Engine Performance & HP Limitations. Discussing How They Overcame them

[keithb7]

I am interested in learning more technical details on engine output. HP & torque, how internal combustion engines evolved from say 1900 on.

I saw the recent thread on T-Head engines. Pretty large bore and stroke engines with fairly low HP output. The topic got me thinking about engine efficiency and output progression.

 

I'll guess at a few of the  few topics, I'd love to hear more about them..

 

Materials: higher quality steel and aluminum maybe allowed for tighter tolerances? Able to withstand higher combustion forces?

Fuel: Improved over time. Creating more violent & efficient combustion. Creating more HP and heat? More efficient transfer to BTUs.

Then cooling systems had to become more effective at absorbing and shedding heat from this improved combustion?

Improved fuels meant higher compression ratios were achievable. Again, more engine power and heat from higher combustion pressure.

From T-head to Flat head, to overhead valves, air intake and exhaust gases flowed quicker and more efficiently.

Valve timing was experimented with to get optimal power. Getting more of the spent gases out. Getting the most fresh A/F mixture back into the cylinders.

 

Perhaps the next weakest link to overcome was carburetors? Tested and tweaked to allow

as best A/F mixture ratio as possible. To again, squeeze out more power, and more efficient use of every drop of gasoline.

 

Internal combustion got hotter, more pressures in the cylinders. Piston rings and bearings had to improve.  Heavy big reciprocating parts must have become lighter. Now engines could rev quicker. Delco-Remy mastered the breaker type ignition system. In time, sparks got hotter and stronger. Ignition timing could be dial'd in with more accuracy?

 

Cylinder head design played a large part. Richardo, Hemi, poly, wedge, and more. Doing what exactly? Hotter more efficient combustion I assume.

 

Shorter stroke engines evolved from the big long stroke engines. Engine RPM's increased. Shorter strokes meant less torque, but high HP and RPMs. Overhead cams were needed to be able keep up?  Preventing valve train whip and floating valves? I suspect as engines evolved, coils has less and less time to recharge and deliver a consistent hot spark. 12V electrical systems likely helped maintain that hot spark in higher RPM& higher compression engines. 12V having a larger voltage differential in the electrical system. Higher compression likely meant the 12V could crank over a higher performance engine much faster for quicker easier starts.

 

Oils improved. Less drag. Less friction. Longer wearing parts. Allowing for tighter tolerances. Able to extract heat better. Less wasted HP from combustion to the crank output.

 

Perhaps one of the most important items invented to allow for engine improvements was the prony brake, leading to the dynamometer. Engineers could experiment, test and prove their lab experiments. Witnessing and documenting gains. 

Thinking further, every single part in the engine was constantly evolving. Quickly too!. Manifolds. Valves. Pistons. Blocks. Exhaust. Filters. Every year, the weakest part or system in the engine had to be improved. What a race it was every year to be cutting edge and sell more and more cars.

Edited December 26, 2021 by keithb7 (see edit history)

[hidden_hunter]

In the early days I’m assuming the biggest jumps were the war and aviation engines that trickled down to automotive 

[keithb7]

That’s a great point. Some much was going on at the time. So many influences that are easy to overlook today. 

[Terry Harper]

Early fuel was a major limiting factor. The other thing to remember is the rest of the vehicle, road condistions and how they were driven.

Well into the teens a desirable trait was adaquate power at low rpm. Remember that most engines of the day were not counter balanced. Thus vibration etc. became a major issue at higher rpms. If you look at the old advertisements they often toute smoothness and lack of vibration. A big, well built, six cylinder T-head a low RPM can run surprisingly smooth at what we today consider rediculous low RPM. (1,200 - 2,000) Big bore and a long stroke gave plenty of torque. Remember its torque not horsepower that does the work. This not only kept RPM low but also minimized the need to shift gears. Once in high gear you stayed there.

 

A good illustration of this is aircraft engines for replica WW1 aircraft. Since original WW1 aircraft engines are made of near "un-obtainium" many builders opt for a modern engine such as a Lycoming or Contenental to hide behind the cowling of a Fokker or Nieuport. On paper that engine  - whatever it may be, may pump out 150 hp at say 2,700 rpm swinging a 68" prop which will drive a Cessna 150 quite well. Yet performance wise it's barely adaquate for the Fokker or Nieuport plane decidedly under powered. Now compare that to the original 80 hp power rotary engine swinging a 10 foot prop. (which the Lycoming or Continental could never hope to swing) at 1,300 rpm. With decidedly less HP it was well matched to the airframe.

