ST GS-40 break-in questions
05-14-2006, 12:29 AM
#1
Thread Starter
ST GS-40 break-in questions
I started breaking in a ST GS-40 today. MAS G/F 3 series 10 X 6 and Omega 10% with Castor Oil. Initially I couldn’t get it to accelerate past half throttle, so I changed to an idle bar plug and it kept running. First tank was sloppy rich 4-stroking (tached 6,000 RPM WOT). Let it cool and second tank I started 1/8 turn lean for 1-2 minutes and then repeated the pinch test 3 time per the ST manual, to another 1/8 turn lean, etc. It was about 7300 RPM after the end of the second tank. When I started up the third tank (stock tank for a WM Sky Raider Mach II – 260 ml) I let the engine warm and went to WOT. After running for a minute or so to warm up it suddenly jumped in RPM, but I had not touched any settings. Tacked at 12,000 RPM. I leaned it half a turn and it went back to 7500 RPM. I repeated the pinch and 1/8 lean method and by the time the third tank was finished it was running about 10,000 RPM.
When I started the 4th tank and went 1/8 lean it kicked from 10,000 to 12,500 RPM. It seems that 6 clicks rich on the needle valve will cause a 4000 RPM drop. The needle just seems very sensitive with a big RPM drop on very little movement. I did set the idle mixture 1/8 turn lean and get a pretty good transition off idle but gurgles a bit as it hits top end (it’s still rich on top end currently tach’s out 11,800 to 12,400 RPM). Since it’s been many years since I have broken in a ringed engine, am I leaning the engine too soon, or is this normal or ??? I just don’t want to run it too lean too soon being a ringed engine or is it ready to lean out more? Total run time so far had been around 20 - 25 minutes it does hold a really nice idle and the exhaust residue doesn’t have any darkness to it – just a good clean castor oil residue. Does it sound like it’s ready to fly and just slowly lean until hit peaks (or more like about 400 RPM rich of peak) or should I run it on the ground some more (richen it up a bit or ?)?
Hogflyer
When I started the 4th tank and went 1/8 lean it kicked from 10,000 to 12,500 RPM. It seems that 6 clicks rich on the needle valve will cause a 4000 RPM drop. The needle just seems very sensitive with a big RPM drop on very little movement. I did set the idle mixture 1/8 turn lean and get a pretty good transition off idle but gurgles a bit as it hits top end (it’s still rich on top end currently tach’s out 11,800 to 12,400 RPM). Since it’s been many years since I have broken in a ringed engine, am I leaning the engine too soon, or is this normal or ??? I just don’t want to run it too lean too soon being a ringed engine or is it ready to lean out more? Total run time so far had been around 20 - 25 minutes it does hold a really nice idle and the exhaust residue doesn’t have any darkness to it – just a good clean castor oil residue. Does it sound like it’s ready to fly and just slowly lean until hit peaks (or more like about 400 RPM rich of peak) or should I run it on the ground some more (richen it up a bit or ?)?
Hogflyer
05-14-2006, 01:54 AM
#2
Senior Member
RE: ST GS-40 break-in questions
Scott,
You seem to have more or less lost me on those RPM readings...
The technique you used seems OK, for a ringed, steel sleeve engine like this Super Tigre.
As to RPM; half the RPM means 1/8 of the horsepower, so having an engine spinning at 6,000 RPM at full throttle, when it can peak at 12K, is a bit difficult, even if the engine is running at a constant four-cycle (firing on alternate revolutions).
My experience says if it peaks at 12,000 RPM, it will be still two-cycling down to about 10,500 and will drop 500-700 RPM more, as it transitions to a four-cycle. Getting it down from 9,800-10,000 down to 6,000 RPM, still at full throttle, will be difficult.
It will also not get much wear-in on the sleeve and the ring at such low power. Combustion pressure at such a low BMEP will not push the ring against the sleeve very hard, so the mutual honing we are trying to achieve will not be.
It will take years to seat the two, and the glazing that will form will prevent this from happening later.
The best procedure for break-in is to follow [link=http://supertigre.com/manuals/sup-manual-v1_1.pdf]the Super Tigre manual[/link]. The section on ringed engines, of course.
You seem to have more or less lost me on those RPM readings...
The technique you used seems OK, for a ringed, steel sleeve engine like this Super Tigre.
