Rick6a

Rick6a

Well Known Member
I'm confused.....somebody help me out here. Rigging the mixture cable to the fuel injection servo, I would think its geometry 180 degrees out from the mixture lever on the throttle quadrant...is it? Pay no attention to the loose hardware, I'm not done yet!

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Rick,

Which FI system are you using? AFP or Bendix? I'll take a look at mine tonight and see how it looks.
 
Vertical Draft Injector?

Rick,

I can't remember which injector you had. IIRC, you have the standard vertical draft? If so, I believe you have the wrong cable mount - it looks like you have the one set up for horizontal draft as that has a reverser on it.

If you have a vertical draft set up, then you need: Part Number = VA-182-PC KIT

You do not want: Part Number = IO-360 THROTTLE/MIX as this is for horizontal induction.

http://www.vansaircraft.com/cgi-bin/catalog.cgi?ident=1190382971-138-357&browse=engines&product=throttle-bracket

EDIT - Rick, I think my advice was usless - the more I look at your pics, the more I think you have a horizontal with the correct bracket. If so, I am equally stumped...


-Rob
 
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For sure you have it backwards. I have not done one of these but try reversing the mixture arm on the throttle body; having it point down rather than up. This will correct the handle in the quadrant to the right position. However it might make the angle of the short push tube bearings a bit to much for them to have free to move at both ranges of movement.
 
Mine is the Precision horizontal induction IO-360 MIB fitted with the FWF kit for this engine.

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My initial impression is this...

You typically want the control cable "perpendicular" to the arm in the MIDDLE of the range of travel. It looks like your cable ends up perpendicular biased much more toward the lean end of the travel.

I would try clocking that arm about 30-40* clockwise (as we'er looking at it in the photos). See if that solves the problem.
 
Ditto to Dan's comment

Thanks for the extra pics Rick. OK, that all makes sense now. I would loosen up the arm, move your mixture lever in the cockpit just shy of full forward so it doesn't it the stop on the quadrant, then move your injector servo stop to full rich, then tighten it down and see what you get for ICO.

That will give you a good starting point.

Get ready for fun with cable geometry problems. I remember with my vertical draft set up (IO-360 with the same Precision/Bendix servo you have) that I get full rich, but just barely get ICO. In other words, you probably will have a bit of compromise with Van's bracket geometry.

Best,

Rob
 
<<try clocking that arm>>

It will still operate backwards.

Any way to rig it without the reverser bellcrank?
 
N908RV said:
....I would loosen up the arm, move your mixture lever in the cockpit just shy of full forward so it doesn't it the stop on the quadrant, then move your injector servo stop to full rich, then tighten it down and see what you get for ICO.......Rob
Click to expand...
Rob,

I tried that but....this is very difficult to explain.....doing so locks the cable in that position.....same deal when I move the mixture lever to lean and the "C" to ICO and tighten it. For lack of a better description, the "C" by nature of its design prevents any further movement. For purposes of illustration, I removed the lever arm to get a better view of the "C"...or whatever you call it. It is very difficult for me to convey its relationship to movement with the lever arm connected to the bellcrank assembly.....lots of monkey motion going on!

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At the risk of stating the obvious, the way you have it pictured there, it's at the FULL RICH stop. The control needs to rotate CLOCKWISE to lean, ICO on the stop being full lean.

Clockwise is leaner, counter-clockwise is richer.

ICO = Idle Cut-off
R = Rich

Does Precision make a version of the servo with a REVERSED mixture control? That may be what you have there...
 
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dan said:
....Does Precision make a version of the servo with a REVERSED mixture control? That may be what you have there...
Click to expand...
Dan,

If true.....that would certainly explain the problem. Guess I'll have to make a few phone calls...thanks.
 
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Rick,

I think I found your problem. The Silverhawk FI is available with a reverse rotation on the mixture control. This seems to be what you have. It would not require the bellcrank to reverse the throw when the control arm is pointed upward. You might ask Van's if they specify this one in order to remove the need for the bellcrank. I wonder if Van's changed this recently and that is the reason they now have the 52.5" cable?

If you look at the installation manual for the FI at

http://www.precisionairmotive.com/Publications/EX-5VA1 detail spec 120503.pdf

which shows the standard rotation, you will see that the markings are reversed on the stop lever arm.

