Velocity Stack Help ???
 

I need some help. I have a G62 and Fuji 43 and both carbs stick out slightly from the cowl. After a flight, I have a lot of siphoned fuel and fule down the side of the plane. I picked up a couple velocity stacks from B&B which are fully radial adjustable. Where should the angle on the inlet of the stack be positioned? Facing forward, backward, up, down? Also, will there be high or low end needle setting changes required with the velocity stack?

RE: Velocity Stack Help ???
 

The stack will certainly help with the carb spit. I've found that the slant cut type like B&B will tune differently pending the direction of the cut. So far in every example, I have installed it with the slant opening facing forward, and re-tune.

Chad

RE: Velocity Stack Help ???
 

Yes, facing backward will create a siphon or vacuum effect and not be good. Sideways or forward is best. Either way, you will probably need a little tweaking on the needles.

RE: Velocity Stack Help ???
 

YUP...get a air funnel from Horizon...around $2 nice! Capt,n;)

RE: Velocity Stack Help ???
 

Thanks guys for the info, this really helps. I should have the velocity stacks from B&B before the weekend.

RE: Velocity Stack Help ???
 

Don't forget to give us an update on just how the positioning of the stack and carb retuning went.

Karol

RE: Velocity Stack Help ???
 

While we're talking about this...anyone have one of the Horizon Hobby black plastic funnels?...can you measure the opening at the carb end? I can't remember how large of a carb they'd be appropriate for.

Chad

RE: Velocity Stack Help ???
 

I have the aluminum angled stacks on both of My Fuji 43's. I have the opening angled forward and it stopped 95% of the fuel spit back out of the carb. It went from seeing a fog of fuel spraying out making a large mess down the side to a very light mark at the end of a days flying. Here is a quick pic of the one on my Stick.

RE: Velocity Stack Help ???
 

I mounted mine backwards and it runs good.
Going to flip/re-tune and see if it runs better after reading this thread.

RE: Velocity Stack Help ???
 

Hi Guys, I have G-45's on my Ziroli DC-3 and I could tune for a smooth rpm all the way thru the rpm range on the ground, but at 1/2 throttle in the air, the prop was unloading so much that the engines would really go rich and 4 stroke big time. Raising the popoff did'nt really help, so I angle cut the black plastic velocity stacks that came with the engines at 15 degrees forcing the air into the motor and that really helped lean the mixure at 1/2 throttle in the air, cleaning up that 4 stroking. Tuning on the ground with a load on the prop, the engine requires more fuel at 1/2 throttle than in the air at 1/2 throttle. At 6o mph, there is not enough prop load on the engine at 1/2 throttle to burn the amount of fuel entering the engine, thus you get 4 stroking. That carb hangs all the way out into the wind on that DC-3. The angle cut forces slightly more air in the carb, thus leaning the mixure. Hope this helps Rick Simmons

RE: Velocity Stack Help ???
 

I have a Q50 with an angle stack the short cut is at the rear. let us know how this all turns out cause now I'm thinking of turning mine to face forward too, as I also get a 4-cycle at midrange and on downline. Cap 232 by lanier only the end of the stack sticks out of the cowl.

RE: Velocity Stack Help ???
 

I use a B&B stack on my G62 in a Giant Aeromaster. It faces forward and got rid of most of the fuel spray. When I put it on I had to lean the engine a bit because the fuel spray was being sucked back in.

RE: Velocity Stack Help ???
 

Got several flights now on my Fuji43 with a B&B velocity stack facing forward. 90% of the spray is gone. Still getting some on the stab but much, much better compared to before. I also had to lean the motor slightly.

RE: Velocity Stack Help ???
 

I think you will see an improvement, but please let us know how it goes.

RE: Velocity Stack Help ???
 

I tried the Great planes version on my G62 that is fitted to a Vailly 90" Seafury. With it fitted I was losing 300rpm on the ground.

Mind you the stack does not extend right out into the airflow, only the tip sticks out past. I did try it with cowl off but saw no improvement.

I'm after an increase in RPM with this excercise.

Wondering how the Zenoah air funnel might help? Any ideas?

What length is the B& B air funnel and where can I get one?

ta
cheers
Peter

RE: Velocity Stack Help ???
 

I'd guess the B&B carb intake is approximately 1-1/2 inches long, straight tube, slant cut at the tip. It is $8.95, pictured below, and available on page two of their site.

I've used several of these, and never noticed any considerable, or even noticeable change in RPM/power after retuning. It was simply used as a tool to assist in preventing excess spit from my piston ported engine, or to get the intake opening to a spot where less turbulent air was for smoother running.....

http://www.bennettbuilt.com/bbtable.htm

Chad

RE: Velocity Stack Help ???
 

ok thanks for that. Looks exactly the same as the great planes version which I have anyway.