Mixture Cable Routing with AFP and Vertical Induction

I am looking for help routing the mixture cable for my RV-7A with vertical induction and Airflow Performance fuel injection. This is not a configuration covered by a standard Vans firewall forward kit but they recommended the FWF kit for the vertical induction with a carb as the closest match so that is what I bought. I know there are at least a few other builders out there with this configuration that have worked through the differences before me but I have not been able to find details on the web describing how others have solved this problem. For myself and others with this configuration I am hoping for some pictures of where the firewall penetration should be, where the cable should be tied down nearest the servo, and the length of the mixture cable used.

I have the servo mounted along with the brackets that came with the AFP hardware so I can check out various routing approaches. I do not have the Vetterman cross-over exhaust installed yet so that might also come into consideration. I started by looking at the location of the firewall penetration recommended by Vans for the horizontal induction layout but it seems too far to the left, way off the direct route, and I am sure the stock 47 inch mixture cable will be too short. Alternatively I am considering putting the penetration through the firewall recess and then taking a relatively straight shot down beside the breather tube and between two of the tubes for the nose gear mount as illustrated by the red line on the photo below. It looks like a 47 inch mixture cable might be just about perfect for that route.



Has anyone tried this routing ... or is there a better routing I have not found?

I have the same setup, throttle and mix both exit below the heater box.

I also have the same setup (except on a taildragger) and like Walt have throttle and mixture both exit below the heater box.

Mixture Cable Length?

Walt,

My throttle penetration is just to the left of the nose gear mount (facing the firewall from the engine side, see below). I assume you mean your mixture cable penetration is opposite it on the right hand side. Any photos available? How long is your mixture cable?



John

jpharrell said:

Walt,

My throttle penetration is just to the left of the nose gear mount (facing the firewall from the engine side, see below). I assume you mean your mixture cable penetration is opposite it on the right hand side. Any photos available? How long is your mixture cable?


John

Click to expand...

I looked and could not find a good photo, but, yes, my mixture cable is opposite it on the right hand side (looking aft). Also, I don't recall the mixture cable length, but I have a DJM throttle quadrant so it is probably irrelevent to your application. I have records of purchasing a 43" quadrant cable and a 45.5" quadrant cable from Van's, but I don't remember which is which.

Just a suggestion but I would mount the exhaust and fuel lines beforehand. It makes the control cable installation more obvious as to the routing. You can then get a better measurement on the cable length for the planned routing.

I have the routing you show ...

...for my mixture cable connection to my Silverhawk servo. The cable eyeball is on the top slanted face of the firewall inset. It was my second try at an acceptable routing and it works great. The first attempt, on the pilot's side of the FW where Vans shows it, was too long for any of the Vans-offered mixture cables.

I have the routing you show ...

Hello John

I have the routing you show ...

An eyeball in the upper (slanted) surface of the recess, for both, the throttle an the mixture cable.

Works well, no binding or forcing in the cable, but not flown yet.

I choosed this setup to have the leg room free of cable.

Regards, Dominik

John,

Thank you for asking this question. I'll be making the same decision here very shortly, and my configuration will be just like yours. Please post some photos and an update when you get it figured out and finished, will you? Thanks!

Be happy to ...

Bruce,

I'll be happy to post what I discover with the input of the community of builders. I'm posting incremental progress on my blog as I go but I will post a summary here when I get to through the learning phase as well. I could not find much on this particular configuration on the web so I think posting some detailed photos might be of benefit to others. I have seen on your web site that you often do the same.

John

This is how I did mine. I know have 300 trouble free hours. I recommend waiting to drill the firewall holes until the engine is hung.

http://imgur.com/eQ0yI

Interesting

Todd,

Nice photo and thanks for posting it. Mine is a 7A so the engine mount is different with the nose gear structure in the middle. I see you jogged the mixture cable to the inward side of the Airflow Performance bracket. I didn't think of that. I'll have to check to see if the geometry of the cable would work if the firewall penetration is moved upward and inward approximately symmetrical with the throttle penetration in your setup. Did you punch a hole for the mixture cable in the F-782 air box louver housing on the inside of the cabin? Does that make it captive to the cable or did you somehow make a slot so the F-782 can be removed without pulling out the mixture cable?

John
I have a 7A and an io360B1B, so went through this same struggle, although it was some time ago. No pics to share right now, but I can tell you to be very careful about the eyeball location for the mixture cable There is very little room for the flexible part of the cable on the engine side of the firewall, and with the additional limitations posed by the engine mount and the firewall stiffeners, its a challenge to make it work, but it can be done. A short piece of tubing to act as a spacer between the arm on the fuel servo and the bering on the end of the mixture cable may help you get the clearance you need from the engine mount. I also remember having to get pretty creative with hacking up the AFP-provided bracket. If you really get stuck, let me know and I will pull my cowl and get some pics of my installation

Good luck
Erich

John

Here is a picture of the cable routing on the cockpit.

http://www.imgur.com/SDV2K.jpeg

[QUOTE=jpharrell;72940
Did you punch a hole for the mixture cable in the F-782 air box louver housing on the inside of the cabin? Does that make it captive to the cable or did you somehow make a slot so the F-782 can be removed without pulling out the mixture cable?