VP-20 pump and .72 Saito?
08-26-2003, 10:55 AM
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VP-20 pump and .72 Saito?
Ok call me crazy, egnouf people do, but I wanted to mount my tank toward the cg, 12oz. is a lot of weight. The prob is, is that some say this pupm cant pupm that far back. Im haveing a propblem leaning out my high end needle valve. Im not getting that nice clear transition. Im only turning a 13x6 power point wood prop at 9200 rpms with 10 % nitro. Whats strange is when I go to turn the needle valve and put pressure on it the engine starts to run faster. Im thinking of scrapping the pump idea. Any thoughts would be much apreciated.
08-26-2003, 03:58 PM
#2
VP-20 pump and .72 Saito?
Is the engine acting rich or lean? If lean, richen the pump. If the engine is rich and the needle is sensitive, lean the pump. The pump can handle pulling fuel from the CG on any plane your .72 is suitable for.
John
John
08-26-2003, 04:04 PM
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VP-20 pump and .72 Saito?
check your engine for drastic changes in vibration level as you throttle up!!
the vp-20 works of the vibration of your engine !! if the engine vibrates erratically as the rpm's change.... then the pump will vibrate erratically..... this will cause the pressure coming off the pump to be inconsistent.
the vp-20 works of the vibration of your engine !! if the engine vibrates erratically as the rpm's change.... then the pump will vibrate erratically..... this will cause the pressure coming off the pump to be inconsistent.
08-27-2003, 12:17 PM
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VP-20 pump and .72 Saito?
Yup, if I start to lean out my needle valve at the point where it should osilate and then start to run the fastest it would, transision, it only gos to about 9200 rpms then will shut down when I turn the valve any more. Iv try to adjust the pump but things change on it, its kinda hard to get it to go consistantly. Im leaning toward what outsider's saying. I am picking up some vibration. Another problem all together, topflight mag ballancer ok but not super good at ballaceing (shaft thingy not ballanced). Im just going to scrap the pump and mount the tank in back of the fire wall. Darnet!
08-27-2003, 03:11 PM
#6
VP-20 pump and .72 Saito?
Originally posted by SpaceCase
Im leaning toward what outsider's saying. I am picking up some vibration. Another problem all together, topflight mag ballancer ok but not super good at ballaceing (shaft thingy not ballanced). Im just going to scrap the pump and mount the tank in back of the fire wall. Darnet!
Im leaning toward what outsider's saying. I am picking up some vibration. Another problem all together, topflight mag ballancer ok but not super good at ballaceing (shaft thingy not ballanced). Im just going to scrap the pump and mount the tank in back of the fire wall. Darnet!
John
08-27-2003, 04:20 PM
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VP-20 pump and .72 Saito?
Are you folks mounting the pump on the engine or the firewall? Im not shure about the vibration problem, its not so bad. But its egnouf so that at times it can be tricky to hold onto the needle valve. Guess I need to ballance out things a bit better.
08-27-2003, 05:41 PM
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VP-20 pump and .72 Saito?
if you mount a large 4-stroke engine on a composite mount...then watch the motor as you slowly power through the entire rpm range.... you will notice that there are certain rpm's where the engine is very still and there are other rpm's where the engine seems to shake quite a bit. the pump is supposed to be connected to the case of the engine ...therefor there are going to be times when the pump shakes " LIKE HELL" and other times when it shakes much less. What's worse, the shaking is not directly proportional to the rpm. for example ...your engine may run smoothly at 8000 but start to shake much more at 7800 rpm.
If the engine is mounted to an aluminum mount, the engine's vibration change may not be so abrupt ...but on a glass mount there is a big difference in vibration. the vp-20's pressure output is "DIRECTLY PROPORTIONAL" to how vigorously it shakes.
this can cause a problem...if it doesn't for you, then you are lucky...i wasn't so lucky
If the engine is mounted to an aluminum mount, the engine's vibration change may not be so abrupt ...but on a glass mount there is a big difference in vibration. the vp-20's pressure output is "DIRECTLY PROPORTIONAL" to how vigorously it shakes.
this can cause a problem...if it doesn't for you, then you are lucky...i wasn't so lucky
08-27-2003, 06:29 PM
#10
VP-20 pump and .72 Saito?
