[NSRCA-discussion] Fuel Regulation in 2C Engines

Tue Mar 14 17:03:44 AKST 2006

Yes, I am back.  I did some test bench and concluded that the by-pass does not make sense.  Also, I concluded that my problem was really temperature changes.  Usually this is the first winter that I fly pattern.  In the past, I have been flying sport planes in winter time.  Last Saturday, I went to fly and during the day it was warm and the engine idle was working like it was last summer "perfect".  I didn't had any problems with transition going from full power to idle.  Suddenly a cold front came and the temperature dropped at least 10 oF.  Remember, I live in Kansas.  When I flew the first time with the colder temperature, I started to have the problem that I had before in colder weather.  Idle was taking too long when going from full power to idle.  I was able to notice in fly and when I landed.  I just richen not only the high end but also the low end and the engine performed very well in the following flights.  Today, I run a test on the bench and noticed that clearly the final solution is to richen the low end.  Usually, I was richening the high end only when flying in lower temperatures.

I also checked the performance of the engine using the OS 140 RX and the Perry pump with the OS 160 carburetor and the OS 140 RX carburetor.  On the bench the combination of the OS 160 carburetor with any of both pumps work equally well.  The OS 140 RX carburetor performed well only with the OS 140 RX pump.  Clearly, the additional cost of the OS 140 RX pump can not be justified.  As all know, the performance in the air not necessarily would be equal to the performance in the test bench.  However, the results could be interesting for some.  Main conclusion and learning experience:  the combination of the OS 160 FX and Perry pump works very well but it is very sensitive to temperature changes.  Finally, I applied insulation as Nat Penton suggested.  I checked in the bench and appears that is working great.  Final test has to be done flying to check if the carburetor would be less sensitive to temperature changes.  

Definitively, the OS 160 FX is like me.  A tropical guy.  Thanks again for all responses.  

Regards,

Vicente Bortone  

-------------- Original message -------------- 
From: vicenterc at comcast.net 

Nat,

Interesting, I do exactly as you described.  The engine perform very well when throttling up and idle is fine.  Power is just incredible.  The problem that I see is that throttling down the engine does not go to idle fast enough.  Probably, I am getting too old.

Vicente

-------------- Original message -------------- 
From: "Nat Penton" <natpenton at centurytel.net> 

Vicente
My experience in setting the idle on a two stroke is to continue to lean until it wont run, then richen slightly. The motor will then be instantly responsive to throttle. If you run with a rich idle you can pinch the fuel line, at idle, and the engine will continue to run, even speed up as it approaches the right mixture.                           Nat
----- Original Message ----- 
From: vicenterc at comcast.net 
To: NSRCA Mailing List ; NSRCA Mailing List 
Sent: Tuesday, March 07, 2006 6:57 AM
Subject: Re: [NSRCA-discussion] Fuel Regulation in 2C Engines

All,

It is evident that I had been setting the low end lean.  Next time I fly, I will adjust to get richer low end.  I don't think I am running the engine hot.  However, I am going to try to improve cooling and see if this helps. 

Thanks to all again.  I got very good feedback. 

Vicente Bortone

-------------- Original message -------------- 
From: "John Pavlick" <jpavlick at idseng.com> 

