TManiaci

My Feedback: (6)

For the Saito Experts out there...

I have a Saito 72 (Funtana 40), Saito 100 (BME Cap Maniac) and a Saito 150 (Funtana 90). I, along with many others, seem to struggle with achieving a good low-speed idle without severe shaking. Even after ample break-in, anything below 2000 rpm begins to produce significant shaking. It's not hard to get them to idle at 1800 or even lower, but they just beat up these frail lightweight planes and the low end needle must be leaned out to a point I become uncomfortable... almost no smoke trail visible. Pretty much everyone I talk to has similar difficulties, so I don't think I have some unique situation.

I have a buddy that put a Perry VP30 and a Pitts muffler on his Saito 150 powered Funtana 90. After helping with tuning the engine for the pump, it became very obvious that there is a considerable increase in performance, and a shake-free 1600 rpm idle. Not only that, but the low speed needle setting can be VERY rich producing a fat smoke trail. The top-end is improved considerably too, where he turns a given prop around 500 rpm faster than mine with the stock muffler and no pump. We have done considerable bench testing, and the numbers are pretty telling and there is no doubt about the improvement his mods provided.

So, I am making an assumption... the the gain is mostly due to reduced back pressure on the exhaust, and the pump is necessary to deliver fuel because the pressure in the muffler is not adequate to drive the fuel to the carb.

Downside: The VP30 is a very finicky setup, and seems to drift a bit from the ideal settings. It floods instantly with the engine mounted inverted (both planes) and causes mammoth starting difficulties. So the pitts-pump setup is not ideal, but once it starts, it runs real sweet .

I have taken the stock muffler apart, thinking I could remove the baffle... it's part of the tail-piece, no-go. So, can't do that. I have purchased and mounted a Perry VP20, which I figure will be less prone to flooding and easier to tune. Now, without blowing another $100 on a Pitts, and rebuilding the front-end of the plane (new cowl and Pitts mounting), I am considering trying a straight-pipe off the header. I would put a silicone muffler pipe extension in place of the stock muffler directly on the curved header pipe.

So, has anyone tried this?
Does it work?
What should I do with the pressure line to the tank?
Will it hurt the engine to run it like this?

Any help would be appreciated! If this works, it sure promises to be an inexpensive way to solve some apparently inherent and widespread issues with these wonderful engines.

William Robison

My Feedback: (3)

Maniac:

When running any pump the tank vent line should go to the atmosphere, and the muffler pressure nipple blanked.

Straight pipe? Try it. Cut it longert than you think you will need, then trim a little at a time and try it again. You will find an open pipe is a bit "Peaky," you can widen the power band by having the pipe taper to a larger end diameter - a megaphone in other words. Everything affects everything else, pipe length, engine rpm, length of the megaphone, the taper, so forth. It has some rough rules of thumb, but it all comes down to experimentation. This holds true for both two stroke and four stroke. With a 2s engine there are a lot of factory made units that are pretty good, I don't know of any intended for a 4s engine though.

Have fun.

Bill.

TManiaci

My Feedback: (6)

Well, I didn't get much play on this question. But, I have gone forward, and what a great success!

For all you Saito guys looking for a little more power and a lower, smoother idle, we have a solution!

I put on the straight pipe, and installed the Perry VP20 pump. WOW! Now turning the APC 16x6 at something over 10,300 rpm (was 9600 rpm). I can't lean it out to see how much higher it will go, afraid of floating the valves. Need to get a 17x6 or try my Zinger 18x5 again, too much power on this Saito 150 for the 16x6 prop now.

I turned the Perry way down till I got a smooth mid-range (it was sputtering wet rich), adjusted low needle till idle is solid at 1800 rpm, and WOT richened down to 10,000 RPM. High needle is out 3-1/2 turns to slow it down to 10K revs (was 2-1/2 turns). I can get idle down to 1600, but it's still a little to rough there.

Transition is now like a top-fuel dragster, and it drops to a solid idle instantly without fade or bobble. I let it idle (purring like a kitten, never a single miss) for more than 5 minutes, then slammed WOT, instant response... no loading up. Starting is first crank every time. AND, it is making monster smoke from idle all the way to WOT. It's everything I hoped it would be. Ran two tanks thru it, no bad habits and revving is amazingly snappy.

