[NSRCA-discussion] Fuel Regulation in 2C Engines

Mon Mar 6 07:30:31 AKST 2006

-----Original Message-----
From: vicenterc at comcast.net
To: NSRCA Mailing List <nsrca-discussion at lists.nsrca.org>; NSRCA 
Mailing List <nsrca-discussion at lists.nsrca.org>
Sent: Mon, 06 Mar 2006 15:49:35 +0000
Subject: Re: [NSRCA-discussion] Fuel Regulation in 2C Engines

Nat and all,

No, I never run the OS91 valve.  The intention is to make the engine to 
go idle faster than is doing now.  Actual idle speed is good. 

The reasoning of adding some kind of by-pass is to reduce the pressure 
or flow to emulate the actual conditions that the OS 160 (using muffler 
pressure and tank behind the firewall).  The process that I am planing 
to do is to put a restricted controlled by-pass so that the high needle 
valve goes from 1.5 turn to 2.5 turns at full speed using the V-30 
pump.  I believe that in the current conditions the pressure is just a 
little too high and the goal is to emulate the original design 
conditions of the OS 160 carburetor. 

Here some of conclusions base on the feedback I have been getting:

1.-  Use the Cline Regulator.  A coupled of fellow pilots are using 
it.  Looks like that majority is using the Perry V-30 pump.  If the 
Cline regulator has the regulating feature that allows the power down 
to idle faster it would be the ideal solution for me.  I guess that I 
will need to buy one and try it.  I don't know were to get it.  More 
information on Cline regulator is welcome.  I would like to know were 
the high needle valve is set using the Cline regulator.  One person 
suggested Iron Bay system.  No comments at all in the Iron Bay.

2.-  Looks like we have been trying the by-pass with not good results.  
I understood that in one case was fully open and the engine went lean 
in the up lines.  Another suggested to use copper tubing with small 
hole to control the by-pass flow worked well.  I am going to try a 
needle valve so I would be able to adjust the flow in the by-pass.  The 
goal is to adjust the by-pass so the high end needle valve would be set 
close to 2.5 open at full speed.  Hopefully, that will bring the 
pressure down so the OS 160 carburetor will work better when power down.

3.  Others suggested to adapt the OS 140 RX pump to the OS 160.  I have 
been thinking to do this.  I have an old OS 140 RX in my Hydeout.  I 
already retrofitted the OS 140 RX with the V-30 pump and OS 160 
carburetor.  Installing the V-30 pump with the OS 140 RX 
carburetor does not work in both engines. Clearly the fuel systems is 
very sensitive to pressure and the OS 140 RX carburetor requires higher 
pressure that the V-30 pump can not provide.  I have been running the 
OS 140 RX with the OS carburetor for 3-4 months with good results.  
However, the time to get idle speed problem still there (similar 
situation with the OS 160).  It is clear that retrofitting the OS 160 
with the OS 140 RX carburetor and pump could be the correct solution 
since the OS 140 RX is a lot better in this regard.  I guess that the 
rule use in the industry to control flow works here also.  A high 
pressure drop valve (OS 140 System) i! s a lot more precise than the 
low pressure control valve (OS 160).  As we know, high pressure control 
systems are always more expensive. 

4.  Many other suggestions on props and adjustments.  Believe me, I 
already tried all of them.  Final combination of three blade re-pitched 
prop with the OS F plugs seems to be popular and is the one I am using 
now with very good results.  The V-30 pump should be adjusted as lean 
as possible and the low end as lean as possible but not too much. 

5.  It is clear that all 2-cycle engines will have this behavior.  
4-cycle engines are a lot better in this regard.  However, I think more 
precise metering system will improve the situation in 2-cycle (just use 
the OS 140 RX system).  Clearly, other solutions are to go 4-cycle or 
electric.  

Probably I forgot other details. 

Thanks,

Vicente 

-------------- Original message --------------
From: "Mark Hunt" <flyintexan at houston.rr.com>
Nat,

Did you ever run the OS91 on your special header pipe with the 
valve?...your intention was to lower the in-flight idle speed correct?

-mark
----- Original Message -----
From: vicenterc at comcast.net
To: NSRCA Mailing List ; NSRCA Mailing List
Sent: Sunday, March 05, 2006 10:00 PM
Subject: Re: [NSRCA-discussion] Fuel Regulation in 2C Engines

It is interesting.  I agree with all comments that I have been 
getting. 

