Hey guys, how many have tried running the Saito crankcase breather tube into the intake manifold? I know, a little oil on the belly of the plane isn't that big of a deal, buy hey, if there's no real penalty for recirculating the oil that would be even nicer.

I understand that the "used" oil and possible grit or contaminants doesn't sound like you'd want to have the engine ingest necessarily but OS has been doing it for a long time. Has anyone ever determined that an OS might have lasted longer if the used oil was just dumped in a constant loss system such as the Saitos?

Thanks for any input!

Ernie

If you're going to recirculate the oil, why not just collect it into a separate container and use it to mix up new fuel? :-)

One thing you have to remember if you're going to recirculate the oil is that it has to go somewhere.

Stuffing it back into the engine means that it'll either be burnt (not a good thing) or come out the exhaust pipe -- whereupon some of it will still end up all over your model.

Hey XJet, if there's a choice with no penalty, why not have it all come out one place (exhaust) with a deflector rather than have half of it dribbling down the fuselage? Just curious. I know a little oil isn't that big of a deal to some, but a nusance to others.

Thanks,

Ernie

I have 3 Saitos, a 125 and 2x 82. On the 82 I put a nipple in the intake manifold and vented the breather there. No affect on performance and a LOT cleaner around the front of the model.

Problem is, these Saitos are prone to leakage around where the inlet manifold enters the head, and adding a nipple & pipe leads to more vibration of the inlet manifold and quicker wear of the seal.

So recently I've been trying a better solution. The problem with the breather is the need to keep the pipe short to allow the oil to vent. So...

You'll need a one way valve (e.g., a perry check valve) and a T piece. Take a short piece of fuel line from the breather nipple to one side of the "straight-thru" bit of the T. On the other "straight-thru" side, put a short bit of tube and the check valve. Orientate the valve so the engijne can suck air through it but not blow air out of it. On the third T outlet put a long piece of tube routed to a place where the oil can egress; I've got about 14" of tube which runs down the main undercarriage leg so the oil ends up nowhere near the airframe.

My thought is this. As the engine blows thru the breather, it blows air and oil along the long piece of pipe. As it sucks, the path of least resistance is the check valve, so it sucks clean air in thru it. End result is the oil makes its way along the long pipe to freedom, but the breather can still breathe.

So far I've run about 4 tanks through on the ground and not seen any problems, but I'd still say I'm experimenting; just waiting for some decent weather to try it in the air!

Anybody else tried anything like this?

HS

Hey Highside (sounds like the way my dirbike used to spit me off sometimes...),

I'll have to spend some time digesting your one way valve setup. Sounds interesting. Of course? you've seen the (2) one way valves setup that Saito sells just for that purpose. They are only 8 bucks and made from nice aluminum it looks like. You have to tap the backplate for the one that sucks, and the put the other one in the (long) breather tube.

Thanks for the input,

Ernie

Like this, it is to pressurize the tank on the 2.20 for the large carb option.

Hey Ernie,

Yep Highside refers to my road racing days where my broken bones-to-trophies ratio was approximately one!

Nope, I wasnt aware of the Saito pressure "pump" setup, so I've just been doing some reading around on it and had a good look at Hobbsy's piccies. Actually quite interesting seeing as I've been messing around with regulators and Perry pumps quite a lot recently for various reasons. I guess the big difference is they are using one way valves to pressurise the tank (with a needle bleed valve to give some "control" of pressure), the ability to vent crankcase oil down a longer line is a by-product.

Next time I'm back at home, I'll take a piccie and post it.

HS

HS, the Saito way was a loser, it worked much better and easier to use the big carb with an IronBay regulator and a check valve in the exhaust for pressure.

Hi Hobbsy, what exactly are we looking at in those photos? Is that an Iron Bay setup on the big 220? Do you like the Iron Bay better than the Cline regulator?

Thanks!

