Fuel efficiency now & then

but it’s also a diesel engine :stuck_out_tongue:

to be fair, carburetors were old hat in the 80s, and fuel injection was pretty much in it’s infancy. Though I do remember hearing a guy talk about a 57 Bel Air “fuely” which was mechanically fuel injected, but they didn’t sell many of those back then.

Quick comparison between my 1965 Dodge Dart (uncontaminated by emission controls and other stuff), and 2007 Corolla:

  1. Weight, about 2950 lbs for both

  2. Interior space (both 5 passenger) and trunk space about the same

  3. Performance, the Dart had better acceleration, but both had top speed of around 100 mph.

4.Mileage; Dart averaged about 18 mpg with automatic and 273V8, while Corolla with 4 speed auto gets around 36 mpg with average mixed driving. Both used regular gas.

I rest my case.

My grandfather’s 1964 Chevy II with its 2.5L four might have been a closer competitor to the Corolla.
I remember he would buy gas a dollar at a time, ~35c/gal.

In concept, yes, but not in performance.

Some clarificatio is in order.

Cat converters have nothing to do with unleaded gas. Or with mileage (unless they’re broken inside and plugged, but that’s a different thread).

Gasoline is a hydrocarbon, hydrogen atoms bonded to carbon atoms. Air is about 77% nitrogen, 22% oxygen, and 1% argon and miscellaneous junk, not bonded but together like marbles in a jar. The conbustion process breaks these apart and recombines them. It produces carbon dioxide (CO2), some carbon monoxide (CO), some unburned hydrocarbon (gasoline) molecules (HC), some water vapor (H2O), and some oxides of nitttrogen (NOx).

CO2 and H2O would be the products of total and complete perfect combustion. The argon, unused oxygen, and nitrogen would just pass back out. Unfortunately, engines are not perfect combustion machines. The cat converter was added back in the early '70s to try to compensate for this. It seperates the oxygen and nitrogen molecules to pass them as N and O. both harmless. It then provides the opportunity for the CO molecules to catch an extra oxygen atom and become CO2, again harmless. Absolutely none of the energy used in these processes either takes away from or adds to the conversion of gasoline to mechanical energy…it all happens in the exhaust, well past the pistons and crankshaft, and does so just by using some of the heat that would have been blown out the tailpipe.

The cat converter does this by passing the exhaust by an open honeycomb of ceramic coated with a catalyst, a material (platinum-palladium) that when hot and brought into contact with NOx causes the molecules to seperate. The rest of the process is just what naturally occurs when the seperated atoms are brought into contact with one another in a hot enclosure. The honeycomb is wide open and designed to allow the exhaust to pass through without restricting it.

Unleaded gas was an entirely unrelated thing. And your Mazda wagon 30 years ago had a converter. My Vega made 38 years ago had a converter. The differences in milage are due to a long list of other diffferences, and are unrelated to the converter.

Oh, and the Smart Car is just a cute category of car. IMHO it’s crosssectional profile needs way too much energy to push through the air at highway speeds to be truely efficient. It takes anergy to part the air. The more needs parting, the more energy it takes. How effectively and cleanly (without turbulance) a design does this determines whether it does so as efficiently as possible, but I doubt that the Smart car has a great drag coefficient either.

I hope this explanation helps.

Concept. Absolutely.

Yeah and you Dart was spewing HC and CO in major quanties. I beathed the air those 1965 cars contaminated in L.A. in the 60’s and it hurt to breath, the situation is much better today.Perhaps I am not insightful enough to see the case you have rested.

Your Dart may not be contaminated but the air it’s exhaust mixed with certainly was.

I used “contaminated” with reference to OP’s opinion that all those engine add-ons have made engines worse in efficiency and cleanliness.

“Cat converters have nothing to do with unleaded gas.”

The whole reason that unleaded gas pumps had special small nozzles and the early “unleaded only” cars had openings too small to accept the normal gas pump nozzles was so people would not fill up the car with the slightly cheaper leaded regular and poison the catalytic converter and render it ineffective.
The original reason for mandating unleaded was to make catalytic converters possible, only later was leaded regular phased out for other environmental reasons.

The mandated introduction of unleaded gas had everything to do with not ruining catalytic converters.

I submit that the motivation to remove lead from gasoline primairly was done as a poisoning prevention measure. This EPA link supports my theory


Surely the removal of lead also made possible the use of catalytic converters,but the reason to remove lead was because it is a poison.

When I see a Honda Insight, I think back to the Nash Airflytes that were introduced in 1949. I was in elementary school at the time and was fascinated by the design. The Nash Airflyte had enclosed wheel wells and a boat tail rear end. It had been designed in a wind tunnel and had half the coefficient of drag of most other cars on the road. The Nash Airflyte 600 got its name because it could go 600 miles on its 20 gallon tank of gasoline. The engine was a flat head 6, not known for its efficiency. I wonder what the mileage would be on this car with an electronic fuel injected overhead cam engine from today.

