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(clip-on rubber) stopping spacer for throttle?

iaw4

Well Known Member
I have a strange question. We have a (non-adjustable) Ellison carb which should never be on full throttle on our fixed-pitch prop. (it gives no extra power and probably contributes to fouling the plugs.)

so I am thinking that it would be useful to put a spacer on the throttle that prevents us from pushing it all the way in. Maybe 0.75 inches long, around the metal throttle. The throttle itself is standard Vans for an RV6a, about 3/8" metal diameter. It should probably go out about 3/4" in order not to interface badly with the screwing mechanism. Ideally, the stop would be rubber and removable, sort of like the old ferrite cores for power cables.

does anyone know of a source for such an item (or the right name)?
 
Throttle Adjustment

You should be able to adjust the throttle via 2 of the 3 following adjustments: the cable adjustment nuts on the cable bracket, rod end bearing, and the throttle arm so when the throttle is pushed all the way forward it only moves the throttle arm on the fuel servo to where you want it maxed out.
 
Full throttle

I can't imagine not wanting full throttle with the Ellison. I run two of them and there is a significant amount of power at the top. You might have to lean much earlier than with other fuel delivery systems, but limiting the throttle opening is probably a bad idea.

On my 8 I inadvertently had the throttle cable set wrong for a few years and didn't reach the throttle stop. I've been moaning that my plane was underpowered for three years now and was ready to pull the whole engine off for overhaul. During the latest cowl off opportunity, I took off the air straightener that I have covering the intake inside the air filter and found the throttle not opening the last 1/4 inch or a bit more. This necessitated completely dismantling the throttle quadrant and getting things set right. The first takeoff was in 500 feet instead of 1000. RPM on level off hopped right up to redline before I throttled back a bit like it is supposed to. With the misalignment it wouldn't get over about 2600. On climbout the engine is taking so much more fuel the pressure drops to zero and it runs great, but turning on the electric pump increases the pressure back to five pounds and it starts running rough (3500 feet), so a big pull on the mixture is required if the pump is on.

I'd strongly recommend you play with your mixture and not limit throttle travel unless you're really, really sure you don't want that much air getting in. Some people have soldered a few of the high end fuel holes shut on the emulsion tube, but I just pull the mixture back a bit.

All of this comes from about 1000 hours of monkeying with the Ellison on an RV-8 and RV-3 that are both fixed pitch. The 8 is more cantankerous as it uses the EFS 4-5 instead of the -4. I think the 4-5 has enough fuel holes to supply a larger engine than the 180 horse, but I still wouldn't recommend limiting the throttle. Mine seems to like it at full throw, but requires quite a bit of mixture tinkering.

Good luck.
 
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