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Old Oct 26, 2011, 12:30 AM
A posse ad esse
United States, FL, Tampa
Joined Feb 2011
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What's the best bang for the buck in Gas Engines?

Actually, I have several questions about gas powered engines, so maybe I should include them in one thread. First, for a little background, I flew RC nitro powered aircraft for better than twenty years before I got out of the hobby in the 90's. Had a lot of success with nitro power and had no problems with them, both two stroke and four stroke. Now that I returned to the hobby over the past year, electric has been my main focus and mostly smaller model aircraft less than 60" wingspan. Electric has been fine for those and I am learning the in's and out's of electric power.

Now, I am ready to move on to some larger models but don't want to get back into nitro power and would prefer gas power. So, my questions are:

1. What are some reliable name brands to consider? I have seen a lot of different names, but am not familiar with any of the manufacturers as I was with nitro power.

2. How does the cc displacement of gas engines convert to the cubic inch displacement of nitro power? In other words, if a model would require a .60 nitro power engine, what is the equivalent gas power displacement that will give equal power and more or less equivalent weight?

3. Is there a chart or similar document that gives a modeler an idea of what cc displacement gas engine would be required on an aircraft by wingspan measurement and/or weight?

4. I have three builds I plan to do in the near future: a Proctor Antic Bipe of 60" wingspan, a Proctor Nieuport bipe of approx. 60" wingspan, and a scratch build of a Pitts S-2 at 60" wingspan. Any suggestions on the proper displacement gas engines on these three models? Of course, I want the Pitts S-2 to perform aerobatics so power is essential for that model.

Thanks for any help and suggestions you can provide.
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Old Oct 26, 2011, 01:41 AM
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CustomPC's Avatar
Australia, NSW, Cherrybrook
Joined May 2004
1,534 Posts
Hi,

Gas engines have always been around for large models but in the last year or so there has been a surge in the smaller sizes of gas engines and they are becoming quite popular and a more viable power plant for small models.

With this surge has come an influx of cheap Chinese made engines in all sizes starting at 15cc and going up from there.
The quality of some of these engines varies so it's wise to do a but of research in the forums for any brands you may be considering.

A gas engine will always be less power than a matching size glow 2-stroke, however the torque curve and power output will be very close to the same sized 4 stroke.

I don't know what size your models are in glow speak but the following is a rough indicator.

.60 sized 2-stroke = .91 4-stroke = 15cc gas

.75 sized 2-stroke = 1.00-1.15 4-stroke = 17cc gas

.90 sized 2-stroke = 1.20-1.50 4-stroke = 20cc gas

1.20 sized 2-stroke = 1.80+ 4-stroke = 30cc gas


The DLE 20cc is in widespread use now and has become "the" engine of choice due to it's quality and power. Personally i think it's a little too much for a .60 sized model but there are plenty of users who have shoehorned them into a .60. If the model can handle the weight up front then the DLE is the one to get.

I have been experimenting with an NGH 17cc in a .60 sized model and it is a nice fit. It's early days with this engine so i'm not going to vouch for it until i've had some more time with it and can assess it's longevity.
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Last edited by CustomPC; Oct 26, 2011 at 01:50 AM.
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Old Oct 26, 2011, 06:56 AM
Registered User
South Africa, WC, Cape Town
Joined Dec 2009
1,401 Posts
Quote:
Originally Posted by daddyrabbit1954 View Post
Actually, I have several questions about gas powered engines, so maybe I should include them in one thread. First, for a little background, I flew RC nitro powered aircraft for better than twenty years before I got out of the hobby in the 90's. Had a lot of success with nitro power and had no problems with them, both two stroke and four stroke. Now that I returned to the hobby over the past year, electric has been my main focus and mostly smaller model aircraft less than 60" wingspan. Electric has been fine for those and I am learning the in's and out's of electric power.

Now, I am ready to move on to some larger models but don't want to get back into nitro power and would prefer gas power. So, my questions are:

1. What are some reliable name brands to consider? I have seen a lot of different names, but am not familiar with any of the manufacturers as I was with nitro power.

2. How does the cc displacement of gas engines convert to the cubic inch displacement of nitro power? In other words, if a model would require a .60 nitro power engine, what is the equivalent gas power displacement that will give equal power and more or less equivalent weight?

3. Is there a chart or similar document that gives a modeler an idea of what cc displacement gas engine would be required on an aircraft by wingspan measurement and/or weight?

4. I have three builds I plan to do in the near future: a Proctor Antic Bipe of 60" wingspan, a Proctor Nieuport bipe of approx. 60" wingspan, and a scratch build of a Pitts S-2 at 60" wingspan. Any suggestions on the proper displacement gas engines on these three models? Of course, I want the Pitts S-2 to perform aerobatics so power is essential for that model.

Thanks for any help and suggestions you can provide.
Ok here my take on it.

ci to cc conversion. Every .60ci = 10cc

In the .60 (10cc) to .91 (15cc) category there are not many choices.
NGH engines and RCGF play in that area.

1.20 (20cc) to 1.40 (23.3cc) or 1.50 (25cc) there are more choices and there are known performers that rival glow engines of similar displacement.
the DLE 20cc is the pick of hte bunch at that displacement then for the larger displacements you are looking at MVVS or Evolution Engines 26cc.
All of these are excellent engines and are very strong performers. they may not rival the 2 stroke glows for absolute horsepower output but they do swing larger props and thus can produce more thrust and hence are better choices for #d type planes or even aerobatic planes. I use a DLE20 in a 1.20 size pattern plane with excellent results.

