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Dieselized .049 with no Teflon disk or o-rings.

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Post  geoffwise on Mon Jun 10, 2019 10:21 am

A direct question two 1/2a nut. Can you explain to me how you can run a tuned pipe with spi Geoff
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Post  1/2A Nut on Mon Jun 10, 2019 2:02 pm

Hi Geoff some of the following you most likely know I will try and keep this brief.

Old Bugger

Many engines that have SPI still run fine I have personally used
the following 1/2A engines (see list below) also other larger engines with SPI.
If you have a Cox .05 RC cylinder piston use that with a Profi 1/2A pipe
or a CS .049 - .061 pipe. I would prefer no SPI with pipes. The SPI
window is very very short time wise per cycle, fuel air intake is good
with no pressure tap needed to function. I prefer a pressure tap all
the same for insurance. Does not need to be high pressure just positive.
The SPI seems to get a boost all the same from the pipe. These simple
2 stroke engines waste fuel there is usable fuel vapor in the header
able to get drawn back in when the SPI gate is open. As the piston
rises up from BDC the pipe charges the combustion chamber with
the it's best possible charge based on exhaust timing duration. Longer
the duration bigger the charge. SPI makes up for some losses by charging
the case it all makes it to the combustion chamber that is why a power
boost is present even with a 140 deg engine.  Consider it a 2 phase boost
rather than a single phase boost with non SPI engines. A single exhaust
port engine is best for best pipe induction less lag time. Therefore a
dual port Cox engine requires one of the exhaust ports to be blocked off
and the header directly located at the open port. Zero lag max influx is
the only positive solution for optimum influx and breathing.

Small engine use to date:
- Cox .049 and .051 and best non SPI  .05 (28.1k)
- Sportwerks .05  (37.7k rpm)
- Norvel .061 (29k rpm)
- Fuji .05  ( 38k rpm)
- Picco P0 .05 ( 50.3k rpm)
- SH .07 (38.7k rpm)
- GZ .049 (36k rpm)

Many Youtube vids with me using 1/2A Profi pipes I have 6 of them and 1 CS/GZ pipe.

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Post  geoffwise on Tue Jun 11, 2019 4:28 am

Hi amp A good read I have not intended tuning a cox done all that a long time ago i just want to start off at the right place for rc carb set up I do not need high RPM !!! For 1/2a mustang.a muffler feed stops vent flapping about. lol .
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