Extreme Speed Prop Planes Discuss the need for speed with fast prop planes (Screamin Demon, Diamond Dust, Shrikes or any REAL sound breakin'''' plane)

OS 46fx Glow plug problems

Reply

Old 03-04-2007, 12:21 AM
  #1  
codyhie
Junior Member
Thread Starter
 
Join Date: Feb 2007
Location: North Newton, KS
Posts: 11
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default OS 46fx Glow plug problems

Hi, I have a shrike 40 with an O.S. .46fx and a mac header and rossi tuned pipe, I trimmed 2 3/4 of the header. In the process of tuning it I blew the first plug os f. Then once I got it to peek rpm, 14,200, with a apc 9x10, I blew two more mc 55's. I know the fuel is really old and don't know if that would have anything to do with it, Omega 15%. The engine will sometimes peek then back off about 200rpm and won't go back up and I will quit and try to restart and the plug is blown. Any advice you expert RCers.[]
codyhie is offline  
Reply With Quote
Old 03-04-2007, 12:52 AM
  #2  
rcflyer1970
My Feedback: (212)
 
rcflyer1970's Avatar
 
Join Date: Dec 2004
Location: SUN CITY, AZ
Posts: 191
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: OS 46fx Glow plug problems

I would do a few flights with a 9x7 or 9x8, set on the rich side and see how it flys before trying to pull that much prop if at all, if the tuned pipe length is too short for the prop your trying to run it will overheat, sag and blow plugs, fresh fuel would be good too, here's a old chart for general tuned pipe settings for rpm ranges, measure from the glow plug to the widest part of the tuned pipe following the exhaust path (not a strait line since it's not a rear ex engine) torque the head bolts after it's warmed up. Good luck!
Attached Thumbnails Click image for larger version

Name:	Mk26267.jpg
Views:	9
Size:	166.5 KB
ID:	634443  
rcflyer1970 is offline  
Reply With Quote
Old 03-04-2007, 02:29 AM
  #3  
codyhie
Junior Member
Thread Starter
 
Join Date: Feb 2007
Location: North Newton, KS
Posts: 11
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: OS 46fx Glow plug problems

Well isn't 14,000 pretty good rpm. It's better than the 10x8 I had, 13,500. Should I use a colder plug? I think blew the os f plug on the tower hobbies muffler I had on right before that.
codyhie is offline  
Reply With Quote
Old 03-04-2007, 07:40 AM
  #4  
GRAND MASTER B
Member
 
GRAND MASTER B's Avatar
 
Join Date: Feb 2007
Location: Continental Divide
Posts: 38
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: OS 46fx Glow plug problems

I run cheap tower plugs in my shrike. 15,000, 46pro and 9/8 apc. No issues on plugs
GRAND MASTER B is offline  
Reply With Quote
Old 03-04-2007, 09:02 AM
  #5  
Ed Smith
Senior Member
 
Join Date: Dec 2001
Location: Brantford, ON, CANADA
Posts: 3,305
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: OS 46fx Glow plug problems

One has to face facts. The O.S. 46 fx is a sport engine. Its port size and timing is meant for that purpose. Some modest power increase may be achieved with a pipe but hardly worth the effort and expense.

Quote from the Tuned Pipe chapter of "The Two Stroke Tuners Handbook"

"Sadly, the real result of most peoples shade-tree experimental work is simply to discover that it remains possible to bring down on ones head all of the tuned pipes considerable disadvantages without being compensated in performance"

Good Luck,

Ed S
Ed Smith is offline  
Reply With Quote
Old 03-04-2007, 07:57 PM
  #6  
rcflyer1970
My Feedback: (212)
 
rcflyer1970's Avatar
 
Join Date: Dec 2004
Location: SUN CITY, AZ
Posts: 191
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: OS 46fx Glow plug problems

I have had many race and sport engines with pipes and I never overproped them, heat will kill engines, rpms are not a problem for two strokes, let it rev, I allways try to prop the sport engines for 15K or more on the ground (with tuned pipe and in a speed plane)and set the needle rich and fly it..... it will lean out in the air. Start with a APC 9x7 and when you can tune it with that prop and it's reliable flying then try a 9x8 and see how it acts, you may end up cutting the prop to 8-3/4 x 8 to keep it running reliable, you can try a cool plug but I just run junk plugs while tuning them when I get everything set right then I put a good plug in. If you make the pipe too short you may need to run a 9x6 to get in the rpm range the pipe is tuned for.
rcflyer1970 is offline  
Reply With Quote
Old 03-04-2007, 10:01 PM
  #7  
d_bodary
Senior Member
My Feedback: (85)
 
Join Date: Apr 2004
Location: trenton, MI
Posts: 1,529
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: OS 46fx Glow plug problems

Try the Fox #8 plug. On my 40fx quicky plane i would waste plugs almost every flight. The Fox #8 lasts quite a lot of flights.