I am getting around 1,650 RPM in the OS 160.  In the 140's a little 
higher (around 1,700-1750 RPM).  I set up a switch (landing gear) so I 
go even lower in the air.  I just go to low idle as soon as I take 
off.  I take the risk and usually the lower setting could be around 100 
RPM less. 

However, the situation is that in some maneuvers and conditions during 
the dowlines the combination works well and suddenly the next maneuver 
does not work as well.  It is not consistent time-to-time.  For this 
reasons believe that doing some re-work to make the inlet pressure as 
close as possible to the original pressures (OS 160) will improve the 
fact that the engine is not consistent.  The OS metering system was 
design for low pressure.

I will do the experiment.  If does not work is not really a big 
deal. Thanks,

Vicente
-------------- Original message --------------
From: "Nat Penton" <natpenton at centurytel.net>
Vicente, I think Ed pretty well answered the questions. OS would not 
use the Perry in the 91SX-H unless it was first class in performance, 
also it is much cheaper than buying the OS pumps. Thats why OS went to 
it.

FYI, to install the 140 pump in the 160 you need that portion of the 
140 backplate the four bolts are screwed into. Cut off the sides, Cut 
an appropriate hole in the 160 backplate to match the pump. With 
attention to detail you will be able to remove the pump from the 160 
after the JB Weld sets, but I think you should use the Perry instead 
and save the money.

With reference to the two stroke idle, is the problem on the ground or 
on the downline ? What idle RPM are you getting with the 140, 160, 
Mintor ? You can't get the downline braking with the two stk, compared 
to the four, regardless of prop selection.                      Nat
----- Original Message -----
From: Ed Alt
To: NSRCA Mailing List
Sent: Sunday, March 05, 2006 8:21 PM
Subject: Re: [NSRCA-discussion] Fuel Regulation in 2C Engines

Is this the VP30 pump that is being experimented with? I have had great 
results with this on several OS 1.60's, but it does require that you 
reduce the pump pressure by at least two turns.  Also, the low end 
needle needs to be leaned alot, usually about 2 turns to start with.  I 
haven't had any issues with mid range at all after fine tuning from 
these as starting points and it holds up very well over time.

Ed
----- Original Message -----
From: vicenterc at comcast.net
To: NSRCA Mailing List ; NSRCA Mailing List
Sent: Sunday, March 05, 2006 8:13 PM
Subject: Re: [NSRCA-discussion] Fuel Regulation in 2C Engines

John:

Thanks for your advice.  I already worked the prop.  The best I found 
is the 3 blade re-pitched.  I just want to improve it more.  Probably 
very difficult task base on the feedback I am getting.

I like your idea to tune the return line.  I have been thinking to go 
that route with a Perry external needle valve in the return line.  The 
process would be, in the OS 160, to adjust the return needle valve 
until the high end needle valve is about 2.5 turns open at full power.  
That is the normal setting when I run the engine with no pump.  In this 
way,  we will be close to the original design pressure.  Normally, the 
OS 160 with the Perry pump sets within 1 to 1.5 turns open.  Than means 
that the pressure is too high. 

Vicente
-------------- Original message --------------
From: "John Pavlick" <jpavlick at idseng.com>
Yeah, I tend to agree with Nat here. After some discussion about the 
Perry loop idea, I know someone who actually tried it. It came down to 
the theory vs. reality thing i.e. "only one way to find out..." It 
seemed like a good idea, but it didn't seem to work on our big motors. 
I think that in order for this to work properly, you would need a pump 
that is capable of way more volume AND pressure than you need. In 
addition to this, the regulator should be an external device, not 
inside the pump like the way it is with a VP-30, or the internal 
regualtor needs to have an eaxternal "return" line. This is how a 
fuel-injected automotive system works, so it is possible. The Perry 
loop thing works for R/C cars and smaller motors but I think the pump 
needs more volume to feed our big motors with that big gaping "hole" in 
the system (the return loop). Maybe tuning the size of the return loop 
wi! ! ! th a restrictor would be worth a try. Is it worth the effort? 
Generally a VP-30 that is properly adjusted will give reliable 
performance with just a vent line and no tank pressure / no return 
loop. Props have a big effect on what happens when you return to idle 
too. If you want to help downline braking, look at props before you 
spend a lot of time re-designing the fuel system. Also, try setting the 
idle a little bit richer. The slow transition to idle condition is 
sometimes aggravated by a lean idle mixture. Not trying to discredit 
anyone's theories,  just passing along some of my observations.

