RE: Help! Overheating/Lean ST G90

RE: Help! Overheating/Lean ST G90
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RE: Help! Overheating/Lean ST G90 - 7/22/2006 4:48:17 AM

KojakDave

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

Well, I tossed the ST plug, put in a OS #8, and retuned the thing....what a difference. I ran a couple of tanks through at full throttle today and was getting tach readings of 11150 to 11200 with a MA 13x6 prop and 15% nitro/18%castor-synth blend. I think that's pretty good considering she's only got about 3/4 gallon of fuel through her. I'm also getting a fairly steady low rpm of 2600 to 2700 and a good transition.

I have the cowl off, so I still don't know how she's gonna handle the heat, but I pulled out the dummy engine that I had before with all of the cylinders cut around (I really opened up the air spaces on that one) and replaced it with one that only has an opening cut for the cylinder head. I hope this helps direct the air directly over the cooling fins better than the previous method. The first two photographs show the way it was done previously with all of the spaces between the heads open, the third one is the new cowl front.

Thanks again to everybody for their help so far.

Dave

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< Message edited by db4962 -- 7/22/2006 4:50:12 AM >

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Dave
It's better to break ground and head into the wind than to break wind and head into the ground

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Post #: 51

RE: Help! Overheating/Lean ST G90 - 7/22/2006 5:50:46 AM

Cyclic Hardover

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From: New Mexico, USA
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Did you mention that dummy engine back at the beginning and we missed it?

< Message edited by Cyclic Hardover -- 7/22/2006 5:51:49 AM >

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RE: Help! Overheating/Lean ST G90 - 7/22/2006 6:04:21 AM

Flyboy Dave

Posts: 13549
Joined: 3/20/2002
From: San Bernardino County, CA, USA
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I see you tossed the rotating Ginsu blades, and put a real prop on it.

FBD.

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Post #: 53

RE: Help! Overheating/Lean ST G90 - 7/22/2006 4:01:40 PM

KojakDave

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

ORIGINAL: Cyclic Hardover

Did you mention that dummy engine back at the beginning and we missed it?

Sorry, no, I was just adding to the confusion

I was just saying that she seems to be running pretty good now and I hope that continues when I put the cowl back on. I know that poor air circulation can wreak havoc on even a finely tuned engine, so I decided to focus the incoming air on the cylinder head where it is most needed. I was afraid that by having air coming in through the whole front of the cowl, it would limit the amount of air that actually passed over the head and OUT of the cowl. Hopefully what I've done won't have the opposite effect. Any comments/suggestions?

quote:

ORIGINAL: Flyboy Dave

I see you tossed the rotating Ginsu blades, and put a real prop on it.

FBD.

I wouldn't say "tossed", I would say transferred to back-up status...lol. Actually I think the APC props give better performance, but the MA's are a little more forgiving and look better when she's just sitting on the ground.

Dave

< Message edited by db4962 -- 7/22/2006 4:06:11 PM >

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Dave
It's better to break ground and head into the wind than to break wind and head into the ground

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Post #: 54

RE: Help! Overheating/Lean ST G90 - 7/22/2006 5:16:04 PM

Flyboy Dave

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From: San Bernardino County, CA, USA
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How about one of these propellors:

http://www.masterairscrew.com/GoCart/itemlist.asp?RootID=7016

The APC looks rather "out of place" on there.

FBD.

_____________________________

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A mechanic says..."Oh yeah, watch this".
"Old Age, and Treachery will overcome youth and skill".
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Post #: 55

RE: Help! Overheating/Lean ST G90 - 7/23/2006 6:45:48 AM

Sturtz

Posts: 1519
Joined: 9/22/2004
From: El Reno, OK, USA
Status: offline

Head bolts loose ?
Lost an OS160FX in a FW190 today. Head bolts and plug got loose. Engine heated up in flight. Perry Pump line from backplate came off. Engine died in flight but not soon enough. Good deadstick landing though.
Sleeve was stuck to head when I pulled it tonight. Slid right off. Very little compression.

Check your bolts.

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Post #: 56

RE: Help! Overheating/Lean ST G90 - 7/23/2006 11:42:28 PM

Ernie Misner

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From: Tacoma, WA, USA
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Yikes Kurt! Did your fuel have any castor in it? Just curious,

Ernie

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Post #: 57

RE: Help! Overheating/Lean ST G90 - 7/24/2006 5:01:21 AM

Sturtz

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From: El Reno, OK, USA
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Yup,, was a sad thing to see. Engine wasn't very old either. About 20 flights on the previous plane. Was running a castor mix at 2 oz per gallon. The head seems welded to the sleeve now.
Where does everyone send their OS engines to these days ? It was still under warranty.

