Hi all

This is not to start another discussion about what is the better system. Perry ore Cline.

I have an Ultra-RC giles 202 with a OS 160FX. The tank is located on the CG, and I was planning to use a Perry VP 30 pump.
I have the motor set up perfectly without the pump, and I planned to hook up the pump and adjust it to achieve the same performance. Sounded sensible to me anyway.
It turnes out to be not quite as straightforward. The high speed is fine, but the midrange and low end is rich. The obvious solution would be to lean the low end, but I would really like to try to leave the needles untouched (if possible). I have the pump adjustment screw out until it almost falls out of the housing, but it is still too rich.

Any ideas on how to reduce the flow from the pump even further??.

BTW . I have the pump mounted in an upright position with the bleed hole "horisontal". This is not per the instructions. I have a hard time figuring out how this can make a difference.

Anders

Do the obvious thing first, I do not think it is possible to do this without adjusting the needles. Follow the instructions that came with the pump.

Any oil or other liquid that gets in the hole needs to be able to drain out.

Anders have you tried the pump with that bypass plumbing ? http://www.perrypumps.com/Pump%20and...s%20System.pdf

Timbba

I considered the eccess return line route. This is very similar to the setup we run on the pumped OS 91 C-speck in helis. The only difference beeing that in this system the thank is pressurized and the pump spring is stretched to two times it's original lenght. This will be a last resort. I would really like to keep this as simple as possible.
I will try to tweak the needles with the pump operating.

Anders

Anders,


If the manufacturer thought it would be possible to adjust an engine without 'touching' the low-speed needle; don't you think he would have omitted it outright, or made it tamper-proof?...


A part left out of the manufacturing process costs nothing, saves the manufacturer money and may reduce the final price of the engine, so it will get a larger market share...

If the item is there, it is necessary and its use is mandatory; not optional.


Until you learn that, you will need to start threads in RCUniverse and ask us 'self-explanatory' questions with obvious solutions...


The low-speed needle is the most important engine adjustment, since it controls the behavior of the engine from idle to 70-80% throttle opening, by fuel metering, i.e. changing the size of the orifice, through which the engine ingests fuel, at all different throttle settings.

If the engine runs rich at part throttle, close the low-speed needle somewhat and try again!

It never ceases to amaze me how many people "don't want to touch the needles" and go through all kinds on contortions and grief trying to make an engine run right without doing so. They are there for a reason, use them .

I also put a pump on an OS 160 and experienced the same thing as you. I adjusted the low speed before my first flight with it and little by little over 3 or 4 flights I got it running perfect. It ran perfect after that first day and I never looked back.

Mosand,
Open up the exhaust if you've had it blocked off, peak the high end, don't back off rich. Go to idle, if engine idles well for 15 or 20 seconds, lean the low speed 1/4 turn, Go back to the top and re-peak, go back to idle, same routine, if it idles for 15-20 seconds, lean another 1/4 turn, continue this process until engine will not sustain a idle, it should speed up and die within 20 seconds. Now richen the low speed 1/16th turn at a time until engine will again sustain a idle,after each adjustment on the low speed repeak the top end, as soon as the engine will sustain a idle leave the low speed alone. Each flying day just repeak the top end and back off 150 rpm for flying.
You have to go lean to the point of no idle then come back up to get it right. Transition from idle to midrange up to full should be crisp without sputtering. If you run the high speed to rich you will have the same problem with sputtering. My O.S. 160 preforms flawlessly with this setup, I had to lean the low speed 1-1/4 turns to get it to run properly, just make sure you peak the high end and only back off 150 rpm, be sure to use a tach. On my 1.08 it took about 7/8 of a turn on the low speed to get it right.

Be sure to mount the pump per the instructions.

DarZeelon

"Any ideas on how to reduce the flow from the pump even further??."

How is this a self explanatory question?
If it can't be done. Fine. I will tweak the low end.

Don M

I said I had the motor running perfectly before installing the pump. So I'm not afraid to
"touch the needles".