Originally posted by SpaceCase
Are you folks mounting the pump on the engine or the firewall? Im not shure about the vibration problem, its not so bad. But its egnouf so that at times it can be tricky to hold onto the needle valve. Guess I need to ballance out things a bit better.
Are you folks mounting the pump on the engine or the firewall? Im not shure about the vibration problem, its not so bad. But its egnouf so that at times it can be tricky to hold onto the needle valve. Guess I need to ballance out things a bit better.
If you have so much vibration that the needle valve is difficult to hold, you really need to get that taken care of first.
JMHO,
John
...i know you guys....hook it up ...then if it doesn't work..... read the directions.... :stupid:
08-28-2003, 01:25 AM
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VP-20 pump and .72 Saito?
Ok got the vibration down a bit. Pump is dialed all the way out then in a half turn or so. I spoke with the people from horizon, tech, they said the pump wont matter in terms of pressure. That the needle valve will do that alone. I guess it makes sence you can only put so much through a couple of brass holes at a time. Its really strange though, Im turning a 13x6 at over 10000 rpms. whenever I back the needle valve off to make it run a bit rich the next time I start it up its still reading 10000 rpms. I got it to 9800 rpms and seems to be holding now. I need to find some difinitive answer on this silly pump thing, any one know anything about regulating the pressur on a pump, does it matter? Or will the needle valve just regulate it (too much that is)?
08-28-2003, 01:58 PM
#16
VP-20 pump and .72 Saito?
The needle valve will only pass so much fuel for a given pressure. Increase the pressure, and the volume will increase (to a point). The needle valve is used to regulate volume, not pressure. So, if the needle valve is more sensitive than you like, you should turn the pump out. If when you point the nose of the model up, the engine leans out, you need more pressure and the pump should be turned in.
John
John
08-28-2003, 11:11 PM
#17
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VP-20 pump and .72 Saito?
you guys just refuse to read the directions before you give your advise....
if you read the directions ... you will notice that it reads .....
to increase volume turn the blue hex nut counter-clockwise
to decrease volume turn clockwise.......
if you read the directions ... you will notice that it reads .....
to increase volume turn the blue hex nut counter-clockwise
to decrease volume turn clockwise.......
08-29-2003, 02:47 AM
#19
VP-20 pump and .72 Saito?
Originally posted by outssider
you guys just refuse to read the directions before you give your advise....
if you read the directions ... you will notice that it reads .....
to increase volume turn the blue hex nut counter-clockwise
to decrease volume turn clockwise.......
you guys just refuse to read the directions before you give your advise....
if you read the directions ... you will notice that it reads .....
to increase volume turn the blue hex nut counter-clockwise
to decrease volume turn clockwise.......
John
08-29-2003, 12:06 PM
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VP-20 pump and .72 Saito?
Yea I guess ultimatly the way to do it is with the pump off and just muffler pressure. But my tanks too far back. I ran yesterday and things went rather nicely (9800 on the top end). I have reset the pump, counter clock wise till you see the o ring. Then dialed it in 3/4 of a turn. One of the only things now that makes me suspicious is that when I idel down I get 3500 rpms, 3400, 3000, 2800 2600, then it stalls. This seems like a low speed idel valve thing, but its only dial in a full turn. woundering if my pump is giving it too much.
08-29-2003, 02:15 PM
#21
VP-20 pump and .72 Saito?
Sounds like it. You should only have the pump opened up enough to provide enough pressure to prevent the engine from going lean when you point the nose up. Any more pressure and you can end up with idle problems, as you have found, as well as the possibility of an overly rich mid range.
John
John
