Saito 30 4S update

Hi Guys,

The fuel foaming problem was fixed with some foam buffering, but the problems with the engine continued.

Then engine would run OK for 10-20 seconds, then would start loosing RPM, got hot, the output oil at the breather and the muffler would darken, and the engine would quite. Same scenario as with the foaming problem.

The culprit was muffler pressure. This engine just doesn't like it. I have no idea why. Runs perfect without it. In fact, the pressure was continuously and progressively making the run worse and worse, until it would stop from overheating.

Setup is now 9x6 Zinger, 7/22 Power Master fuel, 10,200 RPM, metal non-uniflow 2-½ oz. wedge tank, no pressure.

Only ground tested for now. The weather is turning nasty and do not know when I will get to flight test it.

Any idea’s on why muffler pressure would cause this?

Jerry - my .30 will only run on muffler pressure!
Bob Z

>Hi Guys,
>
>The fuel foaming problem was fixed with some foam buffering,
>but the problems with the engine continued.
>
>Then engine would run OK for 10-20 seconds, then would start
>loosing RPM, got hot, the output oil at the breather and the
>muffler would darken, and the engine would quite. Same
>scenario as with the foaming problem.
>
>The culprit was muffler pressure. This engine just doesn't
>like it. I have no idea why. Runs perfect without it. In
>fact, the pressure was continuously and progressively making
>the run worse and worse, until it would stop from
>overheating.
>
>Setup is now 9x6 Zinger, 7/22 Power Master fuel, 10,200 RPM,
>metal non-uniflow 2-½ oz. wedge tank, no pressure.
>
>Only ground tested for now. The weather is turning nasty and
>do not know when I will get to flight test it.
>
>Any idea’s on why muffler pressure would cause this?
>
>Jerry

What tank were you using before, and how was it hooked up? It does seem strange that muffler pressure alone would cause a problem unless you weren't able to compensate the needle setting for it. On a two stroke you need to set the engine leaner with muffler pressure for the same run. But the engine will run at different rpms with a lean or rich setting. I don't know how the 4-stroke would respond, but perhaps since there isn't such a dramatic shift in rpm with rich and lean settings on the 4-stroke that you were too rich with the muffler pressure but didn't realize it? (Guessing only)

Len,

When the pressure hose came off, the engine was about 3000 RPM lower until the needle was re-set. So the pressure was there originally. In fact, I was surprised it ran with the needle so far off.

The other tanks were a plastic non-uniflow and a metal uniflow plumbed with the uniflow vent plugged and pressure to the overflow vent.

Also, the carburetor on a Saito 30 cannot be reversed, so the needle on a profile is on the bottom. It takes some interesting muffler positioning to keep your fingers from getting burned by muffler. But I got pretty good at adjusting it through this horror story.

Hi Jerry:

Am I messed up or should the engine go lean and speed up when the pressure line comes off?

Pressure should richen the setting until the needle is adjusted.

Curt,

That's not what happened. Pressure off ran slower (richer) needled it in (leaner) to get the RPM back up. I changed the prop at the same time. This might have been why the RPM was lower. But since it was a smaller prop it still does not make any sense.

Maybe we need Scotty to step in here and jury rig this thing so we can get warp speed from a dead egine, 'eh captain.

Whoa,

Just spoke with Joe Reinhard. What if this whole time the muffler tap was clogged or partially clogged. The other vent was of course plugged, this would cause the fuel tank to be de-pressurized and lean out the engine until it died, which it regularly did. Will check this out tonight. Wish Joe had thought of this Sunday when we were flying. Actually Joe was flying, I was cursing.

Jerry,
I ran a Saito 30 on my modified Twister and have a comment about muffler pressure. If you are marginally powered (which I was), muffler pressure can be a problem. What I noted was that as I continued the flight, the engine would begin to sag. This of course actually decreased the rpms and as a result also the muffler pressure--which then leaned out the engine even more. So I decided I was better off without muffler pressure, so at least sagging wouldn't have this positive feedback effect.

In the end, I had to go to a more powerful engine to fly through the full pattern. The Saito 30 was "ok" in the shorter beginner pattern. Still was a very sweet engine. If I had a lighter Twister, it might have been ok for the full pattern.

LAST EDITED ON Nov-05-03 AT 11:59 AM (CST)
 
Alan,

How much did your Twister weight? I am flying (or trying to fly) a 37 oz. P-Force.

