[NSRCA-discussion] Fuel Regulation in 2C Engines

Mon Mar 6 13:19:18 AKST 2006

Guys..I've mentioned this before. A friend of mine makes CNC'd back plates for the OS160 to which you can adapt the OS pump. ALL run flawlessly down here and are being used for active F3A competition. Naturally, one needs to set the pipe correctly. Most run the 17 x 12 , 17 x 13 on windy days. The 18 x 10 Mejzlick is also good.

I'll submit an article I did for our organisation to the K-Factor. I have sent a plate to Jim Kimbro-haven't heard how he is going yet, but there is one over in the US.We also lighten the motor itself ( not hard to do).

Tom

-----Original Message-----
From: nsrca-discussion-bounces at lists.nsrca.org [mailto:nsrca-discussion-bounces at lists.nsrca.org]On Behalf Of Nat Penton
Sent: Monday, 6 March 2006 7:48 AM
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 <mailto:nsrca-discussion at lists.nsrca.org>  ; NSRCA Mailing List <mailto:nsrca-discussion at lists.nsrca.org> 
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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