> Jerry, 
> Thanks for confirming my observation re- lean idle = slow transition to 
> idle. I first noticed this on my old Arctic Cat sleds. I've always felt more 
> comfortable with 4-strokes - I guess that comes from wrenching Harleys. I'm 
> finally figuring these ringy-dingy 2-strokes out I guess. So who says toy 
> airplanes aren't educational? 
> 
> John Pavlick 
> http://www.idseng.com 
> 
> BTW - I've been using sealed bearings (seals on both sides / -2RS type) 
> front and rear. In stock configuration, normally the front bearing is 
> shielded on one side only - no seals. This does nothing (or at best very 
> little) to seal the crankcase. With both sides sealed, there is much less 
> ch! ance of an air leak that would definitely causes slow transition AND 
> erratic idle. In extreme cases I've seen motors that wouldn't shut off even 
> with the throttle fully closed. The fix was new bearings. 
> 
> 
> 
> > -----Original Message----- 
> > From: nsrca-discussion-bounces at lists.nsrca.org 
> > [mailto:nsrca-discussion-bounces at lists.nsrca.org]On Behalf Of Jerry Budd 
> > Sent: Tuesday, March 07, 2006 12:28 AM 
> > To: NSRCA Mailing List 
> > Subject: Re: [NSRCA-discussion] Fuel Regulation in 2C Engines 
> > 
> > 
> > >5. It is clear that all 2-cycle engines will have this behavior. 
> > 
> > I guess I have to offer a different opinion on this. If you have the 
> > low end set lean (and most running the OS140Rx are running the bottom 
> > lean to get the mid-range somewhat reasonable) you will not be able 
> &g! t; to get the motor to settle into a low idle quickly. And that 
&g t; > presents itself as poor down line breaking, as well as the occasional 
> > flameout. When I ran the OS140's I bought four motors and then 
> > picked the two with the best carbs (aka midrange) so I could set the 
> > low end where it belonged. I also used higher nitro fuel (Magnum #1) 
> > to help lean the midrange, which also allowed me to run the pipe 
> > about an inch longer (which helped soften the pipe "bump"). 
> > 
> > I had good luck (post '02 Nats) and good power (8400 rpm, APC 17x12) 
> > with the OS's, but I found that the throttle response wasn't the best 
> > if you used a lot of throttle to control speed. When I switched to 
> > the Webra 160 I was able to set the top end rich and still have more 
> > power than I knew what to do with (because of the enormous 
> > torque/very conservative exhaust timing), and also set the idle 
> > sligh! tly rich so the motor would quickly settle into a low stable 
> > idle. Of course this was a lot easier to do with the MC carb since I 
> > didn't have to compromise on the mixture settings. 
> > 
> > But, anyway, to bring this back to point. The most prevalent reason 
> > for a 2c to have an erratic idle with poor down line braking is a too 
> > lean idle and a hot motor (like Evil Eric said). Adding a fuel pump 
> > or a pressure regulator or whatever won't fix that. 
> > 
> > Just my $0.02 worth, 
> > 
> > Jerry 
> > -- 
> > ___________ 
> > Jerry Budd 
> > Budd Engineering 
> > (661) 722-5669 Voice/Fax 
> > (661) 435-0358 Cell Phone 
> > mailto:jerry at buddengineering.com 
> > http://www.buddengineering.com 
> > _______________________________________________ 
> > NSRCA-discussion maili! ng list 
> > NSRCA-discussion at lists.nsrca.org 
> > h ttp://lists.nsrca.org/mailman/listinfo/nsrca-discussion 
> > -- 
> > No virus found in this incoming message. 
> > Checked by AVG Free Edition. 
> > Version: 7.1.375 / Virus Database: 268.2.0/275 - Release Date: 3/6/06 
> > 
> -- 
> No virus found in this outgoing message. 
> Checked by AVG Free Edition. 
> Version: 7.1.375 / Virus Database: 268.2.0/275 - Release Date: 3/6/06 
> 
> _______________________________________________ 
> NSRCA-discussion mailing list 
> NSRCA-discussion at lists.nsrca.org 
> http://lists.nsrca.org/mailman/listinfo/nsrca-discussion 

_______________________________________________
NSRCA-discussion mailing list
NSRCA-discussion at lists.nsrca.org
http://lists.nsrca.org/mailman/listinfo/nsrca-discussion 

Internal Virus Database is out-of-date.
Checked by AVG Free Edition.
Version: 7.1.375 / Virus Database: 267.15.6/257 - Release Date: 2/10/2006
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.nsrca.org/pipermail/nsrca-discussion/attachments/20060314/7f3359f2/attachment.html 