In its favor, the 1949 Nash Airflyte 600 was truly a 6 passenger car–there aren’t too many cars today that carry 6 passengers.

You guys are right. Thhe lead was coating the catalyst rendering the converter inoperative.

I’m embarassed at having made that statement. I’m not sure what I was thinking at the time.

Maxima Mea Culpa.

Fuel injection was pretty well-developed by the 80s, there was just no standardized OBD.

The motivation was twofold; first get the lead out before it kills more people, and second, to protect the catalytic converter (which was necesary to meet tailpipe emissions), any lead substitute would have to be harmless and not leave a coating. MTBE and some others filled that bill.

Yes, MTBE filled the bill of poisoning us. Was that what you meant?

It was the “miracle” solution at the time. However, it has a way of working its way into the drinking water, and is now banned in many places.

As an octane enhacer it was great stuff, and did not interfere with the engine sensors or leave deposits. The only good thing about lead was that it lubricated the valve seats.

Yeah, it’s banned where I live. We had the water problem up here in NH.

 A few points on all this...
 1) As several people have said, cars now are heavier.  The crash standards we have now, they could not really make a car as light as some of the 80's models.  Also, when a car company DOES try to make a light car, car magazines complain about how noisy and tinny it is and how it feels "cheap", then it doesn't sell well.  Then they make the same model the next year but bloat it out with additional sound deadener and stuff, and it's suddenly just as heavy as the other cars on the market.

 2) Catalytic convert, it DOES lower mileage a little bit, it slightly restricts the exhaust, increases weight, and if the car runs *too* lean, the catalyst doesn't "light off" and the car computer actually dumps excess gas in *just* to keep the catalytic converter operating.  Leaded gasoline would coat the catalysts making them ineffective and in some cases plug the converter, so in a sense it has something to do with unleaded fuel.. but unleaded would have been phased in anyway because, you know, people don't want lead in the environment.

 3) Emissions.  A car that runs lean increases the NOX (nitrogen oxide) emissions, to the point that EGR can't lower it enough to be legal. Along with the cat, this also lowers mileage compared to what it could be.

 4) New MPG ratings.  Look at fueleconomy.gov, there are new MPG ratings the last year or two, testing more realistic driving conditions -- the old MPG rating was modelled after 1960s-era Los Angeles and was very unrealistic compared to anything like modern conditions.  (The new test assumes realistically fast acceleration, more stops -- the old test had multi-mile stretches *in the city test* with no stops.  Yeah I wish...  The highway test assumes realistic speeds, the old *highway* test assumed a top of 45MPH!)    Some of those old cars dropped over 10MPG in the new rating compared to the old one.

That said, Chevy of all companies is planning for some high 30 to 40s MPG cars for 2010-2011, and Chevy Spark in 2012 is supposed to get like 80MPG. As long as they don’t screw them up and put inefficient US-specific engines in them like Smart etc. have done – last I heard they don’t plan to. These are NOT hybrids, they are just new, modern car designs with new, modern engine designs – direct injection, variable valve timing, etc. allow for radical increases in efficiency (they’ve been retrofitted to existing engines with good results, but these engines will take full advantage of these technologies.) Car companies have realized people want efficient cars FINALLY and are starting to accomodate this.

  1. excellent points. And I agree that the car critics have an adverse effect on these issues…as well as on the size of the cars.

  2. I’m not convinced that a cat converter creates any significant restriction. The matrices are longitudinally aligned to the flow and while I’ve not tested one I’d bet that the CFM capacity of a cat converter is equal to or slightly greater than that of the pipes. If it’s greater, the flow will slow down going through the honeycomb and speed up again when it exits. My guess is that this is intentional to provide more time for the platinum palladium to do its magic. The volume out must equal the volume in. The converter’s weight is slightly greater than the pipe that would have been there, but I doubt that the difference it creates in mikleage would be measurable.

Yeah, leaded gasoline was a problem for the catalyst. I made a dumb statement and I have no excuse. My error. I don’t know what I was thinking.

  1. the upstream oxygen sensor recognizes the lean condition and tells the ECU, which lengthens the pulsewidth. It’s totally irrelevant to the cat converter. I’m not aware of any system that richens the fuel mix based on the teperature of the cat converter. I’m not even awaye of any temperature measuring device on any cat converter. The downstream O2 sensor simply monitors performance of the converter by co,mparison of its signal with that of the upstream sensor and trips a CEL if it’s unacceptable. I’m unaware of any system that uses the downstream O2 signal to trim the fuel mix.

I’m open to learning if you can link me up with a system that uses the downstream signal in this manner…or one that monitors the temperature of the cat converter.