John Pavlick
http://www.idseng.com

-----Original Message-----
 From: nsrca-discussion-bounces at lists.nsrca.org 
[mailto:nsrca-discussion-bounces at lists.nsrca.org]On Behalf Of Nat Penton
Sent: Sunday, March 05, 2006 3:48 PM
To: NSRCA Mailing List
Subject: Re: [NSRCA-discussion] Fuel Regulation in 2C Engines

Diaphram operated fuel pumps made by OS ( Hanno, 140 RX, 91 SH 
<Perry?>) are self regulating in that output is proportional to RPM, 
proportional to need. These pumps can be adapted to any 90 to 160 two 
stroke with JB Weld and without maching skills. The tank is vented and 
there is no pressure in the system.

I have had impeccable performance using these pumps on the OS91FX for 
the last four years. I believe the logic in the circulating systems is 
flawed.                    Nat
----- Original Message -----
From: vicenterc at comcast.net
To: NSRCA Mailing List ; NSRCA Mailing List
Sent: Sunday, March 05, 2006 12:22 PM
Subject: Re: [NSRCA-discussion] Fuel Regulation in 2C Engines

Hi Brian,

You got it right.  In the OS 160 we would like to set up the pressure 
in the header before the carb as close as possible to the original 
design (muffler pressure with tank close to firewall).  In this way, 
the carburetor metering system will work as was originally designed.  I 
will be doing some test and see what will work better. 

The expert at Perry recommended to send the overflow to the tank.  
However, I agree that loop around the fuel pump could work since that 
is one old method to control pressure in industrial pumps. 

Vicente

-------------- Original message --------------
From: brian young <brian_w_young at yahoo.com>
So I guess the thinking behind doing this is that you deliver the fuel 
to the carb and its there for the carb to take. But the fuel at the 
carb nipple will only be under atmospheric pressure (since the tanks 
vented), anything extra is free to go back to the tank. The venturi 
affect of the carb will draw the fuel into the carb. I dont see why you 
would need to go clear back to the tank, just loop around the pump.

This sounds like it could take the variability of pumps out of the 
equation and at the same time let the pump deliver fuel to the carb, 
but not push fuel into the carb.

Interesting.

Wayne Galligan <wgalligan at texasairnet.com> wrote:
Vincent,
!  
I wonder if this "T" setup would work on an OS 1.40.  I already use the 
check valve in the vent so a couple of "T's" and maybe I would be in 
business.  Would you have to change the pump pressure?

Wayne Galligan
----- Original Message -----
From: vicenterc at comcast.net
To: nsrca-discussion at lists.nsrca.org
Sent! : Sunday, March 05, 2006 8:19 AM
Subject: [NSRCA-discussion] Fuel Regulation in 2C Engines

Good morning all,

I have been using the OS 160, OS 140 RX and Mintor 140 with good 
results in the last 4-5 years.  We have been comparing and discussing 
the advantages of YS compared with 2C.  One of the main advantages of 
YS is that in transition when power down the engine goes instantly to 
2000 RPM or less.  The 2C engines always takes too much time to get 
down to idle and I believe that causes us (in pattern) some 
problems.   

I have been thinking that the problem is that the carburetor and or 
fuel system that can not regulate properly (pressure or flow).  I think 
in these engines, the pumps are set to deliver fuel at full flow (or 
pressure) without any regulation system (like the YS).  ! I had the 
opportunity to discuss this issue with Perry Pump and they recommended 
to install a by-pass line.  The idea is to send the excess fuel 
(pressure) back to the tank during transition.  Perry Pump recommended 
to install the T as close as possible to the carburetor needle valve.  
Also in their web site they have an idea that he said is used for cars 
that is a by-pass line that loop around the pump 
(http://www.perrypumps.com/instructions.htm,  Click on Pump and By-Pass 
Systems).  I think the ideas deserve some checking since it is natural 
to have this type of regulation to maintain constant pre! ! ! ! ss! ure 
in the line before needle valve.  I tried the other day the by-pass to 
the carburetor but I installed the T too far from the carburetor and 
forgot to open the vent in the tank.  Of  course the results were bad 
since I was developing vacuum in the tank.  I wi! ll try these options 
of by-pass lines as soon as get warmer.  However, I think someone out 
there already tried to do this and know results so I am looking for 
feed back.

Thanks in advance,

Vicente Bortone

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Attached Message
From:Mark Hunt <flyintexan at houston.rr.com>
To:NSRCA Mailing List <nsrca-discussion at lists.nsrca.org>
Subject:Re: [NSRCA-discussion] Fuel Regulation in 2C Engines
Date:Mon, 6 Mar 2006 13:46:25 +0000

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