I have heard that the throw on Van's mixture control is a little short so it doesn't allow you to go from stop to stop. I'm not sure if this is true, but I did notice that the the pivot in the bellcrank arm is not centered and would increase the throw slightly. You can also get a shorter control arm to increase the throw if neccessay.

There is more information on the Precision Airmotive website. Also, if you have any questions, give them a call. They real easy to talk to and will answer any of your questions. They also have a CD with maintenance and troubleshooting info that they will send you for free.

Now I have to go look at mine!
 
With a horizontal sump you typically need the bellcrank since there's no "straight shot" for a cable.
 
I checked a picture from another installtion and your unit has the rich and ICO reversed. Call the supplier, it might be a very simple modification to correct this.
 
I don't think the modification is not simple. They had to change some internals to to the reverse control. The best bet is to see if you can find a direct cable run that will fit.
 
It has been a few years since I had one apart but on the bendix system if you remove those two screws the whole mixture assembly pulls out. By simple I mean that you pull out one unit and the supplier sends you the correct one, with any applicable o rings and gaskets, and you slide it in.
You may be correct in that it might not be that simple and the unit may have to go back.
 
Hummmmph...

Dan C is probably right which makes Dan H's comment on the mark about it still being reversed. You might want to call Precision on this one to see if there are other models that are reversed, as I believe there are. There are certainly other arms, but since you are a Tech Counseler you probably know all that anyway.

What a pickle.

Reversing Servo Arm - No
OK, so using what you've got if you reverse the servo mixture arm itself then you will interfere with the fuel line and I can't imagine that the angle would work at all with the reverser crank to the servo arm - it would be too acute an angle.

Reversing the Reverser Crank- Possible, but likely No
I think this would work for Rich, but you would hit the case/sump before you achieve ICO

Different Servo- Maybe but...
I can't imagine the servo is completely different for any model, just the options for arm direction, etc. Here is a crazy thought, so I am just throwing this out there - call it stream of conscisousness engineering. What if you reversed the "C" and switched the stop to the other side? Like I said, just trying to think outside of the box. This may be the only difference in servos. (I am talking about removing the roll pin and reversing the C relative to the shaft and inserting a new roll pin)

I'd call Precision to solicit some input.

-Rob
 
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It will work!

Rick
I have the same set up as you do....exactly.
With the servo mixture arm off, I would suggest putting the mixture knob, on the quadrant, in the full idle cut off position.
Then, position the mixture stop in the cut off position, on the servo itself.
Now, put the arm back on in the appropriate position and adjust the linkages as required.
It should work. It looks like the arm is just not clocked in the appropriate position, relative to the actual stops. Also, make sure you have a little space at each end of the throttle arm throw rather that hitting the ends of the quadrant slots with the arms. It can be done!
Also, in order to get the proper throw on the throttle arm, I had to drill another hole, just above the outer most hole on the arm, and reclock a little, in order to get full throw from one stop to the other. This is pretty common from what I have seen.
 
52.5?

Is it possible that since you don't have the exhaust on that you will need a longer cable to get an "S" turn around the hot section pipe that drops out of #4 cylinder?
 
Bingo.

ptrotter said:
Rick,

I think I found your problem. The Silverhawk FI is available with a reverse rotation on the mixture control. This seems to be what you have....

If you look at the installation manual for the FI at

http://www.precisionairmotive.com/Publications/EX-5VA1 detail spec 120503.pdf

which shows the standard rotation, you will see that the markings are reversed on the stop lever arm.
Click to expand...

Good find Paul! Yep, that's got to be it. I looked that that, printed it out and held it up side by side to Rick's pic of the C arm and that is correct, Rick's "C" arm is the exact reverse of the arm on the stock servo unit. I can't imagine that is difficult to switch it and am sure that Precision can confirm how to do it.
 
Just talking about this problem with you guys taught me much today.

Because of your input, I called Precision and Lycoming. One thing is for sure. Both companies are aware of the problem AND.......thanks to the popularity of VAF, its nice to know some people at Van's occasionally view our posts. Did you make your donation? :)

Short version: The only difference between servo model number 3015010 and 3015002 is the direction of rotation. Mine happens to be the wrong one. No way can the homebuilder change the rotation. It must be done by pros.

Upon viewing the thread, Van's called me and said I was the third person this week to report the condition. Lycoming is aware of the problem, still trying to sort out the details and owners of affected engines will be contacted.

Very little about building airplanes, especially FWF stuff is uncomplicated. Maybe that's why I'm addicted.
 
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