Dennis
d_bodary is offline  
Reply With Quote
Old 03-05-2007, 12:03 PM
  #8  
bob27s
My Feedback: (19)
 
bob27s's Avatar
 
Join Date: Apr 2002
Location: Cleveland, OH
Posts: 5,576
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: OS 46fx Glow plug problems

i will keep this one short....

if you are blowing plugs... the engine is lean

you have (pick any of the below to check)

a) pipe set too short for the props you are using (drop a prop size or two)

b) you have a tank and/or fuel foam issue

Does not matter what plug you are using.... if its blowing, the engine is lean, or is getting very hot.

With a pipe, you want to back off 400-600rpm below peak rpm on the ground.

Bob
bob27s is offline  
Reply With Quote
Old 03-05-2007, 04:50 PM
  #9  
codyhie
Junior Member
Thread Starter
 
Join Date: Feb 2007
Location: North Newton, KS
Posts: 11
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: OS 46fx Glow plug problems

Thanks Bob for the info. Maybe I should just get a Jett and be done with the problem, haha. I have only ran it on the stand for less than 1 minute per run, so I don't think its getting too hot then. I didn't richen it up like you said, so that might be the problem. My pipe might be about a half inch short for the prop. but I can't do anything to that. So I might try and trim the prop down a bit.
codyhie is offline  
Reply With Quote
Old 03-05-2007, 10:10 PM
  #10  
freakingfast
Senior Member
My Feedback: (3)
 
Join Date: Jan 2005
Location: Mather, CA
Posts: 2,222
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: OS 46fx Glow plug problems

9X10 is way too much prop, try a 9X8 as others have said. Try a Fox standard long plug, it's a bit cooler than an OS #8 but it's Cheeeaaap and it Laaaast is some engines. I still use OS #8 plug on other screemers. Make shure your tank is supported/wraped in foam rubber and not in contact with the fuselage, you may be foaming up your fuel. Do you have a lot black smutt from your exhaust....your lean, for the reasons Bob stated.
freakingfast is offline  
Reply With Quote
Old 03-06-2007, 01:54 AM
  #11  
codyhie
Junior Member
Thread Starter
 
Join Date: Feb 2007
Location: North Newton, KS
Posts: 11
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: OS 46fx Glow plug problems

That is exactly what I encountered; the exhaust was spiting black sludge out and I thought that the pipe was just burning the the fuel better. I didn't know you had to richen up for the pipes, but that will only put me about 300 rpm over the tower muffler I had on before.[]
codyhie is offline  
Reply With Quote
Old 03-06-2007, 09:30 AM
  #12  
bob27s
My Feedback: (19)
 
bob27s's Avatar
 
Join Date: Apr 2002
Location: Cleveland, OH
Posts: 5,576
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: OS 46fx Glow plug problems

You noted this is an OS 46FX (not AX). If so...... the engine was made to turn - not to lug real big props.

I suggest putting the engine back on the test stand - install a fresh plug in it (any one you have is fine) put the stock muffler on it, install a 9x6 prop (yes, a 9x6) - run it with that prop, full throttle, set about 700-800 rpm down from peak rpm (Slightly rich) for at least 20 minutes.

Next, keep it on the test stand - install the pipe (as you have it set now). Install a 9x7 prop. Run it with that. Set the high end about 500 rpm down. Check for throttle response - adjust the low speed mixture if needed. The engine should behave well at this point, and should be turning somewhere around 16,500 rpm. Maybe a bit more.

Next, dont touch the pipe - move up to a 9x8 prop. See if the engine runs the same. If you find the engine gets hot, or misbehaves, or does not transition well, then the pipe is set too short for this particular load. My guess is it will run ok with the pipe set as is. In which case, also try a 10x6.

With the BENCH stuff completed, then install the engine into the aircraft. Fly it with 9x7 to start with. Then move to the 9x8 after it has some air time on it. Always set a piped engine 500-600 rpm rich of peak before launch - when the engine unloads on the air, it will stage deeper into the pipe, and it will need more fuel as the rpm increases a bit.

Of note, the distance you cut the header is not really relavent. The measurement for a tuned pipe is the distance from the glow plug, along the centerline of the header, to the "fat" part, or weld in the pipe.

A pipe works like a governor. It will try to force the engine to an rpm. If an engine is under-propped, it will quickly and easily reach the tuned rpm point - and settle in there. Generally will not exceed that point. If the engine is overloaded, it will still try to get there.... if the pipe is too short (rpm set too high) and the engine can not get there..... it will get hot, not needle well, will not transition well, and in short order this will destroy the engine.

Switching to a Jett wouldn't solve your problem here. If the pipe is set too short or you over-prop the engine - its going to become a $250 paper weight in about 30 minutes. Doesnt make a difference if it is an OS, Jett, Rossi, Magnum or SuperTiger.... all 2c engines respond the same, and the pipe physics are basically the same.

(the only reason a Jett would help is the jett-stream muffler - there is no tuning involved, but you still have to prop the engine within the desired rpm band)

If you do indeed want to turn a 9x10 prop with the engine, it is possible..... but you have to tune the pipe VERY long. Pipe length for a prop that size would probably be about 15.5". And, do not expect any substantial rpm from it. Getting up to 14K from that size prop on the 46FX is asking a ton.

Bob
bob27s is offline  
Reply With Quote

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off


Thread Tools
Search this Thread

Contact Us Archive Advertising Cookie Policy Privacy Statement Terms of Service