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Old Apr 04, 2012, 01:15 AM
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Istanbul, Turkey
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Thanks for sharing experience.Then
1- must clamp all fuel line
2-must use a felt clunk
I will try to use a kind of air trap from pump to carb line also.
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Old Apr 04, 2012, 02:07 AM
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turk,

how are u going to make an air trap?

im definitely going to clamp all the fuel lines now and see if I'm still getting bubbles.
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Old Apr 04, 2012, 04:56 AM
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Fuel lines

Be sure to use the correct size fuel line. I found that the 1/8th Tygon slipped and when I used cable ties to clamp it there was a small pinch point that allowed air in. Changed to 3/32 line which was a tight fit but no leaks. Works great and length from pump to carb appears to be no issue.
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Old Apr 04, 2012, 06:00 AM
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As these are for smaller planes and space is a premium the last thing you want is more batteries and more weight. Suggest looking at this item as it will allow you to use one battery for ignition and receiver. It also is connected to your receiver and allows you to assign a switch so is essentially a cut out as well.
Works well and not a bad price
http://www.tech-aero.net/ultra-ibec
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Old Apr 04, 2012, 06:02 AM
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I just received my GT9 engine and it s a great feeling to play with it.
Firstly I made a test by blowing into pump from tank supply nipple and as it should be, no allowed blowing pass into.So how your engine got flooded without run? Do you mean engine flip creates enough suction to pump fuel to carb?(The regulator inside pump will not allow pump fuel without suction by carb).
I mean some kind of bulb as trap,on the line of carb.Air will leak into but cant easily return to fuel current.(Im not sure if I can success)
It seems clamping is a must because nipples are smooth and easily lets hose slip out.
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Old Apr 04, 2012, 07:22 AM
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Couple of things. The fuel line going from the pump to the carb is under pressure so it cannot take in air if it were leaking. It would leak fuel out of it at the hose connections or a pinhole. A fuel line in the tank will not suck air unless the fuel itself were vibrating so bad it would cause bubbles. Glow fuel is is bad for that with an airframe that vibrates so badly that it needs good insulation around the tank to stop it. A filter is not needed on the pickup other than being a filter. If its solid fuel, there's no place for air to get in. Remember that many have a fuel filter between the firewall and the carb. Gasoline is less prone to foaming from vibration than glow fuel. Tie straps don't make good seals for air leaks, as the point where the two strap halfs come together is not tight around the hose. Sometimes it will work if you use two hoses with the joint on opposite sides. Best clamp to stop air is a piece of copper wire wound around the hose two full turns, then pull it tight and twist the ends together. I still suspect the air is getting in through the pulse line from the tank to the pump. Another test is to put a line a couple of ft. long on the pulse line then put the pump with no inlet or outlet lines on it Dunk it under a pot of water or kerosene or gas. and blow on the line with your mouth. Don't use air from a pressure tank as it may have enough pressure to blow a hole through the diaphram. Not nice!! There must not be any air leaking anywhere. hope this helps a bit. Been through all this running a small motor shop and many yrs flying gassers.

Gord.
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Old Apr 04, 2012, 07:32 AM
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Quote:
Originally Posted by brace View Post
Be sure to use the correct size fuel line. I found that the 1/8th Tygon slipped and when I used cable ties to clamp it there was a small pinch point that allowed air in. Changed to 3/32 line which was a tight fit but no leaks. Works great and length from pump to carb appears to be no issue.
With spark ignition engines, you have to keep the ignition system completely separate from the RC system. The receivers and servos can be very sensitive to the RFI noise that can be on the voltage wires. Some RC systems are sensitive to just the spark noise as the spark plug fires close or nearby to it. It can drastically reduce the range in some cases, if the plane will even get off the ground in those cases.

But you could give it a try using a common battery pack and have someone hold the plane with the engine running, while you conduct a range check carefully. It might work with some RC systems whereas other RC systems go crazy. I always preferred to avoid the situation in the first place.

One other thought is that the CDI ignition module works with 4.8v battery packs, maybe it works with 6.0 volt packs, but anything higher in voltage will kill it. The problem is everyone doesn't have any ignition modules to sell separately. So if you use more than 4.8v to power the ignition module it may kill it. About the only small spark plug (1/4x32 size) ignition module available at this time is for the Saito engines and they wanted $179.99 US) for it. So until we can buy extra ignition modules I would be careful with how much voltage one uses with them. My engine and ignition module ran really well with a 4.8v battery pack, so I won't be trying higher voltages any time soon. There have been numerous horror stories already with gas engine folks trying two cell Lipo packs and killing their ignition modules.
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Old Apr 04, 2012, 07:43 AM
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Quote:
Originally Posted by flypaper 2 View Post
Couple of things. The fuel line going from the pump to the carb is under pressure so it cannot take in air if it were leaking. It would leak fuel out of it at the hose connections or a pinhole. A fuel line in the tank will not suck air unless the fuel itself were vibrating so bad it would cause bubbles. Glow fuel is is bad for that with an airframe that vibrates so badly that it needs good insulation around the tank to stop it. A filter is not needed on the pickup other than being a filter. If its solid fuel, there's no place for air to get in. Remember that many have a fuel filter between the firewall and the carb. Gasoline is less prone to foaming from vibration than glow fuel. Tie straps don't make good seals for air leaks, as the point where the two strap halfs come together is not tight around the hose. Sometimes it will work if you use two hoses with the joint on opposite sides. Best clamp to stop air is a piece of copper wire wound around the hose two full turns, then pull it tight and twist the ends together. I still suspect the air is getting in through the pulse line from the tank to the pump. Another test is to put a line a couple of ft. long on the pulse line then put the pump with no inlet or outlet lines on it Dunk it under a pot of water or kerosene or gas. and blow on the line with your mouth. Don't use air from a pressure tank as it may have enough pressure to blow a hole through the diaphram. Not nice!! There must not be any air leaking anywhere. hope this helps a bit. Been through all this running a small motor shop and many yrs flying gassers.

