Go Back  RCU Forums > RC Airplanes > Questions and Answers
Reload this Page >

Question about gas to oil mixture........

Notices
Questions and Answers If you have general RC questions or answers discuss it here.

Question about gas to oil mixture........

Old 08-30-2009, 03:07 PM
  #1  
Matt
Thread Starter
My Feedback: (1)
 
Join Date: Feb 2008
Location: Hammond, IN
Posts: 98
Likes: 0
Received 0 Likes on 0 Posts
Default Question about gas to oil mixture........

I have a US 42 gas engine.....and I am currently running 32:1. When the engine first starts on the ground, the transitions are good. What I mean by this is that I can rapidly move the throttle stick from idle to full and there is no stuttering at all (about a second to get the stick from idle to full). BUT...when the engine warms up on the ground after about 5 minutes, the engine will stutter and quit if I move the throttle stick from idle to full to fast! If I move it slowly (say about 3.5 - 4 seconds until full) it's okay but stutters just a little when I get to fourth throttle and the it's okay. If i change the mixture to 40:1 (which will be less oil and more gas and everybody that i ask says that that's what they run all the time,) will it help with that problem? Also to i took out the spark plug yesterday and there was a lot of brownish residue on the gap and all around. And yes i have adjusted the engine quite a bit and it still didn't get any better. [X(] maybe I’m using too much oil???
Old 08-30-2009, 03:34 PM
  #2  
huck1199
Senior Member
 
huck1199's Avatar
 
Join Date: Jan 2007
Location: Lancaster, NY
Posts: 1,550
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Question about gas to oil mixture........

On a glow engine you would lean it out a little. Can you adjust the mixture on a gas engine? I sounds like it is loading after long idles.
Old 08-30-2009, 03:48 PM
  #3  
ChuckW
Senior Member
 
ChuckW's Avatar
 
Join Date: Jun 2006
Location: Clovis, CA
Posts: 5,165
Likes: 0
Received 2 Likes on 2 Posts
Default RE: Question about gas to oil mixture........

Changing the oil ratio will probably not do anything for the transition issue. It is more than likely a tuning problem. Maybe a mis-adjusted carb, problem inside the carb, wrong carb for the engine or maybe even a spark plug/igniton problem. I'd bet on a carburetion issue personally.
Old 08-30-2009, 03:49 PM
  #4  
Matt
Thread Starter
My Feedback: (1)
 
Join Date: Feb 2008
Location: Hammond, IN
Posts: 98
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Question about gas to oil mixture........

it's not even loooong idles........i've flown this engine before and it's decent in the air........but i'm JUST talking about running it on the ground in this post. i could restart the engine after it's warmed up and move the throttle from idle to full quickly and it will just studder and die out if i don't back off quick. But yes, gas engines have a high and a low mixture setting.....but they work differently from glow engines...i'm still trying to get myself in tune with it. lol (i have all glow airplanes but i got this gas engine and airframe for free....so i figure i mess around with it for a while)
Old 08-30-2009, 05:27 PM
  #5  
Lnewqban
 
Lnewqban's Avatar
 
Join Date: Apr 2007
Location: South Florida
Posts: 4,057
Received 0 Likes on 0 Posts
Default RE: Question about gas to oil mixture........

The oil rate should be as recommended by the manufacturer.
Most of the oil is wasted in order to some of it to reach and lubricate the vital points.
However, the manufacturer has taken that into consideration for the proper cooling of the engine, since the wasted oil cools it down.
For way too much oil, the spark plug would show much carbon deposits.

When the engine and carburetor are cool, the mix has more air and less fuel (cool air is denser and fuel condensates on the cold metal surfaces), hence it is leaner.
When the engine warms up, the situation reverses, and the mix moves to the rich side.

For that reason, the engines should be tuned while warm.
It seems to me that the low end of your engine is too rich, interfering with the transition.
Old 08-30-2009, 05:52 PM
  #6  
Gray Beard
My Feedback: (-1)
 
Join Date: Apr 2003
Location: Hemderson, NV
Posts: 14,396
Likes: 0
Received 7 Likes on 7 Posts
Default RE: Question about gas to oil mixture........

It's a tune thing probably?? 32:1 was almost always the standard oil mix but with a lot of the new oils things have changed. I have one engine that calls for 100:1 synthetic but it didn't run very well with it so I went back to the old stand by and it's been running great ever sense.
Old 08-30-2009, 06:06 PM
  #7  
tryan02
Senior Member
 
tryan02's Avatar
 
Join Date: Aug 2007
Location: Canton, MO
Posts: 153
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Question about gas to oil mixture........

