>  > I did that for 80 MPH because I know the RX8 engine runs
> > at 4000 RPM in sixth gear at 80 MPH. I calculated the
> > fuel burn given the .67 BSFC at about 30 pounds of fuel
> > per hour. That is about 5 gallons an hour or about 16
> > MPG. Not far off what an RX8 will really do at a steady 80 MPH.
> > My measurements using the real time OBD II data indicates
> > the RX8 will get roughly 20 MPG at a steady 80 MPH.
> > You can calculate the pounds of fuel burned by dividing
> > the OBD II mass air flow data by 14.7. 14.7 is represented
> > as one in the OBD II charts. I have included some for
> > reference.
>  >
> > If you changed the RX8 rear axle ratio for 3000 RPM at 80 MPH
> > the BSFC would drop to 0.57. Fuel burn would drop to
> > 15.6 pounds per hour or 4.3 gallons per hour and MPG
> > would jump to 18.6. That is about a 16% improvement
> > in steady speed MPG.
>  > Paul Lamar
>
> ------------------------------------------
>
>    Paul,
>   My "91" RX-7 gets 24-26 mpg, @ 3000 rpm, which for my car is 80 MPH.
> This is actual driving in the high desert of central OR. 3500' Elv. I go
> into the valley all the time, going over the Cascades to get there. I
> usually cruse @ 80- 90, sometimes pushing to 100 to get around trucks. I
> have never seen mpg below 21.5 mpg, that is mostly when I do just city
> driving.
> I don't know what the rear axle ratio is. This car has 140,000 miles on
it,
> and these mpg's are all with the top down!  (;.)
> I keep telling myself, some day, I'll drive at a steady 60-65 mph, just

to

> see what mpg I get. And then I start driving again.
> Tom Phy
>
> -------------------------------------------------
> I had no idea the 3rd gen RX7 was/is geared that high.
> Of course it is a turbo so it generates more torque at 3000 RPM.
>
> I wonder why Mazda geared the RX8 at 4000 RPM at 80 MPH?
>
> As I said the BSFC chart I was working with is 50 years old.
>
> A friend just drove his RX8 to Las Vegas and back to LA
> claiming to hit 103 MPH and averaged 21.4 MPG.
>
> Thanks for the new data.
>
> -- > Paul Lamar ...No rotor no motor.
>

When I am at 80 mph, and need to pass right now, for more torque, I drop

to

3rd gear and take it to 7500 rpm or more. At that rpm, my car doesn't seem
to have much more umph left.

TP

You need to P-port it Tom :)

Paul,
I just checked, The rear axle, final gear ratio for my manual transmission
w/ convertible top   4.100

Tyranny    1st        3.475
              2nd       2.002
              3rd       1.366
              4th        1.000
              5th        0.697
This winter, I hope to street port it and add the 3" exhaust,  Or rebuild,
street port and add a 3" exhaust to a turbo engine, I have available. The
tyranny also needs new syncros and a clutch.
I want a reliable street/ daily driver, that will still allow me to pick up
the women, take them to dinner AND back to my place!!!
Did I mention it's a RED CONVERTIBLE?
The p-porting might go into a auto cross car I have.
TP


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