This thing is awesome now! You guys flying Saito's, this is your answer to boost power! I'm thinking you can gain over 10%. Hope "somebody" gets something out of this besides me!

Harry Lagman

TMan, great piece of experimenting. I have found the same sorts of benefits runnning a straight pipe on my four-strokes too.

Where did you get the straight pipe for your Saito? I'm looking for one for my Saito 100.

Thanks in advance.

William Robison

My Feedback: (3)

Harry:

I think what he has used is the standard curved pipe that comes with the big block engines, and stuck a length of Aero-Trend silicone hose on it.

Since your FA-100 is a mid block, the 14mm big block pipe wont work on yours. Tower does sell a variety of 12mm exhaust pipes and fittings that will work. Among them is a flexible pipe that may do what you want, it's not really "Straight" though, it's more an accordion fold - that's what allows you to bend it to fit your installation.

As an alternate you could cut a short chunk from the supplied threaded connector and weld a pipe to it, shaping it as you wish. The connector is long enough, if you don't cut too much it would still be long enough to put the stock muffler back on.

Please note - WELD not braze or bronze welding. Either tends to crystallize, crack, and fall off in flight. Best would be TIG welding, second best would be MIG. A really good welder could do it with gas, but that really should be your last choice.

Bill.

pnmrr

I recently bought a Satio 56 and was digging up all the info I could and ran across the site that is listed below. There seems to be alot of good info there so it is worth a read. The one thing that stuck out in my memory was this quote:

Most “engine problems� for new users are not really problems with the engine itself but with the operator and a misunderstanding about how to properly set up the low-speed needle.

The amount of smoke coming from the muffler tells you nothing about whether you have the correct fuel mixtures. Usually there will be a puff of smoke when the throttle is advanced rapidly.

Give it a shot, maybe it can help.

A link right to the carb adjustment page:

[link=http://saito-engines.info/throttle_setup.html]Satio info[/link]

blw

My Feedback: (3)

pnmrr,

I've used that method many times and it works well. Hobbysy peaks his HS, then sets his LS, then richens the HS a few hundred rpm. I've been meaning to try it that way. Usually, I can tell how my needle valve settings are by how the idle sounds (after the first flight or a few goes in the traffic pattern).

I can idle my Saitos lower than 2200, but I haven't really felt the need to yet. I usually can't hear my .72 when the plane is idling on down lines, or up high. I sometimes have to blip the throttle to tell if it is stlll running...and it always is.

Saito also sells the flexible pipes, with and without pressure nipple. I've thought of getting one the next time I need to spend $35. I read somewhere about a guy who drilled out the holes in his baffle, but I have no idea if it did anything good.

edit to add: That tuning method on saito-eng is excellent for the first time tuning a Saito engine. It teaches you a lot about the relationships between needle valves and idle. It is a good learning process for Saitos.

Hobbsy

My Feedback: (102)

That is a very good link. lottsa good stuff.

TManiaci

My Feedback: (6)

Bill,

Yes, that is the Aero-trend Tube. Unfortunately, took it to the Flying Cirkus fly-in today at Rabbit Dry Lake-bed. VERY windy, so we just got it out to run it with the Zinger 18x5 to see how it ran. It was only turning 9330 rpm, and was sick-rich starting at 3-1/2 turns from the APC 16x6 setting. Before I got a chance to lean it out on the high needle after about 2 minutes of playing with idle and warming it up, the blue silicone pipe sheared off at the end of the header pipe. That tubing is very brittle, and I had anchored it with a flexible wire brace so it wasn't hanging free. The anchoring must have stressed it too much, but there was no evidence of any heat damage.

Went to the hobby shop and bought a length of a different grade of pipe, the AeroTrend 1061 (fits perfect) and is much more flexible and thicker too. We'll try it and see how it holds up. The wire brace is really simple, and allows things to move around pretty freely.

I hope you guys understand, I know how to tune the Saitos. I have three. I did it by the book, and I understand the process just fine. I went thru this little routine because I am monster over-powered on a light plane (Saito 150 on a Funtana 90). The engine turns so much prop, I get frustrated with it rolling uncontrollably at over 2000 rpm and would not sit still without holding it. Then, when I would tune it below 2000, it was shaking really severely. Then I saw my buddies with the Pitts and Pump, it was so much smoother and more powerful, I had to make the change. I also was experiencing a bit of fuel starvation at WOT with the stock pressurized tank system. It would surge and lean out on the top end after about 3 seconds at WOT.

