Cars have gotten better fuel economy but also more horsepower. I believe some mid-size sedans that get 30-40mpg have roughly the same hp as muscle cars in the 60s that got 10 mpg.
Was this due to dozens of minor technological advances or a handful or big ones? Things like 6 or 7 speed transmissions, aluminum block engines, aerodynamics, etc?
My understanding is 80%+ of the energy in gasoline is wasted as heat. Has any of that been captured and utilized over the last few decades?
A few off the top of my head, more when I get time.
Better fuel/air/ignition management allows optimal fuel air ratios, ignition curves, and higher compression ratios which are favorable for increased power.
More modern catalytic converters clean the exhaust without the back pressure older converters had.
Better metallurgy allowing closer tolerances and higher limits of strength, wear resistance, and heat. You can “push the envelope”.
“I believe some mid-size sedans that get 30-40mpg have roughly the same hp as muscle cars in the 60s that got 10 mpg.”
And modern V8 muscle cars are freakishly powerful and fast, and are capable of 30 mpg.
Yeah, they have. I have a modern muscle car. When I was a kid, I always admired and wanted one, but we were too poor. As I’ve gotten older, I had other (family) needs, so was never able to get one. But the last two cars I’ve had are what I always wanted…a high performance American muscle car (A Mustang GT and now a Dodge Challenger limited edition R/T). Both had 8 cylinder engines and larger horsepower than the old cars they were based on. And both get fairly decent gas mileage (the Mustang got around 25 miles per gallon, the Challenger gets about 20 with my every day drive…they both do better on the highway). That’s…pretty amazing, IMHO. Especially when you consider they are also safer to drive as well as more comfortable. They are, basically, better in every way. Hell, the even LOOK better, IMHO, than the cars they are modeled after.
I think the reason is modern computer controlled systems and metallurgy, in a nut shell. Computer controls allow the computer to control fuel mixes and quantities, as well as to know about problems that crop up and flag them for someone to fix (the Challenger can even monitor tire pressure and tell me when I need to add pressure, as well as a host of other things). The cars are probably lighter as well…the engines are more efficient, and the bodies are more honeycomb structure that is both safer and lighter as well as being stronger. Then there is the chemistry…I think modern lubricants are better, and modern fuel is also more efficient and better, but I think the crux is the technology in the engine and body that makes the cars lighter while making the engines more efficient.
Sadly, I think we are nearing the plateau for ICE technology. My WAG is the Challenger will be the last ICE vehicle I ever own, and I’m actually thinking of garaging it in the next year, putting it away for perhaps weekend trips or special occasions. I’m seriously looking into the host of new all EVs on the market and just figuring out which one I want to get as my next vehicle. They are also benefitting I think from a lot of the material science that has allowed our modern cars to be safer, more powerful and more fuel efficient than the older cars (they also don’t rust out or die after 100k miles like they used to, which is nice).
The suspensions are much better too. The old suspensions wasted way too much of that power.
Since it’s GQ and all, here is an article on why today’s smaller engines have more horsepower:
I’m not a car expert, but I think that this is probably not actually the case. Yes, manufactures may be using lighter materials in some applications, but modern cars are also carrying hundreds of pounds of equipment (particularly safety equipment, as well as electronic systems) that older cars didn’t have.
For example, the 1969-1970 Mustang was 188 inches long, and had a base curb weight of 3122 pounds. The current Mustang (6th generation) is exactly as long (188 inches), and has a base curb weight of between 3520 and 3800 pounds.
That was just a WAG on my part. I’m a bit surprised that the Mustang is heavier today…I would have thought lighter. I didn’t look at your cite, was that for the smaller block engine for the older Mustang? They make a 6 cylinder one today, but you should compare apples to apples, and I think the early Mustangs didn’t have the larger engines initially, at least not the standard model. You had to specially order the ones with the bigger engine, IIRC (I wouldn’t know as there was zero chance my family could afford a Mustang back in the 60’s :p).