Gunfighter II

Thanks for the tip, I'll try that.

Anders

I suggest that you go to http://www.perrypumps.com and read the instructions that you can download there.

Note the damage you can cause if you move the pressure adjustment screw too far in or out. I suspect this is a major reason for peopel who have problems. Most of the time the screw is fine where it is. The pressure is not that differant than muffler pressure with a fairly restrictive muffler, however with muffler pressure the pressure drops at idle, but stays the same or nearly the same with a pump. Because of this there is no way the needles, especially the low speed, can stay the same.

Mosand,
No need to reduce flow from the pump, the needles will take care of that for you. I see all these posts about bypass lines and tee's and other fuel tank related issues, they are not needed. I to was having the same problem as you and many others until a flying buddy of mine found this solution, we spent about 10 minutes tuning on the starting table and when we were done the results are amazing, even at only 150 rpm's below peak the engine blows so much smoke out the exhaust, there's no need to worry about running lean. I would also estimate a 10-15% gain in power.

I have to respectfully disagree with the idea of using Perry's instructions, this is why your pulling your hair out now.

Where does the instructions say to adjust the pump before adjusting the engine needles? In fact it doesn't even say you need to adjust the pump, just that it has that capability to adjust the flow or pressure.

Sport,
I had to go get my instructions and here's what they say, advance throttle arm to full open position, the engine should now be running excessively rich, if not, turn the adjustment screw until a rich mixture is acheived. Now lean the engine by turning in the HS needle until max RPM is obtained, next adjust the idle by closing the throttle arm and adjusting the idle mixture disc.
I have to respectfully disagree with you again as it says that right in the instructions, they make it sound like you can adjust the screw and change the mixture setting. Ain't gonna happen.

Anders,


It can be done using the two T-fittings that came with your Perry pump, to bypass the pump (the second one connects the bypass between the pump and the tank - don't connect the bypass tube to the third tank nipple, as it could empty the '1" reservoir' when you raise the nose up).

It is 'self explanatory', since the manual that comes with the pump (as well as the [link=http://www.perrypumps.com/Pump%20and%20Bypass%20System.pdf]Perry web-site[/link]) clearly illustrates this type of installation.

The eventual flow is what eventually goes into the carburettor.

----------------------------------

Don't bother finding ways to further reduce the flow.

Just use the low-speed needle for intended purpose - to adjust the fuel flow at part-throttle.

I missunderstood that, but it did not say to leave the low speed needle alone. So it had the right instructions because it did not say to leave the low speed needle alone and do nothing with it. And for your information adjusting the pressure up or down will change the mixture, however only on the high speed needle, and only when the pressure is insufficient to provide enough fuel. The instructions are 100% correct for I got it right doing it this way every time. The engine will indeed lean out if the pressure is reduced enough. I have done this many times, I suspect some pumps do not do this as they should, or people damage them by turning it too far in or out.

That does not come with the pump, it is an instruction that comes with the Perry Pump carbs. Twin needle carbs do not need this configeration.

Hugh,


The Perry carburettor and their pump carburettor (like the Moki carburettor), do not have a "low-speed needle" as such.
They have an 'idle mixture disk', which does the same thing, i.e. meters the fuel mixture at part-throttle settings.

So, if the Perry instructions say; "adjust the idle-mixture disk", it is exactly the same as saying; "adjust the low-speed needle".


And yes, in their instructions Perry often refers to their proprietary carburettors and their means of fuel control.


Besides raising the pump's pressure and throughput, to make the mixture excessively rich at full throttle, the further use of the pump's 'screw' is to control the mixture strength in the mid-range.

If both the high-speed and the low-speed needles are adjusted, and the pump pressure is on the high side; the engine will run quite rich in the mid-range.
You then need to lower the pump's pressure and readjust both needles (open then slightly), in order to achieve a linear fuel curve.

