RE: Help! Overheating/Lean ST G90

RE: Help! Overheating/Lean ST G90
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RE: Help! Overheating/Lean ST G90 - 7/27/2006 1:15:17 AM

Flyboy Dave

Posts: 13375
Joined: 3/20/2002
From: San Bernardino County, CA, USA
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If it bogs (lean) it usually quits....or backfires and quits.

If it spudders (rich) and takes a few seconds to get past the transition, into higher
speeds, and it will be spitting fuel and a lot of smoke....it is way too rich. It may
quit if it is too rich as well. It may sound like it is 'cutting out" or "missfiring" as well
when it is too rich.

It is easy to see the difference.

FBD.

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Post #: 76

RE: Help! Overheating/Lean ST G90 - 7/27/2006 8:52:42 AM

Ed Cregger

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From: Ringgold, GA, USA
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Nevermind

< Message edited by Artisan -- 7/27/2006 9:32:16 AM >

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Post #: 77

RE: Help! Overheating/Lean ST G90 - 7/27/2006 8:58:38 AM

Ed Cregger

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From: Ringgold, GA, USA
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I'm going back to bed. <G>

< Message edited by Artisan -- 7/27/2006 9:32:49 AM >

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Post #: 78

RE: Help! Overheating/Lean ST G90 - 7/27/2006 2:58:43 PM

BillS

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From: Greensboro, NC, USA
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Flyboy Dave,

What idle speed would you normally set a .45?

Would you expect low needle setting to be different for same engine at 3000 RPM than 3500 RPM, i.e. for a pinch test to indicate correct at 3000 but rich at 3500?

Bill

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Post #: 79

RE: Help! Overheating/Lean ST G90 - 7/27/2006 3:27:00 PM

Bax

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From: Champaign, IL, USA
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When a SuperTigre GS-45 is properly broken-in and tuned, you can get a reliable idle, transition, and top end. Idle will be about 2,700 RPM, and top-end will be in the mid-12,000's...using the correct propeller. Any idle RPM at 2,700 or lower is considered "good", but if you can get lower RPM with a good transition and top-end, then great!

An idle of 3,000 RPM and and idle of 3,500 RPM will each require different needle and idle-stopper settings.

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Post #: 80

RE: Help! Overheating/Lean ST G90 - 7/27/2006 4:13:17 PM

guille2006

Posts: 131
Joined: 1/11/2006
From: Brindisi, ITALY
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Dave; Could you solve that problem with the STG90?
Keep me updated!!! I bougth a STG90 last week...

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Post #: 81

RE: Help! Overheating/Lean ST G90 - 7/27/2006 5:43:42 PM

Cyclic Hardover

Posts: 7195
Joined: 5/7/2002
From: New Mexico, USA
Status: online

quote:

ORIGINAL: ronwc

The key to all this is muffler pressure. This does not just apply to ST's, but all 2 stroke engines -

Sorry but this is getting ridiculous. We have a guy who says his engine was overheating when it has never even been flown and the only symptoms were that the engine was hot?????? Gee. Then we all pitch in together for several threads before we find out he has a fake engine blocking the airflow if there was any at all. Now we have the key to this whole thing is muffler pressure and to block one of the openings. Wow! Why is it most of us around my neighborhood don't have these problems. Maybe slimline should patent a new muffler. One with two holes who know what ^%$# they're doing and a muffler with one hole for those who don't.

This is like having a guy tell us his plane keeps fl;ipping over on takeoff. 20 replies later, "oh yeh, I forgot to tell you , I don't have wheels on it and only using the struts." I hope some of you guys never go to turbines or your going to be in a lot of trouble. This is not "Estes" rocket science here. If you can't properly dial in an engine or set up plumbing and tanks right, your going to have problems. My solution to it all is this, stuff the plane, bring the wreckage back to the table in a pile and zap it with a temp gauge. That'll find the problem!

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Post #: 82

RE: Help! Overheating/Lean ST G90 - 7/27/2006 5:57:58 PM

KojakDave

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Joined: 3/15/2004
From: Lakeland, FL, USA
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Cyclic Hardover,

First of all, when I first experienced the overheating it was while I was flying. And yes, it still did this with the cowl off, too. What confused me was that I had flown it previously just before the problem started without any problems. Next, I checked for air leaks, replaced fuel lines, and siliconed the muffler gasket. Now this whole time I am attempting to retune the engine, but guess what..without the necessary back pressure to deliver the fuel required to run the system, you can turn that needle open all you want but no more fuel is going to make it to the carb. When I plugged one of the exhaust outlets I was able to then correctly tune the engine. Now, I know that I am not the only person who has had to do this to a Pitts muffler because there are around 200 threads about it having to do it (an exaggeration, I know, but after someone suggested that was the problem I did a search and discovered that there have been a LOT of people who plugged a pitts muffler)... does that mean that everyone that has to do this is an idiot? No, it does not.

As far as asking about whether the NEW dummy engine (with only a space for the cylinder cut out) would cause overheating, that was AFTER I fixed the original problem with the engine. The original dummy engine was entirely cut out all around except for the dummy cylinder heads AND a space in front of the actual cylinder. I was just looking for comments from folks in this thread without having to start a whole other thread on such a similar topic. Now, I appreciate constructive criticism and am always asking for help from more experienced folks in the hobby, but I don't agree with your "my way is the only way and everyone else can't tune the engines because they're stupid" attitude.

How about being a little more helpful and a little less judgemental. If everyone believes me to be wrong for this post, just let me know and I will gladly remove or edit it.