I’m going to guess that the weight for the '69 Mustang in Wikipedia is for the base model. The smallest engine offered in the '69 (as per that Wikipedia article) was a 3.3 liter inline six-cylinder. The modern base model (which is probably at the low end of that weight range) is actually only a 4-cylinder (the 2.4 liter Ecoboost engine).
Again, I’m not a car expert, but my understanding has been that the safety equipment and amenities in modern cars do add a considerable amount of weight; the fact that modern cars can be so quick, despite the heavier load, is a testament to the state of the art in engine and transmission design.
I couldn’t tell looking at the cite. I do like muscle cars, but I’m actually not that well versed in all of the esoterica concerning the various numbers. I think my old GT was a 5.0 liter, and the Challenger is 6 something, which means…big I guess. I know both are 8 cylinders and when you push the pedal thingy they go really, really fast.
Having been the proud owner of a 60’s behemoth with what, even then, was considered a fairly large engine, I can tell you two things right off the top of my head, fuel injection and transmissions.
My 1962 Chrysler had a 3-speed automatic transmission. The shift point from 1st to 2nd was, IIRC, somewhere around 25 mph, with the shift point from 2nd to 3rd at about 40. And consider this, the three-speed automatic was a luxury; for many years, the Detroit Big Three built two-speed automatics. Of course, muscle cars had manuals. Three-speed or four-speed.
As for carburetors vs. fuel injection, there’s no comparison, leaving aside that you had to adjust the carb every now and then or you’d be backfiring and leaving a cloud of black smoke behind you.
Your 1969 Mustang was 71.3" wide and 51.3" high, while the 2019 Mustang is 4" wider and 3" higher. Its passenger cabin and trunk volume are also bigger. The 1969 Mustang carried 20 gallons of gas, while the current generation has a 16-gallon tank.
Meanwhile the Ford Custom 500, the baseline* full-size* Ford, had a curb weight of 3,799 lbs.
Your link doesn’t go to the Custom 500, but it’s interesting that the curb weight of that car is almost identical to that of the heaviest modern Mustang. 
The 2019 Dodge Charger goes up to 4575, meaning it’s heavier than all the 60’s and 70’s muscle cars - How Much do Classic Muscle Cars Weigh? - Popular Hot Rodding Magazine
I have no idea where that car came from!
Bavaria? 
My first car, an early '80s Olds Cutlass Supreme, had the then-ubiquitous Buick 3.8-liter engine. Here are the specs of interest:
-carbureted fueling
-2 valves per cylinder
-vacuum-controlled mechanical distributor for ignition
-compression ratio, 8.45:1
-110 horsepower at 4800 RPM
-145 lb-ft of torque at 2000 RPM
-3-speed automatic transmission
-My recollection is that highway fuel economy was somewhere around 20 MPG when cruising at 60 MPH.
My current car, an Infiniti Q50, has the Nissan VQ37VHR 3.7L engine. Here are its specs:
-computer-controlled port fuel injection, operating in closed-loop
-computer-controlled ignition
-4 valves per cylinder
-compression ratio, 11.0:1
-332 horsepower at 7,000 RPM
-270 lb-ft of torque at 5200 RPM
-7-speed automatic transmission
-highway fuel economy is around 27-28 MPG when cruising at 80 MPH.
That’s three times the power output with slightly less displacement, an incredible improvement. Let’s see what performance improvements each of these differences is responsible for.
