RE: Biggest practical prop for .90 BSE
Hi Mike,
Sorry for the delay replying
The LX version of the .56 and .90L engines are those high timed for very high RPM.
The standard SJ-90L or BSE-90L do require correct prop selection, but offer a bit more in RPM target range.
First off, which aircraft are we talking about here?
Second, the 90L can be quite versitile with prop, depending on the exhaust system. With the stock muffler, you want to prop the engine for a ground peak rpm no less than about 13,000 rpm .. Engine is good with anything up to a 12x8, although a 12x6 and 12x7 seem to be perfect. It will run fine with a 13x6, as long as its a decent prop (not all 13x6 blades will turn the same rpm - a Zinger 13x6 no, APC probably ok , Vess 13x6 should be good too)
Just make sure you can get the engine up in rpm, and launch it down around 12,500 or so.
If you switch to a turbo-jett muffler, or try the "torque" version of the jett-stream, the 13x6 or 13x8 are well within reach. Those are tuned for more the 11000 - 13000 range
If the longer jett-stream will fit, Id try that.
Bob