Paul,

Check these out.  I have purchased four of them.  Fast, small, large flow
and, are OK for flex fuel.   Simens DEKA IV. Four little holes with good
performance even at low flow rates.

Specs here.
http://www.bmotorsports.com/shop/product_info.php/cPath/144_146/products_id/448

Calculation. Given max.  injection duration (intake cycle) equals <120
degrees.  Actually about 105 degrees to avoid port overlap.  At 6,000
rpm, it requires 1/100 of a second or  0.01 second. to complete 120
degrees of arc. Think of this as the intake event.

These  injectors turn on in 1.14 ms and off in .85 ms.  Total is 2.99 ms
or call it 3 milli secs.

or  0.003 of a second.  Even at 8000 rpm and 100 degrees of injection
duration (delay start of injection until exhaust port closes),  there is
still gobs of time to inject the require amount of fuel needed while
keeping the duty cycle low.  If one  injector craps out the remaining
injector duty cycle can be doubled without a sweat.

Doug in Japan

Wow!!! you got that right Doug. 60 pounds an hour is 10 gallons an hour
per injector.
40 gallons an hour for four. At a BSFC of .6 that is 400 HP!!!

Great injector. Small too. Ideal for P-ports.

I am sold. I am buying four. No use messing around with marginal RX8
injectors.

--
Paul Lamar ...No rotor no motor.

Paul,

Great choice. You will enjoy them.   Some people I know run them at
higher PSIs and claim as much as 90 lbs/hour per injector which is way
over our needs.

For direct placement in the housing this is what I plan to try:

Bore two angled holes in the rotor housing on each side and parallel to,
the oil injector boss. Next  lightly press and ring weld two alumunum
25mm dia. 15mm long plugs in the holes with the low melt point new alloy
brazing.  After that, end mill bore a 19mm dia hole through the center
of the  plugs and bottom it out against the back side of the metal rotor
housing line.  Next  take a 19mm OD dia/ 15mm ID pipe and ream the
inside out a hair as well as turn the outside down  for clearance.  An
upper and lower (inside- outside) O-ring groove needs to be cut on the
pipe. The injection hole will be about 5mm dia and slightly tapered from
the inside.   This will put the injector close to the inner housing to
take advantage of the wide spray cone, but far enough back not to
contact the Apex seal.    The 19mm pipe complete with O-rings is hand
pressed into place.  Properly done it can`t leak water either into or
out of the housing.  If desired, a set screw can be installed in the
outer boss perpendicular to the injector mount pipe to assure it does
not move.    Finished with the injector installed into this pipe,  bring
the wire and fuel rail connector real close to the housing so I believe
the manifolds can wrap over head.  Wires and well and fuel lines can
come from the cool side.

The challenge is adjusting the best moment to begin the injection event,
but the advantage is that we put the small slide throttles ( yes thats
plural) right smack up against the housings.

I having a big steel jig being made now by the local shop so I can can
rotate the rotor housings to one of  five fixed  positions within it
accurately and repeatly.  I need various holes on each side and top of
the test engine.  I`ll send pictures when the jig is done


Doug

IMHO I think you will be disappointed in relatively low pressure (50 psi)
direct injection
Doug. The fuel does not have enough time to evaporate. The new direct
injection
diesel systems are using upward of 20,000 psi. First picture. There is a
measurable decrease
in BSFC by injecting at the start of the runner. Second picture. Racing
Beat reported
this during dyno runs. Also the fuel cools the air in the runner
increasing power.

No harm in trying again however. One can always go back.
--
Paul Lamar ...No rotor no motor.

Paul,

We have been down this road before I think.  It seems over the years I
have heard a lot of conflicting opinions on the subject.  Case in point
Mistral got their best BSFC injecting near the housing in the inside
ports, after the tried out near the ends as you suggest.  Steve Beckham
and Everetts had good results (with other side effects of course) by
injecting against the hot rotor directly  thus vaporizing it the spray
but perhaps losing some fuel to the exhaust.,  Lastly, the Lemans engine
had the injection right after the slide throttle and perhaps three
inches from the inside port.  None these situations had injectors that
could deliver fuel so rapidly as the Deka 1V so one half of the time the
Mazda injectors  are spraying into a closed chamber before the port
opening causing the fuel to hit the walls and condense.

Their are advantages and disadvantages of course for,  Correct me if I am
wrong but the gases in the chamber rotating from the  intake port to
about 120 degrees after that is not experiencing positive pressure yet.
In fact when the injection event starts, and there is an hot rotor a few
inches, away, the intake chamber is a minus pressure.

