bob27s
Posts: 4821
Joined: 4/9/2002
From: Cleveland,
OH, USA
Status: offline
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Hi Jamie
Thanks for writing.
Quick question, then on to your questions a bit.
When did you purchase the OS160 muffler? And you noted the Jett 120 was a couple of years old so we know that.
There have been reports to us of a few folks having no success with the OS160 and the turbo. Same thing you noted, the engine got hot. On the other hand, my own 160 runs great, and there are a number of pilots flying the combo who love it. Does not seem to be any rhyme or reason why one person's works, and why someone elses does not.
Your questions...
First, prop selection. My OS160 on the turbo produces a lot of torque. I prefer 18x6 18x8 and 20x6 props. The 17x8 should be ok too. But Ive found the bigger props worked better.
The Jett 120 on a turbojett you would want to run with a 15x8, 16x6 or 16x8 (or similar) around 10K rpm, or lighter prop up to about 12K rpm max. It can go higher, but the turbo is tuned for the 9K to 12K band. Prop in that range.
Overheating.
First, be sure that the engines are broken in and run for a while on a test stand. This gives you a 'baseline' to isolate any problems, and become familiar with the engines. If they act up and get hot on the test stand, there is a problem to look at immediately. If they run fine on the test stand, and only get hot installed in the airframe... then that is another set of issues.
On the Jett, be sure to follow the break-in instructions. You do not want the engine run too rich, especially during initial break-in.
Second, make sure there are no air bubbles in the fuel line - either to the needle of after the needle. Usually on the 160 the pump helps with this a bit. Ensure the fuel tanks are properly padded - not touching structure.
Third - suggestion - remove the needle valve assembly from the engine. Mount it on the airframe.
Beyond that, you noted you were running with no cowl. So it is hard to factor that in at the moment. However, I have seen in the past on aerobatic ships such as the Extra that it is important to close off the un-used cowl inlet opposite of the engine cylinder. This forces all cooling air entering the cowl to pass over the engine and muffler as it exits below. If the other side is open, the air takes the 'easy' way in and out, and you get a stagnation point at the engine cylinder, and it does get hot.
Dub has his Aeroworks Edge 540 flying weekly with the BSE-120L and turbo installed - and it runs beautifully. My own BSE-100 turbo combination ran great in the same airframe. I flew 15x8 apc. I will ask what prop Dub and Mike are running.
One thing I personally noted was that the OS160 runs great on 5% nitro. Didnt seem to like 10% or 15%... had some weird issues. Maybe the fuel change will help ??
If any of this is helpful, let me know. Again, put the engine on the bench, get them setup and running properly. If they do not run right there, let me know. If they do, lets try again in the airframe, and we can isolate a problem.
See if any of what I have there makes a difference.
Bob
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Bob Brassell
Jett Engineering - Engine Mfg Support Forum Host
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OS 160 Turbo Muffler - 
RE: OS 160 Turbo Muffler - 
AT-6 racing aircraft - 
