4 Stroke note and question

LAST EDITED ON Aug-22-04 AT 02:41 PM (CDT)
 
For 4-Stroke users---

Overall, I'm pretty happy with my setup for now. Not to say I won't go back to pipe engines or 4-2-4 engines or something else entirely in the future. But for now, the 4-Stroke setup I'm flying makes me pretty happy. The plane I've been flying is mostly trimmed and reasonable. Nice to just work on my piloting for a bit. I think the thing I like at the moment is, if something doesn't work with the engine, I've had enough time on it to understand how it reacts pretty well and can usually come up with a remedy. It hasn't done anything weird to me in a long while. Just thuds along.

One strange thing I noticed (good) is that the engine I'm currently using, a Saito 56, has a bit of time on it; maybe 250 to 300 fights and it has become very consistent. I can even pretty consistently hand start it (3 out of 4 times). It has become quite predictable. Even the fuel consumption has stabilized to the point that I'm no longer feeling like a have to use a barometer, thermostat and the direct intervention of Mr. Saito to predict how much fuel I'll need for given conditions. The run never varies more than a lap or two from flight to flight. That's a change.

The other Saito 56 I have has been broken in on the bench (about an hour of run time) and has perhaps 15 or 20 flights in a plane and is really pretty inconsistent. A great run, a marginal run, a good run, etc. Never quite the same flight to flight. The fuel consumption is all over the place varying as much as 12 laps on the same amount of fuel as the conditions warm. The power is fine generally, but can vary quite a lot. This with the same tank, venturi, prop, and fuel as the older engine. I remember the older engine acting like this the first season I used it but before the end of that season it had mostly settled down and has just gotten better since.

Is this just a function of these things? Takes a good, long while for them to settle in? Has anyone else experienced this? Besides being more consistent, the older engine is noticeably stronger too. Not by a great amount, but you can tell. Again, is this to be expected with it "coming in"?

Just wondering if others had seen this.

edit: typo...again

Randy,
I think that just about everyone who has run 4 strokes has found the same thing. I found that when the fuel consumption became the same the runs became the same.
Alan

LAST EDITED ON Aug-22-04 AT 12:17 PM (CDT)
 
Randy, what you descibed was just like my Saito 72. Saito's are VERY HIGH QUALITY motors and as such, take a while to break in and get smooth parts matings and fits. Once done, the fuel consumption becomes very consistant and as you said, "it just thuds along." When mine was brand new and on my test stand, it gobbled fuel like a Vampire at a Red Cross blood drive. Gradually, the more I ran it, the more consistant the run became, and the lower the fuel consumption was until, it has become incredibly economical for an engine of this size and power. I have been running my Saito 72 for 4 years now, and the compression is like new. We are talking Enya class quality!!
Like you, I will use other motors which I own, and will also purchase new and different types of engines, but for the foreseable future, assuming Saito maintains this level of quality, they will most certainly form the vanguard of my control line precison aerobatics program.

"I don't know about this tuned pipe business. I practiced on that thing until my lips turned blue, and I still can't play a stinkin note."
"Homer J. Simpson"

LAST EDITED ON Aug-22-04 AT 02:42 PM (CDT)
 
Alan and Milton (sounds like a song),

It was just the idea that it took so long, I suppose. Any engine has a period after break in while parts stabilize and so forth. The Stalker 61RE I flew a couple of years ago took what seemed like forever to break-in and stabilize. Maybe 2 hours on the bench and another 50 flights in the plane before it was even useable. Another 100 before it was dependable. But I've been running this one Saito 56 for the better part of 3 seasons and it's only really come in over the last couple of months (maybe 50-70 flights). I dread something happening to it that would force me to fly the other engine and take 200 flights before it really ran as well. I suppose I could put it back on the test stand and run it some more....

The fuel consumption thing was the tough part. Again, I don't see this as uncommon at all. Even back when using ST60s, the fuel consumption would jump around by 6 or so laps until the engine was really broken in. But Saito 56 seemed really sensitive to changes in conditions. Much different fuel consumption (as much as an ounce difference) from hot weather to cold or if the humidity jumped around a lot. Now it seems, there's very little variation in consumption reguardless of conditions. As Alan knows, I use a setup different than most people use for this engine. This includes (among other things) a pretty big venturi (.310 to .325 depending on tank design). I suspect this magnified the consumption issues when the engine was new. Now, it's 135ML every flight and I get 6 laps after the clover. Every time. Seems it's even more consistent that other engines I've run and almost regardless of conditions.

Hey, no complaints. It just works and I'm happy. I love having a consistent power delivery system. There are plenty of other things to worry about. Nice to have this one thing (the power train) work consistently so I can worry more about my flying than about the engine running right.

edit: typo...I really need to use preview.

Edit 2: Oooops, forgot to mention that I gave up on plastic tanks. I could never get as consistent runs as I wanted. The thing would speed up and slow down in maneuvers as the pressure in the tank changed. I think these engines run better if you can maintain the head pressure at something approaching consistency. I used to use a sort of chambered, modified chicken hopper design back when I used ST60s and I went back to that again recently. It works.

Randy,
I also have a new Saito .56 (20 min on a bench), tried it in flight, very inconsistent, both power and feul consumption, so I temporarily gave up on it and put it back in the box. From all the responses on this thread, I gather that it's typical / normal, and I just need to hook up a gallon jug to my bench, and let it rip all day long. The valves must take that long to get properly seated, as well as all the little cam parts.

Questions for you on your setup: Stock carb or Johnston venturi? what prop size are you swinging? at what RPM - peak / release? Plane size and weight? Line length (center to center)? Lap time? Any windup issues?

