Do any of you guys have any experience with Magnum engines converted to stunt engines.  They have a .25XLS with remote needle valve.  I have also seen a .28XL on the auction site and I was curious if they would make decent stunters.

Thanks,

Hi Jerry,

Phil Granderson was the first I know of to use the "square head" Magnum XLS series.   He used the .36 in a full size stunter w/pipe, but I am sure he also used the .28XLS in a Classic era model.

They are high rpm "wet 2" engines and I don't know, personally, of anyone using them in a 4-2 mode.  We have used the Magnum .36XLS, stock, in a few airplanes and they worked very good.  They are not comparable to the Aero Tiger .36 since they run in a different manner, but put out plenty of usable power.  A 4" pitch prop is recommended.  Best we used was a Bolly 3 blade cut to 10".

Big Bear

Do any of you guys have any experience with Magnum engines converted to stunt engines.  They have a .25XLS with remote needle valve.  I have also seen a .28XL on the auction site and I was curious if they would make decent stunters.

Thanks,

I ran a Magnum XL .25 on a Pat Johnston "Stunt Trainer". I was quite happy with it, and ran a 9-4 Taipan prop. I tried some APC props, but don't recall which, except the 10-3, which wasn't fast enough.  Mike Haverly ran a Magnum XL .28 in his OTS Ringmaster for awhile, and liked it. He ran a 10-4 APC. These two are built on the same case casting, and usually that means the bigger displacement is the lighter.

The .25XLS would be an interesting engine to me. Assuming the design follows the .36XLS, the cylinder stops at the top of the piston at TDC. The head simply sits atop the cylinder. The ST G.51 does this also. It really doesn't make a lot of sense on an ABC/AAC/ABN setup (the Magnums use real chrome, so ABC), but the .36XLS is a wonderful engine, and I would expect the .25XLS to be very worthy of some CL flying. The 9-4 or 9.5x4.5 APC's would be my suggestion for possible props, along with a .257" venturi and 10-22 fuel. Assuming the muffler bolt pattern is the same (and they tend to do that at Magnum), any Fox or OS muffler should fit, but the Magnum muffler is not a bad unit for what it is. The point is that you should have a lot of options, from light to heavy, to help with balancing.

One thing they did when they redesigned the .36 was that they changed the mounting bolt pattern, which I think is inconsiderate, if not totally stupid. But they are R/C engines, and they're always mounted on those cheap plastic mounts that can be easily replaced or modified.  Don't expect to be able to swap between a .25XL/.28XL and .25XLS.

While I have not actually run a Magnum with the RNV, I have looked closely at their RNV unit and found it to be of excellent quality, and I think you would find it to work well. My tests included wiggling the NV to check for thread fit (very nice) and pressure test in closed position (seemed 2b an excellent seal).    Steve