IO320 fuel servo issue help

[RickWoodall]

A buddy of mine is just finishing up his rv and was having a shop do some throttle adjustments.

He has been told that his used engine has an io320 AZTEC set up and that all his throttle and mixture cables will be backwards and its not going to work. Seems to sound like a huge issue and expense. Anybody out there know what is so diff about an AZTEC fi set up and the way the cables run and what the reasonable solution/fix is? Engine etc is all fine, just servo is sideways or backwards for correct throttle mix plumbing?

Do you just go buy a new silverhawk set up? Just figured someone might know so he isnt steered wrong by a certified shop that isnt aware of the experimental engine solutions.

Thanks,

[aerhed]

I dunno, but I do know that Aztecs have O-540's in them

[cln1owner]

Rick,

My setup is probably similar to what your friend has run into. Mine is a Bendix. Not sure what original production aircraft it came from, but I obtained it from an RV6A wreck we bought for parts.

I had to mount it backwards, throttle on the left side, mixture on the right. The control cable bracket supplied with Vans firewall forward kit would not work and had to be modified to line the cables up with the linkages on the FI servo. The default throttle and mixture cable penetration points on the firewall still worked, they were just switched as well. I needed a longer throttle cable than what Vans supplied.

I had Don and Airflow Performance rebuild it and change a couple of minor things in order for it to work correctly in this orientation.

It really wasn't a big deal to make it work, and I didn't have to notch out the air box for the mixture arm.

If it sounds the same, PM me and we'll talk offline.

[RickWoodall]

The mechanic made it sound like this older servo is actually sideways or backwards for a vans install and the throttle and mix will NOT work as they would be plumbed backwards and he has to do all sorts of voodoo magic ($$) to make it work. If it was mine, I think I would just buy the right new silverhawk and bolt it on. Just figured this must have been an issue for others. Will get some more particulars on model # etc and see what others can tell me. Thanks.

[Russ McCutcheon]

Maybe another option. I don?t know what it came off of but my Bendix servo has the throttle on the right side and is operated in reverse of what I would think it would, so my throttle cable is run over the top of the engine and down in front of the #1 cylinder to the throttle arm, I have never seen it done this way so it may be something non-standard, maybe similar to what you have.

[cln1owner]

The servo model I have is an RSA-5AD1

[rocketbob]

Originally Posted by RickWoodall

A buddy of mine is just finishing up his rv and was having a shop do some throttle adjustments.

He has been told that his used engine has an io320 AZTEC set up and that all his throttle and mixture cables will be backwards and its not going to work. Seems to sound like a huge issue and expense. Anybody out there know what is so diff about an AZTEC fi set up and the way the cables run and what the reasonable solution/fix is? Engine etc is all fine, just servo is sideways or backwards for correct throttle mix plumbing?

Do you just go buy a new silverhawk set up? Just figured someone might know so he isnt steered wrong by a certified shop that isnt aware of the experimental engine solutions.

Thanks,

How can someone build an airplane, and when they hook the throttle up not note that the butterfly is working in the opposite direction?

[RickWoodall]

My guess is that is why he took it to a pro to help with. No idea how it all came to pss this way, but if it worked fine and hooked up fine he wouldnt be in this mess, nor would I be asking the questions.

[Don at Airflow]

This set up is not a problem and in fact will work quite well. If you have an up draft sump, mount the servo with the throttle on the left side (as sitting in the cockpit) and the mixture control will be on the right. With the throttle lever in the normal position (down) pushing forward on the lever will open the throttle. Mount the mixture control lever up and pushing forward on the lever will rotate the mixture to full rich. Perfect. Plus with this set up you won?t have interference with the air box. Now for the unorthodox part. You will have to put the fuel inlet on the left side and use a #4 inlet fitting so that the hose clears the idle linkage. This is not a problem, as a #4 hose with 20 PSI will flow enough fuel for a 600 HP engine. All you have to do is get a #6 to #4 adapter for the engine fuel pump.

Simple solution isn?t it. No problem here.

Need it overhauled? Give me a call.


Don

[cln1owner]

Originally Posted by Don at Airflow

This set up is not a problem and in fact will work quite well. If you have an up draft sump, mount the servo with the throttle on the left side (as sitting in the cockpit) and the mixture control will be on the right. With the throttle lever in the normal position (down) pushing forward on the lever will open the throttle. Mount the mixture control lever up and pushing forward on the lever will rotate the mixture to full rich. Perfect. Plus with this set up you won’t have interference with the air box. Now for the unorthodox part. You will have to put the fuel inlet on the left side and use a #4 inlet fitting so that the hose clears the idle linkage. This is not a problem, as a #4 hose with 20 PSI will flow enough fuel for a 600 HP engine. All you have to do is get a #6 to #4 adapter for the engine fuel pump.

Exactly, although Don, for me you guys installed a #6 90 degree fitting on the right, (mixture) side, with an offset mixture arm. Worked very well for me.

Either way, the Vans supplied control cable bracket will need to be modified, to line the cables up with the control levers.