RC India

hi
what is the equivalence factor of gas and nitro engines ?
meant to say that 26cc, 50cc, 100cc, 150cc etc are equivalent to respectively which size nitro engines ?

http://www.rcuniverse.com/forum/fb.asp?m=8480673

From a quick look around, it seems that the power/thrust etc are pretty much dependent on the manufacturer/model of the gas engine, so a direct comparison may end up being misleading. 

Others with more gas engine experience may please pitch in.  My personal gas experience is a Predator Gasser heli, which was 90 size, and was mounted with a Zenoah 20cc engine.

Hi Amir,

I mainly fly gassers although I have had tonnes of glow engines before. Initially, gas engines were very heavy, hence substituting them with a glow engine was not suitable unless the planes were designed for 50cc and above.

Anyway, today, zenoah has quite a good line up and the zenoah 20cc petrol replaces any .91-1.30 size glow engine. Its weight is lighter than an OS120 surpass. The engine is cheap to run, in-expensive(almost the same cost as an OS91 2 stroke), gives you about 7800RPM on a 15-5 and a 16-8.

Zenoah 20cc ~ OS/TT/ASP etc .91/1.20
Zenoah 26cc/RCS 26cc/RCGF 26cc etc ~ OS 1.60FX
Zen 45cc/3W50cc/ZDZ 50cc/or any other 50 cc ~ OSBGX1(35cc)/Moki 2.10 etc. Basically any plane that has a wingspan of 80" can accept a 50cc engine.

There is no glow engine bigger than the OS BGX1(35cc) and the super tigre 42cc glow engine. However, using such big glow engines increases the cost of fuel tremendously as their consumption is extremely high. For example if you use a 420cc tank, the OS BGX1 will give you about 8-10 minutes max, but a 50cc petrol engine will give you 18-25 minutes depending on if the engine has been leaned out or not.

Hope this answers your question. If you have any more specific questions, I will be happy to try an help.

I beg to differ with the comparison made, from which it appears to show that a 20 cc gas engine is equivalent to a 1.20 size (roughly 20 cc ) size glow. However a 20 cc may be substituted for 90 size ( 14.74 cc) glow

The glow would be able to deliver more power for the same displacement on same prop etc, this is where BTU, air volume required to burn a unit of fuel, calorific value, energey density etc of different fuels come in. Yes however I do agree that fuel consumption would be much higer in a glow than a gas.

Again replacing same size glow with same size gas may work if you are looking for sedate scale (not even scale warbird capability) type of flying but then this equation takes on different dimesion if you want any decent aerobatics capability.

There are various threads on this topic at RC Gropups and RC Universe. 

I do agree that a gas engine which is rated as 20 cc may not be equal to a glow engine of 20cc, but I am running 5 zenoah 20's, and so is another flyer who also swears buy this engine and no matter which 1.20 (20cc)glow engine you use and even if you run 50% nitro, the Zen 20 is way more powerful. You may not achieve 9000 RPM, but it still is more than equal to a 1.20 size glow engine. I'm not selling these engines or playing a "i'm right" game, but I think that after running 5 of these engines.................................  :)

Anyway, the other stuff you mentioned is true.

I was just wondering , which engine give more fuel efficiency ?

happy flying ,
sahevaan

gas

Agree with the aviator GAS ;D

I have always wondered why no gas engines below 20cc. Any simple reason for this?

You can make a small petrol engine of less than 20cc size. In fact, people have converted glow/deisel engines to run on petrol.

For, aircraft use petrol engines <20cc is of no use as, the additional overheads like the ignition system, spark plug adds to the weight. So, if you ask me the power to weight ratio of small pertol engines forbids them for aircraft use. 26cc is the point where you see pertol engines to have some useful transition.

However, for land vehicles you may try it out. But again you end up with a large engine at around half the power of a equivalent glow/deisel engine.

-Ismail

Wish there were smaller gas engines with similar power to glow ones, just because of the situation with acquiring nitro/methanol in many parts of the country. 