As to RPM; half the RPM means 1/8 of the horsepower, so having an engine spinning at 6,000 RPM at full throttle, when it can peak at 12K, is a bit difficult, even if the engine is running at a constant four-cycle (firing on alternate revolutions).
My experience says if it peaks at 12,000 RPM, it will be still two-cycling down to about 10,500 and will drop 500-700 RPM more, as it transitions to a four-cycle. Getting it down from 9,800-10,000 down to 6,000 RPM, still at full throttle, will be difficult.
It will also not get much wear-in on the sleeve and the ring at such low power. Combustion pressure at such a low BMEP will not push the ring against the sleeve very hard, so the mutual honing we are trying to achieve will not be.
It will take years to seat the two, and the glazing that will form will prevent this from happening later.
The best procedure for break-in is to follow [link=http://supertigre.com/manuals/sup-manual-v1_1.pdf]the Super Tigre manual[/link]. The section on ringed engines, of course.
05-14-2006, 02:37 AM
#3
Senior Member
My Feedback: (14)
RE: ST GS-40 break-in questions
ORIGINAL: hogflyer
I started breaking in a ST GS-40 today. MAS G/F 3 series 10 X 6 and Omega 10% with Castor Oil. Initially I couldn’t get it to accelerate past half throttle, so I changed to an idle bar plug and it kept running. First tank was sloppy rich 4-stroking (tached 6,000 RPM WOT). Let it cool and second tank I started 1/8 turn lean for 1-2 minutes and then repeated the pinch test 3 time per the ST manual, to another 1/8 turn lean, etc. It was about 7300 RPM after the end of the second tank. When I started up the third tank (stock tank for a WM Sky Raider Mach II – 260 ml) I let the engine warm and went to WOT. After running for a minute or so to warm up it suddenly jumped in RPM, but I had not touched any settings. Tacked at 12,000 RPM. I leaned it half a turn and it went back to 7500 RPM. I repeated the pinch and 1/8 lean method and by the time the third tank was finished it was running about 10,000 RPM.
When I started the 4th tank and went 1/8 lean it kicked from 10,000 to 12,500 RPM. It seems that 6 clicks rich on the needle valve will cause a 4000 RPM drop. The needle just seems very sensitive with a big RPM drop on very little movement. I did set the idle mixture 1/8 turn lean and get a pretty good transition off idle but gurgles a bit as it hits top end (it’s still rich on top end currently tach’s out 11,800 to 12,400 RPM). Since it’s been many years since I have broken in a ringed engine, am I leaning the engine too soon, or is this normal or ??? I just don’t want to run it too lean too soon being a ringed engine or is it ready to lean out more? Total run time so far had been around 20 - 25 minutes it does hold a really nice idle and the exhaust residue doesn’t have any darkness to it – just a good clean castor oil residue. Does it sound like it’s ready to fly and just slowly lean until hit peaks (or more like about 400 RPM rich of peak) or should I run it on the ground some more (richen it up a bit or ?)?
Hogflyer
I started breaking in a ST GS-40 today. MAS G/F 3 series 10 X 6 and Omega 10% with Castor Oil. Initially I couldn’t get it to accelerate past half throttle, so I changed to an idle bar plug and it kept running. First tank was sloppy rich 4-stroking (tached 6,000 RPM WOT). Let it cool and second tank I started 1/8 turn lean for 1-2 minutes and then repeated the pinch test 3 time per the ST manual, to another 1/8 turn lean, etc. It was about 7300 RPM after the end of the second tank. When I started up the third tank (stock tank for a WM Sky Raider Mach II – 260 ml) I let the engine warm and went to WOT. After running for a minute or so to warm up it suddenly jumped in RPM, but I had not touched any settings. Tacked at 12,000 RPM. I leaned it half a turn and it went back to 7500 RPM. I repeated the pinch and 1/8 lean method and by the time the third tank was finished it was running about 10,000 RPM.
When I started the 4th tank and went 1/8 lean it kicked from 10,000 to 12,500 RPM. It seems that 6 clicks rich on the needle valve will cause a 4000 RPM drop. The needle just seems very sensitive with a big RPM drop on very little movement. I did set the idle mixture 1/8 turn lean and get a pretty good transition off idle but gurgles a bit as it hits top end (it’s still rich on top end currently tach’s out 11,800 to 12,400 RPM). Since it’s been many years since I have broken in a ringed engine, am I leaning the engine too soon, or is this normal or ??? I just don’t want to run it too lean too soon being a ringed engine or is it ready to lean out more? Total run time so far had been around 20 - 25 minutes it does hold a really nice idle and the exhaust residue doesn’t have any darkness to it – just a good clean castor oil residue. Does it sound like it’s ready to fly and just slowly lean until hit peaks (or more like about 400 RPM rich of peak) or should I run it on the ground some more (richen it up a bit or ?)?