I've always viewed the adjusters on the Perry pumps as volume controls, not pressure controls. Consider the instructions: The idea is to make sure that the pump is delivering enough fuel to let the engine run over-rich when the high speed needle is adjusted for that condition.

CR

Dar,
The point is that the schematic for the bypass did not come with the pump. If you buy the pump and don't bother with the web site you won't see the bypass schematic. It is only included with the Perry Carbs.

Hugh,


My VP-30 pump came bagged and these instructions were included with it, as were the two T-fittings...

So, I do not know why your pump came without them.

I last bought one a two or three years ago and it had no t fittings and no such instructions. If you download the the instructions from their web site the schematic is on their Pump Carb instructions. Perhaps they recently started doing this, or a forign distributer is doing this.

Sport,
You are correct that the adjustment screw does provide some small mixture change, but in my case not enough to lean the engine on the HS needle and make it run properly. That was my point, is the instructions lead you to believe that you can adjust the pump with the screw and get it close, when you can't.

I did the same as Anders and tried to reduce with the screw and was at the limit. When I started readjusting my engine I just centered the adjustment screw and never touched it again. I bought 2 pumps in the last 15 months and both came with the pressure tap a short piece of tubing and the instruction sheet which makes no mention of tee's and bypass lines.

The V-30's I have purchased (non-backplate versions ) have come in a plastic box with a pressure fitting, and a short piece of red tubing, but no T fittings? I've been using Perry pumps since they first came out (mid 70's) and they work quite well...

The older ones have a brass hex head adj. screw, and there's typically about .100 (give or take a few thou) between the inside of the screw's head and pump's plastic housing.

The later ones w/ the Allen wrench adjustable "set"(?) screw adj. screw I usually back out to the max. recommended amount (don't recall the exact measurement right off hand ) and just leave it there.

Most of the time, with the Perry pump carb, the high speed needle is only open about 1 turn (if that much ) and the idle disk is rotated toward lean about the width of the slot in the disk.

Non Perry carbs can be hard to adjust, especially in the mid range...and certain later model O.S. carbs in particular.

A friend and I have gone round and round with this problem since the pumps were introduced, and after fiddling with the stock carbs, have almost always found that the best carb is the Perry pump carb. (the K&B .61 and Webra Speed .61, and O.S. .60-.61 FSR came with a pump "kit" that included a backplate pump, and big bore carb, as a set...that was/is IMO the best way to go...too bad you can't get the backplate style pumps anymore )

mosand...all of the FX style carbs I have encountered have a rich mid-range, with or without a pump, so you're going to have to lean the low speed quite a bit I would guess...it's just going to take some tweaking.

Cline Regulator.

Install
Adjust needles
Fly

Chris,


I am not discussing actual function, or which is more appropriate for the job.

The Perry pump is made of Perry's proprietary parts and generally goes for a $30- street price.
The parts needed to manufacture this pump and the labor needed to assemble it justify the price you are asked to pay.


The Cline Regulator is made of two plastic pressure castings, worth less than a Dollar and a Walbro carburettor's pump diaphragm, which I doubt its actual compatibility with glow fuel... that costs ~$5- to the end customer... and you are being asked to [link=http://www.billsroom.com/pcfs/pricing.htm]pay $60-[/link] for it.
It may do the job; at least temporarily, but it is not worth the asking price. Maybe for $15...

The Iron-Bay? $44- for the same Walbro diaphragm, but with brass fuel fittings. Still too expensive. Worth $20- at most.


The only one that will not make you feel robbed is the Perry and it could be made to work right, if you follow the instructions.

I've tried all the Perry products and never could get ANY of their pumps to work. Tried following the directions. Tried modifying the install. No luck. Tried different engines in different planes. Tried different tank heights and different tank plumbing. Tried different fuels and plugs. Tried all kinds of tricks. No joy.

Yes, the Cline costs $60. But to me, it's worth it. Install it. Tune the engine. Go fly. Thats worth $60 right there. I'm already loosing my hair--I don't need to pull anymore of it out fiddling with a pump that doesn't work.