The point here was to prove that there is an economical way to solve these problems, and improve performance all in one-fell-swoop. For $34 in a pump, and $8 in pipe, I have accomplished the same thing my buddy did for $100 more. And, I didn't have to buy another cowl and redo all the cutouts. I'm happy, so long as this pipe hold up without breaking off.

So, the combination of reduced back-pressure (like putting headers on your car) and ample fuel delivery has really made this a better plane. I actually flip started her today for the first time... now that was a good feeling to see it start with a couple flips like the big gassers. I could never do that with the old setup, it was just too hard to get it to fire and I would have to spin it for several seconds with the electric starter before it would spark off.

It works!

William Robison

My Feedback: (3)

Maniac:

I'm not surprised the blue Aero Trend hose fell off. It's only good to 300F or so. It stands up fine on a two stroke, but the 4s engine's exhaust is just too hot for it. I think the brown stuff is good to about 600F so it should work fine.

Another thing about the silicone hose, true of the brown hose as well as the blue, is that it is easily damaged by any sharp edges. If you did use the stock head pipe without polishing the threads and rounding the end you might just have been a victim of the automatic cutting from the inside of the hose. As I said, this might give you a problem with the new hose as well.

Another way to go is making the entire pipe from copper tubing. If you have a damaged or broken inlet manifold from a big block Saito you can take the gland nut from it an get a length of 7/16" (I think) tube, flare one end to have a flange for the nut to push against. I have one exhaust made this way, but I cut it too short. I'll try it again someday.

Have fun.

Bill.

TManiaci

My Feedback: (6)

Just an update for anyone checking in on this project...

Have now put in 8-10 flights on this new pump-pipe setup, and it is working SO well. I am really pleased with the solid, smooth low speed idle stability, transition is blistering fast, and top-end power is off the hook. Still getting decent flight times with reasonable fuel economy (0.8-1.0 oz per minute), and still leaving a nice thick smoke trail in the sky.

Getting the starting routine worked out. The biggest challenge with the simple plumbing is the lack of tank pressure to push up a priming load into the fuel system and to the carb. We started using the CUT button to force a pull, which works with the starter, but not flip-starting. Once we get the first start of the day, flip starting works fine.

More info on improved performance: As we can measure, this is the strongest Saito 150 perfomance reported (that I can find). Now turning an APC 17x6 at near 10,000 rpm (afraid to lean out any more). This is ~300-400 rpm better than a similar setup on a freinds plane running a Perry VP-30 with a Slimline Pitts muffler (my inspiration to try this project). I need to measure again, but it was pulling over 17 lbs thrust running fat-rich.

Tiroloco

My Feedback: (1)

There´s a problem you must keep in mind when you take out all back pressure from an 4 stroke engine exhaust system.
You can have a lot of chance to get the exhaust valve seat in the engine head "burned out" and start loosing compression.
Even F1 racing cars have a little back pressure on its exhaust headers to prevent this kind of problems.
The reason is simple: Warm exhaust gas expands when temperature lowers (at exhaust zone), if it doesn´t find any opposition, it will expand more quickly acting as an explossion when it should act as a controled explossion to keep exhaust temperature stable.
If you have a look at YS engines, they are noisy, more than any other 4 stroker, and if you have a closer look to its exhaust system, it is somewhat restrictive. If you take out the muffler, you will notice the engine is little bit noisy than with the silencer, makes not big difference.
So think if you want to be prepared to replace the head from your engine quite often or you want your engine to last for a long time.
If you need more power, try using 30% Nitro heli fuel, must 4 strokers love it!

Best regards.

William Robison

My Feedback: (3)

Tiro:

Exhaust valves are not damaged by running with an open exhaust. Just for one quick and easy example consider the Alison V-1710 and the Rolls Merlin V-1650 engines.

Many installations of these engines (P-38/ P-40/ P-51/ Spitfire/ Hurricane/ Mosquito/ etc.) had only short exhaust stubs, with the ends of the pipes just about 8" away from the exhaust valves. This is the approximate equivalent of a 1" pipe on a Saito FA-150 engine.

