Old School Engines and Fuel Efficiency

[Bill in Houston]

Our 1975 Volvo 244DL had fuel injection and did 0-60 in about 15 seconds, top speed maybe 100 mph, weighed 3100 lbs, and got about 22mpg. My Element is also shaped like a brick, does 0-60 in ~8.5 sec, is speed limited to 108 mph, weighs 3500 lbs, is much safer than the Volvo, and gets 24-25 mpg. It is amazing to me how much better the Element does at all aspects.

[focus1.6uk]

Originally Posted by Arragonis

Later ones in the run-out classic Minis actually got port FI, ECUs and catalysts as well as electric cooling (for noise reasons) but with the low gearing of the Mini they weren't going to be especially good at FE.

Government figures for a 2001 classic Mini from:
Select a search : Directgov - Car fuel data, CO2 and vehicle tax tools

2001 Mini Cooper 1275cc (Twin port injection)
4 speed manual
Meets EU2 emissions standards

Urban 33.4 mpg
Extra Urban 51.8 mpg
Combined 43.0 mpg

CO2: 164g/ km
CO: 0.995g/ km
HC+NOx: 0.225g/ km

It also puts out...
63 hp at 5500 rpm
70 lb ft at 3000 rpm

Pretty poor FE considering its weight (around 700kg) and small frontal area, though admittedly the Cd and gearing are probably dire.

[user removed]

Originally Posted by Joenavy85

my dad had an old Chrysler 300 (I forget what year, may have been a Hurst 300) with a 392 Hemi that got around 20-22MPG, may not seem good but it was a 4200+ pound car after all, and it had the aerodynamics of a smooth brick. And I'm pretty sure he never tried for mileage in the thing

The 392 Hemi was the last of the first series. I know it was in the 1957 300 C and maybe in 1958 but I don't think so. Fuel injected with 392 HP in the last version.

The Hurst 300 came out in the late 60s early 70s, mainly cosmetic stuff like a fiberglass overlay on a otherwise stock hood. The non Hemi 300 K in the early 60s was a 413 wedge with 2X4 barrels with a "cross flow" ram manifolds, where the right cylinder bank was fed by a carburetor that was positioned outside of the left valve cover.

The slant 6 engines in the 60 and later Chrysler products were fairly efficient with the 225 long stroke being capable of mid to high 20 MPG range. I read once about a 55 Chrysler 300, with 4 wheel disc brakes that was hypermiled to 43 MPG.

I owned a 59 Austin Healey Sprite that regularly got 32 MPG when gas was 32cents per gallon, but I drove it like a maniac, and you could smell the rubber going around corners.

The model T was good for 25 MPG but top speeds were very low.

My 37 Ford Flathead was advertised as 20 MPG average. The carburetor was a Stromberg 94 which was supposed to be more efficient than the Stromberg 48 from the prior years. Even though the Flathead was very heavy at something like 525 pounds the coupe weighed just over 2500 pounds, about the same as a Toyota Corolla.

Personally I don't think higher mileage is really a function of engine design, at least as far as valves and breathing improvements. The longer stroke engines running at lower RPM can be fairly efficient especially with the variable venturi carburetors similar to the on on my current Honda Rebel.

It would be neat to see what could be done with modern fuel delivery technology, aerodynamics, and proper gearing, with old engine technology, like the 3.8 liter Buick V6 which was their mainstay for so many years.

Another neat candidate would be the Toyota 1500 CC engine of the mid 70s that was a push rod Hemi. I would bet that they could compete with today's designs if the fuel delivery systems were upgraded. High RPM, high power small displacement engines are good for power when needed but not really the combination necessary for good economy.

regards
Mech

[Frank Lee]

Flatheads have built-in disadvantages of limited breathing, poor chamber shape, and low max compression ratio that even nice modern EFI and other controls can't fully compensate for.

Other than that, the main disadvantage the old stuff had was in fuel delivery. Put a sophisticated modern EFI on just about any old non-flathead and I bet it would have vastly improved fe, perhaps in some cases almost as good as modern day engines.

