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Engine Modification for RC Drag Racing |
| When Mario Rossi left Nova Rossi and teamed up with the GRP brothers and
Mugen to bring a new engine line to life, we were looking forward to getting our hands on
these engines to see what was new and what was the same as all others. The overall
response to the Ninja line has been very positive although i have not seen many of the
Mugen onroad racers take out their JPs to replace it with a Ninja. |
| Ninja Drag Engine preparation: First Impressions. Packaging
is the best i have ever seen. External finish and design are sound and appealing. Now to
the technical stuff. It will seem that i am picking on things which mean little or nothing
to most people but, well, i am picky. Upon disassembly there were two flaws that could be
avoided with more careful manufacturing and quality control. I guess GRP has not aquired
the ISO standards as Nova Rossi had done. The front bearing seat is a little undersize and
the bearings are being forced in there with a pneumatic press during assembly. This
damages the bearing seat in the case and subsequently prevents the front bearing from
fully seating in the case. We cleaned up the bearing seat and the bearing fit properly
after it was reinstalled. |
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The other flaw is a ridge below the carb mounting throat that ends up
being machined paper thin as the crankcase is being bored for the 14mm crank at the
factory.Some of the material had to be removed in order to prevent the piece from
dislodging during operation and damaging the engine. After the clean up the
remaining ridge is inconsequential to engine performance and durability.On to the
preparation of the crankcase. I milled the top of the case to allow for some more air
under the head button, besides, it makes it easier to measure things.Adjusted and cleaned
the bearing seats and mesured the bearing distance to ensure a proper carnk installation.
All threads were retapped as the speedy manufacturing provides a poor lead in for the
screws. The exhaust port was widened and matched to the liner as well as reshaped and
cleaned up. The crankcase was then chemically cleaned and all particles removed in a
ultrasonic cleaner. Ceramic upgrade bearings from TKO were installed and aligned.
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| The crankshaft was pretty much a no brainer since it had the timing i had
in mind. It is well executed and light.I removed the worthless silicone filler and
replaced it with an aluminum insert with a 45 degree ramp. It displaces more volume and is
impervious to fuel and oil. Plans are for a separate article on crankshafts, for
which i will have more detailed pics as well. |
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After finish honing the crank bore it was on to removing some weight from
the connecting rod. I ended up milling both sides, measuring bushing size, polish the
upper and lower end and finally cleaning with the same process as the crankcase. |
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Average run time under full load in drag racing is measured in seconds
rather than minutes or hours even. In order to reduce the weight of the moving parts
i milled away all areas that are not necessary for the actual functioning of the
parts.Thereby saving a lot of weight as well as expose the lower edge of the sleeve for a
longer duration during the transfer process. The balance check of the final assembly
proved to be much more favourable as well. |
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Here are all the parts before final assembly.The sleeve received a few
small alterations to ensure the port areas are equal and the timing i wanted as well as
thinning of the exhaust port dividers.The area below the transfer ports in the liner has
been micro finished. The piston is substantially lightened and the skirt below the wrist
pin has been micro polished to reduce friction.The con rod has been lightened by milling
both sides.The rear cover has been adjusted in depth in order to adjust the clearance
betwen the cover and the rod plus to reduce the crankcase volume as much as possible, this
helps increasing the pumpimg efficiency in conjuction with the larger crank insert. The
head insert depth was set up so it can be set to a minimum deck clearance of 0.008
of an inch with a compression ratio of 10:1. All parts were cleaned and treated with the
same process as described for the crankcase. The outside of the sleeve is NOT polished as
i strongly advise against that for technical reasons.
The only timing adjustment made was a small amount in transfer and boost timing, other
numbers remained stock as they were found to be good. |
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| The carburetor was cleaned and checked during final assembly and received
a 9mm insert rather than the "wimpy" 8mm that comes with the engine. The stock
onroad cooling head was cut down since the run duration is very short. Time to go racing. |
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Good Racing,
Rich Reid
For questions or comments please e- mail me at rich@reidrc.com
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