[ul][li]computer-controlled port fuel injection: A carburetor is, on a good day, a very approximate device. This is true even of the very sophisticated carburetors that were being put into cars in the last years before fuel injection systems. In a carburetor, the incoming air is made to create a slight vacuum in proportion to its flow rate, and that vacuum sucks fuel in through a straw; the more vacuum, the more fuel, so it generally puts in about the right amount of fuel. after that, the next challenge is getting it mixed with the air, and mixed well enough and evenly enough so that all four/six/eight cylinders get a combustible mixture that’s somewhere close to stoichiometric. You’re guaranteed to have variation from cylinder to cylinder and inhomogeneities within each cylinder - so you dial in the carburetor to err on the side of rich rather than lean. That’s a recipe for shitty fuel economy right there. Replace the carb with a computer-controlled port fuel injection system, and things instantly get better. The computer is measuring intake air flow with an actual calibrated meter, and giving each cylinder its own private allotment of the right amount of fuel, delivered right to the backside of each cylinder’s intake valves. To the extent that it’s wrong, it watches an oxygen sensor in the exhaust pipe, and adjusts accordingly. Excess oxygen in the exhaust? It dials the fueling up just a smidge for the next cycle. No oxygen in the exhaust? A little less fuel next time. No wasted fuel, no cylinder-to-cylinder maldistribution, and the spritzing of fuel directly on the warm intake valve helps begin the evaporation process before the next intake event. Now you’ve got the most economical fuel mixture preparation you can get. This is good for cruising economy and for peak power.[/li][li]computer-controlled ignition: Like the carburetor, a vacuum-controlled distributor is an approximate device, and it’s likewise designed to err on the side of caution. The right spark advance maximizes fuel economy, but too much causes knock/ping that is annoying and (if severe) potentially damaging. Want to run on the ragged edge, and get the best spark timing you possibly can? rip out the distributor and put in computer-controlled ignition. Operating on pre-determined maps, it watches throttle position and RPM and chooses the best spark timing it knows. If you’re getting some knock (because your engine might be running a little hot today, or maybe you bought crappy fuel), a knock sensor is listening for those sounds and tells the computer to retard the spark just a tiny bit until the knock goes away. Now you’ve got the most economical spark timing you can actually get, good for maximizing both peak power and cruising fuel economy.[/li][li]four valves per cylinder: if you want a lot of power, you need to move a lot of air. You can do this with a high-displacement engine running at modest RPM, or a modest-displacement engine running at high RPM. But an engine can’t breathe well at high RPM unless you give the intake system a large cross-sectional flow area. So you switch from one intake valve per cylinder to two intake valves per cylinder (and two exhaust valves). Now you can breathe freely at high RPM (notice the above engine specs for the RPM where peak power occurs). For a spark-ignited gasoline engine, four valves per cyl allows a higher peak power output, but it doesn’t particularly contribute to cruising fuel economy. for a given cruising speed you need a given amount of power at the wheels, so the fact that there’s less flow restriction at the intake valves just means you close the throttle a bit further, creating the same total air flow that you would have had with two valves per cyl (and a larger throttle opening). (this is the same reason that changing your intake air filter doesn’t improve cruising fuel economy.)[/li][li]high compression ratio: I won’t try here to explain the thermodynamics behind it, but compression ratio sets an upper bound on overall engine efficiency at all operating conditions. Higher compression ratios allow better efficiency. Diesel engines, because of how they operate, can be made with compression ratios between 15:1 and 20:1. But gasoline spark-ignited engines can’t go that high; if they do, the mixture detonates violently instead of burning smoothly, creating high local temperatures and pressures in the combustion chamber that can damage/destroy the engine. Older engines, with crappy cooling, crappy fuel mixing/distribution, crappy fuel quality, and crappy ignition control, could only run with compression ratios of about 8:1 or 9:1. The more tightly you can control conditions in the combustion chamber, the higher a compression ratio you can run. High compression ratio contributes to high peak power and also to high cruising fuel economy.[/li][li]intake port design: a properly designed intake port can influence the combustion event in the cylinder, which can affect efficiency. In gasoline spark-ignited engines, the goal is to create a rotating flow structure during the intake event, such that the axis of rotation is perpendicular to the cylinder bore. This is called “tumble.” Not only does it help with fuel/air mixing, but as it gets squeezed during the compression stroke, somewhere near TDC it falls apart into small-scale turbulence. This turbulence stretches and distorts the flame front, creating more flame surface area, which results in faster combustion. By releasing more of the fuel’s energy near TDC, the engine can convert more of it to mechanical work, improving efficiency at all operating conditions. Not only that, but a rapid burn helps to stave off knock, which means that good intake port design can facilitate operating the engine at at even higher compression ratio than would otherwise be possible.