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OS 160 FX / Bisson Pitts / Perry VP-20 owners

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OS 160 FX / Bisson Pitts / Perry VP-20 owners

Old 12-31-2006, 05:33 PM
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GMoneyPit
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Default OS 160 FX / Bisson Pitts / Perry VP-20 owners

Although there is lots of info on these things individually, there isn't much on people that have this exact combo. When I originally got my 160 FX this past summer, I started out using this exact combo. I had some success and even though the engine was still breaking in, it was obvious that I still had fuel flow issues. Tuning the engine with 1/4 tank, it ran great. As soon as I filled the tank all the way and ran it, it would be way too rich. I never actually adjusted the flow in the pump with the adjustment screw. Reluctantly, I tried the "plug one of the exhaust port" technique and it did a pretty good job and was reliable, but only if I adjusted the high end half way through the flight to keep it from leaning out as the pressure could no longer feed the system as the tank emptied. As it turned out, I had an air leak in the carb which may have contributed to the incosistent results. But still, I was losing RMPs with that port plugged.

This past weekend, I went back to the pump. The first thing I did was close the pump all the way just to see how far out it was. It was 2-1/2 turns out. Based on the way it performed in the past, it seemed like it was pumping too much fuel. From fully closed, I opened it about 1-1/2 turns and ran it. Tuned at 1/4 tank, it ran great. I filled up the tank all the way (16 oz). Expecting the worse, I cranked it up (always hand starts on 1-5 flips with a good prime) and found it to run great. My high speed needle is 3/4 from fully closed (still my have too much flow from the pump?) and my low needle is 2-1/2 out from closed. I'm getting 8850 RPMs with an APC 18x6W leaned about 200 RPM from peak. Eventually I'll test with my APC 18x8 and see what that does.

I don't know how consistent these pumps and carbs are from person to person, but I wonder if others could post their needle settings just for a comparison. Also, how many turns out is your VP-20? I know I don't have it dialed in just right yet because my midrange isn't great, like lots of people have reported. Perhaps this means that I need to lean out the low end more. Before I do that, I really want to make sure my pump is providing the right amount of fuel. I'm running 10% Omega and flying at about 400 feet elevation. My pump is mounted to my engine as per instructions. This is all mounted to a CMP Giles 202, but will soon be on the Peakmodel 70" Edge 540 T and I want to work out all the kinks on my Giles before I put it on the Edge. There is approximately 12-14" of fuel tubing between my clunk and my carb because of where the tank is mounted. I have run 2 gallons of fuel through it.

Thanks,
Gary
Old 12-31-2006, 07:31 PM
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Don M.
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Default RE: OS 160 FX / Bisson Pitts / Perry VP-20 owners

I had an OS 160, Bisson pitts and a V30 - worked fantastic never touched it, never plugged any exhaust. I always thought the V20 was for 4 - strokes not 2 - strokes, maybe this is your problem.
Old 12-31-2006, 10:13 PM
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Default RE: OS 160 FX / Bisson Pitts / Perry VP-20 owners

G'day Mate,
I'm running the same motor on the same plane, tank is up against the firewall, no pumps just muffler pressure, 17x10 APC prop, balance point, back almost an inch from the starting point, flys superbly, have been practicing knife edge figure 8 circuits, at 3/4 throttle, & no coupling or mixture issues.
I have tried the 18x8 & found that I needed more pitch, give it a go, take off is at 1/2 throttle, I kid you not.
Old 12-31-2006, 10:35 PM
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Default RE: OS 160 FX / Bisson Pitts / Perry VP-20 owners

Allan,

Are you running the Bisson pitts muffler or the stock muffler? Have you tried hovering it? What other kinds of things have you done? Any video? I'd love to see some.

Gary
Old 12-31-2006, 10:42 PM
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Default RE: OS 160 FX / Bisson Pitts / Perry VP-20 owners

Don,

I got the VP-20 to avoid drilling/tapping the backplate. Some people have used this setup and have had success with it. I am attempting to get in touch with those people to see exactly how they did it. I'm coming to the realization that drilling and tapping the backplate for a fuel connector isn't that big of a deal. I will continue to fiddle with this oscillator because I know it can work, but if I get too frustrated, I'll likely get a VP-30 or a Cline (Kline?) regulator.

