I just took my Sophia J-450 apart and cleaned some clogged jets and fired it back up and it starts up fine but when about quarter throttle or coming down from half throttle it makes this sputtering sound. It looks like I'm not getting a smooth trail of smoke but sometimes it sends out puff's of smoke. I have tried adjusting the needle valve for the oil and didn't help the sputtering. Any suggestions?

Thanks,

Barclay

While I'm not exactly sure of what your problem is, a couple of things you might want to check are the fuel pump and all of the fuel line connections upstream of the pump.
It might be that the pump is not providing a smooth stream of fuel at those throttle settings where you are having trouble. If it is possible to run the pump while it is disconnected from the engine, do so and watch to see if the flow is smooth at all rpms.
Check all of the fuel connections for leaks, any leaks that are upstream of the pump will allow air to be sucked into the system, and will only get worse at higher throttle settings.
You did not mention which ECU you are using. The Sophia engines were sold with at least 3 different types of control systems and it would help to know which one you have.

Hopefully Marty Snell will chime in on this one, he has a lot of experience with Sophia's and might have more insight into what is going on.

Thanks, for the reply. I am using a CAI ECU. I think I figured out what the problem is. I think the connection between the oil supply and the main hub is leaking and at the low RPM's it is spitting a bunch of 2380 into the fuel stream. That is why I am getting puff's of smoke instead of a good stream. I'm taking it apart again tonight to verify. It was eating a lot of oil so I bet that is what it is.

Does anyone know what type of sealant they are using on the connection between the main hub and the stainless oil/fuel supplies? I was told to use red loctite?

Thanks!

I used plain ole epoxy on the jpx lines, its a press fit and on the cold side of the motor.

Vin...

That is what it looked like when I removed it. Guess it would work if it doesn't get too hot.

Do you know any secret to getting the NGV off the hub?

Thanks,

Barclay

Hi Heli,

With my sophia's (JetCat ECU), the oil pump pulses. It turns one revolution once every second, pauses, then turns again. This is the pattern when the engine is operating. I usually see three puffs of smoke (one for each revolution of the 3-lobed pump mechanism) every 2 seconds or so.

As for getting the NGV off, you have to remove the compressor, shaft and turbine (the bearings usually come out as well). You can then carefully slide the cumbustion chamber off the shaft tunnel. Mark it somewhere (do not use pencil!) to insure it goes back on in the exact location. This is very important with the Sophias! The injectors must be precisely lined-up with the atomization holes in the chamber! After you get the combustion chamber off, you should be able to extract the NGV by pulling it out. It's pressed into the end of the combustion section. Again, be careful... it's easy to damage the vanes.

Here's a nice website with a J-450 disassembled for reference.

http://www.technologie-entwicklung.d...hia_story.html

If I can be of more assistance, please let me know. Oh...5 minute epoxy works well as a sealant on the fuel/oil manifold pipes.

Craig

Thanks Craig, I will try tonight. I have talked to Thomas from that website about a few things before and he has been very helpful. Smart guy, he is.

Thanks!

Why can you not use a pencil? Thanks

The graphite/carbon in a pencil reacts at high temperatures causing a corrosive failure point. If you were to mark the hot section of a turbine (inside or outside), it would lead to the same type of damage as if you cut a hole in the can with a torch.

I remember a new crewchief of mine, who thought he was doing the right thing, circled every little ping on the hot end of my AH-1F Cobra engine. Our Maintenance Officer saw this and came uncorked! He immediately "Red-X'd" the aircraft and ordered an entire hot end change. From what I understand, even if you attempt to clean the pencil off, the trace amounts left behind in the porous steel is enough to cause failure.

Craig

Hi,
If you think its the fuel supply then you could put in a damper
as an experiment, tee in a length of tube about 18" between the pump and the turbine, run in fuel until it is about 5-6" into
this tube and then pinch the end off, the air in the tube acts
a bit like a damper and absorbs the worst of the uneven pulses.
Mike

Can anyone tell me where to get bearings for my 850

Mick

Mick,

Hows that JetCat 120 I sold you, surely it has been trouble free, it was brand new !!

The 160 sure has a lot of grunt and really makes my F15 go,
BRG,
David G.

There's a Dave Gladwin in another string... strange that.
My DH 110 would fly very well on a 160 if I had one!!!
BRG