In the 1.60 (26.66cc-1.80 (30cc) size I think the petrol engines really start to come into their own. There are plenty to choose from:
DLE30
Mintor 33
RCGF 32
OS GT 33
MVVS 30 are all good choices. I have gone on a limb with the ODS because it is only just released and I have not seen one but OS reputation is fairly good. Other may differ...

a 60 inch span Pitts is around a 30cc size so you're looking at all up weight of around 5kg or 11lbs. this wil provide #d type performance from any of the engines listed above. If you keep the weight below 11lbs then you are really looking at a rocket ship.
Bear in mind that a Biplane has a whack load more drag than a monoplane so its not going to be fast but will hover.
Even a DLE20 would fly it but you won't have fantastic vertical due to the the drag.
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Old Oct 26, 2011, 08:26 AM
A posse ad esse
United States, FL, Tampa
Joined Feb 2011
917 Posts
Thanks guys! Looks like the DLE 30cc would be a good choice for me for the Pitts. For the Nieuport and Antic bipes, could probably get by with a 20cc maybe as they will be scale flyers. Doing a search, it looks like DLE are well supported in the USA with service and parts and the price is good, too.

Couple of other questions: Do these engines come with a template for drilling the props for the adapters? What is a reasonable size fuel tank to consider for these engines. Not familiar with their fuel consumption rates.
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Old Oct 26, 2011, 04:53 PM
SBP
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United States, PA, Waynesboro
Joined Aug 2011
97 Posts
I am thinking about taking the .61 nitro engine out of my Thunder Tiger Trainer and replacing it with a gas engine. If I understand correctly a 15 cc gas engine should have more than enought power for this plane. I'm new to RC airplanes and the grandchildren and I have been flying electric planes. Changing the plane to a gas engine would seem to be a good idea compairing the price of nitro to gas. Any advice would be appreciated. Thanks
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Old Oct 26, 2011, 05:06 PM
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South Africa, WC, Cape Town
Joined Dec 2009
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15cc gasser is going to weigh a lot more than a .61 glow engine, even if you take fuel into account. Also in terms of size the 15cc RCGF is not much smaller than a 20cc and a lot less powerful.
The 15cc NGH seems to be ok but I have run one myself so I can't swear on the bible that its good, just convey what others are saying. Its still rather portly...

I am ditching glow engines for anything below .91ci and going electric. ABove that its petrol/gasoline all the way. Reason is the smaller planes can be flown at smaller airfields and they make little noise so legal. Bigger planes need to be at bigger fields so noise is usually not a problem.

to replace the .61cu I'd opt for electric instead. Petrol starts to be really competitive from the 20cc class and up. Wait a year or so and there will be more options in the smaller sizes and hopefully they will outperform their glow counterparts. For now <20cc just does not hack it for me; not enough power to weight.
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Old Oct 26, 2011, 05:24 PM
SBP
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United States, PA, Waynesboro
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It's just something I thought would be a good winter project. I don't have a lot of money in the Thunder Tiger and to get everything to fly nitro would be money that could be used to buy a gas engine. I'm not looking for performance , just something that with more time flying ,a 10 and 11 year old would enjoy. Of course me too.
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Old Oct 27, 2011, 12:54 AM
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South Africa, WC, Cape Town
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Then I'd say opt for DLE 20 and shoe hoirn it in place.
The NGH 17 may be another alternative but have heard mixed reports about reliability.
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Old Oct 27, 2011, 01:05 AM
A posse ad esse
United States, FL, Tampa
Joined Feb 2011
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Tim

Do you have any idea what the fuel consumption rate is on a DLE 30cc engine?
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Old Oct 27, 2011, 01:58 AM
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tough to hazard a guess without knowing the plane drag your flying style etc.

but on a 12oz tank you will easy get 15min flight time
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Old Oct 29, 2011, 02:23 PM
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Istanbul, Turkey
Joined Aug 2004
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NGH 17 is OK now ,fixed with a new Walbro carb.Also good design with beam type mounts.
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Old Nov 01, 2011, 11:15 PM
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United States, NV, Las Vegas
Joined Apr 2011
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Quote:
Originally Posted by daddyrabbit1954 View Post
Tim

Do you have any idea what the fuel consumption rate is on a DLE 30cc engine?
1/2-3/4oz a min would be in the ballpark. 1oz if you fly hard.
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Old Nov 01, 2011, 11:36 PM
A posse ad esse
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Originally Posted by ScooterInVegas View Post
1/2-3/4oz a min would be in the ballpark. 1oz if you fly hard.
Man, that's fabulous fuel economy. I've got to get into one of these soon, like right after Santa season gets past us.
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Old Nov 02, 2011, 06:57 PM
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Quote:
Originally Posted by ScooterInVegas View Post
1/2-3/4oz a min would be in the ballpark. 1oz if you fly hard.
That's a good range. The rule of thumb is engine displacement = about 1 minute running at full throttle.

Thus. 30cc = 1.0144 oz.
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Old Nov 07, 2011, 01:28 AM
A posse ad esse
United States, FL, Tampa
Joined Feb 2011
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Didn't have to wait very long before I found a trade for a 30cc petrol powered engine for my 60" Pitts build. I traded for a 1.80 Syssa that came with some nice extras.
http://www.syssaaircraft.net/cart/pc...5&idcategory=2

Engine appears to have been very gently used with no signs of abuse or crash damage at all. Now I am more eager than ever to get started on my Pitts.

Do any of you guys have any knowledge of this engine? It's a beautiful piece of machine work and lovely to look at. Hope it performs as well as it looks.
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