Need help with gas engine glitching problem
 

Ok Gas Gurus...

If this is a redundent question, please forgive me...

I am new to gas, my first gas engine ever is the MVVS 1.60 with the tuned silencer mounted on an Extra 330S. I have a HUGE problem with radio interference. I am using a Futaba 9C and a 8 channel FM receiver. I am using a 2700mah 4 cell battery for radio and a 2500mah 4 cell for ignition. I have the ignition module mounted on foam, on the left side of my engine standoff. I also have my throttle and choke servo mounted on the opposite side and bottom of th eengine standoff. (see pics) I have just read seemingly thousands of posts concerning radio problems with ignition units, and now realize my servo location may be part of my problem. I have read serveral different opinion about how far away the servos should be, but is there a standard distance? I also have my ignition battery sitting next to my receiver battery... is this a problem?? The first 3 flights with this motor, was flawless. no interference at all. On the fourth flight it went to crap very quickly as I lost all control of the aircraft (all channels). It was very eradic one moment I had control, the next moment I didnt. I managed to get the plane on the ground, with only slight damage. The Landing gear ended up ripping off as I came down hard on one wheel. That can be fixed, but this glitching problem has me very concerned. The throttle linkage is in a very bad location right behind the header, so I mounted the servos in the engine compartment to ease the install. Just to be sure, I removed the receiver from the aircraft and installed it in my trainer (dont care if I crash it...). I made several flights with no problems whatsoever...

PLEASE HELP ME.

~James

Here is a link to my blog, I posted some pictures of the engine set-up.

http://www.ovalexpressracing.blogspot.com

RE: Need help with gas engine glitching problem
 

First thing I took note of was the fuel filter. I'll bet it's rubbing on the engine. Second thing is the throttle/choke control rods. If it is metal or CF change it because it will act as an antenna.

If you absolutely must have the servos where they are you could always wrap the servo wires around a choke ring. This will help with shielding the servos from tranmitting RF back to the receiver. But again replace those rods. extend the throttle and choke arms if you have too.

http://www.horizonhobby.com/Products...ProdID=JRPA029 (RF Filter rings)

Standard distance from any part of the ignition to any part of connected to the RX is 12 inches. Some planes just will not allow this.

Definitely never put the ignition battery next to the receiver. That battery will definitely transmit RF as it picks up the firing pulses right from the ignition.

Also check your switches. You should be using heavy duty switches on both the ignition and RX. The smaller standard switches cannot take gas engine vibrations and in a very short time will fail

You also want to wrap you plug wire with some of the spiral style automotive cable sheething. Also make sure ALL wires are tied fown so they cannot rub on anything sharp. Both wires coming from the ignition module are prime for rubbing on the edge of the engine box and engine mounting bolts. If they are already rubbed through, then they will need to be replaced. If the metal sheilding on the spark plug wire is frayed, which it looks like it might be, then that will also break the ground it is providing to the ignition module and really play havoc. The throttle servo wire is also rubbing on the hole and will eventually be cut.

Remember, gas engines vibrate and you need to take that into account when doing a gas installation. The prop must also be balanced to help reduce vibrations plus an unbalanced prop will not allow the engine to make it's best power and could easily damage the engine. Balance includes both the blades and hub.

http://www.downonthedeck.com on the left side under "instructional" are some very good videos, especially the one about prop balancing.

Also check out http://www.teamflyingcirkus.com, under the video section, for gas setup recommendations.

RE: Need help with gas engine glitching problem
 

Thanks for the post Bill, what type of rod do you recommend for the push rod? I was un aware of anything except metal and carbon?

~James

RE: Need help with gas engine glitching problem
 

http://www2.towerhobbies.com/cgi-bin...?&I=LXFU90&P=7

This is what I use. I just replace the metal clevis with ball links. They make a few lengths and rod diameters. I use the 2-56 size and it's a bit flexible which can make it nice to install.

They give you two short all-thread rods to screw into the gold-n-rod and your clevis/ball link and then one long all-thread which I cut in half so I can easily get 2 complete rod setups in one package.

RE: Need help with gas engine glitching problem
 

It seems to me that if the first 3 flight were flawless then his installation did not have problems. It sounds to me like he was a victim of interference.

RE: Need help with gas engine glitching problem
 

While I do not disagree, he has a few things there that could cause a problem after a few flights, the fuel filter being up against the engine is one that may work for a few flights then start causing problems (metal to metal contact, especially intermittent contact), what appears to be the shielding fraying on the ignition wire because it is rubbing on the edge of the wood and also looks like on the one engine bolt could be another that could cause a problem after a few flights, unprotected wires going through the fuselage.

