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Gt33 not working properly

Old 02-21-2016, 02:44 AM
  #1  
ameyam
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Default Gt33 not working properly

Hi,

Starting a new GT33 on a Pitts Bipe. The engine runs only just at idle & starts stuttering & cuts off at 40% stick. However, the power is not actually 40%. It barely runs.

Fuel is a 4% mix Motul. We have also tried with a 3% mix with no better results. The same oil runs just fine on our 55, 30 and 35.
Needles are set to 2 turns out from closed as described by manual. We got the engine running & closed the LSN 1/8th turn progressively but no luck.
At first we were using an rcexcl ignition. Then we tried the os module also. But the os module doesnt spark even with a ignition tester
The spark plug is original os / ngk. It sparks fine with a tester
Prop is a master airscrew 18/8. This is the first tank
Battery is a life 6v 2 cell. Same setup works well on the other engines

We are using a electric starter. Engine misfires a lot. We have seen a lot of flames shooting out of the exhaust. Misfires are violent enough to loosen the stock silencer.

Can someone please tell me what the hell is wrong. This is a NIB 4 year old engine

Ameyam
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Old 02-21-2016, 04:11 AM
  #2  
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Back firing sounds like an ignition timing problem with the sensor.
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Old 02-21-2016, 07:46 AM
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My bad actually. There is a lot on the net regarding the OS GT33 not working with the RCexcl ignition. I just assumed that it would work

Just a query though- shouldnt the ignition fire the spark with a tester connected instead of the sensor? I even tried turning the engine over with a starter with the plug in the cap but not installed in the engine. Didnt fire the plug this way either. However, the rcexcl IM was able to fire the same plug with the tester.

Guess the only way to solve this is to get a replacement ignition from OS? What do you think?

Ameyam
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Old 02-21-2016, 09:28 AM
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Two things have to be right for RCexl or RCXP ignitions to work.

First is setting the polarity of the sensor right and second is getting the timing right.


I do not know how the timing is on the stock ignition but it you could put the cylinder as close to top dead center as you can and post a picture of the magnet and sensor location I could tell you.


to get the polarity right you will probably have to use the sensor that comes with the new ignition, Hook a battery to the ignition, plug the sensor into the ignition and rub the sensor over the magnet, if it does not fire the ignition turn it over and it should fire, It will only fire on one side.


Milton
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Old 02-21-2016, 09:59 AM
  #5  
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Milton,

The rcexcl module and the tester are both the one of those you sent us. It fires the engine but the engine goesnt go beyond 2000rpm or so. I tested with the plug removed and in the cap and the plug fires. But the OS module does none of the above.

Anyway, here's a pic of the magnet you wanted with the piston nearly at TDC

Ameyam
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Old 02-21-2016, 10:57 AM
  #6  
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The problem you are having with the RCexl or RCXP ignition is the timing.


In the picture you post it shows the static set about top dead center.


The new ignition you have has to be set at 28-30 digress before top dead center static.


In the link below are a couples ways to do it, The problem is you will have to drill and tap new mounting holes for the sensor.

http://www.rcextremepower.net/timing.html

Milton
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Old 02-21-2016, 05:28 PM
  #7  
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I would rather get a replacement OS ignition for now

Just one query before i order- i tested the original os ignition with the plug in the cap but outside the engine. I did this with both the ignition tester as well as by turning the engine over with a starter. Both times no spark. So should i presume the module us dead?

Ameyam

Last edited by ameyam; 02-21-2016 at 06:37 PM.
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Old 02-21-2016, 07:04 PM
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That would be mu best guess.

Milton
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Old 02-21-2016, 08:03 PM
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If it's a new engine why don't you send it back. Even with a new OS ign you'll still have to time it
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Old 02-22-2016, 12:13 AM
  #10  
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Originally Posted by BadAzzMaxx View Post
That would be mu best guess.

