Switching to taller gearing does not always increase fuel economy. In some cases, especially with urban driving, shorter gears are the way to go. Taller gears make the engine work harder during take-offs and can bog it down when cruising on the highway.
Not when we’re talking about 1930s-40s racing and land-speed engines.
Yes, yes, yes, you can write a history of auto engineering in reverse by listing the technologies that were developed and not instantly rushed to manufacturing by the big makers. And make absolutely no useful points thereby.
the only people who think GM “never did anything innovative” are people who think automotive history began the day they took an interest in it.
Pretty much. More to the point, people who see the big 3 or 4 or whatever as stifling innovation have no clue how long it takes to integrate new technology into a behemothic production system, cost-effectively, while complying with all regulations, and - importantly if not particularly admirably - while making it either zero-cost or profitable.
Auto manufacturers are businesses, not charities or public transit providers, and innovations have to make sense to them as a company as well as to tech fiends, conspiracy theorists and greenies. Do I like that? No. Does it make me understand why Ford doesn’t instantly junk decades of engineering for some new approach? Yep.
You know that displacement isn’t a myth, right? You can apply those same technologies to a bigger engine and get bigger results. Combine the big engine with modern technology and a turbocharger and you can create a lot of power.
There has to be a matching of the gearing to the hp and increased weight of any hp-producing add-ons. An engine that is altered to produce 50% more power can easily turn taller gears. Up to a point. Any vehicle which is trying to run with gearing that is too tall will have have acceleration and towing problems.
To use an easier example that’s a bit off-topic, an outboard motor’s propeller acts as a kind of differential and is much simpler to change. No added weight, no mounting issues, no additional plumbing, no change in compression ratio, etc.
The same 100 hp engine could be used on several different boats but would use different propellers based on the weight, hull design, and intended use of the boat (crusing vs pulling a load (watersking/towing)). Heavier boats and deep V designs would use less pitch than light weight boats with flat/pad bottoms. The choice of propeller would be based on allowing the engine to reach it’s redline RPM on that particular boat. Using a propeller with too high of a pitch for it’s expected use would hurt acceleration and towing capability.
In other words, it’s important to select the proper gear ratio for cars, trucks, and boats.
Eggs-actly. A modern, turbocharged, 3.9L Ford Mustang could be geared to match the acceleration of a 1.6L Honda Civic (not that anyone would really want that 
) and the Mustang would get equal MPG because the engine would be barely turning above idle. Plus it would be able to reach twice the legal speed limit. If the Mustang driver can keep their foot off the firewall, MPG would be even higher.
I’m very sceptical of that claim. Surely the best such an engine can return is indicated by the cruising mpg (when the engine is just pottering along) and the comments out there suggest that is way below the overall average of a 1.6 Civic.
It is a bigger and heavier car to lug around so surely even by keeping the acceleration profile the same as the Civic it’ll take a certain amount more energy to accelerate a larger mass. Can physics be fooled in the way you are suggesting?
Or are you saying that the Civic is more inefficient at it’s maximum acceleration and by dialling down the Mustang you can even things out?
It’s way below with normal gearing, yes. He’s saying it wouldn’t be with super tall gearing.
Different engines do need different gearing in different situations to provide maximum fuel economy or performance or whatever it is you’re going for. However, I don’t think the addition of a turbocharger is going to significantly change the most efficient gear ratio. After all, you don’t really want to rely on the turbocharger when cruising. The engine isn’t running very efficiently when the turbo is spooled up and the intake is under pressure. I have a model of car that is supercharged from the factory and has taller gears than the NA version and many people benefit from putting in shorter gears so that the engine isn’t relying on the supercharger as often.
Innovation? How about an all-aluminum V-8 with a rear-mounted transaxle? No, not Porsche 928, but Pontiac Tempest, 1961. This engine was fine, but didn’t sell. You can still get its direct descendent in a Range Rover, though.
OK, how about an air-cooled flat six in the back with a turbocharger? Chevrolet, 1962. Straight 4 with a turbo, anyone? Oldsmobile F-85, 1962.
GM used to innovate from time to time.
You don’t have the option of turning off your turbocharger once you’ve reached cruising speed. Your factory car came with engine/gear ratio combination that takes advantage of the increased hp of the turbocharged engine. Put in the non-turbocharged gear ratio and you will see increased acceleration, lower top end speed, and decreased fuel economy.
The factory supplied your car with the most efficient gear ratio for that particular model of car. (With some consideration for EPA standards.)
You can’t turn off the turbocharger, but you can play around with it some if you have something like a wastegate and a boost boost controller.
Maybe not turn it off but with the right gearing, you won’t be under boost which is a good thing if you want to go a while before hitting up the gas station.
And no, they don’t supply you with the most efficient gear ratio which is impossible since different people are going to have different ratios that are most efficient. The manufacturer puts in the gear ratio that’ll give the best results on the EPA test. I would put shorter gears in my car if it was a convenient swap and get better economy since the majority of the driving I do is stop and go, seldom any faster than 45 MPH.
“Most efficient” was probably the wrong choice of words. A choice was made to supply each model/engine combination with a final gear ratio. Muscle cars sell better if they accelerate quickly and economy cars sell better if they produce higher mileage. I’ll call it the “most marketable” gear ratio.
I haven’t rebuilt an engine in decades and maybe this is just a nit that needs to be picked but, excluding manipulating waste gates, etc, the turbo is always spinning as long as exhaust gas is being forced into it. If the turbo is spinning, the engine’s intake pressure will be higher than on a non-turbocharged engine.