 

Again it all comes down to torque at low RPM and the needs of the conditions and operating style.

 

[Gary_Ash]

Sometimes we forget how sophisticated early car engines were, in particular race cars of the 1910s and 1920s.  Peugeot developed a 7.6 liter 4-cylinder engine with dual overhead camshafts, 4 valves per cylinder, hemispherical combustion chamber, ball-bearing crankshaft, and dry sump lubrication for their 1912-13 Grand Prix cars.  Other versions were made in 5.6 and 3 liter sizes.  Peugeot won at Indianapolis in 1913.  The Duesenberg brothers copied the Peugeot design for the Miller/Offenhauser/Meyer-Drake engine used for decades at Indy.

 

Here is a description of the 1912 and 1913 Peugeot engines:

https://primotipo.com/2015/12/11/191213-peugeot-gp-car-especially-its-engines/

 

Bugatti released the Type 35 cars in 1924 with 2 liter engines, 8 cylinders, single overhead cam, 3 valves per cylinder, and 6,000 rpm to produce 90 hp.  Supercharged versions of 2.3 liter size delivered up to 138 hp.  

 

By 1937, Mercedes created the W125 race car with 600+ hp from a 5.6 liter straight 8 engine with supercharger, double overhead cam shafts, was capable of 190 mph speeds.  It ran on specially blended racing fuel, not pump gas.  

 

So, the racers knew how to build high-performance engines 100+ years ago.  Maybe they weren't cheap at the time, but the technology was there and the engineers knew how to design them.  The high-end production cars of the period copied the race car designs, though they sold in low volume, e.g. Duesenberg J and SJ.  Henry Ford was building his Model T to be simple and cheap, not powerful or fast.  Imagine parking a 1913 Model T next to the Peugeot for comparison. 

 

 

 

1912 Peugeot DOHC 4-cylinder engine.

[hidden_hunter]

Metallurgy was also a limiting factor, there are urban legends that the quality of the aluminium used in some of the early race cars being the quality of a modern lawn chair 

[edinmass]

Fuel, oil,  metallurgy...........all factors. No one mentioned gasket technology and materials. Many early high compression over head valve engines didn’t have detachable heads.....they couldn’t keep gaskets in them. The W O Bentley’s are one example. WWI with it’s better oil and consistent fuel requirements  was the beginning of the big changes. Carburetors got much better. Ignitions really didn’t change much from 1910 to 1970. A Model J is basically a 1928 modern engine. Big, heavy, but powerful and reliable. Most people don’t realize how good a J really is. It’s one of the few legends that live up to the hype. The J was no where near perfect..........but it was thirty years ahead of all the others. Also......clutch and transmissions were other restrictions. Pound on a Model J.......your gonna get good at installing clutches....and fixing blowen up gear boxes.

Edited December 27, 2021 by edinmass (see edit history)

[Oldtech]

I have been intrigued by the performance increases achieved between 1925 and say 1934.  Huge strides were made in those years in power and performance.  Looking at it, compression ratios - which is linked to fuel was a factor but counterbalancing, improvements in fuel systems such as pumps instead of vacuum tanks allowed for larger carbs as they didn't need to maintain a vacuum at WOT.  Other reliability factors such as pressure lube systems became common at this time. Aluminum pistons allowed for higher revs. It was , in my mind, quite a decade. 

[ply33]

13 minutes ago, Oldtech said:

I have been intrigued by the performance increases achieved between 1925 and say 1934.  Huge strides were made in those years in power and performance.  Looking at it, compression ratios - which is linked to fuel was a factor but counterbalancing, improvements in fuel systems such as pumps instead of vacuum tanks allowed for larger carbs as they didn't need to maintain a vacuum at WOT.  Other reliability factors such as pressure lube systems became common at this time. Aluminum pistons allowed for higher revs. It was , in my mind, quite a decade. 

In general I agree, it really was a golden age for automotive innovation. I liken that era of automotive development to modern electronics with respect to the number of innovations introduced each year.

