Combat OS LA15

I'm looking for some ryme or reason at to why I am having to use such high
nitro fuel to get the RPM's up on my la's. Most of the guys in combat use
5-10% and I am using 30%. I drilled the baffle out in the muffler to 27/32 and
am now getting 17,300-17,600. With 5% I get only 16,500 or so. 1,000 RPMs
makes a lot of difference in Combat. What's the deal here? I have 3 LA's and
all 3 run just alike. I'm just having to use higher nitro fuel than I should.
Any ideas??? Thanks Eddie Fulmer AMA 63713 RCCA 694
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Eddie, As in any testing you need to have some controls and calibrated instruments. At the next combat meet explain the situation to one of the guys who you think has a hot running .15 Find out what prop, plug and fuel he is using not just some "10%" fuel. If possible borrow a 1/2 tank of his fuel and maybe his prop as well. If its an APC or MA and you have one with the same Dia and pitch thats close enough. Use the same plug as well I had good luck with the K&B HP plugs. Have him run his and use your tach! this is very important some tachs can be off by quite a bit so by using as near as possible the same setup you will have abetter Idea of what the true difference in performance is. If you are way off in performance your engine is either not broken in or it is worn out. He has proballped the crankshaft to free it up and you may also have a bind in the engine by incorrectly torqued parts. If you are comparing performance over the internet all bets are off. A friend of mine is an experimental engine engineer for Allison his moto is, "In god we trust, all others bring documentation". Its not beyond some to put 30% nitro fuel in a 15% fuel container as well. Sparky
'm looking for some ryme or reason at to why I am having to use such high
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Are those guys also using 15LA engines? I am by far NOT an expert but I understand the LA series engines have a small restrictive carb to keep the revs down. I have a .46LA that used to be in a trainer and while it was a great running engine, it never was a screamer. Of course I could be completely wrong and I am well familiar with the taste of my foot.
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Fubar of The HillPeople
in article TNa1c.10676$, Fubar of The HillPeople at wrote on 3/2/04 7:46 PM:
Oh, the OS LA .15's a real screamers alright. Take the center baffle or silencer section out of the muffler, and they really wind up! With an 8X3 MAS prop and 15% fuel, the little devils are hitting 18,250 on the ground!
I was skeptical at first myself, wanting to go with a BB engine like the Magnum XL .15. But now I'm sold on the LA .15s for SSC combat.
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If your three engines are consistent, your tach probably reads different from what the other guy uses, or you are honest enough to let rpm stabilize before you take a reading. Do your planes fly slower? If you want to fly circles around an LA.15, why not take an MVVS. It screams a MA7x5 at 19000 on just 5% nitro. As fringe benefit option, the combustion button makes chamber blueprinting an easy chore.
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Pé Reivers

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