TC-W3 ratio

[jakedaawg]

op2:. These are so entertaining!

 

[racerone]

They sure are and , the lubrication inside a 2stroke is not well understood .---That is why 15 people have 20 different opinions !

 

[Cadillac-ack-ack]

My understanding on the subject is that while there were some changes made in the motors, the big changes were in the oil. We all know that running your outboard on a lean mix may cost you a power-head and a paddle to shore. The down side of to rich,,, maybe a plug [ although I have not fouled one yet] performance..

Am I correct in thinking you are referring to ratio of Oil/Fuel when you say "rich" and "lean" or Air/Fuel ratio? I can understand that with a too rich Air/Fuel ratio you'll also be running more oil and gas than needed possibly fouling plugs two ways. By comparison a too lean Air/Fuel ratio will indeed melt pistons and also cut down on lubrication of the spinning parts of the engine. So, correct Air/Fuel ratio and correct Oil/Fuel ratio go hand in hand I would think. I'd have to say that in a perfect world, the goal for each down stroke of the piston would be to burn all the fuel and air and most of the mixed oil after it has done it's job of lubing the interior of the motor - no more no less. - Pete

 

[jimmbo]

In the days before the TCW oid were introduced, non detergent motor oil(mineral oil) was recommended. At 16:1 and 24:1 ratios, carbon build up was a common problem in the engines of the era. When OMC switched to the 50:1 mix they reported a big drop in warranty claims that were the result of engine failure due to preignition, probably from less carbon on the piston and cylinder head. In the mid to late 60s OMC and other engine makers started marketing their own oils, which were the best outboard oils at the time, as they contained detergents that could even remove old carbon from engines. Fast forward to today, and the better TCW-3 oils appear to burn cleanly even at 24:1 or 16:1. By clean I mean little in the means of carbon deposits. As for the smoke, I like the smell of burning TCW and it keeps the Mosquitoes away.

 

[Cadillac-ack-ack]

As for the smoke, I like the smell of burning TCW and it keeps the Mosquitoes away.

I have to admit, a person's sense of smell must be one of the most powerful things that trigger memory, good and bad. I'll never forget the smell of that old girl when water skiing behind her. I hope the new oil smells the same.

 

[todd281]

Sorry for any confusion , for this discussion I was referring to oil/gas ratios when I said rich[ to much oil] and lean [not enough oil] while the former will cause some smoke , the latter may cost a power-head. Fuel to air mix [also referred to as rich and lean] are another matter [ to lean here can be a motor killer also] if you have ever used an oxygen-acetylene torch you will know first hand about fuel to oxygen mix, and the results of not having that set properly. But as far as the oil to fuel mix,, My opinion when there is ANY question,, err to the safe side and run it with some extra oil .

 

[thumbnut]

The 1949 QD 10 had some needle bearings.-------Some just do not understand how oil " works " in a 2 stroke.

so...racerone..kinda like my grandmothers cookies...they were great but she wouldn't give up the recipe..

so...how bout given up on what ya know...I have an idea but not expertise on the issue...there is probably more to it than the obvious..

 

[Cadillac-ack-ack]

so...racerone..kinda like my grandmothers cookies...they were great but she wouldn't give up the recipe..

so...how bout given up on what ya know...I have an idea but not expertise on the issue...there is probably more to it than the obvious..

I'd kind of like to know the actual facts as well. As I see it, atomized oily gas is drawn into the crankcase during the compression stroke, the mix in the crankcase is then pressurized during the power stoke at the bottom of which it enters the intake ports where it is compressed as the piston starts the compression stroke again. I guess it's at that point where the mix is drawn in and then compressed that the necessary lubrication occurs. The crankcase must be so designed so that all the bearings get washed with the atomized mix. In addition I'm thinking that it's mostly just the fuel and air that is atomized and the oil is left as more of a mist rather than atomized along with the fuel. I know that when I first started working on this Lark I Expected to see some pretty dry innards but it fact everything was well oiled. - Pete

 

[jimmbo]

You have it pretty much as I how figure it works. But I will add my 2 cents

The gasoline vapourizes as it enters the carb venturi. The oil on the other hand does not vapourize and proceeds into the manifold and crackcase as a mist, depositing itself on the internals of the crankcase. Various means are used to channel the oil to various bearings on the crank, connecting rods and piston pin. Some oil is carried initially into the combustion chamber, but in eventually all the oil in the fuel mixture does make it thru the combustion chamber and out the exhaust, some burnt, some unburnt. Almost all engines pump oil from the lower main bearing up to the upper main bearings through a recirculation system. Older engine had a purge(check) valve to remove puddled oil from the crankcase, dumping it into the exhaust housing, in the late 60s early 70s all US outboard did away with it and refined the recirc system to handle the excess oil. The 50:1 mix helped in that respect.
In all fairness, the engines that were speced for 50:1, and a few others could survive quite well on 100:1, but there would have to been perfect measuring, and mixing of the fuel(something that happens less than most people admit). OMC did do that with a number of premix engines in the mid 80s, but found out there wasn't enough oil left on the crank/rod bearings to prevent corrosion from happening if the engine was not run frequently
Race engines, even modern ones, maybe especially modern ones were speced with richer oil to gas ratio. The reason there is the racing engine turning higher than normal rpms would be starved of oil for too long if the throttles were slammed shut at these rpms, so an oil rich mix offers a cushion

 

[todd281]

If you want to see it displayed , there is a website, http://www.animatedengines.com/ . While the animations are not in great detail, they will give you the basic idea on how some engines work. Just go there and click on the two stroke diagram , it will take you to a page that will show you a animated engine working and a short description. There are other engines there also , 4 stroke, steamers, gnome, stirling, [sometimes I just load a page and let it run like a screensaver]

 

[Cadillac-ack-ack]

Thank's for that todd281, super interesting, and saved. - Pete