Horsepower per liter is a trend. A trend that engineers can appreciate and MBAs will routinely ignore. Horsepower per liter is something a spread sheeter would never understand and the myopic would rather deny.

Even GM has pockets of unstifled innovation. A recent Corvette engine did 70 Hp/liter with only two valves per cylinder. But when Hp per liter is applies across the GM product line, it becomes painfully obvious why GM cars cost more to build and why GM has no domestic profits. GM cars must install two extra pistons - and all those other expensive parts such as valves, piston rings, cam and crank lobes, fuel system components, etc to only do same as everyone else. GM products have been so bad for so long as even exposed by one little factoid - Hp/liter.

No, I am not just focusing on Hp per liter to say GM products suck. Only a fool would say that number is complete proof for only one model. Provided is one damning number - historically accurate - that every consumer can calculate. GM products are so bad that even Horsepower per liter for GM vehicles is 20% lower.

When VW went from crap products back to being a profitable company, VW's 'Horsepower per liter' increased to seventy across the product line. VW went from 'bottom of the barrel' reliability to mid level reliability at the same time their products started doing 70 Horsepower per liter. Horsepower per liter indicates that VW was going to be profitable because HP/liter is a typical product oriented indicator that MBA types must ignore.

Thirty years ago, GM could have been doing what is now world standard. GM products are so crappy as to still not do what is world standard. xoxoxoBruce noted other reasons why GM products are such crap. They still sell as 2005 technology engines using push rods. That 3.8 liter engines is so crappy that an editorial in Wards Automotive said GM could not even give it away to Honda or Toyota. Obviously. Ward's Automotive said the 3.8 liter engine uses technology that only a bean counter could love. It is a pathetic 50+ HP per liter engine. Products so pathetic as to even use push rod technology.

GM had the technology long before anyone. But when MBAs get finished instituting cost controls, then product oriented advances get stifled. Obviously GM has no profits. Look at the Hp per liter number. Therein lies the reason why. Innovation from even 30 years ago could not be implemented. Today, even the MBA types can now see what the consumer could have seen ten years ago. GM products have low Horsepower per liter numbers which suggests the entire product line is crap. A number that even demonstrates why GM still has no hybrid vehicles.

GM does have pockets of stifled innovation. What has happened in Cadillac is contrary to a trend imposed by GM corporate. How many more pockets could be liberated? So maybe Kerkorian sees a long term profit as he did for Chrysler.

Others had considered doing same as Kerkorian with other intentions. For example Carl Icahn had intended to break up GM into parts. GMs value as separate entities has been long considered worth more than GM as a whole. Even smaller Toyota has an equity (stock market) value five times that of GM.

But Icahn discovered that GM is structured to make a break up difficult. For example, so that each division could not be sold off, 1970s GM created GM Assembly Division that manufacturers cars from each division in the same factory.

Does Kerkorian see part of GM that can be spun off as Delphi and EDS Systems were? Or does he see a company that could trash its current management to liberate pockets of innnovation?

Liberation of the innovators, after all, saved Chrysler. Iacocca simply put bean counters as subordinates the the car guys. Letting car guys make decisions resulted in profits so large and so fast that Chrysler could pay off those emergency loans in less than four years. Maybe Kerkorian sees another Chrysler. But again, that means GM must first perform serious top management shakeouts.

The current top man, Wagoner, never ran a profitable North American operations. So they made him the CEO. Now he is running even the international division into the ground. His entire job experience is a finance guy. Eliminating Wagoner and his peers could quickly liberate GM innovators. And so the question is whether GM stock at $30 per share has dropped enough to make this risky venture profitable to Kerkorian. If he does not intend to break GM up into more profitable entities, then he must be intending to eliminate the problem in GM - its top management. Or he may simply discover what both Ross Perot and Carl Icahn discovered - and back out.

What makes this rather confusing is that Ford is still profitable. GM has long been the sicker company with lesser products. Why is Ford getting lumped in with GM? Ford also has product line problems. One was four years of stifled new product developement when Jacque Nasser was running Ford into the ground. But Ford's problems are not as bad as GMs.