How come no one has really shrunk the size of everything proportionately (including spark plugs etc) ?

I have heard of Glow to Diesel conversion but never glow to petrol. A guy in US has done it successfully on land models, but requires extensive changes as far as I heard. Unless we have converted engines readily available, doesnt make sense to me. Also requires special Diesel blend, Regular pump diesel wont work.

http://davisdieseldevelopment.com/

Yes, Glow to petrol conversion is tricky. You not only need to have the sparkplug and the ignition but also need to change the compression ratio. May be need to fiddle with the piston rings etc,.. Check out for spark ignition engines. They run on both glow and petrol.. of course, they need sometiming changes. I have seen one guy who converted a 60 size to run on petrol but couldn't locate the link.

Alternatively, Gas/Glow conversion is very convinent. You can convert any gas engine to run on a mixture of glow and petrol. The ratio is 1/3 glow fuel (with 10% castor) and 2/3 petrol. The engine, instead of having a spark plug will have a glow plug and there is no need of ignition system. Lets say you convert a 26cc weedeater engine, you get the power of a 120 sized glow engine for a very cheap price. Power/weight will be also be same if not better than the glow engine.

Here is the link to once such conversion -> http://www.rcgroups.com/forums/showthread.php?t=793079

-Ismail

wow i have seen lots of conversion glow to diesel etc but not a gas-glow conversion this is superb

thanks for posting the link ismail

regards

sahil

hey i thought diesel engine were more efficient then glow/gas ??

sahil

17 cc Gas is available and I have one thanks to Aviator.
But then are we all not forgetting that all early spark ignition engines were run on Petrol so to say that gas engines smaller than 26 cc is not availbe is incorrect.
 

How would you compare the power output of a 4 stroke gas to a 4 stroke glow of the same size.
What I am looking at is a Saito 120 4 stroke versus a Saito 20 CC 4 stroke.
The plane i want to power it is a Phoenix Model Accipiter, which is a 90 size model.
From the reviews, it seems that it wouldn't mind the extra weight, I just need to be sure on the power.
Let me know if you think the power on the FG-20 4 stroke would be enough.
-Gaurav

I didn't know that 4 stroke model gas engines are avialable. Due to the power to weight ratio, i thought gas technology has reached only the 2 stroke stage for model engines.
Glow to gas conversion is possible, but not worth it.
Miniature spark plugs are available along with ignition kits.
but you need to change the carb as well. Gas engines run far leaner than glow and adjusting the needles of a 1.20 or 1.40 glow carb to run on gas won't work at least won't work well.

I have a .40 Irvine deisel and a Davis conversion head for a super tigre .40. both r/c. The deisels would best compare to a 60 4 stroke.
They spin slower with more torque. it swing a 12X6 MAS at 10,000 rpm with diesel. you don't get the screaming power of a 2 stroker.

And they are definitely more economical than glows as far as fuel efficiency goes. Bigger diesels are much easier to run and tune as compared to the 2.5 cc C/\L engines.
Avijit

Read through about 30-40 pages on glow -gas in RCG and RCU.
There is a report about using a glow-gas mixture in a  OS FX 60.
So i tried the following mix in my ASP .40 engine.

Glow plug OS F (the 4 Stroke plug)
Methanol 35%
Premium petrol 40%
Castor oil 15%
Synthetic lube 5%
Nitro 5% and
Ether 2% ( as a solvent because methanol and petrol don't mix well)

The engine ran with the glow booster disconnected.
It was dark and drizzling, so i didn't do any tacho readings, but the power appeared less than by regular fuel which is Methanol 75% Nitro 5% Synthetic oil 5% and Castor oil 15%.

Will experiment further and report.
The reason for going to all this trouble is that glow fuel  is expensive and hard to come by in Chennai.
so if a mixture of petrol and glow fuel work it will strtch our preciuos stocks of fuel further.
Avijit

FYI Saito has introduced a range of 4 stroke gassers. Expensive!!