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100 MPG X-Prize Entry

100 MPG X-Prize Entry - Physics Forum

100 MPG X-Prize Entry - Physics Forum. Discuss and ask physics questions, kinematics and other physics problems.

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Old 04-28-2008, 05:39 AM
Posts: n/a
Default 100 MPG X-Prize Entry

I've still be unable to raise the $250,000 I need to field an X-Prize entry
for a 100 MPG automobile.

Maybe if I give details of my plans then the funds will come in...

Well, consider the Audi A2 with the 1.2 diesel engine. The car has four
seats, weighs 1881 pounds, has 60 horsepower, has 103 foot-pounds of torque,
and gets 87 MPG in highway driving. Also the car is probably a little short
of the performance requirements.

Obviously the car could make 100 MPG if it were lightened. But the car
already has an aluminum frame and bodywork. Sure someone could make a carbon
fiber frame and bodywork for it but that is very expensive. And another
problem is that the 1.2 diesel engine likely only meets older Euro emission

In fact the only diesel car engines available in the U.S. in 2009 will
likely be 2.0 or larger.

And while there are some motorcycle engines with water-cooling, four-valve
heads, and fuel injection...the motorcycle engines do not meet automobile
emission requirements.

So my three entries are based on the above fundamentals.

The first entry will be a Lotus Elise with a 1.5 Yaris engine. The Lotus
Elise weighs 1984 pounds while the Yaris weighs 2295 pounds. Since the Yaris
gets 36 mpg and since the Elise weighs 14% less than the Yaris I'll estimate
the Entry1 mpg at 41 mpg. Then I'll further estimate the Entry1 mpg at 50
mpg based on gearing to required performance level. Also I could have a
thinner fiberglass bodywork made for Entry1 and thus will stick with the 50
mpg prediction.

But that's only halfway to the 100 mpg requirement ? Yeah, and consider that
all current cars have an engine control module that can't be directed by the
tuner. However, the ECM sends an electronic signal to the fuel injection and
therefor an electrical engineer could develop a system that interrupts the
signal to the fuel injection every other time on each cyclinder. Then
theoretically the engine uses half the fuel. Then the interrupt sytem could
activate only above 1500 rpm so that the engine is smooth at idle.

Would a fuel injection interrupt system work...meaning would the
four-cyclinder engine be smooth enough ? And would the fuel injection
interrupt system double the fuel mileage ? And finally would the fuel
injection interrupt system meet the performance levels ? Well, without
testing I don't know...

But the hope is that Entry1 has reached 100 mpg...

And that seems like a lot of hope so that leads to Entry2.

Entry2 is the KTM X-BOW with its 2.0 tubocharged VW engine replaced with a
2009 U.S.A. 2.0 VW diesel. Now the X-BOW has a carbon fiber frame and weighs
1650 pounds but the X-BOW will need bodywork added since climate control is
required. So put the weight at 1850 pounds.

Now the 2.0 VW diesel engine will probably get 45 mpg in a 3200 pound car.
Figure on 42% less weight and Entry2 gets 64 mpg. And 64 mpg could also
depend on gearing to the performance level. Now try the fuel injection
interrupt system on Entry2 and hope for 128 mpg...or be very satisfied with
100 mpg.

Oh, Entry3 is the Caterham 7 wide-frame special- ordered in aluminum and the
use a 2009 U.S.A. 4-cyclinder diesel engine along with a rear-wheel-drive
transmission. And subframes along with custom bodywork will enclose the
wheels and make a swing-back top. Of course the fuel injection fuel
interrupt system is also needed...

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Old 04-28-2008, 02:45 PM
Mechanical Magic
Posts: n/a
Default 100 MPG X-Prize Entry

You are missing something here.
Weight is not the biggest problem when designing for high MPG.
If weight were dominant, a motorcycle @ 400# + 150# rider = 550#,
according to you that should get several hundred MPG.
Well it ain't so.
[Only registered users see links. ]


If you spent as much time calculating the dynamics of wind drag, as
you did looking at weights you would know.

Give this a try.
Rough guess at the frontal area for a:
Small car

Look up the drag coeffecient, and multiply tines the frontal area.

The result corresponds inversely to MPG, (nearly straight line).

[Only registered users see links. ]

On Apr 27, 10:39 pm, "PolicySpy" <[Only registered users see links. ]> wrote:
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Old 04-28-2008, 06:53 PM
Posts: n/a
Default 100 MPG X-Prize Entry

> You are missing something here.

Motorcycles are developed for high-performance. They often have one
carburetor for each cyclinder. And in recent years they tilt the cyclinders
forward so that the carburetor can pour into the cyclinder.

But the motorcycle engine could be re-carburetored...

Now in a car I increase MPG by reducing weight but then I also want to scale
the engine size to the new weight. Since I don't have the engine size that
I need then I look at means of making a large engine act like a smaller

Aerodynamics is a relevant fundamental. But both drag coefficient and
frontal area together make the total amount of drag.

Now a car must be wide for stability in corners and for side-by-side
seating. So an aerodynamic car is low to the ground. In fact front spoilers
and side skirts reduce drag by reducing the amount of air flow under the
car. The front spoiler can look bad but work very well. Now the front
spoiler also reduces lift by such a large amount that there will never be a
rear spoiler that reduces lift at the rear by the same amount. That leads to
rear wings but a rear wing might add drag while a rear spoiler will reduce

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Old 04-29-2008, 04:05 AM
Mechanical Magic
Posts: n/a
Default 100 MPG X-Prize Entry

Response inline.
On Apr 28, 11:53 am, "PolicySpy" <[Only registered users see links. ]> wrote:>

Yes, weight is a factor. Excess engine size is also, no argument.