As a non-engineer, I am curious about what HP per liter means in the real world. Sure, the engine is more efficient at producing power for it's size, but I think a better measure is how much power is produced per unit of fuel. You can get a lot of extra power out of a small engine by bolting a turbocharger or supercharger on, but then it also uses more gas. Or you can drop a bigger engine into the car and it also use more gas. Either way, you are burning more gas to get more power.

I'm with you on making as efficent an engine as possible. Dual overhead cams with 4 valves per cylinder are better than the old pushrods/rocker arms I had on my first car. Fewer moving parts, less internal friction. Seems to me it should use less fuel to gain extra power. Along the same line of thinking, the Wankel engine seems promising for using less fuel too.

Some technology like superchargers and turbochargers seem to me to use more fuel per unit of HP than without. You are adding moving parts. More friction. More fuel.

Do you have statistics for which engines (not cars) are the most fuel efficient? Does it matter?

The HP per liter number for a fuel injected engine is not a valid for diesel or super charged engines. The latter only forces more fuel into the engine with an obvious increase in HP/liter. But the ballpark measurement among engines of the same technology is Hp per liter. For example, GM makes a supercharged Buick that only does 63 Hp per liter. And yet supercharged engines should average about 100 Hp per liter. The Buick supercharged engine is so low performance that even fuel injected engines are superior. But Buick does not install a supercharger to make a higher performance engine. They install a supercharger so that naive 'feel' they have a high performance engine.

Advanced diesels do something on the order of 40 Hp per liter. But diesels are more fuel efficient, for reasons below. IOW HP per liter performance number is unique within the technology. For normally aspirated engines, the carburetor engine at 35 HP per liter is usually inferior to a fuel injected engine. Ignoring that GMs throttle body fuel injected engine was about the same inferior performance of carbureted engine. GM used throttle body only because a throttle body injector cost less than a carburetor. GM knew their customers would read fuel injected and 'feel' they had a race car. Eventually GM had to relent - let their engineers do what everyone else had. 70 HP per liter engines use sequential fuel injection as was found in pre-WWII German fighter planes.

Does it sound confusing? It should. The problem gets rather more complex as we add new technologies to the brew.

Diesels are more efficient at using fuel for one simple reason. Application of energy to a changing load. Gasoline engines are poor at adapting to changing loads even with more gears in the transmission. We solve this gasoline engine weakness by making bigger gasoline engines. Bigger hypes the emotion. But making an engine that can adapt to changing loads is clearly sexier. And that too is a characteristic of higher HP per liter engines. They tend to adapt better to changing loads which is why higher Hp/liter aspirated engines more often meet EPA mileage numbers.

We put a 250 Horsepower engine in a 3000 pound car. How many Horsepower to move a 60,000 pound truck? It weighs 20 times more so it must need 20 times more horsepower? 5000 Horsepower? Of course not. The truck may have only 400 or 500 horsepower engines. One tenth the horsepower because diesel adapts better to changing loads. Since diesels adapt so much better, then trucks do not use gasoline.

How many Horsepower to maintain a car at 50 MPH? Well it has a 200 Horsepower engine. Therefore it must need at least 120 horsepower to maintain 50? No. Car maintains 50 MPH using 10 or less horsepower. Therein lays the problem. Because cars spend a small amount of time in acceleration and other higher load conditions, we then enlarge the 10 Horsepower engine to 250 Horsepower. Then a car can accelerate in 10 seconds while climbing the high.

The myopic among us still insist we must always output excessive horsepower so that we have this horsepower during rare acceleration times. The myopic demand that an engine's energy output not change so they don't have to downshift to climb a hill.

The car generates massive amounts of energy when it only needs 10 horsepower because sometimes the driver may periodically require hundreds of horsepower. Since gasoline is so cheap, then oversized engines have always been the simple solution. And yes, at $2.00 per gallon, history says the price of gasoline remains cheap. The bigger engine remains a cheap and simple solution.

