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Old Jun 10, 2007, 06:51 PM
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Joined Feb 2005
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Help!
Perry VP-20 pump

Hi!
Does someone out there have any experience with the perry VP-20 oscillating pump?

I installed one in a new plane with a Satio .82 4 stroke.
After breaking in the engine, I leaned it out to a slightly rich setting.
While at full throttle I pointed the nose up and noticed the engine leaned out a little. Then pointed the nose down and it richened up. I have used the Vp-30 regulating pump in several aircraft and they never changed rpm by pointing the plane up or down.

The other thing I noticed about the VP-20 pump is there seems to be no check valve. I can blow air back thru it. Not as much as going the right direction, but it does not seem to have a check valve or is not working right.
Any thoughts on this would be appreciated.

rcpi
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Old Jun 11, 2007, 01:01 AM
The reviewer
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Tokoroa
Joined Mar 2004
3,827 Posts
I used one without any problems on my P51 Mustang with a TT91FS.

Have you mounted it as instructed -- so that it's mounted at right-angles to the crankshaft, preferably bolted directly to the motor's backplate?

The VP20 won't give you as much pressure as the VP30 but they do provide a useful extra fuel-draw capabilities.

How far is your tank from your engine -- you'll be unlikely to get more than 4 inches or so between the tank and the carby without running into problems.
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Old Jun 11, 2007, 07:24 AM
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I TOBOR's Avatar
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Air should not go through it backwards, they both make .25 psi pressure, the 30 will pump a greater volumn.
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Old Jun 11, 2007, 08:40 AM
Airplane Gearhead
Central N.Y.
Joined Jan 2005
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The one I had was basically just a big ball bearing inside a plastic housing, and the ball shakes from side to side.
Take it apart and look for dirt on the seat...that could be why it's allowing the backwards flow?
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Old Jun 11, 2007, 06:07 PM
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Joined Feb 2005
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I thank all of you for the help.

The Satio .82 is mounted inverted in a Great Planes Ultra Sport 40. There was no room for the pump to be mounted off the back plate. I mounted it on the firewall horizontally and 2 inches down from the crank's center line. The engine is hard mounted on 2 maple rails built into the fuselage.

I took the plane out for the maiden flight today. The pump seems to be working. If I shake the airplane you can see it push fuel. One thing is the engine runs a lot leaner on the ground as compared to in flight. Maybe the airplane shakes less when holding it on the ground.

With the new Satio .82 being inverted, I am only able to get a reliable idle at 3000 rpm. Is that normal? With the heater on, it will idle a lot lower. I did adjust the low speed setting, but that has a fine line between too lean and too rich. Do the inverted 4 strokes have more difficulty idling inverted? Am using the stock glow plug. I do have O.S. type F plugs too.

Started out with a 13x6 Zinger prop. The airplane takes off in less than 40 feet in the grass and can climb vertical forever. Was surprised with the Idle so high it slows right down when landing.

I will take the pump apart and clean it anyway. I do have a in-line fuel filter installed too.

rcpi
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Old Jun 11, 2007, 11:47 PM
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Tokoroa
Joined Mar 2004
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If it idles better with the glow heat on then it's too rich -- you can lean out the bottom end on Saitos by a *huge* amount before you get problems. They'll also run a lot better with an OS-F plug and after a gallon or two of fuel.
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Old Jun 12, 2007, 07:02 PM
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I have a half gallon thru it right now and was able to lower the idle down to 2700 rpm.

This is my first 4 stroke engine. What should the idle rpm be after the engine has been broke in?

I will put in the OS type F plug.

Thank you,

rcpi
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Old Jun 14, 2007, 12:08 AM
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Tokoroa
Joined Mar 2004
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My SA82 (4-5 gals through it so far) idles at about 2,150 RPMs with a 14x4W prop. My SA100 (which has more time on it) will idle all day at 1,850-1,900 RPMs with a 15x4W and then spools up to full RPMs without any hesitation.

You just got to love Saitos :-)
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