Thanks,

Dave

< Message edited by db4962 -- 7/27/2006 8:21:58 PM >

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Post #: 83

RE: Help! Overheating/Lean ST G90 - 7/28/2006 3:51:33 PM

Texan

Posts: 470
Joined: 12/20/2001
From: Georgetown, TX, USA
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Dave,

Don't worry, even the best tuners get befuddled sometimes. The ST G90 is a little more challenging to setup than the average OS. Once you learn how to make the ST happy, you will quickly grow to like the engine.

I have experimented with the G90 and found it to be a very powerful engine. My 3D setup unlocks a SH## load of untapped power from the stock engine. The two power limiting areas of the stock engine are carb and muffler. Drop in a Magnum 91/108 carb $37.00 (direct replacement) and add 1000rpm on a 14x4W APC. An aftermarket muffler adds another 600rpm. Here is an interesting note, with the Magnum 91 carb, you can run a pitts muffler with both sides open and get excellent throttle transition.

TX

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Post #: 84

RE: Help! Overheating/Lean ST G90 - 7/28/2006 6:00:01 PM

KojakDave

Posts: 243
Joined: 3/15/2004
From: Lakeland, FL, USA
Status: offline

Thanks for the advice, Texan. I've heard a lot of people change out the carb and I've been thinking about doing the same. I finally got it tuned in pretty good and it seems to be running great, but I could always use a little more power and smoothness

. It's not overheating and losing power like it was when the problems first started and I'm really liking this engine now. I'm actually glad that I had problems with it in a way because dealing with it has just given me more experience.

Dave

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Post #: 85

RE: Help! Overheating/Lean ST G90 - 7/29/2006 2:39:02 AM

Cyclic Hardover

Posts: 7195
Joined: 5/7/2002
From: New Mexico, USA
Status: online

Sorry, seems like quite a bit of these problems people ask about come from getting bad advice from local banana's. Seems that instead of trying to rationally and simply diagnose a minor problem, solutions are "lets shove a cork in it." Instead of going in some sort of a simple step process to check problems, they are on number 19 and 20 instead of starting with 1,2,3,4 etc. You really have to watch who you listen to (including me). I know some real good guys that taught me well and I know an equal amount of guys who will just never "get it."

I know one guy who gets so frustrated that the plane does not perfom the way in which his math calculations came out. Really, everything is crap to him. He's upset all the time at the field, whining and crying to any fool who'll listen.

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RE: Help! Overheating/Lean ST G90 - 7/29/2006 4:00:12 AM

KojakDave

Posts: 243
Joined: 3/15/2004
From: Lakeland, FL, USA
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No problems Cyclic Hardover...I've seen a lot of your posts and I know that your recommendations are good and sound. Besides, you're right, the best advice is usually to keep it simple. It's just that sometimes, even when you do everything that make sense and try to isolate the problem, there might be something that you can't see or some interaction between a set of problems that complicates things. I was originally trained to be a scientist, so I treat my engine problems like an experiment and only change one variable at a time. But once I've changed that one aspect and it doesn't work, I move on to the next thing fairly quickly without wasting a lot of time. That's not how I make my living now (thank God) but it does help when it comes to technical things. The only problem I have is that I was supposed to be a biologist, not a mechanical engineer..lol. As far as taking advice from everyone who offers it, my current job has made me more of a skeptic. I always appreciate advice that's given but I know that you can't believe everyone, trust me on that.

Dave

< Message edited by db4962 -- 7/29/2006 4:18:48 AM >

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Dave
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Post #: 87

RE: Help! Overheating/Lean ST G90 - 7/29/2006 4:59:48 AM

Cyclic Hardover

Posts: 7195
Joined: 5/7/2002
From: New Mexico, USA
Status: online

My pet peeve is tuning. If the gear won't retract or a servo is bad, the engine is not tuned right

. You can get bits an pieces of good tuning advice from here and there but it's of no value unless you get all of it (which does not have to be much.) Like making a batch of brownies. The eggs , butter, oil and mix taste like ----- when it's separate but all together, it's great.

I have only been at this around 10 years now. It took about 3 years to wake up and do it right. I am not the jedi master here but that what I know is in the manuals in thats fine print none of us reads. Thing is when your a beginner, the fine print does not make any sense because you really don't know what your doing anyways. I tune my low end only one time in any given season. If it's done right, thats all it needs.

I have this nice Modeltech 72"wing with a OS 1.08. I haven't flown this thing in a year. I'll bring it out, remove the cowl, spend maybe a tank or two at most dialing it in right and thats it, low end is done for the summer. There is no need for guys to fart and fart and fart with their engines every single time they show up at a field. It's such a simple thing. I have not had a deadstick due to tuning in years.

Of course I have as many stupid things happen as the next guy, props comes off or mufflers come loose and engine quits and things like that. Fuel tanks split and so on. There are a few back up checks you can do which are in print that check to see if the adjustments that you made had any effect.

Then we have the inverted engine scenario. For some reason mfgs do not design a fuel tank location to go along with an inverted engine in most scale planes. They design them for upright mounted engines. You invert a glow engine and install the tank in it's stock location, your going to have problems. The solution? Well many here want to do 50 things and the engine will never be right and the simple fix is to lower the tank.

I have 4 different brand of engines inverted and with lowered tanks, run flawlessly. None of this flip the plane over start it up flip it back over crap. Theres no need for this. I don't "know it all." I simply pay attention. The manuals are full of information. Granted most of it is "way out their" but there are 5-6 items, when gathered up and placed in a certain order can give you a perfectly tuned engine.

Later

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RE: Help! Overheating/Lean ST G90 - 7/29/2006 12:58:27 PM

BillS

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From: Greensboro, NC, USA
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Cyclic,

I am working on a multi engine project and have a couple of questions.

What idle RPM are you setting your .40/.45/.50 ball bearing engines? How much ground idle time can you get before the engine loads up and will not trans