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Throttle Lever Range

Joe

Well Known Member
Lycoming IO360-M1B with Precision fuel injection servo and Van's "horizontal induction" cowl. "Deluxe" throttle quadrant and standard throttle cable from the finish kit. See the two images below.

Short of drilling a new hole in the throttle lever, is there a way to increase the throttle range? I clocked the lever on the fuel injector servo to allow full (wide open) throttle with the cockpit throttle lever pushed forward. But then pulling the cockpit throttle lever to idle does not allow the fuel servo's arm to contact the idle stop. I can re-clock the lever on the F/I so its arm contacts the stop at idle but then full throttle cannot be reached.

I measured the throttle cable's throw and it's approximately 1.9 inches. The lever arm on the F/I servo requires approx. 2.2 inches of linear travel for full range. Any ideas?

Full throttle:

FullThrottle.JPG




Throttle at idle:

IdleThrottle.JPG



Thanks,
Joe
 
You have three choices:

1. Drill a new hole in the FI servo throttle arm.
2. Drill a new hole in the throttle lever.
3. Rig up a bellcrank to increase the throw of the throttle cable, like this:



OK, maybe there are more choices but that's the best I can do on short notice.
 
Hi Joe

I have exactly the same setup as you, same engine, same throttle body and I hate to say it but my supplied parts fit and work correctly.

Are you sure that you don't have any adjustment on the throttle cable itself that will allow you to achieve the full range of throw, check both ends?

Try starting again, put the throttle arm back where it was when you took the throttle body out of the box, undo all the adjustment nuts on your cable at both ends and see how it goes.

Cheers
 
Well, now I am confused. I'm amazed that yours works, Eddie. In my case, putting the throttle arm back in its original position on the FI servo is not an option: the geometry was totally wrong. The only adjustments on the cable are for position; there is no adjustment for throw. My FI servo body throttle requires 2.2 inches for full travel and the cable only provides 1.9.

Eddie, is it possible that your idle set screw (clearly visible in my second image) is adjusted differently than mine? I'm assuming Lycoming set it when they ran the engine but that may not be a good assumption.

Thanks for weighing in, Ron and Jon. Drilling another hole in the FI throttle arm is beginning to sound like the least onerous solution as I don't want to wrestle with the throttle quadrant in the upper left console again if I can help it.

--
Joe
 
Well, now I am confused. I'm amazed that yours works, Eddie. In my case, putting the throttle arm back in its original position on the FI servo is not an option: the geometry was totally wrong. The only adjustments on the cable are for position; there is no adjustment for throw. My FI servo body throttle requires 2.2 inches for full travel and the cable only provides 1.9.

Eddie, is it possible that your idle set screw (clearly visible in my second image) is adjusted differently than mine? I'm assuming Lycoming set it when they ran the engine but that may not be a good assumption.

Thanks for weighing in, Ron and Jon. Drilling another hole in the FI throttle arm is beginning to sound like the least onerous solution as I don't want to wrestle with the throttle quadrant in the upper left console again if I can help it.

--
Joe

In the past, I have found that if you have the green cable stop nutted as far forward as possible at the throttle quadrant ( meaning, the lock washer is on the fwd, side of the bracket, and the aft locking nut just catches some threads on the cable) you somehow gain extra travel. I don't know why this is but it has helped on carbed engines. If that doesn't help then drill that hole. Better yet, just drill that hole and move on!:D
 
Drill new hole in servo arm.

What Bruce Eicher said.

I had the same problem with the throttle linkage on my IO-360 M1. I drilled a new hole in the servo arm and it has worked perfectly for over 1200 hours.

Dan Miller
RV-8 N3TU 1225 hours of fun
 
Common problem... technically ideal solution is new Throttle Arm.

Precision were helpful and exchanged our arm for one 3/8" shorter - the price for a new one is a lot :eek:
 
Thanks, guys. I didn't realize this was a common problem but the solution is becoming crystal clear to me. Think I'll start by giving Precision a call but I have a drill press and am not afraid to use it :)

Hopefully this thread will save some future unsuspecting builders some wasted time.

--
Joe
 
Had a buddy with the same issue, not sure if it was Precession or not, but he had the hole in the arm welded shut (TIG) and then drilled a new hole.
 
:confused:

What can I say, perhaps I got lucky and mine was shipped with a shorter arm, I am pulling the cowls this weekend for some maintenance and I am curious now, so will take some photo's.

Cheers
Eddie

Hi Joe

I have exactly the same setup as you, same engine, same throttle body and I hate to say it but my supplied parts fit and work correctly.

Are you sure that you don't have any adjustment on the throttle cable itself that will allow you to achieve the full range of throw, check both ends?

Try starting again, put the throttle arm back where it was when you took the throttle body out of the box, undo all the adjustment nuts on your cable at both ends and see how it goes.

Cheers
 
Rv8A. Same exact setup, Mine works perfect. I think i have more cable throw due to differant throttle quadrant. Marc
 
... perhaps I got lucky and mine was shipped with a shorter arm ...

Maybe that's it, Eddie. Buried in Precision Aeromotive's web site is a table of "Dimensions for Common Levers" (scroll down). Mine apparently shipped from Lycoming with p/n 2521196 (2.000 inch length). The lever I want is p/n 2521287 (all dimensions identical except 3/8-inch shorter).

That should make the geometry work out and is right in line with what Andy Hill, Jim P, and others said (3/8").

I'll be curious to learn what you discover.


So I called the friendly folks at Precision Aeromotive in Marysville, WA (360-651-8282) and spoke with Peter Nielson in Product Support. He told me to send in my throttle lever and he'd send the proper one by return mail. No disassembling of the quadrant, no drilling, no welding.

Had the same problem (first reported in this massive thread last summer) ...
Wish I had heard of it before starting this thread. A search of the RV-8/8A forum didn't turn up anything useful for "throttle range" and it wasn't until after hearing all these responses about the throttle lever that I realized the problem is in the fuel servo arm, not the range of motion of the cable or the quadrant.

Anyway, big thanks to those who put me on the right track. Maybe this thread will help some future RV-8 builder. Correct lever from Precision == end of problem.

--
Joe
 
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