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All Forums >> Glow Engines, Gas Engines, Fuel & Mfg Support Forums >> Engine Manufacturers Direct Support Forum >> Jett Engineering Support >> Questions about Jett .90LX
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Questions about Jett .90LX - 8/29/2007 10:49:05 PM   
CrashPro



Posts: 661
Joined: 7/10/2003
From: Indio, CA, USA
Status: offline 		Hello all

I'll be receiving my first Jett engine in a few weeks, and I have a few questions.
This engine will be mounted on the new Cermark F-18, which I should receive Friday.
What is the best size prop for break-in for this engine? Amount of running time to full break-in? What is the prop size range for this engine?
Best glow plug? Best fuel? ( Its hot here, 115 today, and will still be in the 90's when the plane is ready to fly) Engine is the SJ .90LX R/C with LX muffler.
Thanks for any answers you experienced Jett engine owners can give me to these questions.

George
       Post #: 1

RE: Questions about Jett .90LX - 8/30/2007 4:52:15 PM   
bob27s



Posts: 4624
Joined: 4/9/2002
From: Cleveland, OH, USA
Status: online 		Thanks for writing...

The engine will arrive with a full set of instructions, including the break-in proceedure.

But in general......

The engine will have been test run by Dub when you receive it. The low end mixture is set.
You have to complete the intital run-in process.
Put it on a solid test stand...
Break-in prop I choose is an 11x7 APC
Take the engine up to 15,000 rpm ---- it will be slightly rich with that prop at that rpm. That is what you are looking for.

Figure on 15-20 minutes on the bench like that. On the last tank of fuel, you can try and briefly find peak rpm with the 11x7. Find the peak, note it, back it down 500 rpm.... let it run there (should peak WELL over 15,000 with the 11x7).

Flight prop .... APC 11x8 works great. Run this prop on the bench too. Find the peak rpm as a reference. You always want to set the engine 500-800 rpm down from the ground peak rpm for flight. If need be, you can perform some very TINY tweeks to the low end mixture --- but if required, no more than 1/8 turn either way from where Dub had it set.

Installation : I highly recommend removing the needle valve assmembly from the engine, and mounting it on the airframe. (I believe the Cermark assembly manual shows a Jett engine installation, with a remote needle installed on the firewall).

Fuel --- what ever you normally run is fine. Most commercial fuel is good stuff. We baseline on 15% nitro.
I personally run PowerMaster or Wildcat 15% premium blend fuel in every engine I own. So its all I have
The engine is happy with anything from 5% to 30% --- so what ever you have in the field box is fine.
I will suggest using fuel that contains just a bit of castor oil. Omega, Powermaster, Wildcat, Bryon all offer such a blend.

Glow plug.... the engine requries a HOT plug.
It will come with a Merlin Hot glow plug. Good plug. All I use in the LX engines.
Alternates ---- Rossi 2 or 3, MC59, K&B1-L and some have also used the OS-F plug ... actually works quite well.

Key to this engine is rpm. You want to select a prop for this engine that allows it to easily reach 14,500 peak rpm on the ground. If it is hot out, or if you are running a bit lower nitro...back off on the prop just a bit .... the 11x8 should work under 90% of conditions.

Also.... keep in mind.... the LX engines are fairly well behaved, and not extremely difficult to set up...... but they are a bit less 'user friendly' than the regular version Sport-Jett engines. It pays to take the time to "learn" the engine while it is on the test stand. Also, your fuel system MUST be well done ---- ensure the fuel tank is padded on all sides - or you will create fuel foam, with disasterous results. The F-18 tank install is a little snug... so use some TLC there.

I hope this is helpful... feel free to follow up as need.

Bob


_____________________________

Bob Brassell
Jett Engineering - Engine Mfg Support Forum Host

(in reply to CrashPro)
       Post #: 2

RE: Questions about Jett .90LX - 8/30/2007 5:11:23 PM   
CrashPro



Posts: 661
Joined: 7/10/2003
From: Indio, CA, USA
Status: offline 		Wow,..fantastic reply Bob,..thankyou VERY much. All questions answered. I will follow the break-in instructions to a T.
I will receive plane tomorrow,and will get alot done on it this weekend. Can't wait to get the engine.
Thanks again, I'm sure I'll have more questions once I get it all together.

George

(in reply to bob27s)
       Post #: 3

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All Forums >> Glow Engines, Gas Engines, Fuel & Mfg Support Forums >> Engine Manufacturers Direct Support Forum >> Jett Engineering Support >> Questions about Jett .90LX
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