Ernie

Ernie, that is the Saito backplate pump to pressurize the tank a little, it comes with the large carb, the needle valve regulates the tank pressure by restricting the crankcase vent flow, the excess just bleeds off in the normal way. The thing is like a PolyChoke on a shotgun, evertime you shoot at something and miss you become convinced that you don't have it set right. The large carb works very well with the Cline or IronBay, I have not preferrence of one over thae other except in the case of my Saito .30s, the Cline will allow them to idle much slower than the IronBay. Any engine larger than the .30 and they work exactly the same.

Dave,

Have you run the Enya GP?

Brian, I sure have, it turns a Graupner 15x8 at about 9,200 on 5% WildCat fuel. I'm sure it will get better as another hour or two accumulates. I has that same irritating exhaust sound as the 1.55 had. I may play around and see if I can put a Saito 1.50 muffler on it but it won't be easy.

Dave,

I have a R120 Enya remote muffler with the flex exhaust NIB. I'll see if I can Find the receipt if you're interested.

Thanks Hobbsy.... Dave. I wonder if a poor man's homemade version of that large Saito needle valve/pressurizing system would work on most any engine?????

Thanks,

Ernie

Hey Ernie,

Here are those piccies I promised. Should be self explanatory, it's pretty simple.

HS

Ps, I'd agree with Hobbsy, try a Cline regulator in preference to the Saito idea. I have a couple of them, and the only problem I have had is "mounting" them so that they are isolated from vibration. The manufacturer recommends just hanging them on the fuel line which isn't always possible if space is tight, and any vibration can lead to bubbles in the fuel due to cavitation.

Notwithstanding mounting, they do work brilliantly and there is nothing to adjust or tweak. In the model in the piccie above the tank is 6" back from the firewall (as close to CoG as I could get it) and 2.5" above the carb. Thanks to the reg, it runs consistently thru a tank and doesn't syphon when the engine is stopped. Support from the manufacturer is v good.

Anyone know if the IronBay alternative is less sensitive to vibration?

A

Hi,

Weather finally broke long enough for a trip to the field, so I've now flown 5 flights with the breather vented via T piece / one way valve as described above. No problems in the air, engine ran fine and no breather mess on the model. Result!

HS

Hey Highside, the pics should be self explanatory but I keep looking at the plumbing and wondering exactly what is going on. The pic on the left shows the one way valve at the end of the short run, with the T going off to a long run of tubing to the tail or where ever, right? Which way is the one way valve hooked on, so that the crankcase can successfully suck in air on the up stroke? Is that what is making the system work without bogging the engine down?

Thanks,

Ernie

Ernie the one way valve cannot accomplish anything above idle speed, if you closely observe the flow in the vent at idle it is in and out but above idle it is all outward. The one way valve is then just an impedance to the flow that needs to flow freely.

Hi Ernie, your description is correct. The check-valve is orientated so that the engine can only suck air in thru it (as you say, on the up-stroke).

Here is my thinking:

1: The manufacturers of 4cyc engines with crankcase breathers generally say you should only connect a short piece of tube (a few inches max) to the breather. I'm not sure of the reason, but had always assumed it was to do with the fact that the engine sucks then blows then sucks etc. A long piece of pipe would mean that the "blow" would not be able to clear the pipe of oil which would then get sucked back in. I could be wrong in this assumption - Hobbsy, do you know why?

2: A short piece of pipe means mess on the model. I hate mess on my model. I have a couple of engines with circulated breathers (OS and ASP) and the cleanliness is a delight. Recirculating on these Saitos is a bit of a pain due to the sensitivity of the inlet manifold to vibration (see other threads!). So really I want to connect a long pipe to the breather. not a short one.

3: My reasoning for the setup shown is this. When the engine blows, the check valve closes and the oil+air mixture has to go down the long piece of tube. When the engine sucks, the check valve opens and is the course of least resistance (shortest bit of pipe), so the engine can suck oil-free air in. Net result is the oil goes down the long tube. In practice, the "suck" phase might draw in some clean air via the check valve and some oil+air back from the long tube, but the net is the oil goes down the long tube and out to freedom.

