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