Yes, that's what I said.

No, an aerodynamic shape is such by itself, The nearness of the
ground is largely irrelevant.

This is so wrong in so many places, it's hard to start.
Front/side spoilers on race cars are meant to create a vacuum under
the car, increasing downforce, (weight to you).
Rear wings do the same.

Race cars are worse than a brick when speaking of aerodynamics. They
are designed to use airflow to INCREASE the apparent weight of the

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Old 04-29-2008, 04:38 AM
Posts: n/a
Default 100 MPG X-Prize Entry

>> In fact front spoilers and side skirts reduce drag by reducing the amount

Reducing the wind flow under a production based vehicle reduces drag and
lift...and no production based vehicle has net downforce.

But formula racing cars replaced front and rear wings with an
underside-of-the-car-wing-shape and they duct high pressure air under the
skirted car to make downforce without the drag of the wings.

So a formula race car is very different from a production based car that
simply tries to reduce air flow under the vehicle.

In fact Ford has a high mileage concept car where the suspension lowers at
highway speeds to reduce drag...

Now moveable aerodynamic devices are banned on race cars by international
agreement. So those rules should be re-written. For instance we might want a
hinged front spoiler to gives way when it hits something or we might want
bristle brush front spoilers and side skirts. We might want front spoilers
and side skirts that rise when the suspension compresses...

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Old 05-02-2008, 07:33 PM
Mike H
Posts: n/a
Default 100 MPG X-Prize Entry

On Apr 28, 12:39 am, "PolicySpy" <[Only registered users see links. ]> wrote:

I'm not sure you are fully aware of the technology available in the
aftermarket for engine control systems.

The Ford EEC-IV is a favorite of do it yourself engine control system
builders. Add an EEC Tuner product or TwEECer and you have complete
control of all parameters. There are others. This website is helpful
on the Ford EEC-IV processor.
[Only registered users see links. ]

Then there are aftermarket engine control systems from Electromotive
and F.A.S.T. I believe FAST now has a system that will allow
sequential spark control rather than wasted spark.

At a minimum, anyone participating in this contest is going to need to
have a custom engine management solution.
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Old 05-03-2008, 04:25 AM
Posts: n/a
Default 100 MPG X-Prize Entry

>> But that's only halfway to the 100 mpg requirement ? Yeah, and consider

I was thinking that you need the factory ECM but then need to be able to
change just a few settings.

I knew that there were racing parts but didn't think that would be the right

Of course everyone knows about someone who put in a aftermarket ECM and they
think their car is faster but they know that their gas mileage went down...

Now I did find something that probably would not work with direct fuel
injection :

"Throttle restrictor (plate) between throttle body and plenum..."

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Old 05-06-2008, 02:24 PM
Mike H
Posts: n/a
Default 100 MPG X-Prize Entry

On May 2, 11:25 pm, "PolicySpy" <[Only registered users see links. ]> wrote:

Those are not necessarily designed for racing. The EEC tuner for the
Ford EEC-IV is a common platform used for hobbyists interested in
learning about EFI systems.

A throttle restrictor plate has no impact on direct injection or not.
All that will do is limit the amount of outside air that enters the
engine. For ideal fuel economy, you'll probably want to be measuring
the actual air entering the engine anyways to allow you to take that
as an input to derive fuel curves. This is typically done using a Air
Mass Sensor. A Air Mass Sensor is typically placed after the air
filter intake and before the throttle body. Ford and GM use different
methods of measuring air mass. I am familiar with Ford.

Ford uses a heated wire to measure air mass passing through a
cylinder. It's sensor element has two wires. both are heated, one
directly in the air stream. The sensor uses the temperature
difference between the two to output a DC voltage relative to the MASS
of the air flowing across the wire. Output voltage is 0 to 5 volts.
Sensor electronics and sampling tube dimensions are critical to ensure
the sweep from 0 to 5 volts is both reliable, representative, and
allows for sufficient range based on the intake capabilities of the
motor. (I.e. it doesn't do any good if the engine can ingest 1000cfm
of air, but the maf sensor peaks to 5v at 600cfm of air)

Typical sensors in a EFI system with electronic distributorless spark
control are:
TPS - Throttle position sensor
BAP or MAP - barometric Absolute Pressure sensor or Manifold Absolute
Pressure sensor. If forced induction, a BAP is typically used)
ACT - Air Temp Sensor - typically in the intake tract (after the turbo
or blower in forced induction)
Cam Sensor - Indicates Camshaft position for injector timing
Crank Sensor - Indicates Crankshaft position for Ignition timing
Oxygen Sensor - Narrow band Sensor that indicates + or - from Stoic.

If you were to build a vehicle for an efficiency competition, you want
a processor that is faster than current factory processors. You will
want a processor that can support sequential fuel injectors, and
sequential spark control. (Most injectors are now controlled
sequentially, though ignition is still often wasted spark control.)
You will probably want to use a wide band oxygen sensor.

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Old 05-06-2008, 05:51 PM
Posts: n/a
Default 100 MPG X-Prize Entry


I would just be worried about some ECM clone that works but leaves out a lot
of details...

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Old 05-06-2008, 08:34 PM
Mike H
Posts: n/a
Default 100 MPG X-Prize Entry

On May 6, 12:51 pm, "PolicySpy" <[Only registered users see links. ]> wrote:

It appears that your experience with engine management systems is
limited. It's not possible to manage an internal combustion engine
with a system that "leaves out" details. In fact, the majority of
them have so many details you need to learn that it can be quite

There is a school you can go to to learn more.
[Only registered users see links. ]

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