Model Forum / Radio Controlled / Land Models / April 2004

Nitro % is, for most mortals, there basically to help the engine start
and idle.  There are other special cases, but for backyard bashers
that's basically it.

10% will probably cost less and get better mpg.  You'll have to run
the needles a little leaner.

Over years of mucking about with plane motors and only months of mucking
about with car motors, my feelings are that increasing the nitro content up
to about 20 or so makes many motors start easier, idle a bit cleaner and,
paradoxically, run a little cooler. Above 20 percent and I think you are
into the area of diminishing returns. There are, of course, exceptions - the
"Fox" brand of combat engines were notorious nitro gobblers.

Like you, I have a Savage, although mine is a .21. Comparing %10 with %20,
it starts better, idles more consistently and generally seems to just go
better with the 20 percent.

Downsides to upping the nitro content are that you use more fuel, and you
may start blowing plugs, although to be honest, 20 percent is really still
quite conservative.

As someone else mentioned, the engines will run a little leaner as the nitro
precentage goes up, and this may be one reason for using lower nitro when
running in - you are less likely to accidentally run a lean tune.
Personally, if I had a Sav 25 (I will one day - the Picco .26 is sitting on
the shelf waiting until I've run the stock .21 into the ground), I would run
in on 10% and then go to %20 and stay with it.

Bottom line, my Sav .21 runs great on 20%

HTH,

Mike B