Excepting hills and hard acceleration, a turbocharged spark ignition engine is going to be throttled so that the intake manifold pressure is below atmospheric, same as a normally aspirated engine. The turbocharged engine has to make up for the exhaust back pressure losses, so the IMP will be a little higher than the NA engine, but will still be at vacuum in cruise conditions.
If the engine was at idle or very light load, the turbo will be spinning quite slow. When the throttle is opened, the slow turning compressor represents an intake restriction, so the turbocharged engine may initially have lower manifold pressure (and power) than the NA engine. There is a positive feedback mechanism where increasing exhaust mass flow leads to increased intake mass flow. If this feedback builds slowly, then you have bad turbo lag. Reducing the lag requires tighter inlet nozzle for the turbine, which reduces efficiency and may limit max power due to sonic choking, so it is a trade-off. At the cost of additional complication, it is possible (and done) to make variable exhaust nozzles, eliminating a lot of the compromise.
Ignorance fought.
Thanks.
I don’t have a turbocharged engine, but one of my cars has a centrifugal supercharger on it. It’s always spinning, but the boost guage is in vacuum at part throttle. When you go WOT, it jumps to Zero until about 3000, then it starts building boost.
Numerous factors and history are ignored in some above replies. For example, if an eighteen wheeler (ie 70,000 pounds) needs a 350 Hp engine, then why does a 2500 pound car need 350 Hp? Intelligent thought or size of the owner’s penis?
Cars have more than enough horsepower (as made obvious by previously posted numbers such as 10 Hp). Problems lie elsewhere. One problem was a narrow power range of low performance engines. Rather than innovate (make higher performance engines), autos designed by cost controls simply increased displacement. And then preached myths to the naive. The V-8 was an early and easy solution to that narrow power range. In the last many decades, autos designed by ‘car guys’ eliminated unnecessary displacement by making the same horsepower from a 4 cylinder engine. GM demonstrated that technology in the early 1970. It also increased gas mileage and reduced pollution. But ‘car guys’ no longer designed GM products.
A low performance engine (on the road or race track) advertises itself. It makes more noise. Not just in parts that are poorly machined (only to 0.001 inch tolerances). But inferior designs burn (waste) more gas in the exhaust pipe. How to get that a noise that inspires the subjective and emotional? Burn gas in the exhaust pipe. Many kids now advertise insufficient knowledge by changing mufflers. Now they have a car that pollutes more, increased exhaust valve wear, less gas mileage, has less horsepower, and … well their naive friends are impressed by noise from a compromised engine.
Better gas mileage could be obtained by designing a smaller engine with a turbocharger. That was 1960 technology. Back in the 50s and 60s, GM made spectacular new cars because everything was innovated by car guys. Innovations every year were numerous. Including power steering, automatic transmission, rotating valves, tuned manifolds, electronic ignition, superior spark control, better carburetors, new alternator designs, superior manufacturing tools, McPherson struts, and standardization. Actual list would probably be longer than all above posts combined.
By 1970, bean counters literally stopped all innovation. Innovation only appeared on profit and loss sheets as a cost. And so we watched GM use money games to hide products that created less and less profits. Were so technically inferior that by the early 1990s, a GM car sold for less than it cost to build. Innovations that were stifled in and before 1970 meant 1990 products were so technically obsolete as to be the most expensive to build.
Why did turbocharging not appear in the 1970s? Well GM did turbocharge some cars (ie Buick). Its design was so cost controlled as to constantly fail. Technology for superior and less fuel hungry cars was stifled by concepts still taught in business schools today.
Turbocharging is an old technology to obtain higher gas mileage. Today, better solutions appear in products elsewhere in the world. GM was forced to admit their products are some of the world’s worst only when Rick Wagoner said there is nothing wrong with GM. GM’s only problems were the American economy. Only then did even dumbest Americans (ie Wall Street stock brokers) realize how bad GM products have become.
GM could have used an old technology called turbocharging to increase horsepower, increase gas mileage, decrease production costs, and decrease pollution. Instead, everything in GM was designed using the antonym of innovation - cost controls.
That might confuse GM, run by executives that once drove cars, with a GM whose executives do not drive. Are so introverted as to make laws so that GM executives could be protected from the public. GM, in denial, made rules to protect them from reality. According to GM, United and American airplanes were unsafe. Executives could only fly on private jets. GM even installed elevators so that executives need not see any common people in building lobbies.
The most famous aluminum block was Vega. Aluminum so superior (due to 1960 innovations) that cylinders did not even need a ridge reamer. Steel blocks wore so much that a ridge reamer was required to remove pistons. But Vega, even well beyond 100,000 miles, had virtually no cylinder wear. Why did that innovation result in a worst engine in history? Learn technology facts. Bean counters so cost controlled everything as to make changes that warped each engine.
One need only hear oil industry executives who routinely complained about this. GM cars required increasingly more gas because GM innovation died. The executives did not say that publicly. Being that honest was politically incorrect. But privately, oil industry executives discussed disasters they were being blamed for because GM products kept getting crappier. A perfect example - vapor lock. A problem only because GM bean counters removed parts that were ‘unnecessary’.
Turbocharging was an early solution to better gas mileage, superior designs, and less pollution. Unfortunately bean counters from business schools replaced car guys who did innovation. And still some have posted myths (lies) generated by those bean counter executives.
Innovation was alive and well in early 1960 GM. Then America started graduating plenty of MBAs. And less engineers every year. Engineers no longer designed the products.