Yep injecting out near the bell mouths would definitely cool the charge,
and may even cause condensation which is of course counter productive.
Works in racing car environments obviously because they have a
tremendous amount of heat contained in a fairly tight cowling.  I won't
have that problem with only a few inches of boost, Teflon manifold,
ethanol based fuel E-85, and having an intercooler in between. Sorry I
don't particularly like the idea of creating an explosive mixture in a
thin walled container, that is open to the atmosphere all of the time.
One backfire and the manifold and possibly a lot of cowling is toast.

As I understand it, for direct injection engines, the pressures have to
be enormously high because the injection occurs when and where the
compression is at it's highest.

But in any case you are correct, direct low pressure injection is worth a
try and I can always mount them outside on the manifold if I'm not
satisfied with results. The name of the game is striving for complete
fuel burn whether that comes from speeding up the flame front by adding
a smiggen of H202 gas on the end of the intake stroke or increasing the
vaporization of the fuel.

Doug.

The short pulse idea is interesting. I think the Lemans engine mentioned
injecting the fuel at the start of the runner but they chose
the closer position for throttle response reasons. In a road racing
situation
good throttle response is critical. Also it was more difficult to
fabricate because
of the changeable runner length. In Formula 1 the runners are only inches
long
as the RPM is 19,000. In any event the BSFC differences are minor.

I am not advocating injecting the fuel before the intercooler.

Early diesel engines worked on moderate pressure. Nowhere near 20,000 psi.
20,000 psi is a relatively recently development where engine oil pressure
is
used to enhance fuel pressure in special 2 stage fuel injectors.

Lets run through some numbers to put things into perspective.

6000 RPM is 100 revs a second. or .01 seconds or 100 msecs per rev.
The injector fires once per rev. 100 msecs divided by
360 is  .27 msecs per degree of e-shaft rotation.

Injectors are rated for HP at 85% to 95% duty cycle.
Lets say each injector is 10 gallons an hour at 85% duty
cycle for gasoline. Alcohol will be much higher.

At cruise and a fuel burn per injector of 3 gallons an hour
the injector will be on 3/10 of 85% or 25% of the time.

It takes 3 msec to turn on and 1 msec to turn off.
At 6000 RPM we have 100 msecs minus 4 msecs or 98 msec to work with.
25% of 98 msecs is 25 msecs.
We need to be on 25 msecs to get the fuel we need with gasoline for
cruise.
25 divided by .27 msecs per degree is 93 degrees. The intake port is open
270 degrees. Looks good at this point. Shows the advantage to a high flow
injector.

Check my arithmetic and reasoning.

Now as far as the fuel spit back problem of tuned manifolds with injectors
mounted on the runners is concerned the exact time the air flow flows out
the
end of the runner should be avoided when injecting fuel.

If direct injection is chosen just after the intake port closes but the
pressure will build up reducing the flow from the injector during the
compression stroke probably cutting off the flow completely after
100 degrees or so with only 50 psi. IMHO it looks like you need to start
injection well before the intake port closes.


Again check my arithmetic and reasoning.
--
Paul Lamar ...No rotor no motor.

Paul,
I am trying to follow your reasoning and the maths seems ok except 100 less
4 = 96 not 98.

The one thing I'm not seeing is the time taken for the fuel and air mix to
reach the rotor housing. I don't know the Velocity of the 2" inlet tube but
lets say 100mph as a round number to work with. How then does this time
taken to reach the port opening affect the timing.
We want the fuel to commence after the exhaust has closed and before
compression gets to the stage of significant back pressure against the inlet
flow.

If I remember correctly, I believe Tracy mentioned that with his
arrangement, the timing was such that, the fuel arrived at the next inlet
event- with the injectors out near intake tube opening.

It could be without taking this all into consideration you are fighting the
tuned effect and why your getting such a high fuel mist from the opening.
Just a suggestion!
George (down under)

---------------------------------------------------------------------

100 MPH may be on the low side but lets assume for the moment
that is correct.... about 150 FPS.  2 foot-long-runner/150 FPS... it takes
..013 seconds or 13 msec. A msec = .001 seconds.

Since it takes 100 msecs to get to the next identical intake point
at 6000 RPM 13 msecs is not particularly significant.

There is another point to be made about tuned intakes.
When the intake port closes the pressure at the port is above atmospheric
due to the jamming effects of the intake charge velocity.
It must be so because tuned p-port rotaries normally
enjoy 120% volumetric eff.

The fuel pressure regulator puts out 50 psi relative to atmospheric pressure
unless it is connected to the intake manifold pressure. Same goes
for turbo charging.