What kills an exhaust valve is one, running 'way too lean and overheating the valve, then burning a notch in the seat face. Model engines burning alcohol fuel will not run that lean, and will not get that hot. The second cause for exhaust valve damage is shutting the engine down while extremely hot, and having cold air flow around the hot open exhaust valve and warping it. If the valve is closed this can not happen, and model engines burning alcohol fuel will not get the valve that hot anyway.

If you don't need a source for muffler pressure there is no reason not to run short exhaust stubs on a model four stroke engine. At least as far as engine damage is concerned. Noise considerations are a different matter - for that a muffler of some sort should be used.

Bill.

TManiaci

My Feedback: (6)

Thanks Bill, I was beginning to question what I have done here. The LAST thing I want to do is damage my precious engine. I do have a fairly long pipe on it, wanted to keep the goo off the plane a little more, and it does that nicely.

khodges

My Feedback: (1)

Go to the Horizon Saito parts and look up one of the flex pipes for their twins. It comes with the elbow, some have a nipple for a pressure line, or you can drill your own. I have one on my Saito .80 powered WACO, and a guy at the club runs one on his H-9 P-40 with a Saito 100. The pipe is "corrugated" and is no louder than the muffler, but has a meatier exhaust note.
I turned the end down on mine, hardly any residue gets on the plane.

TManiaci

My Feedback: (6)

Yea khodges, I have seen those at the LHS, but $35 and I have heard about several of these cracking and breaking from the vibration. That's why I wanted to try the cheaper tube first. If I have trouble with the tube, I'll go that route and mount it really well...

zvika

Great Idea TMan

We had encountered the same problems as we moved from Funtana 90 to the Showtime 4D and we had to install the saito 120 upside down. (Funtana installation was 90 deg).

As the clearance for the stock muffler with the coupler provided was negative (the firewall was in the way) we had to find 90 deg connecting elbow, finally we found an hydraulic surplus pipe connector that was drilled to the max bore of 11 m"m (instead of 12 in the stock one). engine was installed with the carb about 10 m"m below fuel tank feed.

during this weekend we had the maiden flight only to find the engine unreliable in this configuration, during checks the engine would lean if the plane was pointing up, richening the needle had no effect (engine would die if was left pointing up for 30 seconds).
i've opened the needle 3-4 turns with no affect.

we had installed the same perry pump and were encureged by your messages to dump the muffler and install the tefelon deflector pipe directly on the stock connector.

We also found that the evaporizer groove inside the carburator to face airflow entry (which seems wrong), we' ve turned the groove to the side by losening the nut on the high speed needle.

FenceMagnet

My Feedback: (2)

"We also found that the evaporizer groove inside the carburator to face airflow entry (which seems wrong), we' ve turned the groove to the side by losening the nut on the high speed needle."

the "evaporizer groove" should point down-stream towards the engine, i.e. 180° away from the air intake...

[:-]

zvika

Thanks for the info

We have just tested the new installation and found a BIG impruvment, Perri is doing the job

AGR413

My Feedback: (1)

This is good info I may be looking into in the future, I am running an .82 and was having idle problems also, as of right now I have a very low smooth idle after leaning out the low end considerably, and a great transition. I am running the stock muffler with a dubro deflector, 15% cool power, it will swing my 14x4w at 10,500 rpm but I have it tuned to 10,000.

TManiaci

My Feedback: (6)

zvika,

Glad to see someone has found benifit in the "experiment". Do tell, what prop and how fast is it turning it? Describe "BIG improvement" for us...

BTW: two things...

1. Those Master Airscrew props are terrible in comparison to APC for efficiency. You will see an additional 3-7% thrust from the APC in the same diameter/pitch at the same rpm.

2. The location of your pump is very questionable. It is recomended to be on the motor to get reliable and consistent pumping action. I understand there is a great deal of vibration/shaking transfered to the engine box, but that could be unreliable and you should probably be adding vibration damping anyway to prevent long-term airframe damage. That looks like a H9 Showtime, right? If so, it is built VERY similar to the F90... very light build and vulnerable to glue-joint breakage.

zvika

Hello TMan

We flew the funtana for about 7 months, the bird flies great but alas something is not correct, comparing to Kyle's Funtana ours lack the ability to do such stunts. (well i suspect the blame is on the guy behind the radio...).

