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.

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: Motorcycle EV1 Small car truck motorhome

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

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

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 engine.

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 drag.

Response inline. On Apr 28, 11:53 am, "PolicySpy" 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.

air flow under the

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 vehicle.

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...

On Apr 28, 12:39 am, "PolicySpy" 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.

At a minimum, anyone participating in this contest is going to need to have a custom engine management solution.

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 direction.

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..."

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: MAF 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.

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

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 daunting.

There is a school you can go to to learn more.

All the details are daunting but it's not possible for someone to develop a less than average system ?

In fact engineering involves compromises and judgements...and the amount of development effort can make a difference.

Of course a current master engine builder could work out an ECM for an X-Prize entry but a fabrication shop just needs to find an engine to put in a chassis.

It is extremely simple to create a less than average solution. It's even easy to create a destructive solution. The nice thing is that it is simple to identify when your solution is below average, average, or destructive. engine control systems and what it takes to optimize control is fairly well documented.

The true challenge is in engine design. Modeling an internal combustion engine design on computer is not a trivial task. I'm not sure it can even be done with any true accuracy at this point. In the end, you still have to build it and test it.

Some design improvements currently being tested by automakers: Direct Fuel Injection into the combustion chamber. Variable Displacement based on driver demands. (disable cylinders) Variable Combustion chamber size based on driver demands.