All you RX8 owners that live in states that allow
you to improve your engine I think you can get better
miles to the gallon by using MSD coils.

If so measure the gas mileage before and after.

The most accurate way is get a OBD II software and
USB cable for a notebook computer.

That will give you the mass airflow every second and record
it on the hard disks.

Then set the cruise control to 60, 65, 70, 75, and 80

When you are getting better MPG the mass airflow will
go down for steady speeds. You will know this right
away.

My theory is these MSD coils will help greatly in
those speed ranges.

Paul Lamar

I've kept track of every tankful of gas that I've put in the car
since I bought it in 2003, and have a spreadsheet of all the
mileage data.  About 6 months ago, my average went from 17-20
mpg, to a minimum of 22 miles per gallon for every tank! And was
climbing slightly every tankful until I changed the coils. My
highest was the week before I changed the coils...24.7 mpg. Same
gas, same station, almost always the same pump. Only the price
keeps changing!

Since I put the new coils in, the last three tank fulls have been
18.5, 19.1 and 18.2! I calculate it by using the amount of gas
reported on the pump when I fill it (I fill it up every time I
get gas) and the mileage on the trip indicator, which I then
reset.  After 65,000 miles odometer indicated, the total in my
spreadsheet is within 100 miles.

Harley

Very interesting.
If this proves to be true in the long term my guess is Mazda
changed the primary winding to cool the new 100 B coils. The
effect of this is less spark energy I suspect. I can check this
perhaps on the test bench as I have both the early coils and the
new 100 B coils. If that proves to be true that is a bit of
evidences that more spark energy over a longer period of
time  will improve the BSFC. Something I have suspected
about the rotary moving combustion chamber for a long time.
The MSD coils come closer to this ideal than anything I
have seen so far.

http://www.rotaryeng.net/Why-CDI.html

When you fill up Harley you should make
a note of the OAT temperature. Fuel expands and contracts
with temperature and I don't think the gas station pump can
compensate for that. I think the gas station flow meter just
knows the gallons and not the pounds of fuel.  Another factor
is the percentage of alcohol in the fuel. Since alcohol gives
less energy per gallon that too affects the MPG. Since it has
been steadily getting colder up there I think you were getting
more energy in your tank up until the time you changed the coils
to the 100 B.

When I first got the RX8 in 2004 I did the OBD II trick and saw 25
mpg at a steady 65 MPH. If you know the mass airflow and the mixture
ratio you can calculated the pounds of fuel going into the engine.

The on board computer is very good keeping this ratio at 14.7 pounds
of air for every pound of fuel. It is called the equivalence ratio or
Lambda in this spread sheet of OBD II data. 1 Lambda is 14.7:1.
If I am using 3.6 pounds of air per minute I am using .245 pounds
of fuel per minute. That is 14.69 pounds per hour. So I am going
65 miles on 14.69 pounds of fuel. At a fuel weight of 6.25 pounds
per gallon that is 2.35 gallons an hour or 27.66 MPG!

The excessive fuel consumption of the rotary is an urban
myth perpetrated by lead foots. If you use all the 250 HP
you are going to burn the fuel.

Notice the weight of a gallon of fuel varies according
to the temperature. One must also pick a flat road on
a windless day near sea level.

This is a very accurate way of measuring the steady speed
fuel consumption. It is the way some cars are able to display
the MPG in real time on the instrument panel.

Just about any OBD II software that runs in a note book
computer will work.

Paul Lamar

Spark-current-LS1-V-MSD.jpg indicates the duration of spark from the
LS1 coil is greater than that of the MSD coil, although the MSD coil
has greater energy, it is expended in a shorter time.  While the MSD
spec says spark duration is 1.2 ms, their graph indicates 1.0 ms.
Whether the greater energy or the longer duration is of more value
is probably a question that can only be answered by testing.

Victor

Thanks Victor. As always your messages are insightful.

BTW On my list of things to do is build a CD ignition system
that fires every 10 degrees for 40 e-shaft degrees or so.
Unlike a piston engine the mixture in a rotary is
in close contact with the plugs for at least that long.
The expansion stroke is 270 degrees rather than 90 in a
piston engine. At 3000 RPM one rotation takes 20 ms
so expansion time is at least 15 ms so 1.5 ms is hardly
adequate IMHO. 3000 RPM is the cruising speed of an
RX8 car.

At high RPM the rich mixture is thrown out towards the
plugs. One reason the rotary  will run leaner than a
piston engine.

Paul Lamar

A sparkplug that will spark for each 10 deg, or in a series along a
specific degrees of an engines rotation will be very beneficiary, but
only in the start up sequence. Once it is running, only a very specific
ignition point will do.

The optimum condition sought after, is when the charge has reached it's
burn peak pressure at the time of the engines  highest compression position.

