from this discussion is the effect on engine longevity. How often do you / your customer want to rebuild the motor?
 
Chipg56 said:
Conspicuously absent from this discussion is the effect on engine longevity. How often do you / your customer want to rebuild the motor?
Click to expand...

Absolutely there is that fact as well. And with all due respect to a genius like Randy Dorton something is missing with the above comments. what works or doesn't work in a Cup motor has no bearing on our little splash oiled motors. remember a Cup motor has a vacuum pump and what happens under vacuum is totally different. But what I think Jimbo and others are saying is that when you are building an all out race engine the little things that say I do that you may not be doing can add up if we are counting all the small things. The removal of the second ring in some cases will offer gains in others it will likely hurt. Depends on how the top ring is working and its design. Is it a Dykes ring is it a barrel face ring is it a zerogap ring is it a torsional twist I think you get the picture. If you don't believe the second ring is worth horsepower your missing the boat in my opinion. I was always told that the second ring is more of an oil scraper than a compression ring. Remember our motors have a ton and I mean a ton of windage. That second ring in my opinion still needs to be there as an oil scrapper. But it does have lots of tension just like the true oil control ring does. I learned lots about rings by some very very well respected guys that were building pro race engines before I was born just as notable as Randy and unfortunately two of them have since passed away.. There are things to remember the top ring stays seated better if the second rings lets the small amount of blow by gases past and out the bottom lessening the unseating affect called flutter. If you detention too much I assume that the seating that occurs on the top ring from the combustion expansion gases getting in behind the lands on the power stroke may be lost. Not sure as I am theorizing. I do know this that I worked with Dave Fussner of Wiseco R/D on two ring pistons over a dozen years ago and there is HP in ring combos etc. If you don't think so why the heck do all true hp pistons now use 1mm or less thickness rigs. It is all about the frictional losses. The rings are the highest frictional loss area of the entire motor. Here is a piston I designed with Wiseco over a dozen years ago when strutted slipper skirt designs were just taking off in elite race motors only at the time. This piston was originally designed for the V-Rod stroker kits offered by Wiseco same bore and compression height pin location as BB Mopar. The pictured piston is for a BB Mopar drag motor. It utilizes two rings and 1mm compression ring as well as S/B Chev pin very light piston likely the lightest BB Mopar piston ever built. It also uses radial porting a heat dam as well as pin ovality reduction technology.

Greg
P1080804_zpse8b9aedb.jpg


P1080805_zps202b1a3a.jpg
 
John
There are more rings on the piston than just the second ring.
 
JJ, I may be way off base here, but it was always my understanding that reducing drag was MORE important on a single cylinder engine than a V8. Since the flathead days I have always measured ring tension in my engines, and I can tell you, it is worth it. And I would recommend ALL of my competitors to ignore this advice. :)
 
Jamie Webb said:
JJ, I may be way off base here, but it was always my understanding that reducing drag was MORE important on a single cylinder engine than a V8. Since the flathead days I have always measured ring tension in my engines, and I can tell you, it is worth it. And I would recommend ALL of my competitors to ignore this advice. :)
Click to expand...


Too funny but true!!!

Greg
 
while i dont know the exact composition of the rings used, i can say that the typical situation is this. lowering the hardness wont really affect modulus of elasticity dispite the drop in ultimate tensile strength. unless you platicly deform the part or do a partial temper you will not change ring tension. deformation is not something i would want to do to a ring and maintain sealing. partial temper/heat treat on a part that small is VERY difficult to handle but this would allow higher stress on the outer surface which would draw the ring closed(the same principle behind the curvature of a samuri sword). the only other option i could think of is to decarburize the ring, copper coat. remove coating from outer ring, recarburize to proper level then heat treat again. none of these options are viable without some very high quality equipment and an exact process as the time windows would probably be in the less than a few seconds range for the variable temperature ranges required
 
Ok, so to play devils advocate, how would you quantify the reduction in drag on a running engine? Certainly most of you know that ring seal, especially the compression ring, is accomplished by cylinder combustion pressure and not static ring tension.

Jamie, what sort of tool did you make or buy accurately to measure ring tension?

Wish I had the time to make a longer post.
 
On my racing V-8's we just used a torque wrench to spin the motor over without valve springs and this for the most part carried over to the Dyno. You are correct about the rings not loading like a running motor. We did have gas ported pistons. Some state of the art race shops have used one motor to spin another and measure the hp needed to do this. The results? It generally takes about the same amount of power to spin the motor as it makes. Ring tension reduction can be worth allot of power especially the expander on the oil scrapper. Reducing friction in a motor can reap big rewards if you know where to spend your time. My motors get many hours of friction reduction. I am not talking tenths of a hp gains either.
 
Chipg56 said:
Ok, so to play devils advocate, how would you quantify the reduction in drag on a running engine?
Click to expand...
Dyno.
Chipg56 said:
Certainly most of you know that ring seal, especially the compression ring, is accomplished by cylinder combustion pressure and not static ring tension.
Click to expand...
I do not shrink/detension the compression ring, ever. Any time I have ever tried altering the compression ring (even with fixtures) I warped it and lost ring seal. To me, it's not worth it. I spend my time on the scraper & oil ring. But beware (most already know this also) you can go TO FAR on the oil ring. Even if you don't go far enough for it to smoke, you can go far enough you WILL have problems with the oil ring cracking.

Chipg56 said:
Jamie, what sort of tool did you make or buy accurately to measure ring tension?
Click to expand...
Nothing more than a scale and a fixture to set it up in. I use the same fixture I use to deck my blocks to hold the engine then mount a scale between the piston & mill chuck with a piece of 2" alum round stock between piston and scale.
 
Wes Snow said:
Some state of the art race shops have used one motor to spin another and measure the hp needed to do this. The results? It generally takes about the same amount of power to spin the motor as it makes. .
Click to expand...

If it takes the same amount of power to spin the motor as the input power the net speed of a racecar would be ZERO. Are you sure about this FACT?
 
rib said:
If it takes the same amount of power to spin the motor as the input power the net speed of a racecar would be ZERO. Are you sure about this FACT?
Click to expand...

An example: A 700 hp motor would take 700 hp to spin at high RPM. With no friction the motor would make 1400 hp.
 
You must log in or register to reply here.
Back
Top