The Funtana is a great plane, flew beautifully, nothing to complain, beside tail wheel that had to be replaced all is as new.

as my son found the showtime, we had to get one and try it, we scraped the Funtana equipment in order to fly the showtime. but found some problems:
first, the engine we use the SAITO 120 is a little bit heavy which draged CG forward, battery and receiver had to move further to the back , option of the pull-pull link to the rudder was pointless.
Second, engine installation upside down and carb inlet below fuel tank was prone to engine flooding.
Third: stock muffler mounting was unsuitable due to lack of place, i had to find 90 deg elbow to change the muffler mounting.

finally all was installed and checked, then we found that the known reliable power horse starts to stutter, specially when engine in WOT and the plane is held pointing up. changing needle setting did not help. we decided to go to the field and give it air time check.

The plane was flying beautifully with a very accurate control. roll rate was exceptional at about 360 a second with aileron deflection of about 2/3 of the 3d (4d) setting.
but the engine performance was bad, hiccups and a dead stick landing was pointing to an engine problem.

We dismantled the engine in order to find a cause, checking the carb for air leaks, fuel line and refuel valve checks for clogging showed no reason for the behavior, during checking of the needle setting the !QUOT!vaporising slot!QUOT! (don't know the exact term) location was suspicious - pointing up to the air inlet, as i know from other engines usually the fuel spray is made to the lowest pressure in the carburetor which is the side of the air flow (at the highest air flow place in the venturi pipe) the setting was corrected.

looking in the INTERNET to find fellow people suffering from the same problem i found your thread and as it was logical idea, decided to try it. we had the perri pump set aside for a long time so this was real easy. looking on the perri installations other were doing showed that installing the pump on the fire wall should be OK as long as the rotational dumping is not great, as the engine is installed an hard mounting and the original mounting on the back plate of the engine was un feasable we decided to give it a try.

we only tested this set up on the ground, did not yet fine tuned the engine, but right now it drives the 16x6 Master K series at about 9300, but the main thing is that the RPM drop during tilting the plane and holding it up is minimal !!!

we hope to fly this weekend and give you air time impression.

Prop consideration: by our experience with the Funtana (just empirical) by compeering available force to bail out from hovering/torque roll we found that the master prop is better then the APC prop, visually it looks that the Master prop is wider then the APC C-2 one and maybe less efficient in the humidity and temperature we are having here.

the best

Zvika

AutoMike

Guys, here's what I've done to help get the most from my .72. I took the baffle and , one size at a time, worked the holes up to 5/32 in size. It ran much better but now I've went a step further, as you can see in the pic. I got a metal cutter for the dremmel and trimed away the metal from between 3 sets of holes still leaving enough metal for the whole thing to bolt back together. I got somewhere around 500rpm more from just enlarging the holes so I'll see tomorow how much more if any this will make. Mike

TManiaci

My Feedback: (6)

Mr.Pipercub,

That's VERY encouraging. I have a Saito 72 as well, rebuilding the crashed Funtana 40 that we fly it in. It was always just a little underpowered. I will definitly make efforts to increase power there, seeing that you have successfully seen a gain by reduced exhauset backpressure too.

I am convinced all of these Saito engines have some degree of excessive exhaust restriction. We have now seen the gains on the Saito 72, 100, 120 and 150 so far (SA100 on the Funtana thread). Typically adding 400-700 rpm on the top-end. Nothing to sneeze at!

I will do the straight-pipe w/ pump thing on the SA72 when time permits and report there too. The rebuild is time-consuming. It was crashed pretty bad, and I am salvaging two planes to make one. We are doing the F40 in F90 colors and trim. Should be cute side-by-side.

AutoMike

Well, I've seen no more rpm gain over just drilling the holes in the 72's baffles to 5/32. Seems the the muffler outlet and the holes drilled to 5/32 more or less equal each other in terms of airflow. Thats O.K. though, seems to be ideal anyway as the needle now has a much larger range from lean to rich, about 1 full turn before the motor shows any real rpm loss from "to lean" to "to rich". I like it now, just find where the rpm falls a bit while turning it both ways and stop it in the middle to a click or more on the fat side and it runs the whole tank beautifully. Mike