Q-40 Racing Discuss AMA 422 and any other variants of Quarter 40 racing

Nelson set up

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Old 12-23-2018, 12:05 PM
  #1  
apereira
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Default Nelson set up

Hi guys,

I am new to Q40 and need some kind of advice in setting up the Nelson for it, I just broke the engine in partially, 1.5Lts of fuel at 10.000, 17.000 and 4min at 22.000 with the . 7x4 x 7.5C, but I do not have any instructions at all, so kind of guessing a bit at the moment; so also got a set of shims with the engine I am not planing to use until I know what to do and after running the engine in the air.

Pretty much, I need an idea on what to look for the first flights and how to set it for race, do I close it until it runs clean but not peak and back down 1/4 turn? something like that?

Thank you and Merry Christmas
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Old 12-26-2018, 05:23 PM
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Dear Apereira,

Try to find someone in your area that currently flies a Q40 model. Running a Q40 engine is different then running a traditional model engine.

Here are some of the basics for setting up and running a Q40 engine:
1) Start with a firmly mounted engine in an airframe. Most have a 3/8 inch or thicker firewall.
2) Use a tank that is located high in the fuselage. Use a Tettra or Jett 6 ounce tank located in the top of the fuselage.
3) I prefer to use a motor mount with the built in needle valve assembly.
4) Set up an engine kill that pinches the fuel tubing.

Fill the tank with a Jett tanker or equivalent. Use 15% nitro fuel that contains a blend of synthetic and castor oil.

Running the engine:

1) It looks like you have run the engine enough to put the engine in the air.
2) Use a relatively light 7.4 x 7.5 prop.
3) Back the needle off about 1/2 a turn from the previous run.
4) Start the engine and adjust it until it is running rich near 22,000 rpms. You can fly the engine at this setting and it should be rich and relatively slow in the air.
5) Run the engine rich the first few flights and then gradually lean out the needle. Somewhere near 23,000 to 24,000 it will jump on the pipe. Back the needle out until the engine is trying to go on the pipe but doesn't. Fly at this setting.
6) After about 7 tanks I consider the engine broke in. You should be able to further lean the engine. Be careful and don't go lean. Kill the engine if it appears to be getting hot.

Here is a link to another forum that also has good information:
General Discussions Q500 & Q40 - NMPRA
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Old 12-27-2018, 04:03 AM
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Thank you very much for your advices,

You actually filled in some blanks, yesterday I was looking and found the NMPRA forum with some advices there too, there seems to be a lot of different ways to do this but also look like the Nelson Q40 is an easy engine to operate, being race competitive and getting the edge is something completely different and far from what I wnat now anyway.

Thank you again,

Regards
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Old 01-01-2019, 05:38 PM
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Bozarth
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Sahartman21 knows what he's doing. He is an active (and fast) pylon racer. Follow his list. Here are a few additional suggestions:

1) a new Nelson will probably have a .003 or 0.005 shim under the sleeve. Leave it in there.
2) a new Nelson will probably have a 0.005 and 0.008 under the head. Leave both in there.
3) As Mike Tallman used to say to newbies to make it easy, set it at 24,000 and launch.

Kurt
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Old 01-03-2019, 06:54 AM
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Originally Posted by Bozarth View Post
Sahartman21 knows what he's doing. He is an active (and fast) pylon racer. Follow his list. Here are a few additional suggestions:

1) a new Nelson will probably have a .003 or 0.005 shim under the sleeve. Leave it in there.
2) a new Nelson will probably have a 0.005 and 0.008 under the head. Leave both in there.
3) As Mike Tallman used to say to newbies to make it easy, set it at 24,000 and launch.

Kurt
Hi Kurt,

Under sleeve I have .004
Under head .021 , reduced to .019 already.
(what do you think?)
24.000 is what I will set it to for the first flights.

Thank you very much
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Old 01-03-2019, 09:18 AM
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Apereira,

If it was my engine I would run it rich (22,000 rpms) in the air for a couple more flights. You can start leaning it out later.

The stock head clearance is about 19 thousandths. I typically don't mess with the original settings unless the altitude is high or the engine won't run.

Gabriel Tahhan is a Venezuelan modeler. Try to contact him and he may be able to help you.
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Old 03-18-2019, 09:15 AM
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Each airframe will be different on where you will need to set the needle. saying tune to 24,000 rpm and leave it will not work on every plane. some like to be set near peak other need to be nearly falling off the pipe. Also if you want to be competitive run a tettra bubble less tank. For instance I run timing at .197 measured and .021 - .025 depending on the day. Timing isn't near as important but the head is where the power or lack of is made. To high on the head may not allow it to pipe up when its cold out. My dago with this setting up I would be on the line waiting for the launch at 22,900-23,300 depending on the time of day and see in flight rpm of 28,900-29,400 on the 7.6 prop. If I launched at 24,000 on the 7.6 prop I would be lean on the second lap.

Now for timing I tend to have the liner high when I first run the engine and as I run it for the season if it lasts i can lower the liner some to get some rpm back. IMO starting low takes a bit more time for it to run harder. I also break my engines in at high rpm. I run a small prop and very first run I take it to 28,000 then to just falling off the pipe and then to 28,300 and then to almost falling off the pipe and then to 28,700-800 and then a finger over the venturi cooling before shut down all on the first tank. next run for me will be a 28,500 run for 3/4 of a tank then cooling and shut off. The next will be in flight rich on 7.5 prop and followed up by a rich run on the 7.6 and ready to race.

When you get the tools to measure your engines, use the same method to measure every time. Many racers measure the engine in different ways producing a different measurement. Some take to TDC and tap the engine with a mallet, some just use TDC no tapping, some heat it then TDC and others use a .200 ring under the liner so there isn't any pinch.

The biggest thing I could suggest for a first time racer is to not mess with the engine, run it stock on a 7.6 prop. learn to trim the plane, learn the course and learn to get a good needle each time. once you mastered these then look at the engine for a tiny bit more.
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