Single ring pistons question

[Original Looper 1]

With these rings, I thee wed....

This is quite an interesting thread on piston rings used on a performance racing outboard.

What we found on the Merc racing deflector engines was that the 3 ring pistons contributed to significant horsepower loss due to friction drag. The engine we used on the dyno as a test mule was my personal D AOF modified Merc engine with expansion chambers.

To give somewhat of an idea of the friction loss of 3 rings per cylinder vs one, you can take 2 rings with a proper end gap and put them in a cylinder and feel/measure the drag it takes to move those extra rings up and down in the cylinder. Now multiply the drag and friction loss x 4 cylinders. It most certainly is a significant power loss. That, in conjunction with the magneto drag, we found to be a loss of over 8 or 9 hp at 8000 rpms on a modified for racing D Mercury engine.

Note: On this test engine, we were micro honing the cylinder wall finish with Sunnen 600 honing stones so as to have a smooth as possible surface contact area for the piston ring(s) to ride on to better understand the effect and amount of friction loss of the 3 vs 1 piston ring theory in practice.

We too, as Allen suggested, ended up running one top factory ring with .005 to .007 end gap in conjunction with 2 dead or almost zero tension and end gap aluminum filler rings in the other ring grooves.

I believe the reason why Mercury came out with 3 ring pistons on the pleasure engines, is because most of those engines were used for fishing, idling and pulling loads such as skiers. As the engines normally wear with general usage, along with the cylinder bores and the pistons rings, by having 3 rings you have a much more durable pulling engine that performs significantly longer for pleasure use than if it originally had only 1 ring.

Another factor from a manufacturing standpoint, the 3 ring piston, as everything normally wears from long term usage, is far less noisy when idling, which contributes to a much quieter running engine during it's life span. Plus, by maintaining it's ability to pull loads better for water skiing, tubing, etc, it makes for a more consumer friendly product.

A special note: My wife's uncle, Lester, from Quincy, IL, bought a brand new KG7 Mercury Hurricane in 1950 from my dad at Quincy Welding and ran it every year, all summer long for fishing and every fall for duck hunting, for over 45 years. It still had the factory seal on it and super compression when it was sold at his estate sale after he passed on. That speaks highly for the 3 ring piston durability.

Regards,

Paul

[BmJuby]

Hey Paul,

Correct me if I am wrong. So you did use dead rings in the bottom two rings in the 3 rings pistons. You never had success with 1 ring on top and the bottom 2 empty?

So some people are saying that complete absence of bottom two rings (on a 3 ring piston) messes up the porting and provides less power, a lot less power in some cases. Others are saying that it is an improvement. Is this a case of no one being right and that it depends on each engine by a case by case basis?

[Original Looper 1]

With this ring, I thee wed.....

Good question. Please believe me when I tell you, at Quincy Welding, from the mid 1970's onward, many if not most of our modified jobs (including some of our fierce competitors) used the Mercury top ring in conjunction with the 2 bottom ring groves filled with Quincy machined, aluminum dead rings.

I also agree with the comments on this thread that one shouldn't expect acceptable or top performance by leaving 2 ring groves without proper filler rings. It just makes common sense not to do that, nor did we in our dyno testing find any advantage to doing so.

Regards,

Paul


ps: When it comes to racing, like the song says, 3 rings are kind of a drag...

[BmJuby]

Thanks for the info.

[rumleyfips]

Paul:

Since expansion chambers on deflectors have drawn a lot of interest at BRF, I wonder if the chamber you used is the one shown on the Quincy site ?

John

[Original Looper 1]

The Star Chamber

Hi John,

The answer to your question is yes. To be more specific, go to the www.quincylooperracing.us website and proceed to the Race Legends page. Click on the Larry Latta photo and you will soon see some very detailed, large photos (courtesy of Wayne Baldwin) of Larry by a rather large looking expansion chamber on the 350 Z engine. I'm hoping you can scale the photos.

That was called our senior pipe.

We eventually ended up with a somewhat scaled down version of it that we ran on our M 125 and as individuals on our 2 and 3 cylinder engines in Pro.

When Chris and I attempted to reinvigorate the Quincy racing program in 1975, we were blessed with the previous efforts of Frank Volker, my brother-in-law, in that we had over 35 expansion chambers of his design to start with.

