snip
Just assume 130 BMEP is the same as some torque as 160 foot pounds.
Max torque of the RX8 engine.

Then HP is going to be HP = (torque X RPM)/5252

Those BSFC numbers are pounds of fuel per HP per hour so if you
multiply by HP and divide by six you will get gallons per hour.

Now you can calculate actual MPG if you know gearing I think:)
At 60 MPH in 6th gear the RX8 is doing 3000 RPM. At 80 MPH it is
4000 RPM. So you can plot MPH along the bottom of the chart.

BTW for any hill the level road load is added to a straight line.

For a 5% grade for example which is a rather steep grade at 60 MPH you
will be going straight up at 3 MPH or 15840 feet per hour.
Or 264 feet per minute.

One HP is one pound going straight up 33,000 feet per minute.
So a 3000 pound RX8 going straight up at 264 feet per minute requires
792,000 pounds foot per minute or (dividing by 33,000) 24 HP just to climb
the hill. Now we can draw a stright line on the chart and add it at every
point on the road load curve to get a required BMEP to climb the hill.

If you coast you subtract the stright line.

I think you get the idea here where I am going with this.

One other thing if you adjust these BSFC numbers for a modern engine
multiply all of them by .5/.55 or .9.

Paul Lamar

Hi Paul,

I fully agree with what you are saying.
As you said, the 5 % is rather steep. If you pick a road which has just the
right slope where on the way down you need neither the accelerator nor the
brakes, then going up would likely not require twice the fuel as driving along a
level road, all other conditions being the same, of course. Anyway, it will
depend a lot on the vehicle, the engine and speed used as well.

Regarding your comment on the altitude in Austria and Switzerland I agree that
it may may have had an impact as well. The altitude could change the outcome
too.
Anyway, regarding accelerating and coasting, it was just a thought if one can
get better flying mileage when alternately climbing and gliding on a
cross-country route.

Regards
Rolf

 
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