snip

CONCLUSIONS:

At 40 MPH There is a clear advantage to running in hilly country.  Could
I shift to a lower gear and do better?  I don't know.  I think I would
need another bsfc map.

at 55 MPH, the double/coasting value is better than flat.  I'm somewhat
suspicious about this value, but maybe.  Notice that the progression
from the +/-20 hill to the +/-40 hill is greater fuel usage, then it
gets a little steeper, and fuel usage goes down.  Maybe.

For the 70 MPH case, I couldn't use the double value.  I have no idea
how to extrapolate above that top line, and it doesn't look like a good
idea anyway.  I did get curious and did a +/- 50 bmep.  Using 0.57 bsfc
for the 119 bmep point, and 1.1 for the 19 bmep point, I get a fuel
number of 88.7.  (the bsfc used for 109 was also 0.57, but that value is
actually at least 0.575.  Changes are pretty slow in this area of the
map.

So, it does depend on how you are driving, and driving in hills can give
better gas milage than level ground under certain conditions.  But, I in
the more normal driving ranges, even with better bsfc goin uphill,
better gas milage is obtained driving on the flat.

That was fun,
Bob White

--
http://www.bob-white.com
N93BD - Rotary Powered BD-4 (soon)

You did a great job Bob.

Paul Lamar

Hi Bob,

I am glad you had fun. I see you can not be convinced, you are holding on to
your hat by any means.

BTW, the formulae in the reference link is a mixture between Imperial and SI.

For 4-cycle engines the formula more precise would be:
bmep = HP * 12985 / (n * L);  (L = total engine displacement in litres.)
Since Torque is HP / n, bmep is directly proportional to torque.
T (ftlb) = 5252 * hp / n.

Therefore: bmep = T * n * 12985 / ( 5252 * n * L); n cancels out, so bmep = T
* 2.4724 / L.
Or: T = bmep * L / 2.4724.

So 'bmep' is used just to confuse people. It is the same as torque only
different by a constant factor.

When you have negative bmep you have negative torque, meaning the engine is
breaking you vehicle.

BTW, how is you project, the BD-4 coming? I see you are coming closer to
completing it. This must be exciting times for you. I hope all works out all
right and you will be soon up and flying.

Regards
Rolf

 
The Rotary Engine NewsLetter.  Powered by Linux.
ACRE NL web site. http://home.earthlink.net/~rotaryeng/            
Copyright 1998-2004 All world wide rights reserved.