apwachholz

I'm completely new to 4-strokes and just bought a Saito .62 to put into my Hangar 9 T-34 Mentor. In the image attached, what the heck is this valve for? I understand the fuel input and the line from the muffler but this "3rd wheel" has me confused.

apwachholz

Sorry about the 3 posted images - technical blunder (they're all the same)

2slow2matter

My Feedback: (1)

That third nipple is for crankcase pressure. Put some tubing on it, and route the tubing out the bottom of the plane somewhere, as it will expel raw oil....

brett65

My Feedback: (18)

It is a blow by relief. Same as the pcv valve on a real car.

apwachholz

Awesome! That makes total sense to me now. Thanks. My next questions are:

1) What is a good 3-blade prop to break in the engine with? Or should I not use one?
2) What is a good 3-blade prop to use once break in is done?

I would like to get more "scale" from my model and I'm told 4-strokes can handle 3 blade props nicely. Plus, I'll be honest, it just looks cool on the ground. =)

bigedmustafa

My Feedback: (2)

Master Airscrew makes an 11x7 3-blade prop that should be a nice match for this engine.

jetmech05

Fyi that thrid nipple can be on the backplate...I seem to recall an engine that had that nipple in a third location..but I can't remember where
Good Flyin

MikeL

My Feedback: (3)

It's just a vent. You can't pressurize anything with it. You're right about putting some tubing on it, though. It'll make a mess. Get a fuel dot to plug it up when you're not flying.

More recent 4-stroke designs have done away with the open crankcase vent, so it's not present on all of them.

2slow2matter

My Feedback: (1)

I don't believe I even insinuated that one could pressurize anything with it. I'm fairly familiar with the operation of the crankcase vent nipple.

MikeL

My Feedback: (3)

Nah. "For crankcase pressure" wouldn't at all insinuate that you thought it was for anything to do with pressure, such as crankcase pressure that is used to run Perry pumps and such. My bad!

2slow2matter

My Feedback: (1)

OK.
The nipple is to release crankcase pressure that builds up as the piston travels downward. That pressure has to go somewhere. In a two stroke, there is an exhaust port, in a four stroke, the exhaust isn't released until the piston starts traveling back upwards, and the exhaust valve opens.
In magnum engines, the crankcase pressure nipple is connected via a tube back to the intake, which allows some of the raw fuel/oil to be burned back through the engine again. In most other four strokes, this pressure is just vented to the outside somewhere convenient via fuel tubing.
I understand that this is a very elementary description of what is going on, but I think it completely fulfills the op's needs. If you wish to add that it can't be used to pressurize anything, then that's fine, but why you had to quote me, I have no idea. What I said was right, and in no way misleading. I have no idea how anyone could construe what you did from my post. but some people love to find fault with posts....
I think this post has served it's purpose......

MikeL

My Feedback: (3)

"For crankcase pressure" isn't how most modelers would describe the crankcase vent. Why not use the terminology that is both accepted and common, rather than use a different term that may be technically correct but is most often used to refer to something completely different?

apwachholz

2slow - Thank you very much for your help in explaining the layman's version to the newbie*. I was scratching my head for a while wondering what the heck that nipple was all about. Kinda funny that there isn't really a description w/the engine what that is (or at least somewhere on their website - which doesn't exist!). I felt the need to search online after you posted a response and found the following site (after much searching) to be a sweet location for all newbies out there:

[link=http://www.saito-engines.info/index.html]Saito Engines for Newbies[/link]

Again, thanks 2slow!!


*Terms and Conditions for MikeL: The following post was for the purpose and sole reason of assisting new and incoming remote control enthusiasts (i.e. 'the newbies') with complicated issues or topics. For clarification regarding this specific thread please refer to the section it is posted in (see main subject thread titled "Beginners" in the main topics listing at [link=http://www.rcuniverse.com]RC Universe[/link]. For further discussion regarding 4-stroke engines and functionality please see [link=http://www.rcuniverse.com/forum/forumid_463/tt.htm]Glow Engines, Gas Engines, Fuel & Mfg Support Forums[/link].