RE: Piston ported vs. case (reed/r.v.) induction??    Gallery
View related threads: (in this forum | in all forums)

Logged in as Guest



Users viewing this topic: none
    Search This Thread  
 
Printable Version

All Forums >> Glow Engines, Gas Engines, Fuel & Mfg Support Forums >> Gas Engines >> RE: Piston ported vs. case (reed/r.v.) induction??
Page: <<   < prev  1 [2]

Tower Hobbies Get Coupon Codes Brands  
Login
Message << Older Topic   Newer Topic >>
RE: Piston ported vs. case (reed/r.v.) induction?? - 12/30/2012 11:16 AM  1 votes
pe reivers



Posts: 6497
Score: 646
Joined: 1/23/2002
Last Login: 5/20/2013
From: Arcen, , NETHERLANDS
Status: offline 		Even racing engines use reeds, so yes, they are as efficient as rotary disk or piston induction engines.
Well cared for reeds have no blowback below best power rpm. Rotary disk and piston induction do blow black at lower rpm, and often need carb extensions to cure that.
Not to say that reeds cannot improve with an extension stack. It often even further improves low rpm operation.
Reeds are the norm, because we mostly use lowish rpm due to the direct prop drive. Evey engine application has it's own set of requirements. Chainsaws with rpm around 9000 often use piston induction.

Yes, you can come up with a lot of answers if you google for two stroke induction systems. In fact more than 3.000.000 hits
The first hit is http://en.wikipedia.org/wiki/Two-stroke_engine  , which has all the answers to your question.



_____________________________

Pe, (www.mvvs.nl), MVVS, MOKImotor, RCexl, MTW, Xoar, Mejzlik.
Blessing in ignorance? There is sanctuary in analysis.

Hide Signatures

(in reply to Flight Risk)
       Post #: 26

RE: Piston ported vs. case (reed/r.v.) induction?? - 12/30/2012 2:29 PM  1 votes
ahicks


 

Posts: 1872
Score: 669
Joined: 8/10/2008
Last Login: 5/21/2013
From: Waterford, MI, USA
Status: offline
quote:

ORIGINAL: Flight Risk

This is an old thread, but I felt a need to comment here. I came here with some of the same questions the OP had, but found that evidently free, helpful advice can't be expected on RCU forums. Snide remarks and whining about answering questions for free, until post 15. Yes, if someone wants info about something they can Google it, but isn't RCU the place to ask for and exchange information without being reprimanded? When I searched for piston porting vs reed, only a couple hits showed up, so it appears to be a taboo topic. If you don't want to provide help, then why waste your precious time giving a snide remark.
Stepping off my soapbox.

My questions regarding this topic are: It appears that rear reed induction is becoming the norm, even on cheap, 15-20cc engines. Why is that? Are flyers demanding to have the carb hidden in the cowl?
It seems to me that unless you are going for a scale warbird or such, having a rear carb is much more of a tuning, choking pain, and more depth is needed for the standoffs. Are velocity stacks used on rear carbs? If so, are you cutting holes thru the firewall? I have always wondered how reeds can be efficient considering that they only open 1/8'' or so max.

Thanks,
RS


I asked that question as I was getting ready to dive into gas with both feet. There were some easily ruffled feathers that did their level best to discourage newbies around at the time as you can see. Though their knowledge is to be respected, and may be the reason they take questions WAY beyond intended, I've since learned to ignore some of the replies as there's also some guys in here that will do their best to answer questions to the best of their knowledge as well. Part of that response was my fault as well. I could have/should have worded the questions a little differently.

Regarding your question, my bet is as you suspect. The piston ported engines require the carb be poked through the side of the cowl on many smaller planes. In my (somewhat limited compared to some) experience with both types, I've not found the handling of the reed valved engines objectionable at all, so there's no real need to have that extra hole in the cowl. Some engine designs use a rear exhaust arrangement for the same reason?

Velocity stacks are generally not used on the reed valve engines. They're generally there to control blow back, and reeds don't blow back enough to be concerned about. Kinda nice if for that reason alone actually!

Rear carbs, compared to fully cowled side carbs, not that much more difficult to adjust or choke? Compared to carbs that are out in the open, there's no doubt they're a pain! Thankfully there's some pretty clever methods in use to minimize the trouble, and the gassers themselves generally don't need a lot of fiddling once set up, or not as much anyway...

Valid concern regarding the opening width of a reed valve. The way that's often handled (if necessary?) is going with designs that use more of them? Look at some of the different parts diagrams to see what I'm talking about. The nicer/fancier ones are generally arranged in a "V" or "W".... are pretty efficient!

Cutting holes in the firewall (as necessary) has become an acceptable practice. Many will try to get an idea of what will be required to mount an engine in an airframe by comparing the drive washer to carb dimension with what's available on the plane in question. Sometimes that takes a little research, but this style engine has been out long enough now where that info should be available.

-Al

Hide Signatures

(in reply to Flight Risk)
       Post #: 27

RE: Piston ported vs. case (reed/r.v.) induction?? - 12/30/2012 4:15 PM   
Checklst


 

Posts: 653
Score: 115
Joined: 12/19/2002
Last Login: 5/19/2013
From: Alpharetta, GA, USA
Status: offline 		I have both type gas motors and they both run great...........once the needles are set up proper........I fly and have a great time with both and all are well manor, I did choose reed rear carb 30cc to fit cowl on aircraft just for ascetics of cowl opening cuts ect..............I felt the difference in induction was less important

I watch a lot of engine threads a while to just to see which motor is well mannered, and has good service dealers. I have Zenoah, DLE30, DLE55 and all are running great,when the motors are running like they should, I concentrate on flying and having fun......I see plenty of frustrated engine tuners at the field having no fun.............Thats what it all about to me relaxing day at the field with good people.

I am planing my nest 30cc plane and have started keeping an eye on the Mentor,DLE35R SASSY ect.

Good luck

Hide Signatures

(in reply to ahicks)
       Post #: 28

RE: Piston ported vs. case (reed/r.v.) induction?? - 12/30/2012 6:36 PM   
Flight Risk



Posts: 478
Score: 108
Joined: 6/7/2003
Last Login: 5/15/2013
From: Rocky Flats, CO, USA
Status: offline 		Thanks for these answers guys. I have a couple of engines running piston port, 20 and 40cc , and love them and the way they run, and am planning to use gas wherever practical. It just seems odd that rear reed is becoming the norm, even on the little 15-17cc engines, but I guess they do have some advantages.

RS

_____________________________

Just Fly It.

Hide Signatures

(in reply to Checklst)
       Post #: 29

Page:   <<   < prev  1 [2]
All Forums >> Glow Engines, Gas Engines, Fuel &amp; Mfg Support Forums >> Gas Engines >> RE: Piston ported vs. case (reed/r.v.) induction??
Page: <<   < prev  1 [2]





Jump to:


 
Google 



Search | Marketplace | Event Calendar | Local Clubs | Magazine | Product Ratings | New Products | Discussion Forums

Photo Gallery | Instructor Search | Field|Track|Marina Search

Advertisers | Hobby Vendor Resources | Rate Manufacturers | Sign In/Sign Up

SITE MAP!   : :   FORUM RULES

RC Universe is a service of Internet Brands, Inc. Copyright © 2001-2013.

Charities we support that also need your help
Yorkie Rescue | Humane Society | ASPCA | Crohn's-Colitis America


0.531RCU1