Hogflyer
--------------
Peak the engine out, then back off 400 rpm (strictly arbitrary). Run the engine at this setting. If the engine begins to overheat and reduce rpm, it isn't broken-in sufificiently to fly it. If it will hold this setting, give or take 200 rpm (ballpark figure), then it is ready to fly.
If you want to speed up the break-in, drop to a 9x6 prop and run it rich for a while longer, but at 8,500 to 9,000 rpm - not 6,000 rpm, if the above test wasn't met. If you don't want to invest in a 9x6, just run your 10x6. It will only take a bit longer to seat, that is all.
Sometimes our engine mounts vibrate sympathetically with the engine's vibration. This can cause all kinds of weird running characteristics. Some attributable to fuel foaming and some to just weird things that happen when everything resonates. <G>
Not to worry. It sounds like you have a good grip on breaking the engine in properly. A little extra time taken here can greatly increase your pleasure with this engine.
Don't forget to remove the idle bar plug later on. It won't hurt anything to run idle bar plugs, other than WOT power production, and it might help your idle and transition until the engine is broken-in, but I don't think there is any reason to keep using an idle bar plug past break-in unless you have a card full of them and want to use them up.
I have seen a couple GS-40s at our field and I'm amazed at the power they produce once fully broken-in (this takes a while). Those little rascals really scream and they throttle superbly. I suspect that this engine is one of the best buys in R/C today. Now if they could get it to lose a few ounces of weight...
05-14-2006, 07:11 AM
#4
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RE: ST GS-40 break-in questions
You need a couple more tanks . HS needle that touchy on a ST tells me your LS isn't right yet. They are normally set rich from factory. There is nothing wrong with an IDLE BAR PLUG ........I run them in every engine I own except for 4 stroke. Look it did it's trick for you now ,why not all the time.
05-14-2006, 11:54 AM
#5
RE: ST GS-40 break-in questions
You were running the engine way too rich, and were actually preventing the
ring from seating. Running a ringed engine sloppy rich to break it in, is an
old wives tale, and does more harm than good, especially if you glaze the
cylinder from not permitting the engine to get up to running temperature.
Peak the engine to full RPM, and richen the needle to where the engine slows
down some. That's it. Check the setting every minute or two while the
engine is running wide open....the setting can and will change on you as the
engine runs. Peak the engine to full rpm, and richen it back up every minute
to insure the engine is running just slightly rich.
That's it. Run the engine like that for 5 minutes, and shut it off and let it
cool for about 20 minutes. Do that three more times, about 20 minutes total
running time, and the engine is ready for for flight.
Ringed engines DO NOT need to be run sloppy rich for break-in. Period.
FBD.
ring from seating. Running a ringed engine sloppy rich to break it in, is an
old wives tale, and does more harm than good, especially if you glaze the
cylinder from not permitting the engine to get up to running temperature.
Peak the engine to full RPM, and richen the needle to where the engine slows
down some. That's it. Check the setting every minute or two while the
engine is running wide open....the setting can and will change on you as the
engine runs. Peak the engine to full rpm, and richen it back up every minute
to insure the engine is running just slightly rich.
That's it. Run the engine like that for 5 minutes, and shut it off and let it
cool for about 20 minutes. Do that three more times, about 20 minutes total
running time, and the engine is ready for for flight.
Ringed engines DO NOT need to be run sloppy rich for break-in. Period.
FBD.
05-14-2006, 02:13 PM
#6
Thread Starter
RE: ST GS-40 break-in questions
Thanks for the feedback everybody. It's been so long since I've worked with a ringed engine it's like working with a strange animal. I'll run a few more tanks through the engine keeping the RPM up but on the rich side, peaking and then backing off again, then work on getting the LS needle set.
DZ - I decided just for grins to see how the RPM changes as I break in the engine. I've never check RPM on a new engine so just decided to experiment and see how it changes as it runs in.
Hogflyer
DZ - I decided just for grins to see how the RPM changes as I break in the engine. I've never check RPM on a new engine so just decided to experiment and see how it changes as it runs in.
Hogflyer