Milton
I have never
figured out the timing on the OS 33.My friend has one.I no they will not run on a standard RCEXL Ignition.I put a CH on his and just used a clamp,runs fine and does not start backwards or kickback.The OS ign should have a spark when spinning with a starter,they will not by hand cranking.I am with you I believe his is TU.I put a timing light on the OS ign and still couldn;t tell what it was doing.Never no what XuLiang and engine people will do.Some times Xu will do it wrong and he no,s it's not right. Just does what the engine builder wants.Like the No 4 DL 20 ignition.
BCCHI Tired old CH guy.
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Old 02-22-2016, 03:01 AM
  #11  
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I have a Torqe Pro 33 which is the same as an OS 33. The pictures are identical of both motors. Mine has a Walbro carb and it requires the NV's to open be about 4 turns. I also removed the .020" gasket on top of the liner which upped the compression. I was using a 18-10 prop.
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Old 02-22-2016, 06:44 AM
  #12  
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replace the spark plug with a real NGK sparkplug, available at most autozone type shops

My OS GT33 behaved exactly the same way when new until I replaced the plug, I even posted on here about my problems, you should be able to find the thread.... Turns out the OS ones are junk.

Literally night and day with a new plug. the OS ones appear to operate fine, but they just don't work well...
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Old 02-24-2016, 12:14 PM
  #13  
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All of my OS GT 33s have ngk cm6 plugs, stock from the factory. My youngest engine is about 3 years old so did OS change their plugs since 3 years ago? That's strange.

If the Torqe 33 has to have 4 turns open to operate, it is not the same as the OS. The OS runs great with the HSN open 1 5/8ths and the LSN open 1 1/4. All three of mine have pretty near identical settings.

At 2 turns open the engine will be slobbering rich and will cough and sputter its way through transition. Get the needles right and your mill will work like mine do. Also suggest you increase the load to at least a 19 x10. I fly mine with a 20.5 x10.5 wpn APC props except the engines are all piped and the boost easily turns that much load.

i suggest you use my needle settings. From the photo, the sensor location is fine, don't change it.
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Old 02-25-2016, 09:27 AM
  #14  
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Hi guys,

for some reason I wasnt getting updates from this thread.

Anyway, I bit the bullet and got the $89 (more like $110 for me due to customs) ignition replacement module. It arrived today and I started with a 4.8V battery just to be sure. Sure enough, sparks after just wiggling the prop. Then, very hesitatingly, I connected my LiFe battery and it still works fine. I cant test run the engine in my apartment even at Idle. I will have the neighbours complaining immediately and my mom / dad is scared stiff of the noise. So I and my buddy will test the engine out on Saturday morning.

The plug is a NGK one. I dont think OS came with plugs or standoffs when I bought the engine in 2011-12. Singahobbies was kind enough to give me one with some tubing as well in the deal. Still, I will carry a spare plug. I hope a rcexcl plug icm6 will do.

Regards to the needle setting, its not just the 2 turns out but also that we are running a 4%+ mix. Its just to ensure that the engine runs rich enough initially. I have had too many OS glow engines expire because my trainers didnt bother to break-in properly. I would rather start the engine one tank slobberingly rich on the ground, then lean out just a bit and fly a few tanks and then go to a more stable performance setting.

One thing with OS. Though heavier than Dle, the mass is more concentrated and the body length behind the head is shorter than DLE. So you can move the engine back or forth to get the CG. I am using some DLE standoffs for cowl length purposes but it could probably go back an inch more. Wonder if fitting a velocity stack will give more power like in OS' Alpha series glow engines.

Anyway, hoping for the best now. There is no way this Pitts will balance with a DLE35 (CG is 35mm behind stock), so the GT better work.

Any comments on the GT's 3D capabilities?

Ameyam

Last edited by ameyam; 02-25-2016 at 09:30 AM.
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Old 02-27-2016, 11:40 PM
  #15  
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From the beginning of running the GT33, in 2011, I set the needles pretty much there and have made only slight adjustments to the HSN to accommodate the large props that I use. I mean slight, like the width of a screwdriver. 4% mix is very oily. I use 2% mix (50:1) for break in and regular running; no need to change the mix. I know that some people do but it isn't necessary if you use a good oil. I use an excellent synthetic from the start for break in and after.

