doswings

I recently aquired a Top Flight Gold Edition P51 kit and would like to use gas rather than glow. The kit calls for a 120 size four stroke. I have a DLE 35 in a Stearman that I really like. Not being an engine guy was just wondering how a DLE 20 compares to a OS 120 power wise and if it would be a good choice for the plane.

Thanks,
Rich

ahicks

My Feedback: (2)

As you're in the gas engines forum, it's not going to be hard to guess the outcome regarding your question, so I'll be brief. I would go with the RA (rear exhaust) version of the 20. Also, make sure you consider the fuel tank issue. With gas it's going to be much smaller (lighter!) and you can put it where you want to, but most shoot for something close to the CG so CG doesn't change much full tank vs. empty.

doswings

Thanks for the reply. My concern is that although the specs on an OS120 4 stroke and DLE 20 are close in HP there's quite a difference in RPM The DLE is 2.05 HP at 9,000 RPM, the OS 2.07 HP at 12,000 RPM. I don't know the prop size used to generate the specs but do know the DLE will swing a larger prop. To me it seems as if there close but not having the engine background, I know some of the folks on this forum do, I like an expert opinion before deciding.

Truckracer

My Feedback: (19)

The main difference between gas and glo, as I'm sure you already know if finding a home in the airplane for the ignition module and its power source. If you go with the Tech-Aero IBEC or similar products, you can eliminate the ignition battery and power the ignition directly from the receiver battery. Another consideration is cooling and this is very important. You can get by with marginal cooling for a glo engine but not for gas. You will need to engineer your cooling system to guarantee the cooling airflow goes through the cylinder cooling fins and not just in the general direction of the cylinder as might be acceptable with glo. There are many threads on the various forums about this subject and tight, narrow cowls such as a P-51 are prime candidates for overheating if the cooling task is not addressed.

Now regarding power. As you noted the engines are rated to produce their power at different RPMs. Not really a big deal, you just have to prop accordingly. The neat thing about this is you can prop the gasser with a large diameter, low pitch prop and the airplane can have tractor like pull or you can reduce the diameter and increase the pitch if speed is you thing. Overall compared to standard 4 stroke 120 glo engines, I think I'd give the edge to the 20 when it comes to power. Not so if comparing to a YS! If comparing the 20 to an OS 2 stroke 120, the edge goes to the OS by quite a margin. The first post was not clear which engines were being compared, only that the kit recommended a 4 stroke. Frankly I'd consider a 30 - 35 if it would fit the airframe.

doswings

Thanks Truckracer,
This helps a lot. I'm comparing the DLE 20 to a new OS 120 pumped four stroke Tower sells and they recommend for the kit. I have a DLE 30 in a Great Planes Stearman and it does great, I had a Chinese gas 26 in it and with all the rigging and drag it flew well and to scale but it fell out of outside loops which would not bode well for a war bird. The Mustang's obviously a lot sleeker but if I could get a 30 into the plane I'd do so but there's just no room which I why I'm asking about a 20.

or170b

My Feedback: (3)

I am in the middle of building the arf version of this plane and I installed a 20ra in it. Everything fits great. I plan on using a 15x10 apc should do the maiden next week!

doswings

Thanks, good to know it fits. I just ordered one. Your a better man than me, I don't even pick up a transmitter until it's at lest 50deg.