[/li][li]7-speed automatic transmission: Power is torque * RPM, so an engine can meet a power requirement by putting out low torque at high RPM, or high torque at low RPM, or somewhere in between. A gasoline spark-ignited engine gets good fuel economy when the RPM is modest and load (torque) is relatively high. Want good fuel economy? Select a gear that gets the revs down. Want best acceleration? Choose the gear that keeps the engine up near the RPM where peak power output happens. When you’ve got a 3-speed transmission, it’s hard to achieve those goals across all operating conditions. Replace it with a 7-speed transmission, and things improve quite a bit; now you can keep the engine hovering very close to the RPM of peak power output when you’ve got your foot to the floor, and no matter your cruising speed, the computer can find a gear that provides the optimal combination of RPM and torque to efficiently meet the power demand. When I’m cruising on city streets at < 40MPH, my car chooses a really tall gear, getting the engine RPM down to less than 1500 in an effort to get best economy. Going to extremes, there are even transmissions with ten speeds now. The theoretical ideal is the continuously variable transmission, which can dial in the exact best drive ratio for any given operating condition, but so far this is finding limited application; I think Nissan is the only one putting it on their cars.[/li][li]front-wheel drive: for rear-wheel drive, mechanical power has to make a 90-degree turn between the driveshaft and the rear axle. So the rear differential features a spiral bevel gear, which incurs an efficiency penalty. Front-wheel drive vehicles don’t have to make mechanical power turn through a right angle, so their differential can use a spur-gear or epicycling differential, which is more efficient. This has a lot to do with why econoboxes are always front-wheel drive. All-wheel drive is less efficient than front-wheel drive, but since you’re only sending part of the power through that inefficient rear diff, the penalty is less than you would see with a purely rear-wheel drive. If you have a lot of power, you need the traction that comes from delivering that power through the rear wheels (or all wheels), so this is why sports cars tend to be rear-wheel drive. The Corvette could probably get better cruising fuel economy with a transverse-mounted engine and front-wheel drive, but the traction control system would be very busy.[/ul][/li]
Various other engineering improvements throughout the chassis have helped keep weight under control while improving safety, but they definitely haven’t reduced weight. My old car had a curb weight of 3234 pounds, whereas my new one has a curb weight of 3787 pounds. In spite of that weight gain (perhaps to some extent because of it), I now enjoy better fuel economy, better power, lower emissions (by a long shot), and better safety than I did with my first car.
I’d chalk the vast majority up to computer-controlled port fuel injection and computer controlled ignition/engine control. Those two are likely the two advancements that account for the lion’s share of the increases in power, efficiency AND emissions in the past say… 40 years.
Basically you’re getting the right amount of fuel into the cylinder at the right time, and then igniting it at the right time. Doesn’t sound like much, but when you’re looking at essentially blind mechanical systems in the carburetor and ignition (i.e. there was no feedback loop), versus modern systems with various sensors (knock, various positional ones, oxygen, etc…) there’s just no contest.
To give an illustration, a 1970s 350 cubic inch / 5.7 liter small block Chevy V8 (we’ll say the LS9 for comparison purposes) put out somewhere around 165 horsepower and 275 ft/lb of torque, with a 4 barrel carburetor and at least in my old 1976 Suburban, electronic ignition. By comparison, my 2005 Dodge Dakota’s 3.7 liter / 225 cubic inch V6 puts out 210 horsepower and 235 ft/lb of torque. Their power curves are different, with the V6 revving higher than the V8, but both are measured at their peak HP and torque.
Neither engine has anything fancy like four valves per cylinder, overly high compression ratios (the 350 has a 8.5:1 compression ratio, and the 3.7 has a 9.1:1), or advanced intake valve design. Yet the 3.7 is 65% the displacement, and produced more horsepower and nearly the same amount of torque, as well as burns less gas to do so.
The ability to run at higher RPM is another factor that facilitates greater power output. Mean piston speed (MPS) is an important engine design parameter, and is proportional to piston stroke and RPM. MPS above a certain point tends to reduce longevity. If you want your engine to last, you either need better engineering/materials/lubricants to tolerate high MPS, or you change your engine design to reduce MPS.