Anyway, those of you that have this EXACT setup, I'm sure you can sympathize. Please share your experiences. Allan, I wonder if you are using the stock muffler (works perfect from what I understand) or if you are using the pitts (Bisson?), if the extra 6 inches of fuel tubing is really causing my problem. That's what I need to figure out.

Thanks,
Gary
Old 12-31-2006, 10:53 PM
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Default RE: OS 160 FX / Bisson Pitts / Perry VP-20 owners

None of the parts in your fuel system are made with enough accuracy to make others' number of turns relevant.

Other things, such as length of fuel line to the pickup clunk (which you are aware of), the brand of the fuel line, whether or not the fuel line is an absolutely straight run without any deviation or kinks, type of glow plug, condition of glow plug, type of exhaust, mods to exhaust, blah-blah-blah will destroy any commonality that all of the models may share. This is not to say that it would not make interesting reading. But it would confuse those that haven't managed to load all of these factors into their heads and associate them with their function and effect.

Moving the tank back to the CG is good if your engine is the type that has a robust fuel delivery system built-in. Doing it with third party parts is really stretching it a bit. Engine reliability is more important than making hovering easier, in my book anyway. I'd leave the tank up front and give the engine a break.

The VP-20 pump is not made for four-strokes (other gentlemen). But it was advertised as being good for four-strokes because it did not require crankcase pressure, but it can be used with either type of engine. I'm surprised that you're not running the VP-20 wide open just to keep up with this large of an engine. Oddly enough, you can activate the pump diaphragm in a VP-30 via crankcase pulse pressure, as long as you install a tee and run a piece of fuel line as a vent line for about 4" after the tee. The latter information came via Paul McIntosh of RC Bearings fame. Sorry for butchering your last name so many times in the past, Paul (I know you are out there!). I was raised with some friends by the name of McIntyre and I can't keep you two straight.

Happy New Years, everyone


Ed Cregger
Old 12-31-2006, 11:23 PM
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Default RE: OS 160 FX / Bisson Pitts / Perry VP-20 owners

Ed, as usual, you bring up some very good points. I could save about 4" of fuel line if I brought my tank up to the firewall. Do you think 4" is worth moving it? I have another option as well, even though I want to ultimately put this engine in my soon to be new Edge. I could buy a stock muffler and move the tank to the firewall. However, I don't have the clearance I need with this plane (CMP Giles) I don't think, without an extension and there isn't one made to my understanding. I don't know about the Edge, don't know if there is room for the stock muffler. Anyway, please fill in the blanks I listed above and expound on anything you see fit.

Thanks,
Gary
Old 01-01-2007, 12:26 AM
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Default RE: OS 160 FX / Bisson Pitts / Perry VP-20 owners

G'day Mate,
Bisson Pitts muffler, I have no video yet, but will soon, mean while here are some pix, up close & personal.
It will hover but I'm not good enough for that, so I fly Pattern aerobatics with it.
And by the way, I just noticed that you mentioned an extension for your muffler, I used the one that came with the stock muffler, just bolt through it and, bingo, clearance, & no leaks, no gaskets, just get it tight.
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Old 01-04-2007, 11:56 AM
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Default RE: OS 160 FX / Bisson Pitts / Perry VP-20 owners

For what it is worth I have an OS 1.60FX + Bisson Pitts muffler + Perry VP30 + 10% Omega + APC 18x6W and my needles are as follows:

Pump screw open 2 and a bit threads.
Main needle is opened about 2/3 of a turn.
Low speed I have no idea but when I open the carb, the gap is less than 1mm.

