piston rings & sealing against cylinder wall

[gmax137]

I had someone telling me about drilling small holes, down from the piston crown into the small space "behind" the top piston ring, purportedly to allow the combustion pressure to get into that space and force the ring out against the cylinder wall. The theory is that the gap between the top face of the ring and the adjacent land is too restrictive to permit this pressurization from occuring fully/fast enough. Anyone here heard of that, tried it? Does this really work? This is in the context of race engines. I have difficulty believing that blow-by between the ring & the cylinder is a big concern (that would rob power) in a race engine, which has fresh rings, good cylinder walls, etc.

Thanks

 

[evelrod]

Dykes are still used, mostly on small displacement stuff. A lot of older bikes, like my old Bultaco, used Dykes...Point of fact, some of them were also "piston ported" as I recall.
Anyway, the only Dykes I could find still in use was down at the radio control hobby shop for a quarter scale something or other. I don't fly much anymore, don't have enough $$$ left after bills. (I still like to window shop, perhaps when I get too old to race).

Rod

 

[anotherME]

Is a pressure groove essentially the same thing? I am really interested in this topic now.. I tried finding a picture ofa piston that has this porting done and all the information I can. I have been searching SAE with no luck thus far. ha.

 

[evelrod]

Most of what I post is anecdotal and I mostly post what I done myself or have personally seen. Unless it's something interesting, most of us do not tend to spend time in research...At least I don't.
However, since all seem to know about "gas ported pistons", it's about time to consult the "experts" <smirk> I am refering to JE as I am currently using their "vertical gas ported" pistons in my race car and I sorta knew where to look...Page 6 of their on line pdf catalog.

http://www.who-sells-it.com/cy/je-pistons-708/je-pro-seal-catalog-428.html

http://www.who-sells-it.com/images/catalogs/708/pdf_428.pdf

Shucks...You will need to open the Home page and then go to the pdf catalog. I get a "Forbidden" if I try to link directly.

Rod

 

[anotherME]

well it appears they already did a bunch of research on that, i mean i could measure performance increase for fun now if i wanted as my senior design project, haha. Very interesting stuff. Thanks for the info

 

[Balzafun]

A couple of quick points.
There are 2 different types of gas ports. "Vertical", that are drilled in the top of the piston. And what’s know as a "Lateral" port. Drilled on the side of the piston just above the top ring. Vertical is traditionally used in drag racing. Lateral in circle track and road racing.
(carbon build up is greatly reduced with lateral.)

Yes there is a certain amount of blow-by caused by these ports. But to offset the effects piston makers cut an accumulator grove between the first and second ring. This grove gives the gases a controlled place to go. This actually helps control "Ring Flutter" by providing a cushion between the two compression rings.
From my work with NASCAR Cup teams,NHRA pro teams, and
amature weekly racers, there is merit to this technology.

 

[bentwings2]

I remember the gas ported pistons way back inthe hot rod days. Hot tip I guess. I tried a set on SBC we had inthe shop. It didn't go faster or slower. I also tried onthe same moter 4 with ports and 4 without ports to see if there was any other differences. Cylinder leakeage was the same. If I didn't know which one had the oles I couldnot have picked them out. The response back then was that someone came up with this "super trick" idea to mislead others into wasting a lot of developement time checking it out thus preventing them from spending it on something worthwhile. you could several hours to the shop bill for a motor so the shop made more money. haha It worked I guess as lots of guy used them. The amount of time spent to drill a set of 8 pistons then de-burr the holes behind the rings was incredible.

I made a little plug with the same number of holes on one end and a 1/4 npt on the other that I could hook up a air hose. The amount of air coming out was pretty small. The boss's wife liked it on her watering can for the office plants.

I think this was before the dyke ring caught on for drag racing. The gapless ring has pretty much taken over I think.

 

[evelrod]

I must make a correction in my last post...

It should have said "lateral gas ported". I guess I just had vertical on my mind as the subject of this thread....Sorry...I have not used a set of drilled, ported pistons in over 30 years. However the current pistons seem to be just fine...in fact, if you did not know in advance you might not even spot the difference.

Rod

 

[larrylcoyle]

bentwings2..

If you think a shop makes money gas porting a set of pistons, tell me how much you charge because it is not a money making proposition. You have to contend with breaking a drill bit off and making sure you get half the diameter of the drill bit into the back of the ring land. Placement is critical if this technology is to work properly. No money to be made I assure you as there is no universal setup for doing this. The advent of cnc machines definitely makes it worth while to have the manufacturer do this for you when you order a set.


Larry Coyle
Managing Partner
Cylinder Head Engineering, LLC
CNC Porting
De Soto, KS 66018

 

[dicer]

This all is nothing new its been done for decades now.

 

[patprimmer]

Who said it was new

Regards
Pat
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