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Author Topic: Altering an engine to use fuel sans nitro?  (Read 1447 times)

Offline frank mccune

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Altering an engine to use fuel sans nitro?
« on: October 22, 2021, 06:14:36 PM »
      Hello All:

      What modifications would one have to do to an engine to enable it to run well on no nitro fuel?

       Tia

       

Offline Brian Hampton

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Re: Altering an engine to use fuel sans nitro?
« Reply #1 on: October 22, 2021, 06:39:58 PM »
Short answer is none, all glow engines work perfectly well with zero nitro but to get the most power from zero nitro fuel the compression needs to be raised to around 13.5:1 although all out power isn't really necessary for stunt.

Offline frank mccune

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Re: Altering an engine to use fuel sans nitro?
« Reply #2 on: October 23, 2021, 08:49:21 AM »
     Hello:

     Thanks for the replies!

     I have no idea as to how the engine has been run in the past.  It is an O.S .35S that I have only used 5, 28 castor oil in it since I have owned it.  I am contemplating using 5,10,10 in the future.  It runs very well on the 28% castor oil mix but I am attempting to simplify my fuel inventory.  As of now, I use three glow mixes and one Diesel mix. Lol. One mix is 20% synthetic oil and NO nitro. Lol

     Of course my Diesels require no nitro.  I was planning to fly three Diesels today but I was rained out. Lol

     Stay curious,

     Frank

Offline Dan McEntee

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Re: Altering an engine to use fuel sans nitro?
« Reply #3 on: October 23, 2021, 01:09:48 PM »
     Hello:

     Thanks for the replies!

     I have no idea as to how the engine has been run in the past.  It is an O.S .35S that I have only used 5, 28 castor oil in it since I have owned it.  I am contemplating using 5,10,10 in the future.  It runs very well on the 28% castor oil mix but I am attempting to simplify my fuel inventory.  As of now, I use three glow mixes and one Diesel mix. Lol. One mix is 20% synthetic oil and NO nitro. Lol

     Of course my Diesels require no nitro.  I was planning to fly three Diesels today but I was rained out. Lol

     Stay curious,

     Frank


       The main short coming of the OS.35S is the rod, it tends to wear out quickly . Some cottage industry guys were making replacement bushed tods and you may try locating one of those if you do anything to boost the compression for no nitro. It may run fine as is but need some nitro fuel as a prime to start.
    Type at you later,
     Dan McEntee
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AMA 480405 (American Motorcyclist Association)

Offline Dan Berry

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Re: Altering an engine to use fuel sans nitro?
« Reply #4 on: October 24, 2021, 10:32:39 AM »
Generally, an engine set up to run FAI fuel uses a higher compression ratio. That gets the power back but adds finicky needle settings to the mix.

Offline Dave Hull

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Re: Altering an engine to use fuel sans nitro?
« Reply #5 on: October 24, 2021, 10:00:06 PM »
You may not like the longevity of the .35S on your proposed(?) 0 nitro-20 oil mix. Especially if it comes out of the jug your followup reply describes as all-synthetic.

In contrast, you say it "runs very well" on 5n-28castor, so if you are going to use it much, and have already gotten comfortable mixing fuel, just mix what you need, and enjoy the trouble-free performance.

Switching to less oil will mean less lubrication for the big end of the rod. Trying to increase the compression to get back the power lost by eliminating the nitro may end up with different impulse loads on the rod bearing. If the engine already has the brass-bushed big end, that would improve your odds. If not, stay curious--about where to find a replacement rod.

Dave


Offline Christopher Root

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Re: Altering an engine to use fuel sans nitro?
« Reply #6 on: October 28, 2021, 03:46:49 PM »
I've tried 0% nitro fuel in several engines (Enya and OS mostly) with almost no luck. Is this typical? When folks say that the compression needs to be increased, does that mean milling a new cylinder head to decrease combustion chamber volume, or decrease deck height?

Offline Brian Hampton

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Re: Altering an engine to use fuel sans nitro?
« Reply #7 on: October 28, 2021, 07:06:54 PM »
I have to admit I'm baffled as to why some seem to have trouble using zero nitro fuel because I've never used it or found any need for it. Starting with a Merco 35 back in the mid 60's then progressing through an Enya 45 model 6001, ST G51, Stalker Pro 61RE, OS 40&46 VF, Irvine 40RLS and Enya 61CXLRS, all of them were one flick starters and dead reliable. All of them were stock standard except for the Enya 61 where I eventually raised its compression just to see what difference it made.

Offline Dave Hull

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Re: Altering an engine to use fuel sans nitro?
« Reply #8 on: October 30, 2021, 06:15:33 PM »
Brian,

It's because the Coriolis force acts in the opposite direction here in the USA. However, if we install a reverse rotation crank it is super easy to get good runs--and good starts--with no-nitro fuel. But then we have to find a prop made in the Southern hemisphere because, you guessed it, otherwise the engine bogs down due to the orientation of the plastic molecules as the prop solidified in the mold. It's all in the science....

The Divot

Offline Dennis Toth

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Re: Altering an engine to use fuel sans nitro?
« Reply #9 on: October 31, 2021, 09:22:58 AM »
Brian,
In your post do you mean that you don't use nitro fuel or see a need for nitro fuel? How do you run your engine - 4-2-4, or High rpm/Low pitch? As I understand it, setting up for a reliable 4-2-4 is more difficult with no nitro fuels especially with compression ratio below 10:1.

Chris,
To increase compression yes you need to decrease volume in the combustion camber. Some engines come with extra gaskets and you can remove one (or two if they have three) or make a new gasket from thinner material. The other option is to get an aftermarket head designed for high compression.

Best,    DennisT

Online Robert Zambelli

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Re: Altering an engine to use fuel sans nitro?
« Reply #10 on: October 31, 2021, 01:01:55 PM »
I did some flying with Tom Dixon a few weeks ago.
He flew a Chief powered by a Brodak 40.
He removed the head gasket and ran zero nitro fuel and the engine ran perfectly.
I think it was 22% oil but I'm not positive.

Bob Z.

Offline Brian Hampton

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Re: Altering an engine to use fuel sans nitro?
« Reply #11 on: October 31, 2021, 04:26:02 PM »
Brian,
How do you run your engine - 4-2-4, or High rpm/Low pitch? As I understand it, setting up for a reliable 4-2-4 is more difficult with no nitro fuels especially with compression ratio below 10:1.
Dennis,
It depends on the engine and how it runs at the speed I'm comfortable with flying. With my G51 I ran it in a continuous 4 stroke for the whole flight while the Enya 61RE provided a magnificent 4-2-4 run on its first flight so I left it at that (why fiddle with perfection? :).


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