I read warnings about keeping the radio RX RFI free. Part of that is situating all RX wiring away from the engine and ignition. Yet I often see pictures of the throttel servo in the engine compartment. Is the old warning now obsolete?

All depends on the ignition type. I've had two servos right next to the igniton on one plane. Ignition was also run off the RX battery. No issues at all. Plane set up on FM, flown on 2.4. Guy at the field couldn't believe that I wan't having any problems. He was flying CCRC engines.

The guy I fly with runs 72 mhz and has the servos next to the engine. I've never seen any problem with it.

He has run BME, DLE, and DA engines

I have them farther apart myself.

Scota, Send your RC manufacturer an Email and get their advice. In fact, send any RC manufacturer the same Email and see what they say. Please post their responses. Thanks, Dan.

OK,
Futaba says on their FAQ page,
"Guidelines for setting up gasoline engine models. All ignition equipment, including an electronic kill switch, must be mounted at least 12", and preferably 14", away from all radio equipment, including throttle servos, etc. Ignition kill switch should always be on opposite side of fuselage from radio kill switch. All pushrods going to anything related to the engine must be non-conductive (just nonmetal clevises is not sufficient)."

So, is this just overly cautious hand wringing designed to extra sure, just in case. Or, is there actually something to it with modern ignitions?

i have servos in engine comp in 3 of my planes and no prob whatsoever ...im on 2.4 also

heres an old pic i dug up

Scota, I'm glad you went to the trouble to get such a response from a source that is the most knowledgable. I'll try to post an email I got from JR. Dan.

I'd say that from the radio mfg's point of view, it's actual user problems with poor installations they've encountered, and best installation cures.

Take the following scenerios to get your mind in gear on how to view all of this;

1) You have 5 elements that might cause troubles, 4 are done correctly, 1 is done completely wrong.
Easily you know which was the problem and which to fix.

2) You have 5 elements that might cause troubles, 3 are ify, 2 are are done correctly. Now you have a mystery.
JR/Futaba/Spektrum/Hitec have had tons more experience than us and don't like such customer support issues,
soooooo they come up with their best recommended solutions.

The new 2.4 radios are somewhat more resistant to inteference issues, but NONE are 100%

So follow the radio mfg's best practices/recommendations and enjoy the warm fuzzy feeling of a job well done!
Do otherwise, and you're on your own as to the results you get. Sometimes the best recommendations just
can't/won't be followed (no room, etc).

Some are very lucky doing things ify, some aren't. What value do you place on your model(s)?
Try your best to follow the radio mfg's best practices/recommendations, then all we need do is improve our flying skills!

While I try to maintain a fair amount of distance between ignition and radio components there are exceptions. I have (2) planes where the the throttle servo and the RX batteries are within an inch or so of the ignition box. Absolutely no problems and one of these planes flys on 72 MHz. I do take care that wiring is well separated and make sure there is no way my plug cap can come loose.

Yep, that's one example of some cases we can't separate the way the mfg's suggest.
Still, we should strive to do so IF we have the room.

My GP Ultimate (27.5%) has tons of room to separate everything and I've done so. Same with my SD-260 (30%).
But my H9-Twist-150 has everything crammed close together. Simply wasn't room to do properly.

Well said.

Putting throttle/choke servos close to ignition probably is safe until one day the spark/high voltage cable is not well grounded. So a good separation is a prevention measure. I following the 12" rule whenever I can.