Referencing the two cars in my previous post, operating at their RPM of peak power output:
The Olds had an MPS of 13.8 m/s.
The Q50 has an MPS of 20 m/s.
I expect the engine in the Q50 will probably last longer than that old Buick 3.8L engine did, too. Better engineering/materials/lubricants are responsible for this.
In the late 1990s and early 2000s, Formula 1 race cars were getting 900 horsepower out of a 3-liter engine. Part of this was because they used a 10-cylinder engine, meaning each cylinder had small bore and stroke. This meant they could run at 19,000 RPM with an MPS of about 26 m/s. Higher than that of a modern passenger car, but not outlandish.
It isn’t weight. For the most part, today’s cars are much heavier than their predecessors from the 1960s and 1970s. Compared to downsized cars from the 1980s, today’s cars look like they were made for a different species and weigh accordingly more.
Aerodynamics certainly play a role. There are a bunch of other places where cars have been quietly optimized. No one has mentioned:
[quote=“Machine_Elf, post:15, topic:832915”]
[li]front-wheel drive: for rear-wheel drive, mechanical power has to make a 90-degree turn between the driveshaft and the rear axle. So the rear differential features a spiral bevel gear, which incurs an efficiency penalty. Front-wheel drive vehicles don’t have to make mechanical power turn through a right angle, so their differential can use a spur-gear or epicycling differential, which is more efficient. This has a lot to do with why econoboxes are always front-wheel drive. All-wheel drive is less efficient than front-wheel drive, but since you’re only sending part of the power through that inefficient rear diff, the penalty is less than you would see with a purely rear-wheel drive. If you have a lot of power, you need the traction that comes from delivering that power through the rear wheels (or all wheels), so this is why sports cars tend to be rear-wheel drive. The Corvette could probably get better cruising fuel economy with a transverse-mounted engine and front-wheel drive, but the traction control system would be very busy.[/list][/li][/QUOTE]
Front wheel drive is generally more efficient at distributing power to the wheels and it weighs less but your Q50 is either rear wheel drive, like your Oldsmobile, or it is all wheel drive. The extra weight and friction of the all wheel drive system will always hurt fuel economy. I don’t think there are any car models whose AWD version gets better fuel economy than the 2WD version with the same engine and transmission. (Link to 2017 Nissan Q50 fuel economy ratings: Gas Mileage of 2017 Infiniti Q50)
Agreed. My claim is this:
FWD is more efficient than AWD
AWD is more efficient than RWD
Your post listed a bunch of power/efficiency-improving innovations, in addition to the ones I listed. There are of course a lot of these. One other one that comes to mind is the dual-clutch transmission. These have become standard equipment on supercars (think Bugatti, Ferrari, Koenigsegg) because of their ability to change gears with extreme rapidity, but they’ve also found use on economy cars like the Ford Focus because of their higher power transmission efficiency (compared to conventional automatic transmissions).
I thought your post was great and I just figured I’d mention a few other things, including clutch-type transmissions, that hadn’t already come up in this discussion. I didn’t mean to suggest that mine were the only reasons, or even the biggest reasons, for fuel economy improvement.
If fuel economy is your concern, my claim is that FWD > RWD > AWD. I linked to the fuel economy ratings for the Q50 because it shows, when comparing similar powertrains, the AWD versions get worse fuel economy than the 2WD versions.
You mention the power-sapping ability of the bevel gear. The AWD Q50 has two of them, one each in the front and rear differentials, creating more friction than a single one. Plus the Q50 has a center differential creating even more friction. Finally, the AWD components add weight, which also adversely affects fuel economy. The RWD versions of the Q50 get better fuel economy, as shown in my link. You can see the pattern repeat across the whole Infiniti model range (Gas Mileage of 2018 Vehicles by Infiniti) where the AWD version gets worse gas mileage than the comparable 2WD version. If you look at other automakers, the same pattern will repeat. You are wrong that AWD eliminates the bevel gears and wrong that AWD improves fuel economy over 2WD.