Extreme Speed Prop Planes Discuss the need for speed with fast prop planes (Screamin Demon, Diamond Dust, Shrikes or any REAL sound breakin'''' plane)

nelson question

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Old 09-09-2002, 06:12 AM
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bugsiegel
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Default nelson question

I recently purchased a nelson engine and have an 8.75/8.25 prop on it. I havent tached it yet but i'm wondering what rpm's I should be getting with this engine prop combo on the ground. I have about 10 tanks though it now. the engine has an OS 7D carb on it.
also, what off the shelf fuel can I use for this eneing?
up to now I used coolpower 5%. this weekend I added a little extra synthetic oil. I had two flights with the added oil and both flights ended with deadsticks. I'm wondering if the oil is causing the engine to cut out. the engine is not running hot at all. maybe it too rich and when I throttle back the plug gets too wet to fast.
also, it seems when i run the engine up on the ground. at about 3/4 throuttle there is a little more rpm's then at full. the rpm's drop slightly at full throttle.
I decieded to add the extra oil because after the first few flights the residue on the plane was a little dark for my taste. before the extra oil and after, in midrange in the air the plane lets out plenty of smoke. but wne it goes over half throttle the smoke seems to dissapear. is synthetic oil the right oil to add or should I add castor oil? or mayby don't add oil at all just run it a little richer with stock fuel.
if you're famiilla with these engine let me know what you think...
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Old 09-10-2002, 02:51 AM
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RossiRay
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Default Tuning

I ran into a similar situation.
Setup was a Magnum .36, with a Nelson/PerfSpec Ultrathrust muffler.
Engine ran fine with an APC 8x8, turning low 17s. Went to 8x7 after breaking my last 8x8, and the thing turned upper 18s. But I could not get it to richen up. Went to a 9x7, turned 17s, and needle response was good.
Seems as if the engine turned outside the tuning range, muffler tank pressure went down.

So my question for you would be which muffler do you have. The Nelson Sport .40 was offered with a choice of tuned mufflers. The standard Q-500 version for the 19k range, and a lower rev muffler for spinning a 10x6 in the 15-16k range.

FWIW, I run 20% fuel with 20% oil that is all synthetic in my Nelson Sport .40 with the Q-500 muffler and ST carb. I am getting 19,200 with an APC 8.75x9 peaked. I fly it @18,700. Throttle response is fantastic. No detonation, plugs last about 15 runs.

I hope this helps.

RR
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Old 09-10-2002, 12:51 PM
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bugsiegel
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Default exhaust

i have the performance specialty exhaust. not sure where this exhaust should put me as far as rpm's
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Old 09-10-2002, 11:35 PM
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RossiRay
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Default Give Performance Specialties a call,

Dave will be able to help you sort this out.

www.pspec.com

RR
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Old 09-11-2002, 04:37 PM
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daven
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Default nelson question

I assume you are talking about the Nelson Q500 engine, and not the Q40 engine??

As to fuel, Powermaster 15% Nitro is the fuel supplied to just about every National racing event. Locally, we run Omega 15% in Nelsons, and they run great. Cool power does not contain any Castor, and should not be used on AAC or ABC engines (some will argue this), but even coolpower does not reccomend this fuel for these types of engines.

I would suggest running a Bladder type tank with this engine. They run much more consistant, and do not run lean as the tank runs down. At full throttle you should be able to lightly pinch the fuel line and get a 400-500 rpm jump. No more than that is necessary unless you are turning a bigger prop. You should prop this engine to turn around 19,000-19,500 Peaked. The prop you mentioned should be in that range.

Other props to try would be:

APC 8.75" x 9 W
APC 8.75" x 8.75 W
APC 8.75" x 8.5 W
APC 8.8 x 9
APC 8.8 x 8.75
APC 8.8 x 8.5

All of these props should be available through Dave Schadell at www.pspec.com. Feel free to ask any further questions.
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Old 09-18-2002, 04:38 AM
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Default Nelson engine

First thing, Most nelsons run on 15 percent fuel Like Powermaster or wildcat. Since you are using a after market carb, there will be little loss on the high end RPM. If the engine is an AAC version, You might try running the engine fat then lean it out til it just hits its last step on the pipe then go 1/8 turn ritcher. Once you go lean on a AAC engine it takes a few moments to go back to ritch because the liner takes a while to shrink.
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