Spectra/231 tuning question

[Bill Ludwig]

I have about 3/4 of a gallon through a TRM 231 in my Spectra. After about 1 minute of flight, it has symptoms of running quite lean - head speed increases significantly. If I richen it, even just a little, it's too rich to even get enough head speed for liftoff. I'm at about 1 1/2 turns out on both needles. It idles fine. My throttle curve puts me at about 45% throttle in a hover.

With the governor switched on, the head speed still increases significantly in a descent (after a one minute flight). I think the governor is pulling the throttle to an idle, but the lean run is keeping the RPM up.

No fuel bubbles in the fuel lines and nothing pinched.

Thoughts?

- Bill

[Joe Ubaldo]

Bill,

I remember that happening to my flying buddy Brad Foster's TRM 231 as it started breaking in. What we did to address the issue was to lower the throttle curves. It seemed that as the engine warmed up, it started to speed up (not sure it was getting lean as much as it was just becoming more efficient at combusting fuel). Lowering the throttle curves worked for him.

Joe

P.S. From everything I've read and been told, it's too early in the break-in process to start running the governor.

[WillJames]

Are you set at 0 degrees at midstick bill adn hovering at 3/4?

On my Spectra G with TRM Proto 260, my normal mode curve on a 9CHP was 0,12.5,18(midstick),38,100

In I1 and 2 it was 100,42,20.5,42,100

Sounds like you are overspeeding the motor, that will definitely make it lean out. Have you tached the headspeed? Also if your muffler gets loose, it will cause the motor to lean out.

HTH, PM me for my phone number if you want to call and discuss. I will help all I can.

[Bill Ludwig]

I just got back from trying a few things. Governor disconnected. Standard 'V' curve in idle-up. Zero degrees at mid-stick. It runs just fine until I do a descent. The head speed then goes way up, and is almost impossible to get settled back down again. Hovering head speed is 1750. It's a little over 2000 during and after the descent.

- Bill

[WillJames]

If I richen it, even just a little, it's too rich to even get enough head speed for liftoff.
Which needle are you adjusting? Sounds like you are setting the low needle to rich, but may still have the high needle to lean. The topend needle on your TRM 231 in the Spectra G is going to affect your hovering mixture as the Spectra is hovering at the transition point between the needles.

If it is overspeeding during descents, you need to continue to lower the throttle curves. When I fly without the governor, I click back to normal during descents. Sounds like you just need to massage and lower your throttle curves. What is your mid stick percentage on your idleup curves?

[Bill Ludwig]

I think you're right, William. Isn't it still strange that the governor can't even keep it from overspeeding -- as I said earlier, it's almost like the governor pulls the carb to fully closed, but it keeps on overspeeding. That ain't normal...!!

[WillJames]

Try the CSM Rev Lock. It will cure the overspeeding better as the GV-1 is just not great for gas motors overspeed. Also since you only have a 3/4 gallon through it, It would probably be less hard on your motor to not use your GV-1 unitl you get another gallon or so on it. John tweaks his curves so well that he does not even need a governor and if you flew his Spectra or SE you would agree. It can be done.

Actually is is plenty normal to self induce overspeed in descents on gas machines before you get your throttel curves tweaked. I know from first hand experience. :DOH Glow machines are easy to get the curves right compared to Gas machines. Until you get your motor well broken in and you are running your final gas/oil mix, you are going to need to keep working with your throttle curves. It can be frustrating and hard at times, but that is one of the things that really attracts me to the gas machiens. Plus for me John Garst is immesurable help. I called him and asked his opinion on this topic just a few minutes ago. John ROCKS!!

[Bill Ludwig]

Ok, I'll keep playing with it - without the GV1....I still don't understand why the GV1 won't pull it to an idle when in an overspeed condition.

[Rob Stump]

Bill, sent you an e-mail but when this engine starts to break in the normal type curves you use on a glow machine don't load the engine enough with this gear ratio so you have to lead the pitch a little otherwise you get the RPM run away. Try using a Hockey Stick type curve. An example on the 9Z would be to start around 1=20 and around mid stick 7=29. Start increasing point 8=33, 9=40, 10=52 straight up to 13=100. This is just an example but should help. After this is sorted you can engage your gov. If you continue to have problems contact Bigrcr(John Garst)

Regards,

[Bill Ludwig]

Well, it looks like it was the breather cap as suspected. It's actually the #125-23 'One way fuel valve'. More like a NO WAY fuel valve. Mine was VERY restrictive. Took it off and it runs great now. It was just starving for fuel.

Thanks for the help, guys.

- Bill

[James]

Bill: glad we had a chance to figure it out last night. I got a hunch others may have the same thing happen to them as well. Personally, I always leave my atmospheric line open, I make sure to have several loops in the line above the normal fuel tank level to help trap during inverted and roll flight.

Maybe Min wants to issue a bulletin on this? :hug:

[WillJames]

EXXCELLENT!! Glad you got it figured out Bill!!! The loops do work flawlessly.

[clalo20]

I am having this problem and I drilled 2 holes on the one way valve, it works better but not flawless, it still overspeeds after a little time running and on the descent. I will try out the loop solution. My engine went dead around 40 feet and had to auto it, not very fun.

Is the overspeed definitely because of the one(no) way valve???

[Bill Ludwig]

My overspeeding on descent was definitely due to the malfunctioning one way valve. And, contrary to popular belief, the GV-1 is working perfectly with the Spectra.

I don't know what all the worry is with running a governor until 2-6 gallons. Just like the glow birds, all you have to do is run it rich until you feel that you've completed the break-in process. All the governor does is keeps you from having to fight endlessly with those @#$% throttle curves. It's simple to know if you're running rich enough...just keep richening it until it gets sluggish -- keep it there through break-in.

- Bill

[psawya]

Bill I'm with you on this one. Gas or Glow the engine should go to idle when the throttle is cut back to idle. Gas or Glow there is no load on the motor in a decent so how can that effect it? Just like hitting throttle hold, it should go to idle immediately, if not, it is either not tuned properly, which can be caused by many things, or the hold setting is too high. It may just be my simple way of looking at things but I just can't see it any other way.

Pete

[Bill Ludwig]

You gave a great analogy about hitting 'hold'. That's exactly what was happening the other day -- the governor was in the same mode as hold, pulling the throttle servo to idle, but the engine was still wound up tight. That was a dead give away that it was starving for fuel. Hitting hold would have been a good test to confirm that it was lean.

- Bill