So now we come to what is currently a crude technology. The Hybrid is about putting only 10 horsepower to the wheels when 10 HP is required. And putting 100 Horsepower to the wheels at rare times when high power is required. Electric motors better adapt to changing loads which is why diesel electric locomotives uses electric motors before WWII and why navy ships use electric motors to drive propellers. The hybrid shuts down its one liter engine when so much energy is not required. The conventional gasoline engines (current normally aspirated, turbo charged, etc technology) will never solve this changing load problem.

Adapting to changing loads has long been a simple solution to adapting more energy productively. But notice how complex even the simple solution is. Reality of numbers complicates things.

And yet the numbers are where innovation and the advancement of mankind come from. HP/liter measures performance only within a specific technology. A number that must be taken within context.

Reducing friction would do little to improve the HP/liter number. But things such as getting more useful energy from each gasoline molecule and adapting better to changing loads does result in higher performance.

Another factor in getting more work from less energy is a concept called thermodynamic efficiency. Currently maybe 10 to 20% of the energy in a gas tank is used. That much energy in the gas tank is wasted. Cars with higher performance numbers - greater Hp per liter - would be closer to the 20% number. Electric fossil fuel and nuclear power plants do maybe 30 to 35% thermodynamic efficiency - nuclear plants tending to be lower. Natural gas turbine plants are claiming numbers approaching 60%. The long term solution to innovation - to making smaller engines that produce more useful energy - is also found in addressing these thermodynamic efficiency problems. An engine lined in ceramics that did not absorb heat from the combustion chamber would mean more energy moves the piston or turbine. Other advanced techniques are studied, tested, and refined. But solutions typically take generations to develop.

Hydrogen fuel cells maybe could put higher fuel energy onto the drive wheels. But then we must look at the larger picture. The manufacturing, storage, and transportation of hydrogen means something like 70 to 90% of the energy is lost. Once we look at the bigger picture, then hydrogen fueled vehicles have ridiculously low thermodynamic efficiencies. Shhh. Don't tell GM executives. They are convinced that hydrogen is the future only because pollution does not exist. Those without dirt under their fingernails have used spread sheet reasoning as if it were science. They saw symptoms and then claimed they are scientifically informed.

Random snapshots of the problem have defined two ways of applying more existing energy to useful work. Adapting more energy only when the load changes. Addressing the thermodynamic efficiency problem. Both require innovation. The Hybrid being a superior and proven solution to adapting to changing load as diesel electric trains have been doing for 60 years. The hybrid then may make the turbine a viable solution. Fundamental engine changes such as (maybe) turbines to increase thermodynamic efficiency.

But for the consumer, there exists the normally aspirated gasoline driven vehicle. Within technology restrictions, the consumer maximizes his fuel economy, pollutes less, and gets a longer life vehicle when he uses newer technologies. Technologies that mean the engine gets higher horsepower per liter. Higher Hp/liter being a symptom of superior technologies. A symptom, meaning to better understand the underlying concepts, one must appreciate the adapting of energy to chaning loads and the thermodynamic efficiency problem.

To get more energy from each gasoline molecule, a normally aspirated engine means the HP/liter number must increase. This is what performance is really about. Those who never learned about cars foolishly believe a low performance but bigger engine is 'high performance'.

Well done TW, although I disagree with your take on GM's throttle body injection was about fooling the public.

A carburetor is nothing more than a barely controlled leak and expensive to make with all those little bits and pieces. With the advent of electronic controls made possible by the oxygen sensor it is much cheaper to build a throttle body injection unit that gives you much more control over the fuel flow especially on deceleration where a carb keeps feeding fuel as long as there is air flow.

The real reason they went to throttle body was to save the expense of retooling the intake manifolds, the rest of the plumbing and electronics for port injection. It was all about money.
Even when port injection became standard it was batch with sequential a ways down the road.

Putting a "fuel injection" sticker on the fender is a marketing deal. If they didn't inflate the tires to save air, marketing would say " Now, with new flat tires". Those people don't have a clue.


