Remote needle valve question
 

Just got an Evolution61 and want to mount on hobbieco super star 60. This engine has a remote needle valve and to mount on the hobbie star I would have to cut a deep slot in the side for the remote valve - do Ineed to strengthen that side when I notch it out and if so what is recommended?? help aprreciated

RE: Remote needle valve question
 

No need to strenghten. just cut a slot and protect the bare wood you expose

RE: Remote needle valve question
 

Thanks MinnFlyer

RE: Remote needle valve question
 

or on most engines, you can change the mount and mount the needle vertically so you don't have to hog out the fuse side.

RE: Remote needle valve question
 

Or you can put the remote needle valve adjust someplace else other than where it is. On my Wildstick, I have an evo 40 and put it on the firewall. Works just fine.

RE: Remote needle valve question
 

Listen to Dick. You just may have a better running engine with the NV mounted on the firewall -- less heat & less vibration to disturb the fuel flow.

RE: Remote needle valve question
 

So tell me this- "within reason", can one remove the remote needle valve from the back of the engine and mount it pretty much anywhere? Is there a limit to the distance you can take it from the carb?

RE: Remote needle valve question
 

No way to mount the remote on the firewall on my superstar 60 as it is built. The engine/front gear mount consumes the entire firewall area. Without changing the existing engine mount the only place would be either on top of the cowl behind the firewall or mounted external of the engine compartment. I'm new to this and dont have much experience but my gut feeling is either of those alternatives would not be good. Am I wrong in my thinking?

RE: Remote needle valve question
 

Anyplace (including an external mount) would work, as long as the feed line to the carb isn't overly long -- "overly" being determined by trial & error.

RE: Remote needle valve question
 

Let me qualify my comment. I mounted it on the firewall and I used a Sullivan Soft Mount for the engine. Thus, there was lots of room on the firewall for the needle valve. And, as I said, and as Britbrat said, it works just great.

RE: Remote needle valve question
 

So.... would the effect of a too-long feedline be to make the engine run lean? That's my guess.

RE: Remote needle valve question
 

Mine just hangs on the fuel line between the tank and the carb.

RE: Remote needle valve question
 

Hi!
Place the needle where ever you want, doesn't have to be mounted to the engine.
Regards!
Jan K
Sweden

RE: Remote needle valve question
 

Yes. If it was sufficiently long, you couldn't get adequate fuel flow with the NV turned right out. However, as long as you can actually peak the engine, the line length will be OK.

RE: Remote needle valve question
 

Yes the needle valve can be moved, but remember that the longer the fuel line is the longer it will take for changes of the needle valve to effect the motor. With a normal needle valve that is remotely mounted this delay is usually 1-3 seconds, but moving it farther away will increase that lag time. This needs to be kept in mind when you are trying to tune your motor. If you don't wait for the changes to take effect it's almost impossible to properly tune you motor.

Hope this helps

RE: Remote needle valve question
 

Hi everybody

I'm not very experienced with engines, but I have a question. Why does the distance from needle valve to carb effect how long it takes for a change to happen? When you open the value, the engine should be able to draw more fuel instantly, no mater how far the needle valve is. The fuel tube berween the needle valve and the carb is airtight, the carb tries to draw more fuel than the needle valve allows it to, so when you make a change to how much fuel goes into that part of the fuel line, instantly the carb should be able to draw more or less fuel from the other end.

That's just my theory, based on the little I know about model engines and the knowledge I have on physics. Am I wrong?

Serafim

RE: Remote needle valve question
 

Pressure drop in the delivery line affects the fuel flow. If the driving head (eg. tank pressure) is not raised to match the increased frictional loss in the longer line, the flow will fall. This means that a more open NV setting is required to deliver the necessary flow. The same increased pressure drop also affects the acceleration of the liquid charge in the fuel line, thus slowing the response to a change in NV setting.

RE: Remote needle valve question
 

So, is it the distance of the needle valve to the carb or the total fuel line length? Because if it is the total fuel line length, then I get it!

RE: Remote needle valve question
 

It is the total length of delivery tubing, from the tank to the NV.

Remote carbs have an additional problem. The main pressure drop component is the needle valve, which in a conventional carb is directly upstream of the throttle bore, where the lowest system pressure is found -- the pressure differential between this locus and the tank, provides most of the driving head for fuel delivery, which is helped by active tank pressurization. The low throttle bore pressure also assists in fuel vapourization -- a good thing for well controlled combustion.

With a remote NV, the delivery tube to the carb inserts an additional frictional loss downstream of the NV and ahead of the throttle bore, sometimes resulting in a line pressure that falls below the vapour pressure of the fuel, resulting in flashing in the delivery line (bubble formation), which interupts fuel delivery & results in erratic tuning.

RE: Remote needle valve question
 

wow - didnt know all that as a result of a remote NV. But seem all the new engines I've looked at has a remote NV. This is my first one so we will see what happens Sunday on maiden flight