 

Not all manufacturers kept up with all the latest though. My '33 Plymouth came from the factory with modern thin shell bearing inserts, full pressure feed lubrication, hardened exhaust valve seats, oil filter, fully counter balanced crankshaft, cam ground aluminum pistons, hydraulic brakes, etc. It took some other brands competing in the same market segment, or even some more up market brands, years to adopt all of those things.

[m-mman]

I am beginning to believe that carburation was the biggest hurdle that doesnt get the respect that it deserved. 

 

The Mythbusters worked on the myth of an engine that ran on gunpowder. I knew they couldnt get it to work as the problems with getting a powder into an engine (and out again) with the correct air/fuel ratio was never going to happen. 

 

But cars use liquids. Gravity feed, vacuum tank, up draft, down draft, single and multiple venturies. . . 

Then asking carbs to adjust seemlessly between cold (choke) conditions, warm/hot idle, idle to increasing throttle, Idle to sudden WOT, Flat lands cruising to the increasing throttle of a hill climb, coasting down hill in gear . . . . And all the while trying to maintain the correct 14.7:1 ratio, and doing it all mechanically.

Wow, that's a lot to ask to keep an engine running at maximum efficiency and it is only in the efficient range that you get the maximum power. 

 

The race cars that Gary cites I think are somewhat easier to carburate.

They dont have to run well on a freezing cold morning. They dont have to repeatedly accelerate from stop signs. Their RPM range is limited  to basically high/WOT. And economy isnt an issue. 

The airplanes seem like stationary engines  - mostly consistent high RPM, but they do have to function upside down.

 

My choice for the biggest advances in reliable, powerful, usable, easily drivable engines, is the carburetor.

 

Edited December 27, 2021 by m-mman (see edit history)

[Ben Bruce aka First Born]

5 minutes ago, m-mman said:

I am beginning to believe that carburation was the biggest hurdle that doesnt get the respect that it deserved. 

 

The Mythbusters worked on the myth of an engine that ran on gunpowder. I knew they couldnt get it to work as the problems with getting a powder into an engine (and out again) with the correct air/fuel ratio was never going to happen. 

 

But cars use liquids. Gravity feed, vacuum tank, up draft, down draft, single and multiple venturies. . . 

Then asking carbs to adjust seemlessly between cold (choke) conditions, warm/hot idle, idle to increasing throttle, Idle to sudden WOT, Flat lands cruising to the increasing throttle of a hill climb, coasting down hill in gear . . . . And all the while trying to maintain the correct 14.7:1 ratio, and doing it all mechanically.

Wow, that's a lot to ask to keep an engine running at maximum efficiency and it is only in the efficient range that you get the maximum power. 

 

The race cars that Gary cites I think are somewhat easier to carburate.

They dont have to run well on a freezing cold morning. They dont have to repeatedly accelerate from stop signs. Their RPM range is limited  to basically high/WOT. And economy isnt an issue. 

The airplanes seem like stationary engines  - mostly consistent high RPM, but they do have to function upside down.

 

My choice for the biggest advances in reliable, powerful, usable, easily drivable engines, is the carburetor.

 

 

 And then we REALL kicked it up. To EFI

 

  Ben

[carbking]

1 hour ago, m-mman said:

And all the while trying to maintain the correct 14.7:1 ratio, and doing it all mechanically.

Another myth; carburetors are not trying to maintain a 14.7:1 ratio.

 

Different conditions require different mixtures for maximum performance.

 

How well the carburetor performed its job depends on the time period in question, and the make and model of the carburetor; and especially the skill of the mechanic keeping the carburetor in tune.

 

One of the tenets of "carburetion 101" is that there are 3 major methods to improve atomizing of the fuel to the desired ratio: (1) add heat, (2) add air velocity, and (3) add fuel.

 

Jon.

[edinmass]

Early engine design makes 14.7 to 1 almost impossible......L head, T head, F head, ect............ thats why a five gas, and a dyno are so important....... 👍

[m-mman]

4 minutes ago, edinmass said:

thats why a five gas, and a dyno are so important....... 👍

Yes, for setting up an old car in the 21st century . . . .But I dont think the Pierce and Locomobile engineers had those in 1920(?) 

Increasing performance during the era when the engineers couldnt see exactly what was going on. Changes and modifications they experimented with and then let the engine itself tell them what was best. 