Engines and motors do work by transforming potential energy into torque.
Gasoline engines produce maximum torque at relatively high RPM.
Diesels engines at relatively low RPM and motors(electric) at no RPM.
Diesels and motors also produce more torque for the potential energy used.

Big trucks use up to 27 forward gears to keep the diesels running at the RPM where the maximum torque is produced for maximum efficiency. It's still not great efficiency but they're doing the best they can with what they got.

Motors have the advantage of maximum torque where it is needed most, which is the initial movement from rest, plus the ability increase the torque by feeding it more energy(electricity) with changing load.

This is why motors have always been the best solution for propulsion but unlike locomotives and ships, automobiles have not been big enough to carry means to supply the power for the motor(s). As generating equipment became more efficient the possibility of onboard generation became a reality. Of course California's zero emission mandate rules out hybrids, but until they make some great advances in battery technology the only thing left is hybrids, so CA better get real.

Hybrids provide their biggest advantage in urban stop and go, where the fossil fuel engine shuts off at stops and the regenerative braking recoups some loss. Driving down the expressway at a steady 50/60 mph won't give the hybrid nearly as much advantage over a fossil fuel engine and certainly not enough to offset the expense of buying and maintenance. That's comparing one model like the Honda with and without hybrid technology.

Oh, and "Performance" is exactly that. What she'll do. Doesn't matter how or why.....it's simply what she'll do. "High Performance" means she's faster. Again, it doesn't matter how or why..."High Performance" means she's faster. :biggrin:

Cool. Thank you both for such informative posts.

I was hoping you would ask more questions. I still had one more basic concept to explain. But the previous post was getting too long.

Gasoline engines have a narrow range at which they burn gasoline most efficiently. For most cars, this peaks as somewhere between 2400 and 2900 RPMs. This is why shifting is mostly conducted in a range from 2000 to 3200 RPMs (again varies by engine design).

Most interesting is how an engine manages to idle at 800 RPMs. The efficiency of that engine is lowered. IOW give an idling engine more oxygen for the same gasoline at idle, and the engine will increase speed to something like 1200 or 1600 RPMs. That’s right. Idling is (proportionally) a massive increase in gasoline for energy produced. Idling is intentionally making an engine less efficient.

Some neat tricks used over the past decades. Carburetors would dump rich mixtures of fuel into an engine that is expected to be going slower. After all, the engine thought it should be idling which means dumping more gas and less air in the engine. You heard backfiring as the vehicle decellerated. The foolish 'feel' that is a cool sound. But backfiring was always the sound of a crappy engine dumping gasoline into an engine that does not need it. It is the sound of a catalytic converter being flooded with more hydrocarbons to uselessly burn.

Fuel injected cars substantially decreased pollution by simply turning off fuel when decellerating. No backfiring is the 'cool' sound of a superior engine that is not wasting fuel and not destroying the exhaust system. Some Harley owners won't like that reality. Backfiring means a crappy engine.

Hybrids take innovation one step farther. Idling is the engine burning gasoline in a most inefficient way - ie the rich mixture meaning more gas and less air. Intentionally making the engine less efficient so that it spins slower - 800 RPMs. Hybrids simply turn off the engine rather than run so inefficiently. Why waste gas in idle and 'bumper to bumper' traffic? Idling causes some of the highest percentages of pollution. Obviously. The engine is intentionally running a minimum efficiency. Simply run the gasoline engine only when it can use fuel efficiently to recharge a battery. Hybrids only burn gas when gas can be burned more efficiently.

What is a solution to rush hour traffic? Hybrids waiting and not burning fuel most inefficiently. Watching a car idling in rush hour traffic is, to me, one of the most gross and perverted things we will see during the whole day. But then I appreciate why idling in bumper to bumper traffic (without a Hybrid) is so destructive.

How to make a gasoline engine (or any other fossil fuel engine) more fuel efficient? Operate only at its efficient point (maybe 2800 RPMs), then more energy will be used to useful purpose. This little trick means better thermodynamic efficiency AND better adapting to a changing load.