Is this a new motor?
If so its just a breakin period my Zenoah G26 did the same thing and now it scrams along with the best of them after a gallon of fuel through it but was reliable after just a couple tanks of revving it up in my drive.

I just started flying a gasser and love it I am just about done with nitro's. Oil content is not like nitro content the oil is only for cooling the engine to much and your just gonna ruin the spark plug. Gas engines are definitely different than nitro just let it get hot before you fly otherwise she will sputter at you. Had mine doing it to me today it was 55º this morning and I tried to take right off after starting and go into aerobatics. But after a couple passes at full throttle she never complained again.

Oh and I found out the label on my oil bottle was mislabeled and ran my first gallon at 24:1 now half through my second gallon at 32:1 doesnt seem to run any different to me.
Old 08-30-2009, 09:34 PM
  #8  
Matt
Thread Starter
My Feedback: (1)
 
Join Date: Feb 2008
Location: Hammond, IN
Posts: 98
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Question about gas to oil mixture........

lnewqban: this motor is a US 41 from what I understand. I don't remember, but I might have made the mixture 32:1 so that everything could get lubricated again and broken in again as well. It did look kind of oily in side....not excessively, but i think the spark plug did have a good little layer of probably carbon around the ring that's inside the engine. In fact i think the plug really needed to be cleaned too. I’ll have to look that up what the mixture was. If you know how to work the low and high screws, PLEASE explain to me how to adjust them. I heard something about you will basically only need to touch your high screw....and your low screw is ONLY to get your plane to idle.....? Is that right?

Gray Beard: It's tuned to the best of my ability...the high side runs great......and it DOES idle pretty smoothly....it's just the transition from idle to about half throttle is the problem... Beyond half it's okay.

tryan02: No this is defiantly not a new motor. lol this motor has to be probably 10 years old. I got it used basically. The box that it came in had a sticker that had "Arizona" on it.....so I’m thinking that the person who had it before me got it rebuilt. It looked almost bran-spankin-new when I got it......(The engine does have a magneto on it to if that rings a bell for anything) This gasser is not your ideal airplane to get you hooked on it. I have an 80-inch wingspan and it weighs 20 pounds!!!!!!!
Old 08-30-2009, 09:42 PM
  #9  
ChuckW
Senior Member
 
ChuckW's Avatar
 
Join Date: Jun 2006
Location: Clovis, CA
Posts: 5,165
Likes: 0
Received 2 Likes on 2 Posts
Default RE: Question about gas to oil mixture........


ORIGINAL: Matt
I heard something about you will basically only need to touch your high screw....and your low screw is ONLY to get your plane to idle.....? Is that right?
Not necessarily. The low speed screw will affect idle mixture and mid-range so it does have an affect on the transition. I'd turn the low speed screw 1/16-1/8 of a turn at a time until it transitions well after 30 seconds or so of idling. My guess is that you'll have to lean it slightly (clockwise) so I'd start there. Hard to say without actually seeing it though so you may end up having to go the other way. Do this with a warm engine.

32:1 will be just fine. It's also easy to remember and measure 4 ounces of oil for 1 gallon of gasoline.
Old 08-30-2009, 10:02 PM
  #10  
Gray Beard
My Feedback: (-1)
 
Join Date: Apr 2003
Location: Hemderson, NV
Posts: 14,396
Likes: 0
Received 7 Likes on 7 Posts
Default RE: Question about gas to oil mixture........

If you go into the gas engine forum you can read up on how to tune a gas engine, there are several in depth threads on the subject. If you do a search there on your engine you will find a bunch of other people still using them and probably find all and any help you need. I have been using gassers for years and I still go there to find answers or help, even parts that I thought were out of production years ago.
Old 08-31-2009, 08:13 AM
  #11  
Matt
Thread Starter
My Feedback: (1)
 
Join Date: Feb 2008
Location: Hammond, IN
Posts: 98
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Question about gas to oil mixture........

I think you're right...i'm try leaning it out a bit then. It does seem kind of rich because the engine has to catch up with it self coming off of idle.

And I will definatly look up the gas thread too!
Old 08-31-2009, 08:29 AM
  #12  
mandtra
Senior Member
My Feedback: (29)
 
Join Date: Apr 2005
Location: clermont, GA
Posts: 344
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Question about gas to oil mixture........