[m-mman]

44 minutes ago, carbking said:

Different conditions require different mixtures for maximum performance.

 

31 minutes ago, edinmass said:

Early engine design makes 14.7 to 1 almost impossible......L head, T head, F head, ect..

So, if 90% of carburetor repair problems are electrical, what percentage of "in the era" performance increases (overall dirveabilty, not just racing type performance) came from better carburation overall and how much from engine design etc? 

 

Example which innovations would you experts say gave better daily performance; dual ignition, compression ratio, head design, fuel mixture, or something else?

Could a small block Chevy with an updraft carb run as sweet? 

Edited December 27, 2021 by m-mman (see edit history)

[carbking]

I have no idea when gas analysis machines became available, especially to the general public.

 

The first one I ever purchased, I purchased in the late 1960's from a Ford dealership going out of business. It was old then. It didn't really help me to do a better job of tuning, rather, it reinforced the tune that I had already done.

 

My first diagnostic oscilloscope was an Allen, from about 1950. This was more useful to me than the exhaust gas analyser, as a perfect carburetor won't perform with a less than perfect ignition; and ignition troubles ARE MUCH more likely!

 

I would really hate to try to pick just one area that had maximum effect of efficiency change.

 

All of the areas Keith mentioned in his original post have their improvements.

 

If I had another lifetime to live, I could probably write a book on carburetor improvements, but they are already well documented, just not in one book. Besides, everyone would want it on line, and no one would buy the book!

 

Probably the two milestones in carburetor improvement would be the invention of the pressure fuel pump allowing downdraft carburetors in the late 1920's; and Carter's introduction of metering rod technology in 1929.

 

If I had to pick a single area, it would be the car manufacturers willingness to spend large amounts of dollars on test facilities.

 

Jon

Edited December 27, 2021 by carbking (see edit history)

[edinmass]

exhaust gas analyzers were offered for sale in 1936 to the aftermarket repair shops........ I doubt very many bought  them. There’s absolutely nothing wrong tuning by the seat of your pants, if you have a lot of experience. Problem is that many people don’t. Having a stationary dyno in my business for emissions testing was a fantastic advantage. On rainy days I would place a few pre war cars on it and play around with ignition and fuel. Playing with timing curves, fuel pressure, float height, jet size, you name it......we experimented with it. Also a close personal friend worked at Shell fuels and Morton Thiokol was a great help doing the chemistry and explaining carbon chains. Understanding blending stocks and heat content was also a interesting school to attend. We focused on L head engines because that is what 80 percent of what we were playing with at the time. Taking power readings with E10 vs regular pump gas was also interesting. The earlier you go, the less things tend to improve no matter how much you play with things......it’s relatively easy to get 15-20 percent better performance with most 1929-1935 cars if you spend time dialing them in. The extra 20-30 horsepower makes a huge difference in the driving envelope of the car. The most important lesson I learned was any L head under 325 cid was just wasting my time.........they just don’t make the power I want to go down the road. The 385 cid straight eights made by Packard, Pierce, Chrysler, Reo, and a few others can and will perform well.......even the 340-370 cid motors will do ok........get below 320, and things fall off fast.....

Edited December 27, 2021 by edinmass (see edit history)

[Bloo]

I suspect the first practical gas analyzers are the Hamiltons of the late 1970s. By practical I mean having at least 4 gasses. Do any still exist? I haven't seen one in several decades, and it is literally an Internet black hole, the only references seem to be passing mentions in old EPA documents. It would be kind of a hoot to own one now, but those, like all other old gas analyzers, are temperamental beasts with showstopping "gotchas" located at every turn.

 

Various kinds of gas analyzers and mixture meters go back to at least the 40s (I had an Allen from that era), and probably earlier. It measured one gas. There were scopes floating around in the late 60s that had a gas analyzer measuring two.

 

Using anything less than 4 gasses for tuning is in my opinion a waste of time. Two gas machines (HC, CO) work great if the car is running perfectly. But, if the car were running perfectly would you be working on it? Maybe for an emissions check or something. As a troubleshooting tool a 2 gas analyzer is useless.

 

As a troubleshooting tool, you need a 4 gas analyzer, measuring HC, CO, CO2, and O2. Or if you like, a 5 gas analyzer, which adds NOx. NOx has become a common addition since some states started regulating it and testing for it.