For 3D you may want to reduce the prop load to a 19x8 or 20x6. Use apc props as they are the best: best means they are the most quiet, converting more power to thrust

Do yourself a favor and lean the needles. Gas engines don't require the slobbering rich break in of glow engines, ever, during their lifetimes. Very slightly rich for the first couple tanks is fine. That means HSN 1 11/16 and LSN 1 5/16 open from fully closed. Even that is probably too rich. Your transition will cough and sputter but the engine will continue running.
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Old 02-28-2016, 10:00 AM
  #16  
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Was at the field yesterday & it worked very nicely. The engine started in one go with the starter. You could hear it was running slobbering rich, so one of the more experienced modellers went up & closed the needles a bit. Not sure where the needles are now but they are still on the rich side because the lack of traction. Did a little bit of conventional aerobatics & stall turns but the plane flies more pattern like & runs out of traction in the vertical. This is down to the 4% mix & the MAS 18x8 prop that we know flattens out when the rpm increases. Subsequently the engine started with hand flick every time in one go

I am going to stick with the prop & oil combination till the first can (4l) of 4% mix is consumed. Then will lean out with a 3% mix. Using motul for now.

One thing, plane flies & lands very nicely. Very draggy frame & no cowl
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Old 03-01-2016, 09:16 AM
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Guys, what prop do you suggest to run on? Should I stick with the MAS black prop or should I change over to a wooden 18x8 or 19x8 or 20x8 prop. Also, when should I make the change given I have less than 1 litre through it

Ameyam
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Old 03-03-2016, 09:14 AM
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20X6 Wood. Black MA is good for ground strikes. Run fuel that you plan to use from day one till the end. No need for special fuel and oil for break in. Break in might take a few liters more on good oil.

Nice pic, where is your Funtana?
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Old 03-03-2016, 05:44 PM
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Thats my Funtana in that pic. I flew it for a bit, then ended up concentrating on the mx last season. This year, my buddy crashed his 50cc at an event. Since he is still a student, he cant afford a new plane just yet & letting him fly my active airplane will rob me of my stick time. So i let him take my ready setup funtana with the dle30

Oil i am using is motul. Is it necessary to change over to amsoil? My buddy is running amsoil but thst 30 has already run a bit now

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Old 03-04-2016, 11:41 AM
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I would use any and all oils that meet API TC. If they don't say that, I would not use them. If they do, they are OK by me.

IMHO
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Old 03-05-2016, 02:34 AM
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At the field today and the engine was running very rich again & we leaned it out. Its still running a bit rich from the burble. However the MAS grey grp 18x8 is pathetic. Even at full throttle, i kept feeling insufficient energy to do consecutive loops while the engine just screams. Thinking of putting a wooden prop on now, just not sure whether it should be a 18x8 or 19x8. 8tankfulls through

Ameyam.
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Old 03-12-2016, 01:10 AM
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Whats the correct prop for this engine? I tried a Xoar 19x8 and the plane was well transformed with the ability to any conventional aerobatics and could do a loop from any approach. However, the plane still lacked the supple feeling of power that my well run in 35RA has. I had gone but couldnt fit the 20x8 prop due to the spinner (in hindsight, I could have just flown without the spinner, but anyway). The engine still burbles rich and its nowhere close to fully tuned just yet. Still, I could hover with some sluggish pullout

Ameyam
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Old 03-12-2016, 06:01 PM
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Re-read post 15. Do what it says. And put some load on that engine. You are using toothpicks. The 35ra simply can't compare power wise so you have some way to go in the tune and load departments
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Old 03-13-2016, 05:38 AM
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I flew the 20x8 before I read the post today. At this point I am flying without the cowl (may be for the last time) and the engine is still way rich as I can hear from the transition. I felt that 20x8 seemed to have slightly less authority than the 19x8 though. I didnt go at it with a tach though.

All my larger props are wood. Going through the Tower catalog, there is no 19x8 or 20x6 APC GRP props. Whats available is all wood, so may be you mean to say to put a maple prop, but I can tell you this- with the 19x8 at idle in a dive (from a stall turn), I can hear the whine that is characteristic for these 3D props in that move. Secondly, with the engine in this rich tune, the 19x8 has better handling but the airflow isint there because I couldnt control the torque roll in a hover and both the ailerons and the elevators were ineffective till I dropped started flying straight again.

Being a radial cowl model, I gave up on all setup and trimming till I have the engine tuned and cowl installed. Next weekend, I will be there with the cowl and will tune the engine also with a safe 3% mix. Lets see what happens

Ameyam
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Old 03-13-2016, 08:48 AM
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