Barring OTHER problems with your engine. This is how you tune. If it runs fair start with the HIGH side needle. FLY for five mins of so and if the plane surges at full throttle it's too RICH and will need leaning , if not land and check the temp with a quality temp gun. it should be around 195 or so. if it's more than 195 richen to cool the engine or increase the airflow. if it's way below 195 you need to lean a bit . usually on the low end i like to run very SLIGHTLY rich the low end will perform badly if it's even a little rich or a little lean. If it gurggles (some call this four stroking)at low rpms in FLIGHT it's a little rich , if it stumbles then catches up or stumbles and dies it is usually LEAN. adjusting one will slightly affect the other. but in saying that if you have the top end very RICH it could be flooding over to the low end. So like I said start with the top end FIRST
Old 08-31-2009, 01:14 PM
  #13  
Matt
Thread Starter
My Feedback: (1)
 
Join Date: Feb 2008
Location: Hammond, IN
Posts: 98
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Question about gas to oil mixture........

The top end i have tuned in pretty good and it sounds good!....i've flown it with the current settings that i have and the engine is right around the correct temp. SO gas is some what like glow then....sort of. lol So you're saying that my low end might be to lean then? I'm a little confused now.....[]
Old 08-31-2009, 05:22 PM
  #14  
tryan02
Senior Member
 
tryan02's Avatar
 
Join Date: Aug 2007
Location: Canton, MO
Posts: 153
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Question about gas to oil mixture........

SO gas is some what like glow then....sort of
I hope its not smoking like a nitro!!!!

In my .30 size helicopter I noticed oil content and nitro content change in nitro fuel from vendor to vendor due to their secret blends affecting tuning per brand. Dirty old pump gas is only gonna have so much octane regulated by local government. And the oil fortunately is up to you not very brand specific I have been using wallyworld briggs and stratton 8oz for $3.50 makes qty: 2 32:1 gallons and usually pull my plug and inspect and clean after a couple of days of flying 5-10 flights.

I would suggest not burning any more oil than 32:1 I made a mistake and trusted the upside down label on the bottle and mixed my first gallon at 24:1 left me with a dirtier plug and plane. Second gallon I am still on mixed at 32:1 is much better. I am considering moving up a bit somewhere between 32 and 40:1 my engine with recommended prop should turn at 4900rpm I am at 4400. but with it that close I may just leave it alone dont want to ruin a good thing.
Old 08-31-2009, 06:00 PM
  #15  
BarracudaHockey
My Feedback: (11)
 
BarracudaHockey's Avatar
 
Join Date: Jul 2003
Location: Jacksonville, FL
Posts: 26,959
Received 343 Likes on 274 Posts
Default RE: Question about gas to oil mixture........

Low end sounds rich. The biggest thing about tuning a gas engine thats different to me is needle sensitivity. When you're close, adjust the needles a screw driver blade width at a time.

Try leaning the low end, sounds like its fat during transition.

And if you want to clean out the engine, get some Royal Purple 2 cycle and mix it at 90:1
Old 08-31-2009, 08:26 PM
  #16  
Gray Beard
My Feedback: (-1)
 
Join Date: Apr 2003
Location: Hemderson, NV
Posts: 14,396
Likes: 0
Received 7 Likes on 7 Posts
Default RE: Question about gas to oil mixture........

There is about a nickles worth of difference between tuning a gasser and a glow, maybe only two cents if that. A high end and a low end. Set the high end first then the low. If it idles then let it do so for 20 or 30 seconds, crack the throttle open, if it dies right now then your low end is too lean, if it burbbles then the low end is too fat. Nothing to it if you don't over think it. When it goes from low to high smoothly then you adjust the high end one more time, bring it to max. RPM then back off a few hundred so it doesn't run lean in the air. Like any engine you need to know the working RPM range. Prop the engine so it never goes over the top of the engines RPM range or you will get a lean run.
Old 08-31-2009, 09:05 PM
  #17  
Lnewqban
 
Lnewqban's Avatar
 
Join Date: Apr 2007
Location: South Florida
Posts: 4,057
Received 0 Likes on 0 Posts
Default RE: Question about gas to oil mixture........


ORIGINAL: Matt

lnewqban: this motor is a US 41 from what I understand. I don't remember, but I might have made the mixture 32:1 so that everything could get lubricated again and broken in again as well. It did look kind of oily in side....not excessively, but i think the spark plug did have a good little layer of probably carbon around the ring that's inside the engine. In fact i think the plug really needed to be cleaned too. I’ll have to look that up what the mixture was. If you know how to work the low and high screws, PLEASE explain to me how to adjust them. I heard something about you will basically only need to touch your high screw....and your low screw is ONLY to get your plane to idle.....? Is that right?
Basically all carburetors operate under similar principles: mixing the proportion of air and fuel that best suit each regime of the engine.
More complex carburetors do that job better than simpler ones.
For high rpms there is a great suction in the throat and proper air-fuel mix is easier to achieve.
That suction is close to zero for idle rpm; hence, the carburetor needs a little help being fed with fuel: that is the low end circuit supply controlled by the low end screw.

