Subject: RX-8 Oil injection questions and thoughts
From: Rotary Engine
Date: 4/3/2011, 11:32 PM
To: AAA Put this in the To box


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
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That sounds like a good solution, but it is not what I really want to make
sure of.

I already have one of Richard Sohns RX-8 oil adaptors and a meter adjuster
plate. This allows the oil injection system to vary oil rate injection
based on RPM, which means the electronics are no longer required.

What I want to ensure is whether adding an extra oil injector or injectors
into the intake system for 2-stroke oil injector would be a good option or
addition. If it is, then where is the best place to add them or it in the
intake system, the stock manifold is being used for this project.

I thought this might be a fairly elegant solution. The RPM of the engine
controls the flow of 2 stroke oil that is injected. I've attached the
adapter information that Richard provides the prices in are out of date I think.


Regards David

That RX8 oil metering pump adjuster is a clever idea Richard.

The best place is inject it into the fuel on the low pressure
side of the fuel pump. Mount the oil storage container high and use a
needle valve to control the gravity flow into a T in the fuel line.

Probably a better idea is to use a venturi in the fuel line so
the oil flow is proportional to the speed  or amount of the fuel flowing
through the fuel line.

Putting the oil in the fuel also means it lubes the housing better
as it is automatically distributed through out the housing.

BTW it is by no means certain that low apex  oil injection caused the problems
with the early RX8 engine apex seals. The current thinking is failure of one
or more ignition coils caused misses that washed away the apex seal oil with
too rich raw fuel.

If you mix the oil with the fuel this cannot happen.

Paul Lamar

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