Maker Pro
Maker Pro

100 MPG??

D

daestrom

Jan 1, 1970
0
wmbjk said:
Something tells me that the difference between valves and lifters is
just one more thing that Gymmy Bob is confused about.

Daestrom, here's something that might interest you if you haven't come
across it before - http://www.ducatitech.com/info/desmo.html. Very
cool, although others managed to do as well with regular springs.

Thanks, that is something. No need for strong springs with hi-speed valve
train. But I'll bet adjusting the 'lash on those is a bit trickier than
your usual solid lifter system ;-)

daestrom
 
W

wmbjk

Jan 1, 1970
0
Thanks, that is something. No need for strong springs with hi-speed valve
train. But I'll bet adjusting the 'lash on those is a bit trickier than
your usual solid lifter system ;-)

daestrom

Adjusting the valve clearances wasn't really all that hard, although
it was common for some to hype the Desmo mystique. My only
contribution to that was wearing a clean shop coat when presenting the
bill for work on any Italian sport bike. ;-)

Wayne
 
J

JoeSixPack

Jan 1, 1970
0
A hybrid could top 1000 MPG if I plug it in all night and then go for a
short trip.
You are right, 100 MPG is possible. However, vehicle weight will have to
come down substantially. There just isn't enough energy in gasoline to get
100 MPG from a 2500-3000 pound car. At this point in time, reducing
vehicle weight has more potential for raising MPG than engines, fuel, and
hybrid schemes. Another possibility is radical changes in tire/suspension
design. Going from bias ply tires to radials got a 2-3 MPG improvement
even
in big draggy gas guzzlers of the 1960's and 1970's. Thinner, harder tires
could get another few MPG at cruising speed. Better suspension design
could
compensate somewhat for the harsher ride.

Water injection has been tried over the years as a way of capturing some of
the energy lost as heat out the exhaust. The problem is that it hasn't been
captured very successfully, because putting water in the combustion chamber
to create steam isn't the best approach. Although it cools the combustion
process and aids in reducing pollutants, a secondary heat-recovery system
would be required. A Stirling engine attempts to capture more of the heat,
but it's practicality in automobiles has not been fully realized.
 
D

danny burstein

Jan 1, 1970
0
In said:
Lesser efficiency on the highway? I wonder why that is? Perhaps the engine
is less efficient at higher horsepowers and could be factory tuned or
selected by user for specific usage personality?

Not quite. It's simply a matter of mpg vs. speed. As you move
faster and faster (i.e. highway speeds) you run into an
exponential increase in air resistance.

So... all things being equal (which they're not, see next parag) you'll
get _zero_ mpg when stopped in traffic maybe 10 mpg moving at 5 mph
(you're using up plenty of fuel just keeping the engine running) perhaps
60 mpg when going 40 mph
.. and ..
drop a bit to 50 mpg when going 60 mph.

Now those figures are kind of back of envelope,
but the progression is correct. Your best mileage
will be at something like 40 mph.

Now for the hybrid trick... the better designed
ones do an "idle shut off" so when you're stopped
at a traffic light, you're _not_ burning/wasting fuel.

Nah. They do better. At least the properly
designed ones.

A typical US gasoline car uses an engine that's way
over powered for cruisig speeds. While this gives
you the ability to rapidly come to speed at a highway
entrance, it's a big waste once you're up to that 70 mph.

(The physical size and weight of the engine means you
have to burn quite a bit more fuel tha you would
with one that didn't have all that extra horsepower).

So... a well designed hybrid, like the Honda Insight,
uses a smaller gasoline engine that's just large
enough for cruising (well, somewhat bigger than that,
but not as horrendous as standard), thus saving
you all that extra, wasted, fuel. When you're on that
highway "on ramp", (or passing a truck, etc.) and
push the accelerator pedal, the electric motor
kicks in and gives you that extra horsepower.

As to weight? The battery pack and motor plus circuitry
add about 125 pounds to the car. A lot of that is saved
by using a smaller egine. And, again, the physical
engine size/mass is smaller, thus saving fuel right there.

fyi, my own Insight mileage (auto transmission) is
about 55-60 on the highway, and 35-40 in NYC traffic.