For low end screw adjustment start from openly rich mix and lean it just a little at a time until reaching the optimum mix.
Run full rpms for short time between each idle adjustment, venting excess of fuel from the crankcase.
Each time you lean the low end mix, the rpm will rise up a little; then reduce the minimum rpm by closing the flow of air with the butterfly valve.
Repeat that process until you reach the point where one hair more of leaning reduce the rpms, instead of increase them: that is the point you were looking for.
You can leave it there and check transition, or richen a hair back.
Old 08-31-2009, 10:11 PM
  #18  
Matt
Thread Starter
My Feedback: (1)
 
Join Date: Feb 2008
Location: Hammond, IN
Posts: 98
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Question about gas to oil mixture........

Gray Beard: What if it blurbs and then dies? Is it still a little rich.

And no it's not smoking like a nitro.......lol

Also to i forgot to mention is that a few times when i was landing and after the wheels got back on the ground, the engine died on me....so i am still thinking that the low end is still a little rich from what everybody has been telling me.


Thanks for all the information guys! It really helps me out when i need answers to my problems! Hopefully this Saturday when i'm out flying i'll be able to play around with it for awhile to get it right..........................hopefully. =)
Old 08-31-2009, 11:57 PM
  #19  
andrew66
Senior Member
 
andrew66's Avatar
 
Join Date: Jan 2006
Location: Brandon, MB, CANADA
Posts: 1,057
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Question about gas to oil mixture........

One thing with a gasser is: DO NOT go rich of peak. set the high end for max rpm and keep it there. Gassers have a carb with a regulating pump. Kinda like using a perry pump on a glow engine. It will not go lean in flight. Going rich on the high end will only foul the plug and leave carbon deposits on the piston and ring. This will cause more problems down the road. The low end will affect the high end. On initial startup, set the high end so its close, and then work on low end. Once the low end is set, then the high end will need to be adjusted again. With a gasser, a little goes a long way.

Happy tuning,
andrew
Old 09-01-2009, 07:30 AM
  #20  
Matt
Thread Starter
My Feedback: (1)
 
Join Date: Feb 2008
Location: Hammond, IN
Posts: 98
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Question about gas to oil mixture........

Yeah i know that gassers have a sort of pump opn them. and that you don't have to set them richer than they need to......but doesn't the engine lean out a git once it warms up?....therefore probably tune it when its warm then. lol
Old 09-01-2009, 10:43 AM
  #21  
Gray Beard
My Feedback: (-1)
 
Join Date: Apr 2003
Location: Hemderson, NV
Posts: 14,396
Likes: 0
Received 7 Likes on 7 Posts
Default RE: Question about gas to oil mixture........

Just like any glow engine if it blurbles then quits it has a fat low end, same with a gasser. I always go a tad fatter on the high end because the engine does unload in the air and you can go lean. The carb has a diaphragm inside that is the pump. There is also a very small screen inside that is a filter. If that screen gets crud in it then tuning the engine is always going to be a mystery. I got my G-62 in a trade and it had been in a crash. I cleaned the carb then fired up the engine and couldn't get it to run for beans?? I opened the top and that screen was packed full of nasty. Cleaned it out and it went into tune very well, two flights later and it ran for beans again. Got home and opened up the carb again and it was packed with crud again, not as bad but enough to mess up the tune. I also went to my local lawn mower/small enging service shop and bought the new carb kit they now make for this gas they are selling us with alcohol in it. Alcohol and rubber don't mix well!! If by chance you decide to rebuild the carb buy a can of the spray carb cleaner and make sure you blow out all the passages and jets!! The carb cleaner does a good job and I had a lot of crud in that carb. All is working well now.
I did find a Walbro site that has some good prints of the carb break down, ones that you can really read!! It helps a lot when I need part numbers. Nothing inside these carbs that most anyone can't figure out if you need a rebuild. Very easy!!
Old 09-01-2009, 04:26 PM
  #22  
k3 valley flyer
My Feedback: (18)
 
Join Date: Jan 2004
Location: Bourbonnais , IL
Posts: 549
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Question about gas to oil mixture........

The advice on tuning should help, but why do you let a gas engine run on the ground for 5 minutes?
Old 09-01-2009, 08:57 PM
  #23  
Matt
Thread Starter
My Feedback: (1)
 
Join Date: Feb 2008
Location: Hammond, IN
Posts: 98
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Question about gas to oil mixture........

Because i want to make sure it's running right....and after about two minutes...it started to blurb...........i;m a tinkering kind of guy. lol

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 -

Copyright © 2024 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.