I'm thinking about building a motor, or having on built, that's tighter than the usual built motor. Specifically, in the ring area. I want to know more about ring tension, and how I would go about increasing it. Would I just have a smaller ring gap? Do I need to have the rings made so that the overall tension is greater ? Can one do that ? I'm kind of trying to figure out how to decrease blow-by. I was talking to a friend about running synthetic oils in their drag car. He says they run good old Valvoline because they lose horsepower with the synthetics because the rings unseat themselves. Can sonmeone offer insight? Thanks

 

Ring tension is decided by the material used in manufacturing and the unsprung diameter (free) versus the installed diameter (bore size, compressed). The difference in ring tension going from a gap of .020" to .012" or something like that is negligible. As far as building a motor with tighter clearances in order to eliminate blow-by is not really a good idea. You do your ring clearances based on the ultimate horsepower goal of the engine. Very bad things happen if the rings touch when the motor heats up at max output. My advice is run on the loose side of the clearance and run a better crankcase ventilation system so the blow-by causes less problems. Generally .006" per inch of bore is a good gap for the top ring and .0065" to .007" per bore inch is good for the second ring.

Increasing ring tension can have plus and minus's. The more ring tension the more parasitic loss.

 

This I can uderstand and deal with through the manufacturer of the pistons and rings.


I appreciate you knowledge here, specifically about when the rings touch, but I am trying something a little different than the status que.


Please don't take this the wrong way, but I am not looking to run on the loose side, thanks for your suggestions.

I'm not too worried about the parasitic loss.

Can someone please take a look at my original post and offer outside the box solutions ? I am trying to further expand some ideas I have. Some of the ideas stem from oil/lubrication conversations I've had in the past and recent observations. Specifically, light weight oils, where the lubrication is so good that it unseats the rings and causes a loss of horsepower. Horsepower loss seems to be about 100 hp with synthetic, on a 2500hp+ motor. I'd hate to think that nothing could be done, and to just deal with the hp loss along with the oil loss as the rings unseat themselves. Could one add an additional ring to combat the losses?

 

I think you're wrong to be comparing a 2500 HP engine to your own. That's obviously a race only engine, (I'm going to assume a V-8) probably with ring gaps at around .007 per inch on the top ring, only in an engine with a much larger bore (assumed) your engine does not need to be that tight. but the ring gap closing altogether is gonna get catastrophic real quick. Also, how on earth is good lubrication going to unseat the rings after break-in? Every manufacturer says not to use synthetic oils until after break-in, but I don't understand what you're talking about.

 

What happened to the thread OP? Any updates to the route you took with the engine build?

 

I've been takling with some of the guys about ring gaps, and bearing clearances. I understand your concern, as I too would like to keep the motor in one piece. I think what I may need to research is a ring material the creates a great resistance against the walls of the cylinder. I could be totally out of my tree here though.


I can only comment here that the oil I've been using causes fairly good blow by after about 5,000-12,00 miles, and then I'll have to consistantly monitor the oil usage. If I use a dyno/break-in oil after that period, I can get the rings to not pass oil for about 5,000 more miles.




The project is on hold, for now, thanks for your interest. I'll try to post as I gain traction in the project.

 

Ring tension is not something I usually associate with oil consumption very much. It sounds like maybe the honed finish in the bored is not matched well to the ring's material, and I guess, tension.
I don't see parasitic losses from higher ring tension being significant, or maybe even measurable. I really think it's silly to mention unless we're building an engine master's competition engine.
This does not change the fact that there is not a real downside to running looser clearances, especially on bearings. Rings will obviously allow more past them with wider gaps, but the amount of blow-by present (speaking volume) when an engine is actually running is utterly insignificant.
To finish myself off, I don't think that the rings unseating themselves is why the drag engine is losing power with synthetics. I think it's more likely that conventional oil does not remain as stable under extreme power demands as synthetic does. The "weaker" conventional oil is actually creating less friction because it's viscosity is falling off as compared with synthetics, which suffer less change. That's my conspiracy theory anyway.

 

The oil consumption fluctuation that I speak of (between dino/Syn) is on a stock motor for me... The race motor is different...

Actually, what seems to be happening, is the oil is causing the walls and rings to become very smooth. It's not, that I know of. When the syn is in the motor the oil is so refined, to like 2 microns, that the oil is actually sliding in between the rings and the walls it's so slippery. It's basically the refining of the oil that makes it work as well as it does. The molecules and particles in the dino oil are just bigger and can not be passed as easily. So it appears that the blow by is gone, but its just that the gaps are too small to pass the dino oil, and the actual truth to the rings, state of being set . I hope now you can see why I am trying to find a solution to the sny oil blow by.

 

The job of oil is to stay on the cylinder walls. Otherwise the rings would gall and seize to the cylinder walls. I could see too fine a hone causing more synthetic oil to stick to the wall than necessary, causing oil to be burned. though now I can't remember why I think it would be less likely with conventional.