Joe Reinhard had a general rule to try and keep the weight approximately the same as the engine displacement. This was for two strokes; do not know how it would relate to 4 strokes. Guess mine is somewhat too heavy according to this rule.

I am not sure of the weight. I'll have to weigh the "pieces" when I get home!

Just for an additional reference, I placed 3rd in Intermediate at Brodaks two years ago with a Saito 30 on a 37 ounce Twister. No muffler pressure running YS 20-20 fuel. It would do fine as long as the wind wasn't blowing. It now has a Saito 40 and weighs 47 ounces with all the camera gear, will still fly a pretty good pattern.

Jerry,
Put all the Twister pieces including the metal tank, prop, and Saito 30 on my new electronic scales and got a weight of 40.2 oz.

LAST EDITED ON Nov-08-03 AT 12:53 PM (CST)
 
Here are some before and after pictures (not sure of the order)

The muffler tap is not clogged.

Wow, I would have placed a bet that you found the problem, sure sounds like it isn't getting any venting from the muffler. Glad I don't bet

Do you think it could be a problem with the engine? Come to think of it I have the Saito 30 I took off the TwistMaster, I know it runs good. If you want I could ship it to you so you can stick it on for a couple of flights to see if it will tell you anything. I removed the muffler pressure fitting and replaced it with a screw, I also cut off the exit tube and enlarged the hole to get as much power as I could out of it. It would be kinda tough to put on pressure with the muffler modified but at least you would have a known good engine to compare yours with.

I also have a P-Force kit I am planning to build one of these days and have a new Saito 30 Golden Night I was going to power it with. I really thought that would be a good combination. Hope you find the reason your 30 isn't acting right and let us know how the P-Force/Saito 30 turns out with a good engine run.

By some chance do you have some type of filter or one-way valve between the muffler and the tank. If so I would make sure that isn't clogged or the one way in backwards.

If you put your finger over the muffler exit hole, and turn the prop over, is fuel forced into the carb? From your description, it certainly sounds like you have a blockage somewhere in the muffler pressure line. If you had to close the needle to run without muffler pressure, that is telling you that you are just not getting any pressure (for whatever reason).

What happens if you run this on the bench (with and without muffler pressure?)

If you had to close
>the needle to run without muffler pressure, that is telling
>you that you are just not getting any pressure (for whatever
>reason).

Correct.

Guys,

I should have realized the muffler vent was not blocked. The muffler is directly below the engine. Fueled it thru the top vent on the tank. When the tank was full, the fuel ran out of the bottom vent, thru the tubing and out the end of the muffler, then capped the top vent. There is no other valve in the muffler pressure line.

To prime the engine the muffler line was left on, the end of the muffler plugged by a finger and the prop flipped. Fuel flowed into the fuel line. When my finger got wet I knew fuel had gone in the intake valve and out the exhaust. The muffler line was removed from the tank, prop flipped to check for hydraulic lock, light the plug, turned by hand until it bumped, and started with an electric starter.

There is no other easy way to prime it. The intake opening is very close the profile fuse and a curved, special hose from the syringe would be needed.

Bob,

I am not a very good flyer and wouldn’t want to try it with someone else’s engine, but thanks for the offer.

Brad,

I know it doesn’t make sense, but that’s what happened. ???????????

Anyway, it is running OK on atmospheric, so until it is flight-tested, which may well be months from now, we won’t know the final outcome.

LAST EDITED ON Nov-06-03 AT 02:20 PM (CST)
 
I'll make one more comment. Are you sure you actually were leaning the needle rather than richening it when you took off the muffler pressure? You may have been so lean that it was sagging, and opening the needle actually made the engine run faster, which could be interpreted under confusing circumstances as thinking you were leaning it out, not in fact as richening the mixture!

As you mentioned, the needle is on the bottom, and it is easy to get confused, especially if you are experiencing problems ! Don't ask ME why I know this!

Yeah, pretty sure. The engine was running at about 7500 RPM, and pretty steady, though it did sound just a little ‘fat’, like a 2 cycle running rich. None of the herky, jerky’ness like when the pressure was connected. Turned the needle toward the engine slowly, and the RPM steadily increased until it peaked at 10,500 where it started to sag, then backed it off to 10,200 where it held steady and ran smoothly. It kind of surprised me that it was increasing so much, and holding so steady, after all the trouble it had over the past few weeks. That was, of course, the 1st time it ran like it was supposed to.

