Norvel BB .15
09-06-2012, 07:29 AM
#1
Thread Starter
Norvel BB .15
Norvel .15 BB, 7-5" MA G3 prop, 10% nitro, no muffler, RC carb 16,900 rpm, Home made control line carb. .202" dia. clear hole(no spraybar poking through) 18,900 rpm.
09-06-2012, 11:21 PM
#2
RE: Norvel BB .15
The stock RC carbs are very restricitve, but gives you an idle down to 25000rpm for those who are into that. The MVVS .15 carb is direct drop in though, and will give you about 1500rpm extra, i.e. close to your home made venturi.
Here are some numbers with the muffler on:
Stock carb, APC 8x4 prop, 10% nitro: 14400rpm
MVVS carb, APC 8x4 prop, 10% nitro: 15800rpm
With the MVVS carb the performance pretty hard to match by any other .15 engine, especially if you consider the low overall weight of the engine.
Here are some numbers with the muffler on:
Stock carb, APC 8x4 prop, 10% nitro: 14400rpm
MVVS carb, APC 8x4 prop, 10% nitro: 15800rpm
With the MVVS carb the performance pretty hard to match by any other .15 engine, especially if you consider the low overall weight of the engine.
03-05-2014, 05:00 PM
#3
Thread Starter
Just digging up this old thread, I have been thinking of making a Turbo head for this motor. I have a good feeling about it. It is a strong motor already, and I have been having good luck with these heads. I just have to make a wrench to remove the head, fix my indexing head, wait for winter to end...
03-07-2014, 07:44 AM
#5
Thread Starter
The stock venturi is .196" or 5 mm. That is an ok size, but there is a spigot and needle that restricts the hole to almost half of that. The carb was designed to run reliably, and not so much to outperform other motors IMHO. The motor itself is pretty good. Other .15's that I have are 6mm with a clear unrestricted hole, so the Norvel is quite conservative. In contrast, the LA .15 has a small carb, but a bigger hole (no carb at all) makes very little difference. That is more of a porting restriction for ease of use. It is a good motor though, well engineered and tested.
03-07-2014, 08:00 AM
#6
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Yeah it sounds like norvel manufactures a hot little motor there and unfortunately detunes it with a choked off intake. Thats really cool. Normally you dont see the big performance gains like that on these little motors with carb swap. Its usually just a reliability change. Pretty cool in my eyes, glad you got some positive results.
03-12-2014, 06:31 PM
#7
Well when choosing a carb or intake and making it useable can be tricky. Using a smaller bore in the carb improves the fuel draw, as the bore gets larger the engine gets less able to draw fuel well. So they have to compromise it so that it can have decent fuel draw and not be too picky on fuel tank location and fuel line length. A big bore carb may cause the engine to be very sensitive to fuel tank location and it may have to turn higher RPMs to get the fuel draw to be acceptable, and then in a particular airplane it may not be very flyable.
04-18-2014, 12:23 PM
#8
Thread Starter
Made a Turbo head for it. It wasn't making more than a couple hundred rpm more. Couldn't measure it anyway. Looked at the stock plug, and there was a .030" step down to the plug on the inside. Removed the .030" and got another 400 rpm on top of what I had. Up to 20,400. An OS plug would need a further .030" removed to be correct. 15% fuel gave me another 400 rpm. up to 20,800. Fairly comparable to the Fora. (the Fora is meant for a smaller prop though) and 1/3 of the price. I hogged out the muffler, but haven't ran it yet. I should have got a baseline with it stock. Kind of disappointed that the Turbo head didn't give me any gain, It took a while to make, and the other motors really woke up with it.
