can Imount the throttle servo in the engine box as long as the receiver is still 12 to 15 inches away from the EI? and do Ineed to twist the lead from the servo to the receiver?

I would prefer you keep as much of the radio electronics away from the engine as far as possible. Reason one: Vibration and heat. Reason two: Electrical noise from the engine could be picked up easyer the closer you get to the engine.
Terry

depends on the engine....

with lots of the quality engines and shielded ignitions there is rarely a problem..

I know with my DA's the servo is right in the box with no problems....


if it is an older engine, non-shielded ignition, conversion, etc.  then it is more important to keep them apart

RFI is irregular in the model engines. You can set up and test everything on the ground

Fly for a couple weeks with no RFI and then suddenly everytime you fly by from the left you get hit?

The RFI can get into the servo amplifier itself

Why take a chance over convienence?

Well this nothing within 12" used to be a "no way, no how" install, but that's pretty much long gone unless you're running something that's an older engine with a magneto or something or a conversion.</p>

Lots of ARF's come with a servo cutout for the throttle servo in the engine box and I've had no difficulty with any of mine mounted that way.</p>

I would where possible, keep the electronics other than the ignition module as far away as possible if you can't get 12" away just as a matter of course. Make sure you don't use metal to metal connections on the linkage and do the ground range checks including with the engine running. You don't say what radio, but the 2.4GHz systems are more resistant than 72MHz systems to interference from most of the possible causes except loose sparks intended for the sparkplug and those will give you headaches with any system. Such things as a non resistor plug installed when it's supposed to be a resitor type, cut shielding on the sparkplug wire, poor contact with the sparkplug electrode and so on can cause grief. Also some engines require a ground lead.</p>

Your ground range checks should tell you if what you've installed is going to work, but there are certainly other places where you can pick up interference and/or radio problems so don't just pay attention to the engine related stuff at the expense of the rest of the setup.</p>

I have mine in the engine box, no problem. Just like always, make sure to keep spark plug wire and ignition battery wires away from the servo extensions. Good wiring practices always apply.