One reason we are getting a high fuel mist is we are using a carb. A carb does
not care much about the direction of the air flow. In or out it matters not. It
will supply fuel regardless and almost 100% of the time. As the air is flowing
out of the carb located at the end of the runner it adds fuel to the mixture that
is already in the runner.

This is not a problem as we are running a constant load and RPM during
cruise. You just manually adjust the mixture to get only what you need.
assuming of course the carb is an aircraft carb and the mixture can indeed
be leaned. On the dyno we were using a Weber which cannot be leaned while the
engine is running. Ken Welter uses a trick to lean the Weber carb while the airplane
is moving at 100 MPH by using dynamic air pressure. I can see why tuned intakes are
rarely used in car racing where carbs are mandatory. It is close to impossible
to get a carb to work automatically under those circumstances.

The challenge for all tuned intake systems is getting the mixture right.
The fuel required is not a straight line function of RPM or throttle opening.
When the intake is "on the pipe", to use an organ term, the engine needs
disproportionately more fuel.


Paul Lamar ...No rotor no motor.

Paul,

Ok here we go:) Your approach to the calculation is interesting but makes
the idea perform better than they actually will. We have to calculate
the needed flow during the optimal injection window and then choose the
injector and duty cycle to achieve it.

Several points need to be expanded on. We won$B!G(Bt be able to, nor desire
to, inject during the full 360 degree rotation of the e-shaft even
though a P-port is at least partially opened most of this time.  I agree
we have to begin injection on the backside of the rotor after the intake
port is open. I don`t understand your comment that the port is open 270
degree of the time though. Not for a P-port. The earliest we can
practically start the injection cycle is a few degrees after the intake
port is fully open and the injector port holes (same degree location as
the oil injection holes) are uncovered.  The latest, "stop-injection,"
timing moment would be when the apex seal closes the intake P-port.
Testing may show that the sweet spot is only a few degrees but we really
don`t have much leeway to explore for it much in the higher rpms. Lets
just say for calculation purposes the acceptable injection zone is about
200 degrees of e-shaft rotation.  It could be more though we still need
to give these bad boys some  time off for good behaviour and allow for
their response time. The  Deka IV turns on in 1.14 ms and off in .85 ms
so we have plenty of time before and after the injection window to
handle this response.

Yes, we aren$B!G(Bt direct injecting on the pressurized side of the rotor. We
are, however injecting directly into the intake chamber part of the
stroke through the housing and that will eliminate the challenge of fuel
bouncing off the manifold walls, and side ports,  and condensing into
bigger droplets.  Of course the proof of the pudding is how good these
injectors really are at providing a fine mist and what happens when that
mist hits a hot rotor and incoming air.  I am boosting 2psi so  the VE
goes up to 150%. This means that my fuel pressure will need to be
higher. At least 4 bar. Otherwise near the end of the intake sweep the
fuel pressure  is fighting against the manifold pressure and flow
suffers.

I think most injectors are rated at 80% duty cycle and that generally is
the max. recommended as they start to get warm at higher duty cycles.
This is not to say they can$B!G(Bt or aren$B!G(Bt driven harder though for short
durations. Three minutes TO power  before reducing to climb power should
be OK at 90%. duty cycles.

Because the rotor will be so near to the fuel injectors inlet, as the
apex seal passes by, we will need to shorten the injection timing window
near the beginning as well.

Ethanol evaporates faster than gasoline and cools the interior 100
degrees so that will be an advantage but the disadvantage is we need
more volume (cc) of it in most parts of the power ranges.

 Yes, 6000 RPM is 100 revs a second. or once every .01 seconds or 100 ms.
 If we follow your example and agree that the injector accomplishes the
squirting event once per e-shaft revolution then at 6000rpm we have 100
msecs divided by 360  of e-shaft rotation to do it.. Degrees/time  is
then .27 msecs time per degree of e-shaft rotation.   To repeat myself
let us just say out of those 360 degrees of e-shaft rotation only about
200 of them are optimal for $B!F(Bintake chamber' fuel injection.

 So now our injection time window of opportunity is down to 55.5 ms.
( .277 ms times 200 degrees = 55.5 ms)  Again on each side of this window
we still have 160 degrees or 44.4 ms to turn the injectors on and off.
We only need about 2ms for this job. The remainder of the time is for
rest.

Lets approach the problem from a flow perspective and calculate in mass
flow. Using the DEKA IV injectors as an example, at the full rating of
60 pounds gasoline per hour each, that is the equivalent of 453 grams
per minute. (See spec. sheet) At 18 pounds per hour that injector is
flowing our 3 gallons a minute as  selected for cruise flow. This in
only is only 1/3 as rated,  or 151 grams per minute,  2.51grams per sec,
and divide by one thousand   .00252 gms per ms.