The flame front in gasoline  is so slow, that ignition spark has to
be administered well before peak compression position, in order for
the gas to reach it's own higest burn pressure to coincide with that
point. ( that is our famous "advanced timing").

The time when the engine moves towards it's higest mechanical
compression point, and at the same time, the gasoline is burning and
busy expanding to it's peak pressure, is wasted energy, where the engine
has to move against a continous build up of pressure.

Another spark 10 deg after, is going to be a waste spark, and do
nothing, but if instead , another spark could be administered
simultaneously at another location, the expanding  burning gasoline
sphere each sparkplug is responsible for igniting, will be travelling
lesser distance , than one single sphere caused by one sparkplug.

Thus shorter time can be achieved to reach peak pressure and thus
advanced timing can be set closer to peak compression position, ( or
in pistons..TDC), thus lesser back pressure in the compression stroke.

Downside is a possibility of knock, when two flame fronts are expanding
from two different positions in the combustion chamber, and the
travelling shockwave is compressing unburned gas/air mix in front of
it, this however usually not an issue, airplane engines and many car
engines have double spark plugs.

Another way to cheat the backpressure in the compression stroke is to
introduce an aromatic like Acetone, (If you have a compsite aircraft,
stay out of that)  or Hydroxy gas.

The idea behind the Hydrogen generators sold and installed, ( lot of
hype and lot of scams, and a lot of overinflated numbers....but they
do actually work though) is to have a hydrogen cell that will run
out of the alternators pull, thus produce hydrogen and oxygen..
Typically they pull about 20 Amps, so that is around a half of a
horsepower, they ( the good ones) can typically produce about 1.5 to
2 liter /min.

A normal soccer moms van, a 3 liter V6 ...typical,... that runs in
freeway speed will run in maybe 3000 RPM, and thus exchange 1500
liter of gas through that engine every minute, that pretty much
shows that the Hydrogen ( in this application) is not a fuel,......
1.5 liter against
1.5 cubic meter....one tenth of one percent in volume.

The way it acts is to treat the back pressure during the build up.

Hydrogen and Oxygen ( Hydroxy) have a flame front of 10.000 ft/sec.
Probably one of the highest flame fronts amongst explosives, not many
things will beat it.

Hydrogen, the smallest existing atom, will in comparison with fuel
particles, be like Hindenburg and Hydrogen will be like indians
everywhere shooting fire arrows on the blimps, setting the
whole Hindenburg on  fire...(...-" Oh the humanity"....,) quicker
than quick. Gasoline is still the fuel, Hydrogen is merely the firestarter.
Gasoline will still burn slow, but we will get close to simultaneous
start of the fire.

Here we come back to the topic again, thus, we will be able to retard
the advance timing for a lesser pump loss during the compression
stroke.  Many that run Hydroxy set the advance timing to 10 or 15 deg.
(the exact point will only be known in a dynamometer though)

So either way it is done, with added components, like Hydroxy, or
Acetone, or with a very strong spark that will really get the  fireball
going ( preferebaly with a pretty good shockwave in the beginning, to
cover a bigger initial ignition volume) , or with multiple points of
ignition, or a combination of applications,  is a matter of choice
and method, as long as the air/fuel mix is put on fire, and are
given the opportunity to build up to it's peak pressure as soon as
ever possible,
( and at the same time get no knocks) , and be able to start and
complete the process as close to TDC as possible.

Anything that will help avoid as much as possible the backpressure
building up during the compression stroke, will be beneficial.

I have never seen a four or six spark plug engine, that would be a
kicker, placed in such a way that they strategically cover the floor
so to say, each one simultaneoulsy fired with a snappy spark.

A rotary will, by it's basic design, lend itself to that much better,
than a piston engine where the valves are competing with space.

Roger


Hello Roger,

Re:  2nd spark wasted. Go to the web site and read the Le Mans 26B techincal
data sheet. They used a third spark plug to ignite the residual fuel in the
trailing area of the rotor. This gave more torque and better BSFC. The article
speaks of the flame fronts. Rotor motors are vastly different than boing boing
engines.

Re: dual plug engines. Nissan amoungst others have used dual plugs. In
automotive circles it is invariably as a concequence of reducing emissions. On
the Nissan 2.4L, if the intake side failed, (usually a coil problem) the thing
ran like crap. If the exhaust side failed it ran like any other single plug
engine. AC service is a safety issue, not emissions yet.

Re: Hydrogen as an additive. This is like putting a bit of Propane or CNG into
a diesel. Perks up performance due to a small extra bit of combustible fuel.
The big advantage though is it helps them burn cleaner.

Re: burn time. Check the web for Somender Singh groove technology. He has a US
patent. Reduce ignition lead when using.

More food for thought while the learning curve is heading for the high nines.

Dale Davies