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All Forums >> Glow Engines, Gas Engines, Fuel & Mfg Support Forums >> Engine Manufacturers Direct Support Forum >> Jett Engineering Support >> More break in questions.
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More break in questions. - 10/7/2005 4:44:28 AM   
Rebellion


 

Posts: 982
Joined: 2/22/2004
From: Central, GA, USA
Status: offline 		Hi Bob,
I have a Sport Jett 50 which I haven't had time to break in yet. The intended use is a composite Q500. I currently have the red Jett Stream muffler, but I recently ordered the black racing muffler for use on the Quickie. My question is: should I break the engine in with the red Jett Stream muffler and the usual 9X6 Apc prop or wait until I get the black ( Jett Scream ? ) muffler and use it ? If using the black muffler, what prop would be good for break in ? I have a small selection of pylon props ranging from 8.75 X 8W to 8.8X8.75. Or does any of this matter ?

Thanks,

Dave
       Post #: 1

RE: More break in questions. - 10/7/2005 4:17:26 PM   
bob27s



Posts: 4819
Joined: 4/9/2002
From: Cleveland, OH, USA
Status: offline 		Hi Dave....

You can break-in the engine with the standard muffler, but the engine is going to be used exclusively for the Q-500....... perhaps wait just a bit for the black muffler. The reason being, is the red muffler is not going to allow the engine to run properly much over 18,000 rpm. With the black muffler, you want to run at a minimum of 18,000 rpm - Preferably toward 19K.

As for break-in prop...... skip the APC 9x6. If you have a small supply of APC D-1 series pylon props, use one of them (if you have one with some tip damage...that is a good candidate). You want to use one of the D-1 heavy-hub type props for these rpms. If you have a spare 8.8x8.75 (or any of these), clip the tips off of one so its down to about 7.75" or 8" diameter. Balance it. Use that for the break-in prop. The clipped prop should get you pleanty up into the rpm range with the engine just a bit rich... figure on it running near 19K rpm while a bit rich. Let it run there with the light load. If it turns more, back off the needle a bit more to keep it close to 19-19.5. If it comes up short of 19, that is ok... just back it off about 800 rpm from peak and run it 15 minutes.

For flying, any of the D-1 props will work. Use what you have for now. The 8W is ok. The 9W will work very well. The 8.8x8.75 will give you about the same performance as the 9W. Again, the key here is with the black muffler, you want the engine turning no less than 18,000 rpm at take-off, so you want the engine to peak somewhere at or over 19K, and then back off the needle a GOOD 600-800 rpm.

Word of caution - if not already doing so ..... use a bubbleless tank in the aircraft. Tetra or Jett.... you will need it. On the test stand, never let the fuel tank get below 1/2 - give it no chance that it will get bubbles and lean out on the test bench.

Bob


_____________________________

Bob Brassell
Jett Engineering - Engine Mfg Support Forum Host

(in reply to Rebellion)
       Post #: 2

RE: More break in questions. - 10/8/2005 3:22:32 AM   
Rebellion


 

Posts: 982
Joined: 2/22/2004
From: Central, GA, USA
Status: offline 		Thanks for the advise Bob. I'm in no hurry so I'll wait for the black muffler. It is scheduled to be here on the 12th. I have a few of the 8.8x8.75 props so no problem there. Wish I had ordered a Bubble Jett tank for break in purposes, but I'll be extra careful for now.

Again, thanks much.

Dave

(in reply to bob27s)
       Post #: 3

RE: More break in questions. - 11/3/2005 5:59:35 PM   
Rebellion


 

Posts: 982
Joined: 2/22/2004
From: Central, GA, USA
Status: offline 		Bob, I'm finally going to run this engine today. Will it hurt to try a few different props on the test stand with this engine after the run in period ? I know that some of the high performance engines need to be flown for proper cooling.

(in reply to Rebellion)
       Post #: 4

RE: More break in questions. - 11/6/2005 3:57:10 PM   
bob27s



Posts: 4819
Joined: 4/9/2002
From: Cleveland, OH, USA
Status: offline 		No problem trying a few props.

Do the initial rpm/break-in proceedure first. Get about 20 minutes on it, then switch over to an expected flying prop.

After trying a few props, pick one you want to fly with at first, and perform the last run on that... get the needle about right.

Just be careful - do not run the engine at peak rpm for more than a couple seconds. find where it peaks, and back off 1/2 a turn quickly. If you hear it get hot or go lean (sag) do not try to recover with the needle. Back it out a full turn, then shut the engine down and let it cool off before proceeding.


_____________________________

Bob Brassell
Jett Engineering - Engine Mfg Support Forum Host

(in reply to Rebellion)
       Post #: 5

RE: More break in questions. - 11/6/2005 6:51:47 PM   
Rebellion


 

Posts: 982
Joined: 2/22/2004
From: Central, GA, USA
Status: offline 		Thanks again Bob. Ran the engine about 20 runs with the recommended break-in props. Runs consisted of a warm-up period at about 1/3 throttle then full power for one min., 2 min. in the later runs. I'm amazed at how easily an engine of this performance handles. Easy starting and just RUNS. Needle seemed very non-critical, even near peak. With a 7.75x8.75 ( cut down form 8.75 dia ) I peaked at 19,000 and it would still idle nicely at around 3200, perhaps a bit less. Peaked it about 5 times during these runs, but for no more than 10 seconds each time. Also added 4 oz of castor in the gallon of fuel for the breakin period. It's fun watching this engine as the pipe stages. Goes very rich right before the pipe hits and then it just screams! I'm hugely happy with this engine to say the least. I've decided to go ahead and put this little screamer in a Q40, probably a Vendetta.

One more thing, is there anything I need to check now that the engine is run in ?

Thanks again,

Dave

(in reply to bob27s)
       Post #: 6

RE: More break in questions. - 11/7/2005 3:42:43 PM   
bob27s



Posts: 4819
Joined: 4/9/2002
From: Cleveland, OH, USA
Status: offline 		Just check all of the bolts. The head bolts in particular.

The 19K is perfect for the black muffler. You are good there.

You may also want to try a clipped down 8.8x9.25 - cut it down to about 8" dia for the QM.

Bob


_____________________________

Bob Brassell
Jett Engineering - Engine Mfg Support Forum Host

(in reply to Rebellion)
       Post #: 7

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All Forums >> Glow Engines, Gas Engines, Fuel & Mfg Support Forums >> Engine Manufacturers Direct Support Forum >> Jett Engineering Support >> More break in questions.
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