Hello,
I would like to know if I should connect the muffler pressure fitting to the tank or if it is not necessary?
In one thread I read that someone suggested to connect a tee fitting between the pump and the carburetor and sending this tubing to the tank. The instructions don´t say anything about this.
Any suggestions?

Thanks

When using either version of the Perry pump you do not need to use muffler pressure. Some people have put a Tee close to the carb and route one end of it back to the tank. I have not found this to be necessary with either type pump. The line fromt he tank that would normally go to the muffler needs to be left open to the atmosphere so a vacuum does not form in the tank.

Ed M.

yep that's right. vent the tank. i also went ahead and took the pressure nipple out of the muffller and put a screw in it to plug it up.

Not necessary, it no longer goes to the tank. Normally on a 2 stroke the VP-30 needs a pressure tap made in the crankcase. So with a 2-stroke you would plug up the pressure tap in the muffler, it's not used. The pressure pulses from the muffler are not strong enough to power the pump.

That T fitting is used to make a bypass loop back to the tank. It's only needed if the mid range turns out to be too rich. With bigger bore engines, it's not usually necessary. With my Moki 1.80 I did not need it.

I have a Moki 1.8 and the mixture changes as a function of airspeed. I'm thinking that a regulator/pump will solve this problem. Question: Which do I need or both? and where can I read more about these systems (online help or catalog site)?

Greg.

http://www.perrypumps.com/

Mixture changes with air speed? Wow, that's a new one for me. Maybe you're refering to the prop unloading at full speed straight and level flight?

The pump or regulator will solve any mixture problems. You need one or the other, not both. People have success with both. I personally tried both and the Cline regulator would not run right after a while. It ran perfectly at first and then just would not work right after a while. I probably did something wrong but I gave up and got a Perry VP-30. I actually really struggled to get that working right also but it runs great now. I had to turn it in 2-3 turns (rich) to get it to run right. It's true that the pumps/reg's take a little more work to get working properly but to me it's worth it.

Joe,

What I notice is that about 2/3 to 3/4 throttle, I get a peak rpm sound when flying level (i.e. full throttle is not the highest power setting). I tried various ground settings and found that ground peak does not equal best in air performance.

I currently use a Bisson Pitts muffler to pressurize the tank. I've had other conversations about when to adjust the needle (full tank or near empty). The latter in my mind means that the extra airspace is "damping" the muffler pressure pulses for a smoother flow of fuel.

Greg.

this may or may not help you with your moki. i had a 1.35 moki with a bisson muffler that was giving me fits. What i did was drill and tap the muffler right by the exhaust port and installed the nipple there. then plugged the stosk hole with a bolt and some red rtv on the threads. Hope this helps for you

Greg,

I'm no expert on prop loading while flying, but I understand that the engine is full loaded on the ground since air speed is zero. So in the air, the engine unloads and changes the position that the engine is operating on the torque curve. But I would have thought that the RPMs would continue to go up as you roll on the throttle to WOT. I can't explain why your peak RPM would occur lower than your max throttle position while in the air. Maybe it's leaning out from the reduced load? Try richening it up little by little on the ground and see if it gets better in the air. I sure would avoid WOT in the air, you could burn up the engine.

If using a Perry VP-20 oscillating pump, can I install it directly to the firewall? I want to install it in a OS 52 surpass four stroke but I do not have space in the plane to install it in the back cover plate. Any experience here?

No you can't mount it on the firewall. It has to mount to the backplate of the engine either on the top two bolts or the bottom two bolts. It needs the vibration of the engine to power the pump. The firewall will not vibrate enough. There are instructions on the Perry Pumps web site that was posted earlier in this thread. It really details how to install it.

Hey Joe.

I have a OS 1.60 FX and installed a perry pump V-30, I tapped the engine like the 1.60FI, and I'm using a Slimline pitts muffler and now the engine runs great,,, but I did not get the vent line that goes from the muffler to the tank off, i'm still using it. do you think I should take it off the muffler and leave it hanging in there..

I'm using this motor with an APC 18x6W in my Yak QS 54 72''

I have a Perry VP-20 oscillating pump but have lost/misplaced the instruction sheet. Can anybody confirm that the blue nipple is the side the fuel exits the pump. It's already fixed to the engine, and in the aircraft. It's tightly cowled so I can't see the arrow on the pump indicating the direction of fuel flow.

Also which way do I screw the blue nut to lower the pressure? Common sense would dictate out (anti clockwise looking at it), but it would help if someone could confirm this for me.

I've checked the Perry site and can't find the info and have emailed hoping they will send it. The petrol/smoke version of the VP 20 has the colored nipple exit, so I'd assume it's the same for the nitro version.

It would be even better if someone could direct me to a site/link where I can find the instructions to print out.

Thanks for any help

Edit 03OCT08

I found the info on the perry site www.perrypumps.com under 'instructions' tab. I just didn't look hard enough it seems.