(I'd do better in the City except that my idle
shut-off isn't working. I'll fix it RSN)
 
T

Tom

Jan 1, 1970
0
Typical road load HP on an average size vehical at 60 MPH is in fact
around 12 to 15 HP. That assumes not much wind and flat road. I
know this becuase I work with vehicals on dynomometers.


In said:
Lesser efficiency on the highway? I wonder why that is? Perhaps the engine
is less efficient at higher horsepowers and could be factory tuned or
selected by user for specific usage personality?

Not quite. It's simply a matter of mpg vs. speed. As you move
faster and faster (i.e. highway speeds) you run into an
exponential increase in air resistance.

So... all things being equal (which they're not, see next parag) you'll
get _zero_ mpg when stopped in traffic maybe 10 mpg moving at 5 mph
(you're using up plenty of fuel just keeping the engine running) perhaps
60 mpg when going 40 mph
.. and ..
drop a bit to 50 mpg when going 60 mph.

Now those figures are kind of back of envelope,
but the progression is correct. Your best mileage
will be at something like 40 mph.

Now for the hybrid trick... the better designed
ones do an "idle shut off" so when you're stopped
at a traffic light, you're _not_ burning/wasting fuel.

Nah. They do better. At least the properly
designed ones.

A typical US gasoline car uses an engine that's way
over powered for cruisig speeds. While this gives
you the ability to rapidly come to speed at a highway
entrance, it's a big waste once you're up to that 70 mph.

(The physical size and weight of the engine means you
have to burn quite a bit more fuel tha you would
with one that didn't have all that extra horsepower).

So... a well designed hybrid, like the Honda Insight,
uses a smaller gasoline engine that's just large
enough for cruising (well, somewhat bigger than that,
but not as horrendous as standard), thus saving
you all that extra, wasted, fuel. When you're on that
highway "on ramp", (or passing a truck, etc.) and
push the accelerator pedal, the electric motor
kicks in and gives you that extra horsepower.

As to weight? The battery pack and motor plus circuitry
add about 125 pounds to the car. A lot of that is saved
by using a smaller egine. And, again, the physical
engine size/mass is smaller, thus saving fuel right there.

fyi, my own Insight mileage (auto transmission) is
about 55-60 on the highway, and 35-40 in NYC traffic.

(I'd do better in the City except that my idle
shut-off isn't working. I'll fix it RSN)
--
_____________________________________________________
Knowledge may be power, but communications is the key
[email protected]
[to foil spammers, my address has been double rot-13 encoded]
 
D

danny burstein

Jan 1, 1970
0
Typical road load HP on an average size vehical at 60 MPH is in fact
around 12 to 15 HP. That assumes not much wind and flat road. I
know this becuase I work with vehicals on dynomometers.

As you're measuring this on a dynamometer, is that 12-15 hp
just rolling resistance or are you somehow figuring out
the air resistance as well?

Thanks
 
As you're measuring this on a dynamometer, is that 12-15 hp
just rolling resistance or are you somehow figuring out
the air resistance as well?

Thanks


Electric vehicle experience has shown a 96 volt motor will draw
between 300 and 400 amps at 60MPH in a Chevette sedan. 400 amps is
38.4KW - which in the real world is 35 HP, more or less.

At 37MPH, a 72 volt system draws about125 amps (9hp +/-). 43 MPH
draws 175 amps.(aprox 13HP)
28 MPH is only 80 amps.( less than 6 HP) This is on a 2990 lb EV.
This is also running relatively high pressure fabric radials.

From other data, using a Fiat 128 sedan at 40MPH, wheel torque of 76.5
ft lbs at 936 revs per mile translates to 10 HP. Car weight is 2900
lbs.

60 MPH requires 125 ft lbs.which translates to just under 25 HP.

That is theory.
Real world experience with a 48 volt motor on MY Fiat 128 L coupe was
top speed of 50MPH at 400 amps. That's 19.2KW. The motor I was running
was roughly 82% efficient, according to specs I was given (Converted
B52 generator) My Fiat was about 2255 lbs plus passengers.
 
Top