LAST EDITED ON Nov-08-03 AT 01:27 PM (CST)
 
Do you suppose the pressure tap in the muffler is in a low pressure zone and is creating a vacuum? It should be possible to take a long piece of silicon fuel hose, let it sag into a "U", fill it with some green or pink fuel, and see if it is blowing or sucking. Just a thought. Also try flipping the airplane over, so the NV is on the top...maybe you were screwing it the wrong direction, and didn't realize it. Good luck. Steve

PS: I really like Alan's yaller "ATwister6".

Got out to fly the plane this weekend. Cold and nasty. First flights were too slow with the 9x6 prop. Switched to a 9x4 APC at a screaming 13,000-RPM. Flew a 5.3 lap which still seemed slow, so I slowly started some loops and inverted. Did just fine, in fact it pulled hard going up and held good line tension. Then did the wingover, more loops, the horizontal eight and the squares. After the flight the weather turned really nasty and started a heavy cold drizzle. Wrapped up and called it a season.

LAST EDITED ON Dec-05-03 AT 08:10 AM (CST)
 
Had one more chance to fly the next weekend. Weather was even better.

Finally got it to run perfectly. At 13,000 RPM with a 9-4 APC prop. 20% nitro, 50/50 oil, no pressure. It pulled the P-Force thru most of the maneuvers cleanly and ran for 7 1/2 minutes. Was just a tad lean so I made it one click richer and flew the pattern clean with plenty of power. Finished the pattern with in 6 1/2 minutes so I started to do 2 outside loops to unwind. On the upstroke of the second loop the engine quite. Tried running back and almost made it, but not quite, it was toast. Tore the outboard wing off, damaged the spinner. The engine and prop survived, no apparent damage. After the crash time was still under 7 minutes. Post crash inspection showed a dry fuel tank. Those 4 strokes give no warning at all, just cut off dead with absolutely no change in RPM. The airframe is un-repairable, Wing torn off flush with the fuse, both spars are loose and still glued to a small part of each rib.

Conclusion: you can make a 4 stroke work, just be sure after ANY needle valve change you fly it for time. Put in a larger tank than needed and work backwards towards the pattern. Not sure if the extra maneuvering used that much more fuel or one click on the needle made that much of a difference.

Just received a ARF Flite Streak. The engine will go on that for further evaluation.

You can throw out everything you ever learned about 2 stroke engines when dealing with a 4 stroke. Since no one in my club has ever used one for control line it's all a new learning curve for me. Better get this figured out 'cause next season I'm running all of my new planes with 4 strokes.

LAST EDITED ON Dec-05-03 AT 09:07 AM (CST)
 
Jerry... I currently have a Saito 30 on the bench breaking it in. (Plan to put it one of Walter's Zilch X's). I have the recommended 10-6 prop on it and it's now on about it's 20th run cycle. When I first set it up I used muffler pressure and a wet needle setting. When I would tilt the engine stand up the engine would sag and quit. Thought this strange because it acts like it's going lean even though it's so rich that I could touch the mufler without getting burned. Pulled the muffler pressure and it will speed up slightly when I tilt the stand ?????

Second thing is that this engine won't turn more than 9200 RPM with this prop compared to your 13K+ on a 9-4. Very strange

Added info - Using Powermaster 10 /22 and topflight wooden prop - valves are adjusted

LAST EDITED ON Dec-05-03 AT 09:12 AM (CST)
 
Dick,

Yeah, was amazed it would turn that kind of RPM. I found that the pitch and apparent load that it generates makes a huge difference on this particular 4S. Think it is due to the small size of the engine. Whenever I changed props the RPM had to be readjusted, even between manufacturers when using the same length and pitch. It seemed the weight and blade size made a difference. Also, always go to a richer setting and SLOWLY come up until it peaks then starts to sag, then back off 2 clicks. This was how it flew on the next to last run. It definitely did run leaner on the upswing of maneuvers. That’s why it was richened another click. Just a tad ‘fat’ in level flight but leaned out perfectly when going over the top or in round maneuvers.

Just received a bunch more APC props in odd ball sizes direct from APC .
www.apcprop.com
Not the usual selection available from retailers. They have ½ in. increments and many more pitches, like 9.5 x 4.5 for example. Will have to wait ‘till next season to try them out.