Now again it requires 100 ms for 360 degrees e-shaft rotation, and we
know we need .00252 gms per ms.   So each injection volume required
during this event is 100ms X .00252 or 0.252 grams.

However our chosen injection duration window is only 200 degrees or only
55.5% of the time.  We therefore need to increase the mass flow from the
injector.  We can increase the injection  time window, the fuel
pressure, or duty cycle.  We rather not (at this point in the
discussion) touch the first two variables so that leaves increasing the
duty cycle.

Now I don`t have information on the duty cycle verses flow curve of these
injectors.  We  assume flow vis-a-vis duty cycle is linear.  It may not
be.

For calculation purposes we are at 1/3 flow or 18 lbs per hour, per
injector so that means (if a linear curve) 33.33% of the 80% rated duty
cycle. This gives us a duty cycle of 26.7% if my math is correct.
Increase this 55.5% to get the flow we need into our 200 degree window
of opportunity and duty cycle becomes  1.555 X 26.7% = 41.5% . No sweat.
 This gives us some manuevering room if we want to increase the flow
more and shorten the time duration. The challenge of course is as we go
up in rpms we have less and less time to inject more and more fuel.
Fuel injection effieciency perhaps drops off near the end of the window.

At idle speeds it is easy to imagine the consequences of injecting too
near to the over lap period.  Result.  Some raw fuel going into the
exhaust.

At 8,000 engine rpm on E-85 ethanol and making 300hp,  with 2psi boost
and  .7 BSFC it gets rather marginal but I$B!G(Bll leave that calculation
for your homework.  The advantage may be easier tuning as the injection
happens closer to where you want it.
.....
George and others. These are extremely rough calculations and my engine
as now planned will not have a tuned intake as it is slightly boosted.
How an injector or two in the housing plays out with tuned intakes
manifolds is beyond my understanding.  Either way it requires a boat
load of dyno time to make, understand and tweak a good map.  I am
assuming it won`t be easy and the sweet (best bsfc) injection timing
windows will move around depending on MAP, and rpm. Wouldn't it be nice
if the best burn efficiency could be dialed in to corresponded to the
least engine friction rpm?


Doug in Japan

It truly is open 270 degrees of E-shaft rotation. The rotor is
moving backwards at one third e-shaft speed :)
One of the reasons the clever Wankel engine breaths so well.
The piston engine intake is only open 90 degrees roughly.

I maintain you don't need a good map in a rotary.
It will run over a wide mixture range. 10:1 to 20:1
At constant RPM, constant prop load cruise you adjust it for the mixture you want.

It is also possible to run a piston engine with a sunk float in the carb.
In effect.... way over rich. You use the mixture control to keep the engine running
smoothly. I have done it. Sunk floats were common in 172's carbs  until the AD.

Klaus has run his engine with nothing more than a small pipe, gravity feeding
fuel from an aux tank, directly into the engine intake manifold. The same
as the Wright Brothers.

Of course we don't have a map in a 555 system. The fuel going into the engine
is directly proportional to the air and the RPM. The mass airflow sensor
adjusts the basic pulse width up and down. The main parameter or primary control is RPM.
No computer to program or map. Not required. Far easier to trouble shoot and
maintain. What you see is what you get. No mysterious computer program to deal
with.

Paul Lamar ...No rotor no motor.

Paul,
You are right that the port is fully open for 270 degree, however the
exhaust is still open for another 70 degrees, so Doug is suggesting the best
time for injection is after the exhaust is closed, as Tracy does it. I must
agree that this sounds like the best solution to eliminate fuel into the
exhaust ( in overlap), so the most effective fuel injection time is 200
degrees. As Doug suggests the timing varies a little at every faze so some
time should be allowed for this variance, this may reduce the time to180
degrees, however for basic calculations, lets keep it simple.

Paul what is the ID of your PP, I have worked out a method of calculating
the inlet speed. I need this to confirm that there is sufficient time to get
the outboard injectors to deliver fuel to the combustion chamber. I have no
doubt there is sufficient time, I only wish to confirm it to myself. This
whole exercise something I have been wanting to do for some time now and I
need to compare my figures with yours and Doug's figures. I did do some last
night but I need to rehash them as I think there are some basic errors in my
calculations.

I will run my calculations by you and Doug as soon as it is done. I thank
you both for your contributions thus far, as it has been a great help to me.
George (down under).


1 7/8" dia.