[edinmass]

Hamilton Standard four gas machines were common in Western Massachuetts around 1978, we had one in our local shop in 1979. I owned about five of them through 2005. The five gas was was needed to deal with smog. In reality, the best performance improvements we got from all the fancy test equipment was figuring out that 2/3 of the cars we were working on had incorrect carburetors bolted on them from the old days when “all those things are the same”...........well, they are not.......not even close. Half the cars didn’t have a timing advance unit that was working at fifty percent. The lesson? Look at EVERYTHING......and make sure it’s PERFECT.........if you can get a car to 100 percent of its factory condition it usually will run fantastic......kind of obvious isn’t it? There are so few unmolested cars it would really surprise you. 80 percent of the Pierce Arrows we come across have Stude carbs on them........and a 385 cid doesn’t want a 320 cid set up carb on it. The other secret is take your time.....and make everything the best it can possibly be..........do great work.....not just good enough. We always strived to have a car leave that was “perfect.” While nothing is perfect, if you peruse perfection it is possible to achieve excellence.........and that is truly a reasonable result.

Edited December 27, 2021 by edinmass (see edit history)

[carbking]

The testing machines are useful for mechanics, but get away from the original focus of the thread by the OP; which is the area that gave us the most improvement.

 

However, the testing machines do augment my choice of large test facilities by the car manufactures.

 

Would be interesting to know how testing by the manufacturers evolved over the years. There is one really interesting (at least to me) story of how Ford chose a Zenith instead of a Holley for the Ford Model A (and then gave the carburetor to Holley to copy  )

 

Supposedly, the chief engineer at Ford recommended the Zenith as it produced more power and economy compared to the Holley. Ford was a die-hard, and told the chief engineer that he didn't like the Zenith because it had too many bolts holding it together. If Zenith would redesign the carb to only have one bolt, then Ford would use it. They did, and he, and the rest (if the story is true) is history.

 

Jon

Edited December 27, 2021 by carbking (see edit history)

[edinmass]

It’s my humble opinion, that the industry was fairly well established with research and development by 1910. Look at the progress every five years that internal combustion engines made over twenty five years. One also must remember.....bad roads meant you didn’t need to go fast. So you also didn’t need better fuel. Tire technology wasn’t great.........it took all the stars to align to get to the mid 30’s when cars started to really function and perform at a level that made them “just better than a horse”.  By 1936 She’ll Oil started to experiment with what we call high test from our youth, and the manufacturing of all that gas for aircraft during the war allowed the manufactures to go to over head engines right after the war. Also, fuel was so cheap.....efficiency wasn’t even in anyone’s thoughts. Everything in time.......it’s own time.

 

Compare the first Tesla roadster to their top of the line car today.........you see similar progress. What will a Tesla look like ten years from now.......I don’t think anyone is working more than 24 months down the road.........

Edited December 27, 2021 by edinmass (see edit history)

[Gary_Ash]

A year or so ago, someone here on the Forum referred me to "The High-Speed Internal-Combustion Engine" by Sir Harry Ricardo (1885-1974).  My apologies that I can't remember who put me onto the book.  It was first published in 1923, updated through about 1968, and recently reprinted.  The book covers many areas of engine development, including valve placement, combustion chamber shape, ignition timing, etc.  Ricardo started doing engine research before 1910 at Cambridge University in England. 

 

In 1919, he completed building his E35 single-cylinder test engine with a 4.5 inch bore and 8 inch stroke.  A geared mechanism allowed moving the top of the engine to change compression ratio between 3.7:1 and 8:1, even while running. Lots of instrumentation permitted getting exact measurements of engine performance under a wide range of conditions.  It was used extensively to study the effects of fuel quality, particularly on knock and pre-ignition.  A dozen of these engines were supplied to other groups, and a later smaller version (3" bore, 4-3/8" stroke) with variable compression ratios of 4.5:1 to 20:1 resulted in 100 copies being made for fuel research.  One result of this work was the development of octane numbers for fuels.  Engine output was measured with an electric dynamometer, and many other variables were measured and controlled.  Ricardo claimed repeatability to 0.25%.  So, soon after WWI, these engines were useful tools in the hands of oil company labs and car manufacturers.

 

Ricardo's E35 engine test apparatus. 