Thanks

I operate my 72 "just like the RC Boys": plastic tank, wired open carb, APC prop, go fly!!
Actually not quite like the RC Boys; I don't use a servo on the carburetor! But, I happen to have a few Futaba 3003's, and I just might cook something up

"I don't know about this tuned pipe business. I practiced on that thing until my lips turned blue, and I still can't play a stinkin note."
"Homer J. Simpson"

Randy/Milton/Alan:
Although I have minimal experience with the large 4S engines, I have found the same to be true on all the smaller ones - .20 to .40. They all need lots of time before coming up to true potential.
The most dramatic performanance increase was with the SAITO .30. I would guess that it had close to a gallon through it before it was acceptable. The .30 on my Little Cherokee, which has been flying for over three years, is as close to perfect as I could want from any engine. The .30 in the Argus is getting there but still needs a lot of time. The most noticeable indicator I've found is that the required amount of fuel to complete the pattern will continue to diminish - when it's stabilized, your engine is properly run in and at its best. I've also found that most of the engines will require one valve adjustment after running for around an hour and none thereafter. Case in point, the Cherokee's .30 - nothing has been done to it - valves or even the glow plug for the last three years.
My fuel of choice is still the Powermaster GMA, 10% nitro, 22%, 50/50 oil.
I have also found that the best performance is with standard metal non-uniflow tanks.
Bob Z

OK ive never run a 4 stroke and probably never will.
However, I will offer my advice.

On all my engines Im a firm beleiver in "bench time"
Ive had a couple of people use the engines ive run in the past and ask me " I cannot get it to run as good as yours "
Ive even had people say " ohh you got a good batch of engines "

now this to me is all rubbish.
When you "bench run" an engine you are wearing in the piston, setting the temperature, securing the fit ect ect ect.

I give ALOT of time on the bench running in. On average I will put ( NO JOKE ) 10 - 15 liters of fuel ( 4 gallons ) through my engines on the bench.

Ive also had others suggest this isnt the best thing to do as it wears out your engine. But last year I clocked close to 1000 flights with the same engine, and she still runs perfectly. Again, BENCH TIME!

If what your saying is true about the 4's " after 300 flights its now consistant. Isnt that telling you something??

Think about it.

20 - 30 mins bench time ISNT ENOUGH. I dont build engines, but ive been running them for years )
All im doing is telling you what I do. You can draw your own conclusions. I will not be changing my methods.

PJ,

Of course, all engines need time to run in. Depending on manufacturing tolerances, metallurgy and assembly, the time it takes to seat things and get the engine to peak performance varies pretty widely. I just thought it was interesting that the Saito 56 I run took something like an hour of bench time AND 200 flight to reach it's be running. That was more than even the Stalker 61RE I have that I thought would never actually break in.

Bob,

I think I've "had" to adjust the valves on the 56 maybe 3 times and it has about 300 flights on it. I check them a lot (maybe once a month) just due to my own paranoia, but haven't actaully adjusted them since the end of last year.

Something else I noticed is the engine is a lot happier (at elast mine is) if I don't fly "back to back" flights and allow it to cool a bit between flights. Maybe 15 minutes or so. There's a lot of venting so I don't think it's getting too hot or anything, just seems to run the best if I let it cool off after a flight.

Gday randy.
Well my last engine was the Stalker 61 RE LITE and I did put 15 liters through it.

My new engine is the Stalker .61 longstroke LT L/S and Ive put exactly the same amount through.
1st fligh was jsut the same as the last flight I had last week.

I'm a FIRM beleiver in Longer bench time than the manufacture suggestions.
I find when they hold rpm at both LOW and HIGH rmp they are getting close. Also I find after longer running in time, they reac a higher max rpm.
Again im not labeling myself as an engine guru by anymeans. Im jsut saying what works for me, might work your you also??

Something else I noticed is the engine is a lot happier (at elast mine is) if I don't fly "back to back" flights and allow it to cool a bit between flights. Maybe 15
minutes or so. There's a lot of venting so I don't think it's getting too hot or anything, just seems to run the best if I let it cool off after a flight.

This is what we call Engine cooldown.
Metal expands, when its hot, and you get erratic runs. I set my watch to 10 mins after every flight. I get consistancy everytime.
No sooner.. No later !

PJ,

Yea, that's about right. I believe that most engines, what, get used to a specific run time? Get stabilized to run a certain length of time from cold to done. I think this creates a preferred cycle. I know back it the days when I was involved in drag racing (a long time ago), most mechanics I knew believed this. It's one of the reasons that after initial runs on the bench, I set up the test stand with the tank I plan to use in the plane, fill it with the amount of fuel it will use and run the engine the length of time it will run in a pattern. Maybe silly, but what the heck; it can't hurt.

Plenty-plenty bench time is the marching orders for me. Has been since my early teens. I learned that at Flushing Meadows, New York. While a lot of RC engines are designed for quick break-in because of the nature and demographic of RC pilots, I equate quick break with fast "wear out." It seems like, the better class of motors take longer to break in. Kirk Mullinix told me it took quite a while for his PA engines to break-in. He stated that they were absolutely some of the highest quality, longest lasting motors he has ever owned. In the case of my Saito, 2 gallons on the bench, then take it easy in the air at first, then let her rip!!
When it comes to control line motors, I like quality. My Supertigre 46's are still running perfectly, and one of them has been in use since I was 14 years old!
We all know about Enya's, and mine are no exception. I believe long lasting, high quality engines provide a tactical advantage as well, in that, the extra time you spend with the motor, helps you to develop critical expertise and a knowledge database that is needed in high level competiton. In the case of my Saito 72, it has became almost "intuitive." There is virtually nothing that motor will do that I don't know about.

"I don't know about this tuned pipe business. I practiced on that thing until my lips turned blue, and I still can't play a stinkin note."
"Homer J. Simpson"