OK..... got the RAM back from MBUSA. Alberto said it ran good at the factory. Ran it on test bench on Sunday and seemed to run OK except for some "popping" at idle. I am a little concerned about this since the fuel manifold was repaired for some REAL rough idling before - it is definately better now but still "pops" every few seconds. So I left the field with mixed emotions thinking I might be ready to put it in an airframe.

Once I got home I though I better check it out again - no people around, I can really try to figure out what was going on. So I fuel up and commence with the autostart - Holy $%^# !! it looks like a comet when ramping - (wanting to run away like a little girl) I stayed with it and the temps stayed within range (somehow) and just as it started to stabilize it shut down with a "tx - off" message. I didn't cut the throttle trim so I immediantly thought I better re-teach.

I did that and got the guts up for another start - same thing, lots of flames on the start - actually made it to "Run" mode this time and stabilized (if you can call it that) at idle. The popping was back and since it was dusk now I could see that with every pop there was about a 12" flame - this would only last as long as the audible "pop" but is obviously very concerning - thinking to myself - "I better shut this down" when all the sudden it shuts down again on it's own with "tx - off" message. OK...... now I'm thinking "I know I didn't do that" and I look down at my trim that is definately not at kill.

There obviously are several things at play here and I need to get them solved pretty quick before I return or sell all the electronics. (add currently posted and if I find a buyer I'll have down payment for another something purple if this doesn't work )

Ok...... So to sum up:

RAM 750p Autostart ECU Ver: T03

1) Did the fuel pump get looser after the first start? And do I need to lower the voltage? There were not flame problems with the first ramp and I used hemostats on the fuel line to the turbine when refueling in addition to having the valve closed.

2) What are people using as a starting pulse width? (mine came back from MBUSA at 57)

3) What would cause the tx-off event to keep occuring? Fuel pump or ECU noise?

4) What about the popping at idle? Has anyone ever experienced that?

As a final note I will say this - the first run seemed to go really well (besides the idle) and the power of this engine was very apparent- and all this at pretty low temps - it was in the high 400's at 100k and only 500's at 120k.

As always, your input is always appreciated.

I own a Ram, but not the ECU you have. I'd play with reducing the pump voltage at the low end. Sound like too much fuel being dumped in the the combustion chamber. The manifold work you had done may have unclogged the arteries of your motor and now it needs less fuel pressure. Also check festo connection inside the inlet cover. Leaking fuel entering the compressor can cause the poping.

Mike

On my Rams, I go 10 less than idle for a start pulse. Get it to run, look at the idle pw, then shut down and set the start pw 10 less. One of mine (a 1000) pops at idle also. I dont run it at night so it doesnt bother me. As far as the shutdown, If it was a deliberate transmiter shutdown, it would display TXSHUTDN, I do not know what the message you have means.

Anthony

smitty1001


Give me call 832-221-8413 I can help you out. Mine had the same problem after getting it back from MBUSA and Steve Ellsey helped me out at Waco last month. It's an easy fix but easier to explain over the phone instead of typing it out all.

JR

Thanks for all the good info everyone. (called JR also) Will try a run again tomorrow. Adjusting starting pulse pump width from 57 down to 40 or below and going to go for a manual start from the data terminal. If that resolves the heavy flames at startup but the popping at idle is still there I might bump up the idle rpm from 33k to 35k and see if that cures it. If anyone can see any problems with this plan let me know - otherwise I will let you know how it goes.

I will address the RF link problem after I have reliable starts and idle from the data terminal. Some suspected culprits for that issue are: 1.) RX too close to the ECU/Pump (mounted on test stand) 2.) Trim set to "hi" for idle instead of middle. 3.) Cheap Hitec Rx (PPM)

Sure would be nice to know the fixes for your problem and the popping. Please post when you get it sorted out.

Smitty,
The popping at idle is fairly common with Rams, and is nothing to worry about. See this thread for an explanation of why it happens.
http://www.rcuniverse.com/forum/m_32...tm.htm#3240486

My Ram 500 popped at idle. I put about 70 flights on it that way and it ran fine otherwise. After sending it in for new bearings and service it didn't pop any more. I never mentioned it to Modellbau USA and I don't know what they did to fix it.

Just fly it as is and mention it next time you send it in for service.

Joe

Update!

I had a successful start this evening. It was raining all day yesterday so I didn't get to go at it until today. So the latest info is:

Adjusted start pump pulse width down to 38 (from 56 [X(]) - very few flames and a pretty smooth start. I first tried 32 & 34 but I got low RPM. 38 seems to work well. This is all from the start box so I don't have any new info about the rx link.

As for the idle, there is still popping - doesn't seem as bad as I described first but it is definately occuring along with a corresponding small flame at the typical hot spot (4-5 o'clock) I didn't try up-ing the idle rpm as I am afraid of a gain in residual thrust. But maybe it is something I should consider. Anyone else running their 750 idle above 33k?

Some people have said not to worry about the popping, others have said it shouldn't do that and to send it back to modellbau or even to Carlos so I am not really sure what to do. I am a little concerned of installing it in an enclosed installation or one with horiz stabs nearby as it is now.

I could stick it on the Roo but that is about all I would be comfortable putting it on right now!

Steve and Dawn, I might give you a call and see if I can bring this bad boy over.

P.S. Where do you get an extension for the RPM lead? I definately don't have enough slack to get to the ECU.

"Where do you get an extension for the RPM lead?" -----> I made my own by splicing the wires and adding some new wire. Soldered each joint and used heat shrink tubing on each wire then a few bigger pieces around the grouped wires.

Glad to see you are getting better starts. Come to think of it now I believe I still get some popping at idle but nothing that I've had to worry about. As soon as I bump the throttle it seems to go away and it is smooth after that all the way to full power and back.

JR

In my experience (many moons ago) the RAM 750 idle popping was caused (not saying it can not have other causes such as fuel entering through the compressor) by drips of fuel from the vaporizer tubes. As you know, the fuel manifold needles squirt fuel onto the inside of the vaporizer tubes to use the large, hot area of the tubes I.D. to efficiently vaporize fuel prior to entering the primary combustion zone. At idle (when mass flow through the engine is rather low), if incomplete vaporization occurs, some liquid fuel can build up on one or more tubes on the inside until a big drip forms. This drip will then "drip" off the forward end of the tube and enter the primary combustion zone. That obviously causes the rather sudden fuel "rich" situation with a blast of flame out the rear (fuel rich gasses exiting the turbine wheel) and the popping sound.

I am not so sure about the root cause, but Carlos would know. I suspect it is most likely the fuel needles not being properly bent or pointed on the inside of the vaporization tubes thereby causing incomplete vaporization of fuel. An easy fix for someone who knows what they are looking for like Carlos. I would stop short of saying that it can not harm the engine. It certainly can not be good for it. A steady state idle with no transients would certainly be better, but you can probably live with it. I know I did for a long time in a RAM 750!

Contact Andy Low at Electrodynamics. He can make you a lead in whatever length you need.
http://www.electrodynam.com

Joe

Thanks for all the great input guys - everything seemed fine except for the popping so I'll order a longer RPM lead from Andy and will install it on the Roo. I'll let you know how it goes.