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Velocity Stack Help ??? - 8/26/2008 6:22:25 PM   
P47 Thunderbolt



Posts: 365
Joined: 2/1/2002
From: Brighton, MI, USA
Status: offline 		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?
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RE: Velocity Stack Help ??? - 8/26/2008 6:46:04 PM   
arobatx


 

Posts: 1792
Joined: 1/18/2006
From: Kalona, IA, USA
Status: offline 		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

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RE: Velocity Stack Help ??? - 8/26/2008 8:21:31 PM   
ram3500-RCU



Posts: 1872
Joined: 8/17/2002
From: n. canton, OH, USA
Status: offline 		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.

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RE: Velocity Stack Help ??? - 8/26/2008 10:54:42 PM   
captinjohn


 

Posts: 6288
Joined: 1/25/2002
From: Hesperia, MI, USA
Status: online 		YUP...get a air funnel from Horizon...around $2 nice! Capt,n

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RE: Velocity Stack Help ??? - 8/27/2008 5:42:55 PM   
P47 Thunderbolt



Posts: 365
Joined: 2/1/2002
From: Brighton, MI, USA
Status: offline 		Thanks guys for the info, this really helps. I should have the velocity stacks from B&B before the weekend.

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       Post #: 5

RE: Velocity Stack Help ??? - 8/28/2008 9:14:50 PM   
karolh


 

Posts: 2416
Joined: 5/15/2002
From: Mandeville, JAMAICA
Status: offline 		Don't forget to give us an update on just how the positioning of the stack and carb retuning went.

Karol

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RE: Velocity Stack Help ??? - 8/28/2008 9:31:42 PM   
arobatx


 

Posts: 1792
Joined: 1/18/2006
From: Kalona, IA, USA
Status: offline 		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

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RE: Velocity Stack Help ??? - 8/29/2008 2:12:14 AM   
Super08



Posts: 505
Joined: 12/17/2007
From: Fort McMurray, AB, CANADA
Status: offline 		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.



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RE: Velocity Stack Help ??? - 8/29/2008 3:08:09 AM   
tkilwein



Posts: 441
Joined: 3/20/2002
From: denver, CO, USA
Status: online 		I mounted mine backwards and it runs good.
Going to flip/re-tune and see if it runs better after reading this thread.

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RE: Velocity Stack Help ??? - 8/30/2008 8:48:43 AM   
2engsout


 

Posts: 119
Joined: 2/8/2003
From: omaha, NE,
Status: online 		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

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RE: Velocity Stack Help ??? - 9/2/2008 11:10:04 PM   
rcnutstoo


 

Posts: 15
Joined: 3/4/2008
From: Caledonia, IL, USA
Status: offline 		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.

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RE: Velocity Stack Help ??? - 9/3/2008 3:20:11 PM   
Big_Bird



Posts: 3345
Joined: 12/18/2001
From: Arlington, TX, USA
Status: online 		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.

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RE: Velocity Stack Help ??? - 9/7/2008 3:24:43 PM   
P47 Thunderbolt



Posts: 365
Joined: 2/1/2002
From: Brighton, MI, USA
Status: offline 		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.

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RE: Velocity Stack Help ??? - 9/7/2008 8:42:17 PM   
ram3500-RCU



Posts: 1872
Joined: 8/17/2002
From: n. canton, OH, USA
Status: offline
quote:

ORIGINAL: tkilwein

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

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

(in reply to tkilwein)
       Post #: 14

RE: Velocity Stack Help ??? - 9/23/2008 4:54:31 AM   
Peter_OZ



Posts: 4781
Joined: 6/5/2002
From: Brisbane, , AUSTRALIA
Status: offline 		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

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