Frank was the originator of the huge (for the time) Quincy expansion chambers.

At the same time Chris and I were doing the R&D programs for the Pro motors, I had a D deflector mod Merc engine that I was working on, and that's how I ended up with the senior pipes on it. The thing I found about the Merc deflector mod engines that was unique was that they performed best with the biggest sized expansion chambers. In other words, deflectors like huge volume and capacity on the exhaust side.

One other note -- we found that the timing on a D mod Merc worked best at 235 to 240, with chambers, as we also found out then that most other attempts at that time with problems and chambers on Mercurys were because they were way over timed for megaphones.

Regards,

Paul


ps: Pay special attention to the tapered, non straight section of the pipe. After we established that unique design, many of the go karters and motorcycle racers followed our lead. Of course, they had expensive dies that we as a small manufacturer could never have afforded.

[johnsonm50]

1 big thing that everyone is hip on is compression, 1 of the best runnig engines I ever had , only had 70# in each cylinder, way low comparing to others , but i did run well and out front at times,you all have to remember that a compression gauge is just a tool to use and may not give the same as other gauges.and as the rpm climbs in a merc the compression builds, so realistically you really dont know how much compression you truly have at 8,000 rpm. also I was once told by a guy that has built mercs most of his life < that in a merc once you get it started you really dont have to have rings in the pistons,the oil will do all the sealing you need, hence labrith seals, just like in the center main and reed cages

I was wondering about the seal effect of oil in relation to the very short time compression has the opportunity to leak.

[rumleyfips]

Thanks Paul. The images were large and clear and now I know.

John

[deverhart1]

Deflector timing

If the timing for chambers should be about 235 what should the timing be for megaphones. I was told a long time ago 370 max but if im not careful pistons burn on the exhaust side. Can I run at 235 with power. Thanks
David Everhart S52

[deverhart1]

Chambers

By the way can decent chambers be bought that will work not just somebody's mistakes that they want to sell. For Dmod 44 mercs
David Everhart S52

[Bob Rusnak]

By the way can decent chambers be bought that will work not just somebody's mistakes that they want to sell. For Dmod 44 mercs
David Everhart S52

Have a set of expansion chambers and manifold for a 30, 40 &44 ci merc. It will fit a Quincy filler block. They did work but I felt the megaphones were more to my liking. They are available if anyone wants them. I have been thinking of putting them on E Bay but want to clean them up first. I feel with some experiment time they can be really good.....Bob N-96

[Original Looper 1]

The Timing is Now

Hi Dave,

Good questions.

The first one pertaining to ignition timing settings -- there are many variable inconsistencies with boat racing engines besides the type or design of the exhaust system, such as air temperature, barometric pressure, humidity, race course water temperature, boat design and condition, wind (direction and speed), motor temperature, RPMs, propeller, racing weight of outfit, length of course (or distance of kilo), etc.

This is why we have come to the age of engine computer management systems becoming the rule not the exception. To think how sophisticated and scientific Nascar and other auto sports have become, one would have to conclude, I think, that boat racing has the potential to throw even more curve balls and unforeseen obstacles that must be overcome by the advancement of technology. So therefore I put boat racing at a more challenging level than many other motor sports in the evolution of technological progress.

My father always told our Quincy customers, when they asked what their timing should be set at, to set it where it maintains the most top speed. He also told customers it's not necessarily the fastest boat that wins the races, it's always the (legal) firstest that wins.

My opinion on ignition timing is that if it's a kilo attempt, my father's philosophy is fitting. But if it's an oval race course or similar, I'd have to say the timing should be set to wherever it sustains the consistent, lowest lap times.

I can't speak for the current expansion chamber manufacturers. All of the information I've given on timing and exhaust in this thread has been based on real dynamometer time and documentation for the time period that the tests were performed by my father, Chris, and myself. I do have some ideas, philosophies and theories that I think would bring more progress to the current engine development program levels.

Regards,

Paul


ps: Time and again, I've heard that the dynamometer doesn't win races. What I've found to be the case is that there are exceptions to everything, but usually if everything else at the race course adequately fits the dyno progress, the advancements and speeds achieved at the race course remarkably match dynamometer results.