Also something I just realized, there is nothing holding the fuel filter to the fuel tubing. Sooner or later, that tubing is going to swell and allow the tubing to slip off the filter.

It's his first gas setup and while not too bad, he did make a few common mistakes that may bite him later

RE: Need help with gas engine glitching problem
 

I highly recommend the following for any gas engine setup to avoid interference caused by the ignition:

1. use a PCM receyver
2. use nylon push rod for throttle control
3. maintain at least 12 inch between receiver system and ignition system
4. ground the ignition wire to the body of the engine
5. secure any loose wires

--qc

RE: Need help with gas engine glitching problem
 

I have been flying gas engines since they came out about 1976 or so. I have violated evey single one of your rules most of the time. Especially the nylon push rod. I use a steel cable with a plastic quick link.
You left out the most important rule. That is use a resistor spark plug or a shielded system, or both

RE: Need help with gas engine glitching problem
 

Right with you dirtybird. Violated every one and still doing it. Check what db suggest.
Wayne

RE: Need help with gas engine glitching problem
 

Bill, The fuel filter is atleast an inch from the anything, and even futher from metal, so I know thats ok. The ignition cable sheathing is not frayed anywhere, The pictures are apparently misleading. I did however cover the entire length of ignition wire and pick up wire in thick walled rubber tubing. Not sure if the pickup wire contributes to any of the interferance, but I guess better to be safe than sorry. I have installed a rubber grommet for the Ignition unit power wire where it goes throught the Fire wall. While working on this thing, I realized that the Ignition wire runs VERY close to my throttle servo(mounted on bottom of the standoff) and pushrod. Unfortunately, this is the only way I can route the Ignition wire to the plug, so I am in the process of moving the servos (choke also) to the inside of the plane. I happened accross some good pictures of MVVS 1.60 linkage setups using bellcranks that seem to work much better than what I have. (I tried a bellcrank system, but after staring at it for a couple hours I gave up on trying to get it to function properly and settled for the current set-up).

I am going to mount the ignition battery on the opposite end of the cockpit area to get it as far away as possible, I will try all of this and ground check the crap out of it with my PPM receiver until I am satified that there is no more glitches. Afterwards, I will probably switch to a PCM, once my wallet gets over the sting of my latest purchase.... A New Funtana... PCM Receivers are EXPENSIVE....but then so are planes....so...

~James

P.S. Dually noted about the fuel filter hose clamps.... I have some I can install. I will keep everyone informed once I am satisfied the problem has gone away.

RE: Need help with gas engine glitching problem
 

How does the plane do on the ground with your range check?

RE: Need help with gas engine glitching problem
 

I ranged checked it a few times on the ground with no problems, unfortunately the engine wasnt running... However, I taxied quite a bit at a fairly large distance also with no problems, as soon as it hit the air the last time, it started going crazy, no matter what speed the engine was running. I quickly thought of killing the engine in mid air while it was acting up so I could eliminate any ignition related interference and come in deadstick, but things happened so quickly and the plane was so low I didnt have time, so I managed to bring it down under power, but it wasnt pretty. The prop broke, and landing gear broke off, so I havent had a chance to ground check it with the engine running. BUT I guarantee it will be done before the next flight.

It was pretty nerve wrecking seeing my freshly built money pit flailing around uncontrolably in the air, now that my first crash is out of the way, hopefully I figure this thing out. The little bit I was able to fly it, the engine is AWESOME. Tons of power.

~James

RE: Need help with gas engine glitching problem
 

I would try having someone restrain the plane and range check with the engine running at different rpms..If the range check with the engine running is good and you only get the RFI while in the air then like Bill suggested it could be some vibration..Check any lock nuts that come in contact with any metal parts..I started getting some RFI on a plane out of nowhere..turns out the lock nuts that held the gear on were slightly loose and were vibrating against the aluminum gear plate..

Cant tell from your pics but put some foam under the ignition also

RE: Need help with gas engine glitching problem
 

I think most of you are on the right track. I had a similiar problem with a G62 I was flying in a Biplane every once in a while I would be flying and get a glitch my plane would do all kind of stupid stuff I swear I was getting hit, or some one turned their radio on , on my freguence. The correct way to range check a plane with a gas engine is to have the engine running antenna down walk off you distance and watch and listen to your plane throttle it up and down. At this point my plane went crazy thats when I realize it was my plane either something rubbing or my mag. After talking to a friend of mine he showed me these buffers that wrap around your wires going to the receiver I never had any more problems. Their 20.00 for 5 if anyone needs any more info you can email me at [email protected]