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Post #: 58

RE: Help! Overheating/Lean ST G90 - 7/24/2006 5:14:32 AM

KojakDave

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

Ok, I threw a few more variables in, but at least I did it one thing at a time. I changed to an OS A3 plug, which helped hold a steadier idle, but seemed to be pinging a little bit at the top end with 15% nitro fuel, so I dropped it down to 10%, retuned the needles, and got it working fine. I flew it for a circuit and it was doing good, but the danged thing would not slow down and didn't have enough pull for me, so I switched from a 13x6 MA prop to a 14x6 MA...that helped a lot with the vertical and slowing her down for a landing. Overall, she is doing a LOT better. Since I was still tinkering with the needles a little bit I flew her without the cowl today, so I will have to wait until tomorrow to see if she's going to overheat. I'm thinking about going with a 15x6 prop, which is a little larger than ST recommends for the G90, but Dave Gierke wrote that is a great prop for this engine for scale flying (slower speeds but a lot more vertical). Whaddya think?

Dave

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Dave
It's better to break ground and head into the wind than to break wind and head into the ground

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Post #: 59

RE: Help! Overheating/Lean ST G90 - 7/24/2006 7:19:51 AM

Ed Cregger N2ECW

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From: Ringgold, GA, USA
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quote:

ORIGINAL: db4962

Ok, I threw a few more variables in, but at least I did it one thing at a time. I changed to an OS A3 plug, which helped hold a steadier idle, but seemed to be pinging a little bit at the top end with 15% nitro fuel, so I dropped it down to 10%, retuned the needles, and got it working fine. I flew it for a circuit and it was doing good, but the danged thing would not slow down and didn't have enough pull for me, so I switched from a 13x6 MA prop to a 14x6 MA...that helped a lot with the vertical and slowing her down for a landing. Overall, she is doing a LOT better. Since I was still tinkering with the needles a little bit I flew her without the cowl today, so I will have to wait until tomorrow to see if she's going to overheat. I'm thinking about going with a 15x6 prop, which is a little larger than ST recommends for the G90, but Dave Gierke wrote that is a great prop for this engine for scale flying (slower speeds but a lot more vertical). Whaddya think?

Dave

-----------------

Just for the record, a 13x6 is really a .61 - .75 sized prop. A 13x8 is more appropriate for a .90.

I am glad that you are making some progress with the G90. It is a good engine. I have several myself.

Just be sure to keep the mixture rich enough when flying the 15x6. It is very easy to quickly overheat the engine and lose ring tension. Fortunately, it is an easy repair when needed.

< Message edited by Artisan -- 7/24/2006 7:21:52 AM >

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RE: Help! Overheating/Lean ST G90 - 7/24/2006 8:35:41 AM

Ernie Misner

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From: Tacoma, WA, USA
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>>> It is very easy to quickly overheat the engine and lose ring tension. >>>

Just curious, how did your G90 run with the damaged ring in it?

Thanks,

Ernie

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Post #: 61

RE: Help! Overheating/Lean ST G90 - 7/24/2006 12:51:02 PM

KojakDave

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

quote:

ORIGINAL: Artisan

Just for the record, a 13x6 is really a .61 - .75 sized prop. A 13x8 is more appropriate for a .90.

The 13x6 was the prop I was using to break it in, it's the prop recommended by ST for this purpose.

Dave

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Dave
It's better to break ground and head into the wind than to break wind and head into the ground

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Post #: 62

RE: Help! Overheating/Lean ST G90 - 7/25/2006 2:12:25 AM

KojakDave

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

All I can say is bee-yoo-tee-full....that's how she did today. I put the cowl back on my P-47, turned her into the wind, and turned her loose. She did really well today, good response on the throttle, good idle, and lots of beautiful smoke coming out the exhaust. I tached her at about 10500 with a 14x6 MA prop, so she's probably got a little bit to go before she's at full break-in and power (I hope). And it looks like she's going to run at a good temp even with the cowl on. I used my IR thermometer as soon as she landed and the cylinder head was around 230F. She pulled the jug around really well without any glitches, I just have to get used to how throaty the engine sounds when's she's chugging around at about 2/3 throttle, it almost makes me worry that she's too rich (and maybe she is), but since she's finally running good I don't really want to mess it up. Thanks to everybody for all of the help and I hope this engine grows into it's reputation (which I'm beginning to believe it can).

Dave

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Dave
It's better to break ground and head into the wind than to break wind and head into the ground

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Post #: 63

RE: Help! Overheating/Lean ST G90 - 7/25/2006 2:49:49 AM

Ed Cregger N2ECW

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From: Ringgold, GA, USA
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Mine did not overheat and ruin the ring.

However, engines that lose ring tension will display poor compression and poor fuel draw. Believe it or not, engines tend to idle a bit better with low compression, as long as they can still draw the fuel to the carb. Naturally, with the compression down, power too will be down.

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RE: Help! Overheating/Lean ST G90 - 7/26/2006 5:54:42 AM

Flyboy Dave