That said, there are other disadvantages old engines are burdened with. Air-cooleds like VW and Corvair experience wider temp operating ranges (less controllable heat mgmt) so the pistons and rings are set up a bit looser causing more blow-by, and the carbs are set to run a bit rich to aid in cooling, neither of which help fe. In spite of that, VWs and Vairs can get good fe because of the efficiency of the rest of the vehicle.

Even the older liquid-cooleds don't have the nice tight tolerance control today's engines have. Combined with today's improved pistons and rings, there is less blow-by now.

Today's better chamber and piston crown shapes further enhance complete combustion. We can run higher compression ratios on lower grades of fuel. Yes some older engines had very high CRs but they required premium.

Today's materials are better too. For example, small block Chevys were usually made from a really soft grade of cast iron because GM was more concerned about the longevity of their factory boring tools than the longevity of the cylinders in the hands of the customer. Achieving 100,000 miles back then was a rarity; now we would be angry if an engine didn't go 200,000 miles (well, some of us anyway).

There have also been improvements in internal friction reduction via lighter rotating assemblies, smaller bearing surfaces, lower distortions in cylinders, better piston skirt and ring designs, and better balancing.

[War_Wagon]

I can't claim to have had anything old that was good on fuel, more like some of them weren't as bad as others. A family friend had a late '70s Dodge Monaco with a lean burn 440 set up in it, and it actually got decent mileage considering the size of the car and the engine. Granted it's all 3rd hand information, but he claimed to get in the low 20 mpgs on the highway, and that would have been with a non-overdrive transmission. The lean burn used a different carb and distributor, and had to be tuned in a certain way. No doubt most of them probably got scrapped a few years later by local mechanics that would have told owners "Get rid of this crap and put a regular carb on it" when they couldn't figure out how to tune it correctly. I have always wanted to find one of these cars just to see if the system actually worked like it was supposed to. If so, it was pretty impressive for the time I think.

[Bill in Houston]

What Frank Lee said.

[Arragonis]

Originally Posted by focus1.6uk

Government figures for a 2001 classic Mini from:
Select a search : Directgov - Car fuel data, CO2 and vehicle tax tools

2001 Mini Cooper 1275cc (Twin port injection)
4 speed manual
Meets EU2 emissions standards

Urban 33.4 mpg
Extra Urban 51.8 mpg
Combined 43.0 mpg

CO2: 164g/ km
CO: 0.995g/ km
HC+NOx: 0.225g/ km

It also puts out...
63 hp at 5500 rpm
70 lb ft at 3000 rpm

Pretty poor FE considering its weight (around 700kg) and small frontal area, though admittedly the Cd and gearing are probably dire.

Gearing would probably be 17 mph / 1000 (or slightly higher on the 13in wheels) and the cd figure of a classic mini is dire - 0.47 or something like that.

[Frank Lee]

Originally Posted by Bill in Houston

What Frank Lee said.

You are welcome.

[fud2468]

I had a 1966 Ford Falcon with the 200 6 and A/T that regularly gave me 27 mpg without trying for FE on trips down the CA central valley. Same mileage with a '61 Corvair with A/T, 35 lb in rear and 20 in front to make it handle properly.
The best was my 1971 Datsun 4-speed 1200 sedan that consistently gave me 41-43 mpg, again without trying for FE. I wonder what a 1200 coupe would have done if driven decently, and with a few mods like radial tires, electric fan, etc.(couldn't do electric fan on the Corvair though).
Ray Mac.

[NHRABill]

Can't say I have had many cars that were anything but gas guzzlers over the years. The more efficient of the lot would be my early rides like the 1983 Chevrolet Chevette I learned to drive in. That was a little 4cyl 1.6 or 1.8L not sure? 5 speed manual was good on gas and had 200,000 miles on it before it was 10 my dad used it for commuting to work back then.

The other better MPG car I had little after that was a 1983 Dodge charger Shelby edition non turbo 2.2L I learned to swap motors and replace head gaskets with that poorly designed POS Fun little car but man I would crack a head or pop a gasket nearly every 6 months the cylinder wlls were so thin it would overheat too easily poor design.

I had a bunch of pickups with 6cyl seems no one wanted a 6 so i would get them super cheap I loved them and didn't mind cause they got better mpg and I wasn't towing anything mileage low 20's with most of the straight 6 motors was typical with average young driver behind the wheel think I could probably pull a mid 20's if I really tried now.