Question and thoughts about Oil injection.

Because the series 1 RX-8 engine is a bit short of oil injection as
 Paul
has mentioned could or would an option be to add some sort of oil
injection into the intake system to spray a fine mist into the intake
system? I think this would be rather like a 2-stroke oil injection
system/s used on Rotax engines and the like.

My thoughts were use the oil injection system that exists on the Rotary
but add another injector into the intake system to spray 2-stroke oil
using a Richard Sohns adaptor.

Does anyone have any thoughts about this?

I'm just thinking out loud with ways to add lubrication oil for the
 Apex
seals, without requiring to premix it. My thoughts about this is you
don't need much oil at low RPM eg when idling on the ground, warm up,
low rpm for descent and the like but you do need more oil for high
 power
settings to ensure that there is enough lubrication for the seals when
they are under high power.  What do other think of this and if so what
size spay nozzle/s would be needed?

Regards David (Australia)

--

The oil injection takes place when there is a vacuum in the intake
 chamber. The injector has a one way valve so atmospheric pressure does
the actual injection. The metering pump does just that. It meters the
oil to the injectors. The metering pump controls a stepper motor by
sending out pulses on four wires. The cheapest and easiest way to
 modify
the amount of oil metered is to insert a low cost microcomputer in the
wiring harness that reads the pulses and modifies them in such a way
that increases the amount of oil metered.

http://www.imagesco.com/articles/picstepper/02.html

I recommend something like a BASIC stamp as a 3rd grade student can
learn to program it in BASIC. Here is the company I would go with as I
have extensive experience with their product and their $100 prototype
board is extremely easy to use.

The final product could cost under $20 for parts.
 http://www.zbasic.net/

Paul Lamar

---

I have every intention of still using the original oil injection holes.
I did find this info on the racing beat website.



http://www.racingbeat.com/mazda/performance/rotary-tech-tips/oil-filters-mop
 .html


It is near the bottom of the page.

RX-8 - Race Tips:- While undertaking development work on the RX-8
Renesis engine for SCCA T2/T3 use, we decided to introduce extra oil
into the fuel to monitor the effect. To our surprise, this additional
oil increased power! Further dyno testing found that by adding 10
 oz. of
Royal Purple 2-Stroke Oil to 6 gallons of fuel, we gained an average of
1.7 HP from 2000-9000 RPM, along with an increase in peak power of
 4 HP.
We validated this increase by changing back to a "non-oiled" fuel - and
the power returned to the previous level. Later, we tried the same test
with another brand of synthetic oil with nearly the same results. For
racing applications, the addition of a high quality synthetic oil
increases power and most certainly decreases wear. The only negatives
are the cost of the oil and an increase in the tendency to foul the
spark plugs. (Note: We have not performed these tests on non-RX-8
engines yet, these results are unknown.)

I guess that injecting or premixing some additional 2-stroke oil into
the fuel is apparently a better option and as such worth doing although
not at the rate that racing beat suggest for high end racing
applications, however any improvement in power is a bonus, improvement
in lubrication obviously is the aim without causing plug fouling.

Also from the Racingbeat site:- The metering rates for stock engines
vary, so consult an appropriate shop manual for your carâ??s
specifications. In normally aspirated racing vehicles we use either a
setting of 5cc/5minutes (total flow - 2,000 RPM, warm engine, arm
 in the
"full throttle" position) on the metering oil pump or premix 3.5 oz of
good quality synthetic oil (preferably 2-stroke motorcycle "oil
injection" oil) to 5 gallons of fuel. The requirement for turbo engines
in racing is high enough that use of a metering oil pump is
 impractical.
Therefore, we premix up to 22 oz of oil to 5 gallons of fuel in a
 600 HP
2-rotor. If you are not pressing your engine this hard, you can use
proportionally less oil.

 From this and other past posts in the newsletter. It would appear that
somewhere between 100 ml and 200 ml per 20 liters (200:1 - 100:1) would
be about the optimum amount to inject for use in flying.
If the oil is injected both into the original oil nozzles and then
 using
another oil nozzle to push oil into the fuel system right before the
injection pumps that should be fairly elegant and would not require
 premixing oil into fuel.

I'm in the process of doing my engine now within the next few months it
should be finished on a test stand and ready for running using Tracy's
Computer system and engine monitoring system,

At the moment the making the adaptor for the gearbox is in progress,
that will be finished shortly.
Then it's on to putting it all together and building the wiring system
etc for it.

Regards David.


Paul, Re oil injection if the oil in injected on the suction side
 of the
fuel pump, after a little while the fuel in the tank/s will have
 lots of
oil in it/them, because the fuel pumps flow at least twice the
 amount of
fuel required by the engine, so each time it goes around the fuel gets
another dose of oil, unless of course you are referring to a
 carburetted
version.

John Burey

Good point. Back to the dwg board :)

Paul Lamar

--

I did think about that it appears that the default way for the RX-8
engine is a return-less fuel injection system. Maybe based on that it
could work. However if using a return based system then the issue
becomes interesting. Maybe injecting into the fuel before it enters the
fuel rails might be an option, provided the return line was based
 on the
pressure regulator being before the fuel rail/s and use a check
 valve to
ensure no back wash of the fuel. However I suspect that the OMP
 does not
have the pressure for this to work.
Otherwise maybe a couple of nozzles one in each primary intake port
for each rotor and spray it in directly, the ventri effect should help
 this. which is what I was musing about to start off with.

Regards David

 Paul,
 if you sent the return back to the header tank, then it still works.
 Larry

 So you are saying inject the oil into the line from
 the main tank to the header tank?

 Paul Lamar


 On a simpler, more basic level, when adding the oil to the fuel
 tank(s). How
 rapidly does oil disperse in the fuel? If filling a partial tank, do you
 guess the amount of fuel you will load, and add the oil first, or
 will it be
 OK to fill your tank(s), then do the math and add the precise amount
 required?
 Herb Karkheck

 We have no numbers on this. As far as I can tell in 12 years it
 does not seem to matter. Taxiing way from the fuel pump probably
 disperses the oil in the fuel. Sloshing in the air probably helps.
 The vast majority of people flying use premix.

 Paul Lamar

With my EFIS and capacitive fuel probes, the fuel level readings
are pretty accurate, so I have a pretty good idea of how much fuel it
will take before I pump the fuel.  I usually don't fill up until I'm
down to about 10-15 gallons per tank.  Since each tank will hold 47
gallons, I can usually put one quart in each side and stop at 32
gallons/tank.  I pour the oil in while I am pumping the gas.  (This
takes a little practice.)  If I go over the 32 gallons, I can add a few
extra ounces after the fact to bring the oil/fuel ratio to 1 oz/gallon.

My fuel system returns the unused fuel to the currently selected tank,
so running the pump for a minute or so will guarantee a good mix.

I recently had my credit limit raised so that I can fill up with
only one credit card.  ;-(

Mark