Gord.
Good points will make some tests over the next few days.
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Old Apr 04, 2012, 08:00 AM
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Here is a excerpt from the RCexl instructions I got with a ignition module from another engine I have.

Quote:
4.8 VOLT PACKS
The Rcexl Ignition is rated for 4.8v to a max of 6v. A 4-cell 4.8v pack with a minimum of 800 mAh is
fine (1200mA is better) and creates a hot spark. The Rcexl Ignition runs most efficiently on 4-cell
packs. We recommend that you always use a new 4.8v pack.
6 VOLT PACKS
We have found that 5-cell packs at peak charge can be over 7 volts. Therefore, if you are going to
use a 5-cell pack, you must use a voltage regulator. The RCEXL Ignition runs more efficiently on
4-cell packs and will draw more much current at 6v, as well as operating at a higher temperature with
no performance advantage. You also have a higher chance of RF interference. We recommend the
use of a 4-cell 4.8v pack. Do not use an old pack to power your ignition!
INSTALLATION
and....
Quote:
MOUNTING
Mount your ignition in the engine bay, if possible. Wrap the ignition in
foam to reduce the effects of engine vibration, as you would do with
your receiver. We do not use the mounting tabs on the ignition but
recommend using rubber bands to secure it against the firewall. Do
not install your ignition in the fuselage. Do not use a metal throttle
servo or steerable nose wheel pushrod. Keep the ignition as far
away from your receiver as possible and never use the same power
source to run your ignition and receiver jointly.


CONNECTING THE BATTERY
The RCEXL Ignition utilizes Futaba plugs and comes with an additional pigtail to make up an ignition
switch harness, if necessary. Be sure to follow the colour coding (Red+, Black-) when attaching your
battery and on/off switch to the ignition power leads. The system is not reverse polarity
protected. Wrap the battery with foam and mount it as far away from the receiver as possible,
preferably on the engine bay.
I hadn't thought about the peak voltage before, but that explains why some people killed their ignition modules using 5 cell packs.
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Old Apr 04, 2012, 08:09 AM
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I was reading a RCGF manual.
earlwb did you clean the fuel pump filter ?

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Old Apr 04, 2012, 08:37 AM
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I didn't see a fuel pump filter when I had taken apart one of the fuel pumps I have.
I wasn't using one in my engine bench tests.
if I remember right one of my 50cc engines has a little screen filter built into the pumper carb on it.
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Old Apr 04, 2012, 08:37 AM
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brace's Avatar
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Quote:
Originally Posted by earlwb View Post
Here is a excerpt from the RCexl instructions I got with a ignition module from another engine I have.



and....


I hadn't thought about the peak voltage before, but that explains why some people killed their ignition modules using 5 cell packs.
Please read the details of the ultra ibec as it has been specifically designed and filtered for this very issue. I have it set up on my test stand and have had no issues with range test and this is using an orange receiver. Not suggesting that everyone use this but it does give some options if room is an issue on the plane.
Glenn
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Old Apr 04, 2012, 08:44 AM
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I saw that, but I haven't tried it yet. I was mainly concerned with folks trying to plug things in directly and then killing their ignition module and discovering much to their dismay, that they couldn't buy another module to replace it.
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Old Apr 04, 2012, 10:03 AM
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Quote:
Originally Posted by earlwb View Post
I didn't see a fuel pump filter when I had taken apart one of the fuel pumps I have.
bizarre... all walbro carbs have a little fuel filtre if I were you I would install one for testing.

Quote:
Originally Posted by earlwb View Post
I hadn't thought about the peak voltage before, but that explains why some people killed their ignition modules using 5 cell packs.
the best voltage for the ignition unit is about 5V so you need a BEC when using a 5 cell pack or light 2S LiPo/LiFe.
in any case RCEXL will come out this year a new batch of ignition modules compatible with 2S lipos.

Quote:
Originally Posted by earlwb View Post
About the only small spark plug (1/4x32 size) ignition module available at this time is for the Saito engines and they wanted $179.99 US) for it.
tha's not true, you have many supliers around the world even there where you get your engine.
http://www.himodel.com/engines/Rcexl..._90degree.html

Quote:
Originally Posted by earlwb View Post
There have been numerous horror stories already with gas engine folks trying two cell Lipo packs and killing their ignition modules.
it's the same story for servos if they are rated for 4.8 to 6.0 I wouldn't run them over 7.0V...
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Old Apr 04, 2012, 10:49 AM
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Istanbul, Turkey
Joined Aug 2004
847 Posts
Hi guys, I did a quick measurement for ignition advance on my GT9 engine and I found 40+ degree ignition advance.
Can you check yours and any idea, can it be such a degree because engine gets 11000+ RPM s?(RCEXL recommends 28 deg. advance)
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