 

E35 single-cylinder engine with adjustable compression ratio.  The handwheel on the right side

moved the top of the engine up or down.

[Bloo]

I once read a comment from one of the engineers of the Bendix Electrojector, the first electronic fuel injection, who said that (heavily paraphrased) "it worked great, but we had invented something that cost $800 and worked about as well as a $20 carburetor".

 

I have a couple of old automotive engineering texts from the 40s, one of them is from 1941. I can tell you that what was going on both chemically and physically with that little flame in the cylinder was already well understood. Many of the ideas being implemented in electronic engine controls the 1980s and early 90s were just answers to limitations well understood in 1941. They already knew what needed to be done.

 

Interestingly, one thing that was NOT clear at that time, or in 1948 when the other book was published, was any advantage of overhead valves for ordinary road cars.

 

Companies like Chevrolet and Buick had been touting the advantage of overhead valves since their beginnings, and so were sort of stuck with them. For one thing, you have to oil the rocker arms. If I'm not mistaken, Buick had you manually oiling them well into the 20s, while a lot of their L-headed competition hadn't had a similar requirement since the teens if ever. You could pressure feed them, but with the oils of the day the lines would probably plug up. Also you have to have pushrods and probably run the valve clearance pretty wide due to the heat expansion of all the parts. All that makes noise, and at the time "smooth" and "you can't even hear it running" were huge selling points. Overhead valves are not quiet. It's much easier to make a flathead quiet. The cam is very close to the valve stem, and the valve clearance can be pretty small. Meanwhile, someone, I think it was Pierce, invented hydraulic lifters, and Buick jumped on the hydraulic lifter bandwagon very soon after. No surprise. Buick's competition was primarily if not entirely flathead.

 

It wasn't until the horsepower race heated up that Chevrolet and Buick were vindicated. There is a limit to how high the compression in a flathead can go, and not for the reasons you might think. You get to a point where if you increase the compression any more, you restrict the breathing enough that horsepower goes down. It probably varies with the engine design, but I think it's fair to say most of the 30s designs are stuck at about 6.5-1 or less. Maybe 7.0-1 if you are lucky. This was a non-issue with 1940s gas. When the horsepower was about to heat up in the 50s, there was gas available with more lead in it. Compression wasn't limited by the fuel nearly as much, and the breathing of overhead valve engines is not limited by compression. Suddenly everyone needed an overhead valve engine.

 

Edited December 28, 2021 by Bloo (see edit history)

[ply33]

1 hour ago, Bloo said:

. . . Interestingly, one thing that was NOT clear at that time, or in 1948 when the other book was published, was any advantage of overhead valves for ordinary road cars.

 

. . . There is a limit to how high the compression in a flathead can go, and not for the reasons you might think. You get to a point where if you increase the compression any more, you restrict the breathing enough that horsepower goes down. It probably varies with the engine design, but I think it's fair to say most of the 30s designs are stuck at about 6.5-1 or less. Maybe 7.0-1 if you are lucky. This was a non-issue with 1940s gas. When the horsepower was about to heat up in the 50s, there was gas available with more lead in it. Compression wasn't limited by the fuel nearly as much, and the breathing of overhead valve engines is not limited by compression. Suddenly everyone needed an overhead valve engine.

 

The early 1960s vintage Encyclopedia Britannica we had when I was getting interested in cars said that the practical limit for compression of an L-Head engine was about 8 to 1 and that it was limited by breathing. Going by memory here, I guess I should look it up next time I visit that old house.

[keithb7]

Great conversation points here folks I am really enjoying the reading. The details about Ricardo and testing engines is intriguing. I will try and seek out the book mentioned.  Thanks!

[m-mman]

During the recent HCCA Holiday Excursion tour here in California I spoke to a female, European news reporter who was shooting film and doing interviews. 

 

She was struggling to understand the concept of "ancient cars". One question she had was "Why the 1932 cut off year?" (shouldn't any old car be ok for the tour?)  I tried to explain that that was the introduction era of downdraft carbs, fuel pumps, syncromesh transmissions and Henry's low priced V-8, etc, etc. 

The relative technology stagnation of the 1920s and the significant changes that happened at the beginning of the 1930s. She tried to understand and made some notes but I imagine that she will go back to review them and dismiss them as being unintelligible.

If you are not car fluent its a difficult to grasp all that happened and why it was all important.