Works pretty good. I think I need to lean the low speed a bit more because the transition is not what I would like.
Old 01-04-2007, 12:04 PM
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Default RE: OS 160 FX / Bisson Pitts / Perry VP-20 owners

Thanks PlagueWielder, that was helpful. I know that our needles won't be exact, but it's nice to know that your high end is less than one full turn out. Mine is at 3/4 turn. The only difference in setup seems to be the VP20 vs VP30, and they seem to be delivering close to the same amount of fuel (if the high end needle is any indication). I'm curious how many turns out your low end is. It is good to know that it is < 1mm gap when the carb is wide open. I'll check mine when I get home, but I recall the gap being a lot larger than that, perhaps even 2mm. I thought my low end was too rich and if my memory is correct, it is, based on your needle gap.

Thanks,
Gary
Old 01-04-2007, 12:59 PM
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Default RE: OS 160 FX / Bisson Pitts / Perry VP-20 owners

This is good info for me as well. I'm getting ready to set mine up. I'll try these settings as a starting point if it works good for you guys.

What size tubing are you guys using? I was told on multiple ocassions to use the large one (which I did) but it seems to big now when it goes to the pump. It just falls off of there if you don't restrain it.
Old 01-04-2007, 01:03 PM
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Default RE: OS 160 FX / Bisson Pitts / Perry VP-20 owners

Just checked and mine is open 2.5 turns also. I closed a bit more right now to check how it performs.
Old 01-04-2007, 01:04 PM
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Default RE: OS 160 FX / Bisson Pitts / Perry VP-20 owners

I use medium. If you have a pump dont be afraid to use normal as well... the pump will take care of the flow.
Old 01-04-2007, 02:05 PM
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Default RE: OS 160 FX / Bisson Pitts / Perry VP-20 owners

I am currently using large fuel tubing. I originally used medium. I changed two things at once (med to larged tubing and closing the pump adjustment screw) so I'm not sure which helped most. I have heard from experts on these boards (I believe BAX said this) that the medium tubing is more prone to collapsing under pressure as it sucks fuel from the tank. That alone made me change to use large tubing, even though the holes on the connectors (carb, pump) are smaller (but can't collapse).

In order to use the large tubing, I had to tiewrap the lines to the connectors for a tight, leak-free fit. I believe I accomplished that. The weather has been poor here lately and I haven't had much time to run my engine lately. Hopefully that will change in the next few days. I'll post more findings as soon as I run it again, especially if I make any adjustments to the pump or low end needle.

Thanks,
Gary
Old 01-04-2007, 04:38 PM
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Phil Heller
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Default RE: OS 160 FX / Bisson Pitts / Perry VP-20 owners

Gmoneypit-

Don't drill the backplate, remove it, get a pressure fitting to replace the top left backplate bolt (looking from the rear) CAREFULLY drill through into the crankcase. Flush any chips or shavings, making sure none remain. Use this to pressurize the tank through a one-way valve, and use a Cline regulator.(Way overpriced, but they are faultless!) I changed to this setup last year after fussing with a P-30 for months and never looked back! Oh, yes, I am using a Bisson muffler.

Phil
Old 01-04-2007, 06:50 PM
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Default RE: OS 160 FX / Bisson Pitts / Perry VP-20 owners

This will likely be my next step (Cline install). Here's another possible next step: anywant want to buy an OS160FX/Bisson Pitts/VP-20? Perhaps that should've been the thread title. Then I'd just go with a 40cc gas. I may consider that actually.
Old 01-07-2007, 05:35 PM
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Default RE: OS 160 FX / Bisson Pitts / Perry VP-20 owners

I just thought of something...Doesn't the carb spray only what's needed to the motor? Doesn't it have the last say how much fuel goes into it (I don't mean of it doesn't get enough fuel flow)? So shouldn't the setup work well as long as the pump delivers enough fuel? The fuel still goes through a tube before it gets to the carb and from there the carb regulates it. So why are there problems of it getting too much flow and having to turn the needles way down. Doesn't that mess with the air/fuel mixture ratio?
Old 01-07-2007, 06:01 PM
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Phil Heller
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Default RE: OS 160 FX / Bisson Pitts / Perry VP-20 owners

GMoneyPit - list it in RCU "Buy & Sell" - but the OS 160 is a great engine!

strulag - one thing you left out of the equation - Pump pressure! and the needle valve is not a "demand regulator" as is the Cline or Walbro type carbs.

Phil

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