The above saved for last because it is some of the easiest to explain and comprehend.

I must relate one personal experience. I studied the electronic fuel injection on the 280Z(?) (1976). It featured no fancy computer. Control electronics even used 1960s technology - 741 op amps. It was one of the most simple and yet most fascinatingly advanced design I had ever seen. The Z was but another reason why I was driven to learn more. First pass through those tech manuals and I knew fuel injection was the future long overdue.

I did not realize trucks were using 27 gears. Is it three overlapping ranges of 9 speeds?

I have long been intrigued by the CVT (Continuously Variable Transmission). But have not had the opportunity to study the CVTs found in the Toyota Prius or some Fords. This too has long been an overdue technology that may become obsoleted by Hybrid advances before it ever gets a chance.

CVT long ago being another method of adapting to a changing load.

I also agree with your perceptions on GMs throttle body injector. But that design always made me sick. For example, GM management went through painful intermediate designs - throttle body and multi-port - before they finally let the engineers design the injection system even found in WWII German fighter planes. Now you would think GM would then only put the sequential injectors on all cars. Nope. The accountants said if they abandoned throttle body and multi-port, then they would lose all that development (invested) money. So GM made three different fuel systems. That meant stocking and buying different fuel systems for all factories and stocking spare parts for all three designs. Just another reason why GM products cost so much more to build.

How did Honda do it? When Honda designed a four speed, they stopped making all three speed transmissions. When they made a five speed, then the four speed design was immediately discontinued. Therefore their factories only purchased and installed one part. Their dealers only stocked spare parts for one transmission that year. Honda made it simple - rather than cost control. When Honda made a fuel injection, then only made sequential. They did it right the first time.

:typing: "Help! I can't stop typing!" -- tw


Just kidding, tw. Very informative and clearly explained.

I'd be incredibly surprised if the majority of modern cars were most efficient below 3000 RPM. Maybe pushrod V8s, but DOHC 4s are a different animal entirely. And spark-ignition engines are typically most efficient near (but not at) wide-open throttle.

The (thermodynamic) efficiency of an engine at idle is not particularly important. The fuel efficiency of the vehicle containing that engine is zero regardless; an idling engine isn't moving the vehicle.

CVTs have long had a small niche in the economy segment of the market. The two big problems they have is that the rubber belts they use can't handle a lot of power, and they cause poor throttle response and even worse perceived throttle response (you push the pedal, hear the engine rev up, and THEN the car speeds up). Audi has a steel-belted electronically controlled CVT which supposedly solves both these problems, but it's only available on a few models. It's unlikely CVTs will be obseleted by hybrids, as often CVTs are paired with hybrids.

As far as I know, no one has yet managed to get a practical _serial_ hybrid (like that in a locomotive) into a car.

CVTs are on Nissans and Infinitis now. I drove a G35 with it. It was faaaaabulous. And I hate driving automatics, but I would drive this thing.

I don't know how CVTs are made today, but I saw some old antique car from the early 1900 that had a CVT. It was pretty basic. The driveshaft ended in a flat disk that was maybe a foot or two in diameter. Then a rubber wheel rode that disk like a needle on a record player, except without that groove. The driver could move the wheel in and out on the spinning disk to either go slower in the center or faster in the edge. The wheel drove the axle. I was with my grandfather at the time, and we both marveled at this thing that was so cool, and so simple. I wonder how efficient it was. The friction fit of the wheel against the disk was the weak link.

tw likes to talk about technology so old it was on WWII planes. This thing was from the 1920s or so.

I found it with a Google search. No identifying information though.

Very, very weak. :lol: Yes, 9 in the trans and 3 behind it.

I've never heard a catylitic converter equiped car backfire. The cat being so hot and close to the engine should burn the excess fuel as quickly as it is presented. Backfires usually require a build up of fuel to a concentration where it will flash explode. I'll have to get new hearing aid batteries. ;)