2/4 stroke gasser question
 

If a plane called for a 15cc 2 stroke gasoline engine what size 4 stroke would be needed? I am guessing that just like in glow engines, you have to go up a few sizes when using a 4 stroke. Thanks fellllllas

To add to my question, 0.61-0.91 2-stroke glow, 1.00-1.25 4-stroke glow, 15cc 2-stroke gas is what the plane calls for as far as engines go. I have heard gas has even less punch than glow so would a 4 stroke 1.00 glow engine be more powerful, for lack of a better word, than a 4 stroke gas equivalent to 1.00?

What plane is it? 15cc correlates to .90ci generally, 20cc correlates to 1.20ci generally, 10cc correlates to .60ci generally. I say generally because not all gassers are created equal, but that would get you in the ball park. The 15cc or 20cc is pretty close to the 1.0ci.
Edwin

Hi Edwin. Its the Hangar 9 P-47D-1 ARF. I figured since it says 1.00-1.25 in glow 4 stroke that maybe a 4 stroke gasser in that range would work but wasnt sure. Horizon has a sale on the Saito FG17 that I would like to jump on if it would be adequate.

While not an exact science, you can get pretty close by just looking at the recommended props and seeing what RPM it will turn them. The tachometer readings forum is helpful for that since it gives real world data instead of the wishful thinking of the factory specs. Saitos are more powerful than most other 4 strokes in a given size, so I'd expect the 17cc to fly the plane fine. Of course, that's not all of it. The gasser is going to make its power at a lower RPM, therefore will need a higher pitch prop. That means it will accelerate differently and likely wind up with a different top end speed.

Nice plane, a .91 size 4-stroke will do fine for scale flying with a some extra for emergencies. I'm helping a former student right now with that plane putting in an old OS.91fs. I have three H9 fighters (F6F, P-40, P-51) and all fly with .91 4-strokes. Its said the perfect match is the saito 1.00. People have put up to 20cc gassers in some of the H9 fighters. I personally wouldnt do that due to the extra weight. The stock landing gear works mediocre up to about 9lbs total weight. More than that, and they suffer. The struts are spindly and the plane sometimes does a chicken hope down the runway. Looks embarrassing. The saito 1.00 will help keep the weight down. I modified mine by putting the servos all up by the CG, made a new servo tray. I didnt put the servos in the tail like the instructions stated. For every oz in the tail, you need about 4 oz up front to account for it. Except for my P-51, that was a swap meet plane. It will still fly alright with tail servos, I just dont like them back there.
Edwin
I missed the 4-stroke gasser point completely. Jester has it right.

So theres no real difference between gas and glow 4 strokes of the same size?

Well, yes there is. But in my opinion the difference is not that much. And this is just my opinion.
Edwin

I would agree that the difference isn't that much.

But there is a HUGE difference that does come into play with glow vs. gas engines

Glow fuel - $20/gallon
Gasoline - $4/gallon

:D

Ken

Good enough for me, as long as it will make the plane go!

Yes this is why I am considering going the gasoline route, I'll miss the smell of the glow exhaust but for the savings, I am willing to sacrifice.

I should mention a buddies experience with his first OS 40cc gasser (4-stroke). He had a lot of problems with it initially which turned out to be operator error and some setup issues. After he figured it out he absolutely loves the engine. Its just a bit different in operation and setup. Sounds great too. You might run into the same scenario, just stick with it and you'll get a lot of help here and eventually figure it out if there are problems.
Edwin
Yeah, my whole fleet is slowly converting to gas. I have one of the EVO 15cc to try out on a TF Corsair.

Thanks for the input guys

If that is the new razorback version (http://www.hangar-9.com/Products/Def...ProdID=HAN2790), go with a 20cc gasser like the DLE20. While H9 state that the evolution 15cc gas motor is fine, you'll notice in their promo video that they actually state that they are using an Evolution 20cc gasser themselves on the plane that is shown flying.
The other thing to note, is that specific plane is a little bigger than previous 60 sized P47's at 67" wide (the old bubble top version was 65"), and with a cowl that size, you'll fit a 20cc gas motor in and it won't even be visible. Not to mention cheaper to run, BUY, giving you longer flight times, no oil mess like nitro etc etc etc.

Also, as for your question "So theres no real difference between gas and glow 4 strokes of the same size?", as a DLE20 has the same capacity as a 1.20Ci motor, you'll have fun finding a 1.20Ci 4 stroke nitro motor that produced the same amount of power as the DLE20 does. The DLE is a right little brute of a motor. And the DLE20 is normally cheaper to buy that a 1.20ci nitro 4 stroke motor.

Well just cause they put a 20cc for the video doesnt mean I need it right? And isnt that DLE20 a 2 stroke? I am strictly 4 stroke, I cant take the chainsaw noise

If your adamant on a 4 stroke option, perhaps go for a Saito FG20 gasser. It may lack a little in power over the DLE, but you'd have the 4 stroke sound track that would more easily drag her around, and still have all the benefits that come from going with a gas power-train.
As for their motor choice in their promo video, I'm sure that with an vast supply of options for motors from Saito & Evolution, that they are going to install the one that best works for the given model. One where it is correctly powered, and not too heavy for that given plane.
I may be a little bias when it comes to gas, as even though I have two gas powered planes in the works (a H9 Blue Nose P51, and a 73" Sbach), I still have a nitro heli and a nitro powered Yak54 that have been my go to models for some time now ..... but I can say hand on heart that I'll never buy another nitro model, they will all be gas in the future as I cannot see any positive on going to nitro for anything I want to fly, gas always makes sense over nitro (to me at least).

4cc's will make that big of a difference? The 17cc is $330 and the 21cc is $500, Thats a big difference in price for 4 CC's.....

It's all relative I guess. While the FG17 would odd's on do just fine, when your talking $330 vs $500 for the FG21, I wonder if the extra $80 the FG17 would cost over the DLE20 just to get a specific sound, even when it's still not a scale sound, to (personally) be a waste of money for a a motor that is less powerful.
The only thing to worry about is how heavy that new P47 would be. My H9 P51 which is done with almost the same scale level is a heavy pig, which was part of the reason I went with the DLE20 - well that (power), cost, running cost, flight times etc etc. NB, I just checked their website, and at a listed 11.5lb, she is just like my H9 P51 - ie she's FAT! (LOL)
At the end of the day you'll get what you want to get, and if it works, it will be the right decision regardless of what I or anyone else may have done in your shoes. All the best!!

Yeah I don't go with 4 stroke to achieve a scale sound, they arent full sized aircraft so of course they wont sound like full size aircraft, but to me 4 stroke is much nicer of a sound than a 2 stroke. To me its well worth the price

Let us know how the build goes, as I'd be really keen to see a thread on her build that's for sure (the P47 Razorback is my all time favorite warbird).
Like I said, all the best with her!

I have a friend I was telling Bob about that went with the DLE 20. That plane is going to fly awesome! Bob I am looking over on the Warbirds site and couldn't find your build thread.

So Bob. That's at least three of us.....:D that want to see you put this bird together........ Waiting..........:D :D :D

kiwi and I are on the same page...but I have to say, I have two, P-47, and Spitfire..... will never try to pick just one. :confused:

But Razorback over Bubbletop....hands down Razorback :D