4: Of course, the belt-and-braces technique would be to have a check valve in the long tube too, so that the engine can ONLY blow down the long tube and ONLY suck thru the short tube. But it doesn't seem necessary to do this.

It seems to work, I've now run about twelve 10oz tanks through in a mixture of ground running and flying with no problems. My long piece of tube runs through the belly pan and down the main undercarriage leg to get the exiting oil clear of the airframe; maybe I should do some ground testing with the model inverted to check it still pumps the oil out against gravity (the main undercarriage leg would be sticking upwards) (it's a pattern model so in the flying I've done its spent a fair amount of time inverted).

I suppose for completeness, I should try replacing the check-valve with a blank to see what effect running the engine with just a long piece of tube on the breather would have. Furthermore, Hobbsy could be correct that the check-valve is only helping out at low rpm.

All good fun!

HS

HS- I don't think there is any specified restriction on the length of the vent tube. I would not hesitate to run 10" if that is what is needed on a Saito. I suggest that you run just one vent line down the landing gear like you want to have it. If you see excess oil seeping out of the front bearings, then *maybe* the tube is too long, but I doubt that would ever happen.

------------------


Ah, and there is the rub. I'm not convinced that recirculating the used oil does not come without a penalty. Surely, it must cause at least a very slight power loss, not to mention the fact that the oil, not being virgin, has had to have picked up contaminants, both chemically and in the particulate sense. I'll just let me do its thing traditionally. If goop bothers a person that much, perhaps electric or gasoline would provide a better, cleaner power source.


Ed Cregger

Highside, if'n you get a chance, please tach the engine (after it has been running for a while) at full throttle with and without your setup. If there's excess oil building up in the crankcase I think we would see at least a slight difference in power.

Thanks,

Ernie

Hi Ernie,

Finally got to the field for a bit of fun time.

I ran the engine (APC14x7; model technics dynaglo 16; just engines quiet muffler) in flying tune as follows:

With one-way valve & long vent pipe: ~8980rpm held for 1m30s with no fade. Tickover stable at ~2300 for 1m30s.
With only 2" of fuel pipe on breather: ~8980rpm held for 1m30s with no fade. Tickover stable at ~2300 for 1m30s.

i.e., no difference. I then inverted the model so that the long vent pipe was pointing up (it is routed along the main undercarriage), so that the breather was having to blow the fuel "up" the vent pipe rather than having gravity assist it. Performance was the same as above once I'd tweaked the needle (it runs a little rich inverted).

I had a good play around trying to watch what was happening to the oil going along the vent at full throttle, at tick-over and with the one-way valve working and with it blocked off (with a calibrated finger :-)). To be honest it was very hard to see what was happening (the fuel isn't of the dyed variety). In all cases at full throttle, oil was being blown out of the vent. At tick over it was too hard to see what was happening, and the tickover stability itself didn't seem to be affected by whether the one way valve was working or blocked off, at least over about a 1 minute period.

So not overly conclusive. But I've now had about 15 flights of (bad) pattern style flying and seen no problems from the long-vent / check valve combo. There is a trace of oil which may have come from the front bearing, but that has always been the case with this engine even before putting the long vent on. So I think I'm going to refit the cowl and put some hours on the model...

One final thing. A flying friend of my father has an OS52FS in a low wing sportster. When he built it last year, he was having trouble with the engine at tick-over and transition; not all the time, but it wasn't 100% reliable. All the usual was done, tweaking, cleaning, new plug etc. to no avail. When my father looked he found about 7" of tube on the breather; they shortened it to an inch and the problem went away...

Hope this helps.

HS

Hey Highside, you really came through with the tachometer! Thanks for all the work. Very interesting.

I might be concerned about the long run of tube when the weather gets real cold. Also, are you running any castor (thick!) in your fuel?

Thanks,

Ernie