Location of BVM mixture control?
 

I've bought a built but unflown JHH F-86 that has a new Turbax/OS 46vx in it and I'd like to install a Bob Violett mixture control. The problem is, there's no good place on top of the fan unit to mount it as the canopy blocks that area. The next convenient place is right in front of the fan. Since there's no inlet ducting going all the way to the fan lip I've got plenty of room to secure the mixture here, but that'll give me about 10 to 12 inches of fuel line between this and the engine. I'm using large size tubing but that's still a long distance.
Does anybody have experience with operating a mixture control this far from the engine? Will it cause a problem for me?

RE: Location of BVM mixture control?
 

My advice to you is not to use the inflight mixture device. The Turbax I + OS 46 VXDF combination does not need an inflight mixture device. All you need is a remote needle valve (K&B has one, but I use the OS 91 remote needle with my VX) which you use to set the mixture on the ground and then go fly.

Peter

RE: Location of BVM mixture control?
 

While I haven't actually tried it a long piece of line between a needle valve and carb it shouldn't make any difference. The needle valve is just a restriction in the fuel feed which is adjusted to give the pressure to flow relationship required for the carb to do its job. The carb does not care how the fuel flow is restricted as long as it is consistent.

RE: Location of BVM mixture control?
 

Miragepilot: If you don't have a servo controlled mixture, doesn't your engine go lean as the fuel burns down? I'd like to install this just for 'insurance' against that happening...this engine isn't exactly cheap. I do have one of the K&B remote needle valves and mounting this on one of the top stator bolts would be simple though.
By the way, the builder of the plane put a Sullivan DF saddle tank on the left and a 12 ounce slant oval on the right and both have their centerlines even with the carb. It also uses tuned pipe pressure to the tank vents. We're covered in snow up here so it'll be a while before I can test fly this thing, but I do have to sort out the fuel system and run the engine enough to set the needle valves.

RE: Location of BVM mixture control?
 

Between my 4-6 friends and I who fly .46 DF (and all use the Turbax I + 46 VXDF combo), we have well over 1000 flights and NONE of us utilize inflight mixture adjustments. We all just set the high end on the ground and go fly. Over the years, we have found that the primary cause of erratic fuel flow to the carb is due to the the following:

1) Use of the Y/A conformal/"funkey" fuel tanks without the use of a header tank, and
2) having the fuel tank located too far forward of the CG (this leads to mixture variations with pitch of the aircraft in flight: nose low=lean, nose high=rich.

Finally, pipe pressure helps alleviate 2) since the higher fuel pressure reduces the fuel flow deviation effects due to gravity.

Regards,
Peter

RE: Location of BVM mixture control?
 

Thanks Peter, I may as well just mount this K&B needle valve on the fan and go with that. It definately will simplify things. By the way, do you use a header tank? Right now, my two tanks are plummed to a 'T' and that line runs back to the engine.
John.